Studies of control samples and backgrounds for the measurement of direct CP violation with interferometric methods at KLOE
Author: Szymon Gamrat
Supervisor: dr Eryk Czerwiński
abstract
Defence year: 2023
The main goal of these studies is to determine a correction factor for the efficiency of selection obtained using KSKL -> pi+pi-pi0pi0 Monte Carlo events using experimentally collected data in the function of time difference Deltat between decays of kaons. It constitutes a continuation of an analysis for Re(epsilon'/epsilon) and Im(epsilon'/epsilon) parameters, which began in [1].
Measurement principle is based on the selection of background channels having common properties with KSKL -> pi+pi-pi0pi0. The chosen decays were KSKL -> pi+/-l-/+nipi0pi0, KSKL -> pi+pi-3pi0 and KSKL -> pi+pi-pi+pi- corresponding to signal-like parts K -> pi0pi0, K -> pi+pi-, respectively.
The first step was to perform a selection under the hypothesis of each tagging decay (K -> pi+/-l-/+nipi0pi0, KL -> 3pi0 and KS -> pi+pi-) and reach the highest possible purity. Then, the number of tagging events was weighted with a branching ratio for each signal-like part to obtain so-called expected distributions of the time difference. The additional selection under the hypothesis of K -> pi0pi0 or K -> pi+pi- was imposed on the events after tagging to mimic the selection performed for KSKL -> pi+pi-pi0pi0 using MC. Importantly, independence between charged and neutral parts of decay had to be conserved, so the method of trilateration was adapted to reconstruct a neutral vertex. Finally, having determined the expected and selected distributions of Deltat, a correction factor can be calculated via the division of efficiency obtained from data by the efficiency from MC. The result is not
a uniform distribution, so there exists a specific factor for each bin of the Deltat histogram. Final uncertainties were determined using a standard propagation of a measurement error. A measured correction will be used in the further studies over CP symmetry breaking in the entangled kaons? systems.
Development of experimental conditions for measuring the ortho-positronium lifetime in extracellular vesicles obtained in vitro
Author: Julia Nizioł
Supervisor: prof. Ewa Stępień
abstract
Defence year: 2023
Investigating the ortho-positronium (o-Ps) lifetime in biological materials holds promise for enhancing our understanding of biological processes and pathologies. This master?s thesis aimed to develop experimental conditions for the measurement of the o-Ps lifetime in extracellular vesicles (EVs) isolated using the low-pressure filtration method. EVs in question were derived from a largescale 2D human pancreatic beta cell culture (1.1B4 cell line) maintained under normoglycemic conditions.
In order to check the effectiveness of the chosen method of isolation, environmental scanning electron microscopy (ESEM) images of the dialysis membrane were taken, which allowed to determine the size of its pores. Fourier transform infrared spectroscopy (FTIR) was employed to characterise the chemical composition of EVs. The qNano device, which operates on the principle of tunable resistive pulse sensing (TRPS), was used to determine the size distribution and concentration of EVs. Transmission electron microscopy (TEM) was employed to visualise the morphological features of EVs and validate their structural integrity. Finally, positron annihilation lifetime spectroscopy (PALS) was used to investigate the o-Ps lifetime in the EV sample. In
addition, the PALS technique was also used to study the lifetime of o-Ps in pancreatic beta cells from which the vesicles were derived, and in PBS buffer in which they were suspended after the isolation. The o-Ps lifetime and intensity for the sample containing EVs measured at 22°C were 1.87 ns and 15.4%. The same sample investigated at 34.2 °C gave results of 1.83 ns and
15.0%, respectively. These results were not significantly different from the results of the PBS measurement.
This study allowed to test several technical solutions to measure the positronium lifetime in EV samples. It underscores the need for continued efforts in exploring EVs with progressive methods such as PALS, as they hold immense potential, for example as carriers of biological cargo or biomarkers.
Wyznaczanie parametrów czułości i swoistości testu dla czasu życia orto-Pozytonium w tkance nowotworowej raka jelita grubego
Author: Agnieszka Babińska
Supervisor: prof. Ewa Stępień
abstract
Defence year: 2023
This master thesis aims to present a study using Positron Annihilation Lifetime Spectroscopy (PALS), which allows the study of matter at the nano- and subnanometer level, to analyze the ortho-Positronium (o-Ps) lifetime and intensity in healthy and cancerous colorectal tissues.
The study presented in this research investigated the possibility of using positronium as a new biomarker in the diagnosis of colorectal cancer. The study aimed to verify the following research hypothesis: in healthy colorectal tissues, the average lifetime of ortho-Positronium (o-Ps) is longer than in cancerous tissues.
The measurements carried out allowed us to determine the average lifetime and average intensity of o-Ps in healthy and cancerous colorectal tissues. The sensitivity and specificity of the diagnostic test showed that 27,3% of colorectal cancer
patients were correctly diagnosed with a positive test result, while 15% of healthy patients (those without colorectal cancer) were correctly diagnosed with a negative test result.
The results do not allow us to indicate clear differences in the o-Ps lifetime and intensity in healthy and cancerous colorectal tissues. In order to confirm the proposed research hypothesis, more measurements of colon sections would be necessary.
Polarization formalisms and quantum entanglement in the positronium system
Author: Mateusz Bała
Supervisor: dr Michał Silarski
abstract
Defence year: 2022
Quantum entanglement of the group of particles, is a fascinating quantum mechanical phenomenon, without the classical analogy, which happens when the system state can be treated only as a whole, and the constituent particles cannot be described separately. The simplest example in which the quantum entanglement can be manifested is the polarized two -photon system.Indeed such a case was analyzed both theoretically and experimentally many times. However, most of the studies were concentrated on the optical photons regime. For higher-energetic photons, the polarization cannot be measured by using standard devices such as polarizers. However, the partial polarization estimation is possible by exploiting the Compton scatterings process. In this work the analysis of high-energetic, polarized two-photon system is considered, probed by the doubly Compton scattering process. The model is described using the quantum information theory formalism. In addition, the model is incorporated to the Monte Carlo C++ library. The simulations of the various quantum states are performed and the results are compared with the expectations from the theory.
Study of the Total Body J-PET sensitivity with the Toy Monte-Carlo model
Author: Szymon Parzych
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2021
The main aim of presented thesis is to investigate sensitivity of the Total Body J-PET scanners as a function of their axial field of view and inner module construction, as well as assessing the influence of the angular acceptance criterion (used for PET performance optimization) on this characteristic. In order to achieve this goal a simulation-based study was carried out with a use of the standard Monte-Carlo simulation software - Geant4 Application for Tomography Emission (GATE). Moreover, a Toy Monte-Carlo model has been developed as a simplified approach to the sensitivity investigation. Its principle of operation, as well as detailed validation by comparison with GATE software is presented in this work. The obtained results demonstrate that the standard imaging total sensitivity achievable with the Total Body J-PET scanners equals to 25.92(05+/-04) [cps/kBq] for the
2 meter long two-layer tomograph and 84.74(0.9+/-1.1) [cps/kBq] for the 2.5 meter long fourlayer tomograph. Such results exceed the conventional PET systems (represented by the Biograph Vision) by a factor of ~4.5 and ~15 respectively. At the same time sensitivity at the center of the tomograph can reach up to 124.1(1.0+/-1.1) [cps/kBq]. Furthermore, due to the possibility of the positronium mean lifetime imaging guaranteed by the J-PET technology, its sensitivity based on the triple coincidence technique has been evaluated. The acquired maximal total sensitivity of 30.63(06+/-31) [cps/kBq] proves to again surpass the traditional crystal-based system up to ~5 times. Ultimately, the sensitivity achieved with the studied Total Body scanners is almost uniform along the whole patient with an additional increase on its sides for both double and triple coincidence imaging. This creates
a possibility for high-quality simultaneous imaging of the whole human body.
System akwizycji danych dla modularnego skanera PET oparty na układach FPGA
Author: Maciej Bakalarek
Supervisor: dr Grzegorz Korcyl
abstract
Defence year: 2020
The aim of the thesis was to design and implement a preprocessing system for tomographic data in FPGA devices. The system has been designed with high parallelism of calculations in mind, thanks to which it works in real-time. Additionally, applications were prepared for live-visualization of the results (i.e. Lines of Response). The paper describes the architecture of the CM-PET scanner (with which the implemented system has been integrated) and the technologies used. In the paper results of tests with the use of four CM-PET?s modules are presented. The estimated maximum system throughput is around 14 MSps.
Characterization of gamma quanta detector for the SABAT sensor
Author: Anna Miś
Supervisor: dr Michał Silarski
abstract
Defence year: 2020
The aim of this work was to characterize the scintillation detector with LaBr3:Ce:Sr crystal for SABAT project, involving the use of neutrons in the detection of hazardous materials. Such a detector has the best energy resolution among such materials. The performed research included measuring energy resolution for standard radioactive sources (22Na, 137Cs, 133Ba, 60Co and 152Eu) and for elements activated by fast neutrons (in AmBe source) emitting high energy gamma quanta. The performed measurements concerned such quantities as: energy resolution, time resolution, light attenuation length and light output. The energetic resolution for the Cesium line (662 keV) was about 3%. This is the best result that can be obtained when using a crystal as a scintillation material. Taking into account the results of the energy resolution, its dependence on the energy of gamma quanta was plotted and arameterized. Also it was checked the results depends on the distance between crystal and the collimator with source. The study showed that such a detector is linear. The measurements of light attenuation length revealed, that for higher voltages the charge output of the detector decreases exponentially with decreasing distance of irradiation point to the photocathode.
Neural networks application in hazardous materials recognition
Author: Diana Janik
Supervisor: dr Michał Silarski
abstract
Defence year: 2020
This work presents the feasibility studies of mustard gas recognition using neural network algorithms and data samples measured by a novel, non-invasive device, which is being developed at the Jagiellonian University within the framework of the SABAT (Stoichiometry Analysis By Activation Techniques) project. The data samples used to train and validate the performance of the used algorithms were based on realistic Monte Carlo simulations which formed histograms of energy depositions for three intervals of detection gamma quanta time. Multiple neural network models have been trained and tested using 7-folds cross-validation in order to analyze how does detector?s sensitivity impact model?s precision. The best results have been achieved for the LaBr3:Ce detector. Nonetheless, based on simulated data from inexpensive, less sensitive NaI:Tl detector obtained model?s accuracy has been only slightly lower. It is expected, that training a model on a larger dataset, without a burden of correlation caused by a limitation in the size of the simulations, may improve the results for NaI:Tl detector.
Study of the ortho-positronium mean lifetime in cancerous and healthy human colon tissues
Author: Zuzanna Bura
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2020
Currently, cancer is the second cause of death worldwide. The most effective method for cancer prevention is early diagnosis. This thesis describes an innovative method for cancer diagnosis that provides not only information about the localization of tumor in the human body but also about its structure. The purpose of this work was to examine the correlation between
orth-positronium (o-Ps) mean lifetime and the degree of malignancy, size, type of cells and other factors which can be associated with colorectal cancer, contemporaneously demonstrate the potential of simultaneous PALS (Positron Annihilation Lifetime Spectroscopy) and PET scan (conduct on Jagiellonian Positron Emission Tomograph, developed at the Jagiellonian University). For this purpose, a series of measurements were performed on normal and cancerous colon tissues. This work also describes details of measurements and their analysis (chapter 4). Chapter 5 shows the results of PALS measurements on living tissues (and fixed in formalin), as well as the impact of environmental factors such as temperature and humidity on the mean lifetime of o-Ps.
Adaptation of image reconstruction algorithms with time-of-flight for the J-PET tomography scanner
Author: Kamil Rakoczy
Supervisor: dr Wojciech Krzemień
abstract
Defence year: 2019
The main aim of this thesis is the implementation of various analytic image reconstruction algorithms in the frame of the J-PET Framework analysis package. The implemented algorithms: Kernel Density Estimation, Filtered Back-Projection and Time-Of-Flight-Filtered Back-Projection have been tested both using Monte Carlo simulations and experimental data gathered by the scanner. Obtained results show that the implemented algorithms reconstruct correctly the shape of the phantoms. Comparison studies between implemented algorithms have been performed. In reconstruction of the NEMA phantom, the best results have been obtained using the Shepp-Logan filter with the cut-off parametr equal to 0.75 of Nyquist frequency (corresponding to the Background Variability of 0.13 and the Contrast Recovery Coefficient equal to 1.03 for high activity region of radius 22 mm). For the Time of-Fligth Filtered Back-Projection algorithm, the best reconstruction was obtained using the Hamming filter with the cut-off parameter equal to Nyquist frequency (corresponding to the Background Variability of 0.17 and the Contrast Recovery Coefficient equal to 0.96 for high activity region of radius 22 mm).
Tomographic data processing and visualization on programmable devices
Author: Karol Farbaniec
Supervisor: dr Grzegorz Korcyl
abstract
Defence year: 2019
The aim of this work is to implement selected data processing stages for Digital J-PET detector readout and explore feasibility of hardware acceleration of image reconstruction. Moreover this work covers main aspects of FPGA design process. First chapter contains introduction to PET tomography, data processing followed by image reconstruction. Second chapter present fundamentals of digital electronics in reference to FPGA technology. Later Digital J-PET detecting system is described with system architecture and readout procedure. In fourth chapter implementation details are presented on data processing for detecting module and image reconstruction kernel. Next chapter contains results of implemented components.
Drift Chamber Track Reconstruction for the P349 Antiproton Experiment
Author: Dominika Alfs
Supervisor: dr Marcin Zieliński
abstract
Defence year: 2017
The aim of this thesis was to perform the drift chamber calibration and charged particles 3d track reconstruction for the P349 antiproton polarization experiment. A~dedicated procedures were designed, implemented and tested on the experimental data for the the D1 drift chamber. The calibration consisted of the drift time offsets determination, estimation of the initial drift time - space relations by means of the homogeneous irradiation method and the iterative procedure for the time - space relations optimization. Calibration curves for all wire planes of the detector were determined. The obtained uncertainties of the hit position reconstruction are in the range of 150 - 220 $
m mu m$. Furthermore, based on the prepared 3d track reconstruction angular distribution of tracks passing through the drift chamber were determined.
Assembly and calibration of apparatus for Positron Annihilation Lifetime Spectroscopy
Author: Kamil Dulski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2016
Positron Annihilation Lifetime Spectroscopy (PALS) apparatus was assembled using two
BaF2 detectors, and oscilloscope. Assembled setup then was optimized, by finding the best settings and parameters to collect large number of events, used in further analysis. Sodium isotope 22Na was used as source of positrons. A constructed setup measured time difference distribution between acts of positron emission and its annihilation (positron lifetime in the studied material). A computer procedure developed in the framework of this thesis enabled to analyze measured spectra and to extract average lifetimes distributions including contribution from direct annihilation as well as from the annihilation from para- and ortho-positronium atoms. Two samples, silicon plates (Si) and polyvinyl toluene (PVT) were measured. Results from analysis showed that, these two samples differ significantly in distribution of lifetime, as one of them is porous (PVT) with pore sizes of around 0.277 and 0.356 nm, while other is crystalline. Moreover, a new research proposal was described aiming at the investigations of SAMs(Self Assembled Monolayers) and low-? dielectrics.
Feasibility studies of measurements of annihilation photons polarization with the J-PET detector
Author: Nikodem Krawczyk
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2016
Application of 3D computer graphics techniques usedin video games for Monte Carlo calculationsof multi-particle transport code
Author: Sławomir Tadeja
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2016
Hazardous materials such us drugs, biological weapons and explosives posses a very distinctive chemical composition. They consist mainly from carbon, nitrogen, oxygen and hydrogen elements. This unique characteristics makes them an ideal target for the novel detection method called atometry, which allows non-invasive, real-time, chemical analysis of any kind of substance. The basis of this technology is stoichiometry analysis of a given object conducted with the neutron beams. The Stoichiometry Analysis by Activation Techniques (SABAT) Collaboration is a team of experienced scientists and students from the Jagiellonian University, working on these novel, atometry-based, systems for chemical threat detection. To support this research, a sophisticated Monte Carlo simulation package was developed to model in detail the neutron emissions. Due to the computational complexity of this simulation, plenty of optimization techniques needs to be used. One of them is an application of the technologies borrowed from the field of computer graphics and video games, such as the ray tracing or the specialized acceleration data structures such as the k-d trees. This thesis will describe the motivation behind the selection of this particular algorithms and data structures, and also the direct application of them in the simulation package
Development and implementation of Electronic Logbook for J-PET research groupusing Symfony2 framework
Author: Mateusz Haber
Supervisor: dr Marcin Zieliński
abstract
Defence year: 2015
The main aim of this thesis was to develop and implement an interactive ElectronicLogbook for Jagiellonian Positron Emission Tomography research group. Using the modernand innovative Symfony2 framework, Bootstrap, jQuery and Angular.js technologies we havecreated a fully working client-server web application based on the Model-View-Controllerarchitecture. The data storage was organized using two database engines: MySQL, andPostgreSQL, served in back-end by the Doctrine package. Application was designed in theResponsive Web Design (RWD) approach, making it possible to use it on the any portabledevices (e.g. like tablets and smartphones).Application was prepared according to the functional requirements provided by the J-PET group. The main functionality of the application is a multifunctional and intuitiveactivity logging system, which allows to register and further monitor the situation of theexperimental work. Secondly the application allows to associate the laboratory work infor-mation with the experimental parameters available from external database. Furthermore,we have implemented the error and warning handling system, allowing to monitor and reportall the custom situations encountered during the laboratory work. Application was supple-mented with the Shift Management module, allowing to organize weekly laboratory work ofthe research group.
Zrównoleglenie i optymalizacja algorytmów w pakiecie symulacji wykrywacza materiałów wybuchowych
Author: Michał Smolis
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2015
Współczesne metody wykrywania materiałów niebezpiecznych
są ograniczone, szczególnie ze względu na brak mobilności. Do
materiałów niebezpiecznych zalicza się między innymi materiały
wybuchowe i narkotyki, których głównymi składnikami pierwiastkowymi
są azot, tlen, węgiel i wodór. Na Wydziale Fizyki, Astronomii
i Informatyki Stosowanej, w ramach projektu SABAT (ang.
Stoichiometry Analysis by Activation Techniques), prowadzone są
badania nad atomometrią - metodą pozwalającą zdalnie wykrywać substancje niebezpieczne. Atomometria polega na analizie
stechiometrycznej badanej substancji w oparciu o widma energii
kwantów gamma emitowanych w wyniku napromieniowania badanego
obiektu strumieniem neutronów.
Aby wspomóc badania nad tą metodą, rozwijany jest pakiet
oprogramowania do symulacji emisji neutronów, ich oddziaływania
w zadanym materiale oraz rejestrowania kwantów gamma.
W tej pracy przedstawione zostały podstawowe algorytmy oraz
metody statystyczne, które zostały zaimplementowane we wspomnianym
pakiecie symulacyjnym SABAT. Praca zawiera opis oraz
wyniki testów jednostkowych wykonanych na opisanych metodach.
Omówione zostały także problem optymalizacji wybranych metod
oraz zrównoleglenia całego programu symulacji. W pracy
zawarte są także opis działania symulacji oraz jej przykładowy
wynik. Zrównoleglenie działania procedur spowodowało 4-krotne
zwiększenie szybkości działania pakietu symulacyjnego SABAT
dla takiej samej liczby procesów uruchomionych na czterordzeniowym
procesorze.
Studies of changes of signals shapes in plastic scintillator strips
Author: Monika Pawlik-Niedźwiecka
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
The main aim of this master thesis was to study properties of signals in plastic
scintillator detectors with different shapes. The scintillators with the length
of 500 mm and cross sections of square (14 mm side), hexagonal (9 mm side),
triangular (17 mm side) and circular (16 mm and 10mm dia.) were studied.
A series of measurements were done with 68Ge radioactive source placed in lead
collimator. 500 mm long scintillator connected to two photomultipliers by optical
gel and reference detector were used to make an experimental setup.
Measurements were performed at 5 positions across each strip. It was observed
that the rise time increases and the fall time decreases with the distance between
the irradiation place and photomultiplier.
The impact of a patient's size on a spatial resolution of PET scanner constructed of polymer scintillators
Author: Ewelina Kubicz
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
The aim of this thesis is to determine how size of a patient influences the
temporal and spatial resolution of a double module of Strip PET prototype
based on polymer scintillators. Such a scanner is currently being developed
at Jagiellonian University by the J-PET collaboration. All measurements
were conducted using a double module of a Strip PET prototype with a 22Na
source. Four different sizes of phantoms filled with water or ethyl alcohol
were used as a simulation of a patient?s body. The achieved time resolution
along Line-of-Response is around 146 ps, and it is the same for all tested
phantoms within the uncertainty range and as a result spatial resolution
along Line-of-Response is equal to about 22 mm. Both these values are two
times better than in currently used PET scanners.
Reconstruction of hit position of gamma quanta in scintillators based on sampling of signals in voltage and fraction domains
Author: Natalia Zoń
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
With the ongoing development of novel Positron Emission Tomography solutions, there exists a demand for researching methods of processing data allowing for the reconstruction of 3D human body images from signals gathered by the device?s detectors.
This thesis describes a method of reconstructing the position of gamma quanta hit along a single polymer scintillator based on the calculation of similarity of signals incoming from a PET device with respect to signals in a previously created database.
The similarity of two signals is computed using either a set of times corresponding to a set of voltage thresholds common for the two compared signals (Chi-square method) or two sets of points designating two curves representing the signals (Frechet distance method). The theoretical basis of the concept and its general idea as well as individual steps of the proposed algorithm are explained in detail in the next chapters of this thesis.
The realization of the method in form of a computer program was implemented in Python (version 2.7), a high-level, general purpose programming language which allows for employing multiple programing paradigms including object-oriented, functional, procedural or imperative programming.
This thesis is supplemented with Appendix containing the source code of the computer program.
Measurement of the charge asymmetry for the KS -> pi e nu decay with the KLOE detector
Author: Daria Kamińska
Supervisor: prof. Paweł Moskal, dr Eryk Czerwiński
abstract
Defence year: 2014
The aim of this work is a determination of the charge asymmetry in semileptonic decays of KS meson. The measurement was performed using KLOE detector localized at DAFNE accelerator in the National Laboratory in Frascati, Italy. The experimental data used in this thesis has been collected during 2004-2005 data campaign of KLOE. The final values of charge asymmetry determined for KS meson semileptonic decays, obtained by registering the phi -> KL KS -> KL pi e nu process, amount to AS = (1.5 ? 5.8 stat ) 10^(-3). Obtained result does not indicate the CPT violation and received statistical uncertainty is, as expected, about two times better with respect to previous measurement.
A novel algorithm for the K->pi0pi0->gggg decay vertex reconstruction for the KLOE-2 experiment
Author: Aleksander Gajos
Supervisor: prof. Paweł Moskal, dr Eryk Czerwiński
abstract
Defence year: 2013
The aim of this work is to devise an auxiliary method of reconstruction of the K->pi0pi0 decay vertex for the KLOE experiment. The requirement for reconstruction is not to depend on quantities that may be affected by kaon regeneration and thus to allow for its rejection as background for the phi->KsKl->pi+pi-pi0pi0 process. A new reconstruction algorithm is proposed and implemented which uses four photons from the K->pi0pi0->gggg decay chain recorded by an electromagnetic calorimeter and is based on finding their common origin point. A kinematic fit is included in the algorithm in order to tune the quantities used as input to vertex reconstruction and thus increase spatial resolution of vertex location. The final resolution achieved by the new reconstruction algorithm was found to be about 0.5cm in each spatial coordinate for vertices of kaons decaying very close to their production point and about 2.5cm for the most interesting region where the spherical beam pipe is present. The prospects of application of the new algorithm to rejection of regeneration background were tested in several ways.
Synteza scyntylatorów polimerowych
Author: Anna Wieczorek
Supervisor: dr Andrzej Kochanowski
abstract
Defence year: 2013
Scyntylatory to substancje, których cząsteczki ulegają jonizacji lub wzbudzeniu pod wpływem oddziaływania z promieniowaniem jonizującym, a powracając do stanu podstawowego, emitują fotony.
Przedmiotem badań prezentowanych w niniejszej pracy są scyntylatory polimerowe. Ich głównym składnikiem jest polimer ? poliwinylotoluen lub polistyren, który samodzielnie nie może być efektywnym scyntylatorem, gdyż średnia droga emitowanych przez niego fotonów jest zbyt krótka. Niezbędne jest stosowanie dodatków fluorescencyjnych.
Zadaniem pierwszego z nich jest odbiór energii z polimeru
i emisja światła z zakresu UV. Następnie promieniowanie to jest pochłaniane przez drugi dodatek fluorescencyjny ? wavelength shifter, który emituje falę świetlną z zakresu widzialnego, a więc taką, której długość dopasowana jest do elementów układu detekcyjnego.
Celem pracy magisterskiej było otrzymanie w warunkach laboratoryjnych efektywnego scyntylatora. Aby tego dokonać należało zoptymalizować warunki procesu polimeryzacji, takie jak przedział temperaturowy prowadzenia procesu czy dobór stężenia dodatków fluorescencyjnych. Dokonano pomiaru krystaliczności metodą XRD, wykonano analizę termograwimetryczną, potwierdzającą wysoki stopień konwersji monomeru do polimeru oraz określono ich właściwości scyntylacyjne.
Otrzymywane scyntylatory mają być wykorzystane, jako detektory promieniowania gamma w Pozytonowej Emisyjnej Tomografii Komputerowej.
Badanie rozdzielczości czasowej detektorów scyntylacyjnych pod kątem ich użycia w Pozytonowej Tomografii Emisyjnej.
Author: Marta Ciszewska
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2012
Pozytonowa tomografia emisyjna polega na określeniu rozkładu przestrzennego stężenia
wybranej substancji chemicznej w organizmie człowieka oraz zmian tego stężenia w czasie.
Pacjentowi podaje się farmaceutyk znakowany nuklidem promieniotwórczym. Znacznik
dobiera się tak, aby ulegał rozpadowi ?+. Tomograf PET pozwala na zlokalizowanie
znacznika promieniotwórczego poprzez pomiar kierunku lotu wyemitowanych kwantów
anihilacyjnych. W tym celu wykorzystuje się system kilku tysięcy detektorów, które
rejestrują kwanty gamma w koincydencji. Cały system podłączony jest do komputera, za
pomocą którego wykonywana jest rekonstrukcja obrazu oraz wizualizacja rozkładu gęstości
farmaceutyku w ciele człowieka [1, 2].
Studies of detection of gamma radiation with use of organic scintillator detectors in view of positron emission tomography
Author: Szymon Niedzwiecki
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2011
Positron emission tomography (PET) is experiencing nowadays a lot
of interest. PET scanner measures density distribution of radiopharmaceuticals
with radioactive isotopes emitting positrons in human body.
annihilation of positrons with electrons from the body of the patient
results in emission of two gamma quanta, going back to back which are
then measured in detectors surrounding the patient. After applying
reconstruction algorithms density distribution of annihilations is determined.
PET modalities can eectively vizualize metabolic processes
inside examined patient, unlike other kind of scans like Computer Tomography
or Nuclear Magnetic Resonance, which tell us only about
anatomy of the patients body.
In recent times even more sophisticated method of scan was introduced
- the Time-Of-Flight PET. TOF PET measures time dierence
between arrival of gamma quanta in two detectors. Hovewer due to lack
of fast scintillaton materials this method weren't applied in practice.
Availability of new, faster scintillators and cost-eective photomultipliers,
as well as improvements in eld of electronics enabled usage
of TOF PET modalities. Resolution of measuring time dierence in-
uences spatial resolution of reconstruction thus making this quantity
most important when designing TOF PET scanner. One of the best
presently available scanner achieved time resolution of about 550 ps.
In this thesis feasibility study of using plastic scintillators in TOF
PET reconstruction is tested. At present TOF PET scanners are based
on crystal scintillators, which compared to plastic scintillators are much
slower and more expensive to manufacture. Measurements of amplitude
spectra of polymer scintillators, which were irradiated by gamma
quanta from annihilation, made by dr A. Kochanowski and mgr .
Kap?on in Chemistry Department of Jagiellonian University, allowed
for determining best composition of base, primary and secondary additive.
As a result of the test performed in the framework of this thesis a
PVT+PPO+POPOP was found as the best combination out of eight
examined. Experimental measurement of distrubution of time dierence
between signals from both sides of RP422 scintillator strip has
been also performed with result of 680 ps. This result can be further
improved by upgrading electronic components of experimental setup.
Measurement of the neutral kaon regeneration cross-section in beryllium at P=110 MeV/c with the KLOE detector
Author: Izabela Balwierz
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2011
The main result of this thesis is determination of the neutral kaon regeneration cross-section in beryllium for momentum of p_K=110 MeV/c. It was obtained by analyzing data for K_L->K_S regeneration in the cylindrical beam pipe of the KLOE detector. The corresponding cross-sections for the KLOE drift chamber inner wall and the spherical beam pipe were also evaluated as well as values for aluminium and carbon. The K_L mesons were produced in the center of the detector in the collision region of e^+ and e^- beams of the DAFNE collider that worked at the phi meson resonance peak. The analysis was based on identification of regenerated events e^+ e^- -> phi -> K_S K_L -> pi^+ pi^- K_S^reg -> pi^+ pi^- pi^+ pi^- and their extraction from the distributions of the vertex position of the K_L meson decays into pi^+ pi^-. The regeneration cross-sections were determined based on the extracted number of regenerated events and number of the K_L mesons passing through the regenerator. Obtained results are equal to: sigma_reg^Be=(50.0 +/- 0.7^stat +/- 5.0^syst)mbarn for beryllium, sigma_reg^BP=(77.6 +/- 0.3^stat +/- 7.8^syst)mbarn for the beam pipe, sigma_reg^DC=(75.7 +/- 0.3^stat +/- 7.6^syst)mbarn for the drift chamber inner wall, sigma_reg^Al=(170 +/- 3^stat +/- 38^syst)mbarn for aluminium and sigma_reg^C=(61 +/- 1^stat +/- 11^syst)mbarn for carbon.
Bulk polymerization of styrene and its derivatives as material for construction of scintillators
Author: Łukasz Kapłon
Supervisor: dr Andrzej Kochanowski
abstract
Defence year: 2011
The purpose of this study was to produce a plastic scintillator, i.e. material which exhibits scintillation ? the act of luminescence when excited by ionizing radiation. Synthesis of this material is based on dissolving scintillation additives in the monomer (styrene or vinyltoluene) and bulk polymerization by free radical mechanism. Several series of samples were prepared with different content of scintillation additives and polymerization conditions. Afterwards they were submitted for testing at the Division of Nuclear Physics, Jagiellonian University. The results confirm the effectiveness in the detection of gamma radiation. The resulting plastic scintillators, due to its advantages such as short response time, low production cost and the ability to produce samples of different shapes and sizes, will be used to build ionizing radiation detectors, for example in positron emission tomography (PET).
Feasibility study of measuring CP symmetry violation via eta->4pi decay using WASA-at-COSY detector
Author: Tomasz Bednarski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2011
It is known that the Standard Model does not describe all phenomena related to subatomic particles. This thesis presents feasibility studies of the measurement of eta meson decay using WASA-at-COSY detector which tests predictions of the Standard Model. The aim of this thesis is to estimate the time of measurement for which the current branching ratio limit of eta -> 4pi0 decay can be improved. In order to estimate the time of measurement Monte Carlo simulations were performed. Kinematics of the pp -> ppeta -> pp4pi0 -> pp8gamma reactions were simulated using PLUTO program. Next, by means of the GEANT3 program the response of the WASA-at-COSY detector was simulated for each particle. Received signals were analysed in RootSorter software package based on ROOT. Studies of the reaction with many gamma quanta in the exit channel required the investigation of WASA-at-COSY calorimeter functioning. Tests of a cluster building algorithm with emphasis on merging and splitting of detected signals were done. The obtained result shows that only about 3% of eta -> 4p0 decays can be properly reconstructed. The identification of the eta -> 4pi0 -> 8gamma decay was based on the invariant mass method for both pi0 and eta mesons. As a result, the resolution of the invariant mass determination of the eta meson was established to sigma = 31 MeV/c2. The acceptance of the WASA-at-COSY detector for pp -> ppeta -> pp4pi0 -> pp8gamma reaction was determined to Aeta=(Neta detected) / (Neta produced) = 1.5%. The time of measurement for obtaining a statistical precision equal to the current branching ratio limit for Tbeam = 1.3 GeV is about 13 hours. It was also established that the lower the excess energy in the eta production is the shorter the time of the measurement needed.
Investigations of the time interval distributions between the decays of quantum entangled neutral kaons
Author: Tomasz Twaróg
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2010
Feasibility study of eta-mesic nuclei production by means of the WASA-at-COSY and COSY-TOF facilities
Author: Magdalena Skurzok
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2010
Despite the fact that existence of eta-mesic nuclei in which the eta meson might be bound with the light nucleus by means of the strong interaction was postulated already in 1986, it is still not experimentally confirmed. Discovering of this new kind of an exotic nuclear matter is very important as it might allow for better understanding of eta meson structure and its interaction with nucleons. The search of the eta-helium bound states is carried out at the COSY accelerator in the Research Center Juelich in Germany, by means of the WASA detection system. The search are conducted with high statistic and high acceptance for the free production of the 4He-eta bound states. It is also considered to search for eta-tritium in quasi free reaction which might be realised with COSY-TOF facility. In this thesis the results of the Monte Carlo simulations of the eta-helium bound states and eta-tritium bound state are presented and discussed. The acceptances of the WASA-at-COSY and COSY-TOF detectors for the free and quasi-free eta-mesic nuclei production reactions were determined, respectively. Furthermore acceptances were compared for three different models of nucleon momentum distribution inside atomic nuclei and three different values of width of a considered bound states. In case of COSY-TOF detector it was established that the most effcient measurement of quasi-free dd --> p_sp (T-eta)_bs --> p_sp dp pi- reaction can be done at beam momentum of p_beam =3.1GeV/c.
Merging and splitting of clusters in the electromagnetic calorimeter of the KLOE detector
Author: Jarosław Zdebik
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2008
The work was carried out in the framework of the KLOE collaboration studying the decays of the phi meson produced in the DAFNE accelerator in the collisions of electron and positron. The main aim of this thesis was investigation of the influence of the merging and splitting of clusters in decays with the high multiplicity of gamma quanta, which are at most biased by these effects. For this aim we implemented the full geometry and realistic material composition of the barrel electromagnetic calorimeter in FLUKA package. The prepared Monte Carlo based simulation program permits to achieve a fast generation of the detector response separately for each interested reaction. The program was used to study the reconstruction efficiency with the KLOE clustering algorithm as a function of the photocathode quantum efficiency. It was also used to investigate merging and splitting probabilities as a function of the quantum efficiency. The conducted studies indicated that the increase of quantum efficiency does not improve significantly the identification of clusters. The influence of these effects was estimated for eta meson decays into 3 neutral pions and K_short meson into 2 neutral pions.
Liniowy model pozytonowego tomagrafu emisyjnego
Author: Ewelina Czaicka
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2008
Celem niniejszej pracy było opracowanie nowego ćwiczenia na II pracownie
fizyczną Instytutu Fizyki Uniwersytetu Jagiellońskiego. Ćwiczenie to ma na celu
zaprezentowanie zasady działania pozytonowego tomografu emisyjnego.
Analysis of the differential cross sections for the reaction pp --> ppK+K- in view of the K+K- interaction
Author: Michał Silarski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2008
Measurements of the pp-->ppK+K- reaction, performed with the experiment COSY-11 at the Cooler Synchrotron COSY, show a significant difference between the obtained excitation function and theoretical expectations including pp-FSI >. The discrepancy may be assigned to the influence of K+K- or K-p interaction. This interaction should manifest itself in the distributions of the differential cross section. This thesis presents an analysis of event distributions as a function of the invariant masses of two particle subsystems. In particular in the analysis two generalizations of the Dalitz plot proposed by Goldhaber and Nyborg are used. The present Investigations are based on the experimental data determined by the COSY-11 collaboration from two measurements at excess energies of Q = 10 MeV and 28 MeV. The experimental distributions are compared to results of Monte Carlo simulations generated with various parameters of the K+K- and K-p interaction. The values of the K+K- scattering length, extracted from two data sets for Q = 10 MeV and 28 MeV amount to: a_K+K- = (11 +- 8) + i(0 +- 6) fm for Q = 10 MeV, and a_K+K- = (0.2 +-0.2) + i(0.0 +- 0.5) fm for Q = 28 MeV, Due to the low statistics, the extracted values have large uncertainties and are consistent with very low values of the real and imaginary part of the scattering length.
Feasibility study of the eta-prime -> pi+pi-pi0 decay using WASA-at-COSY apparatus
Author: Marcin Zieliński
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2008
One of the objectives of the vast physics programme of the recently comissioned WASA-at-COSY facility is the study of fundamental symmetries via the measurements of the eta and eta-prime mesons decays. Especially interesting are isospin violating hadronic precesses of these mesons into 3pi systems driven by the term of QCD Lagrangian which depends on the mass difference of the u and d quarks. When an eta or an eta-prime meson is created in the hadronic reaction signals from such decays may be significantly obscured by the prompt production of pi mesons. In this thesis we present the estimation of the upper limit of the background due to prompt pion production for the eta-prime ->3pi0 and eta-prime->pi+pi-pi decays. Using the data from proton-proton collisions measured by the COSY-11 group we have extracted differential cross sections for the multimeson production with the invariant mass corresponding to the mass of the eta-prime meson. Based on these results and on parametrizations of the total cross sections for the eta-prime meson as well as parametrization of the upper limit for the prompt pi+pi-pi0 production in the collisions of protons we discuss in details the feasibility of a measurement of the eta-prime meson decay into 3pi channels with the WASA-at-COSY facility. Based on the chiral unitary approach the value of the branching ratio BR(eta-prime->pi+pi-pi0) was recently predicted to be about 1%. We show that the WASA-at-COSY has a potential to verify this result empirically.
Symulacje komputerowe reakcji pp->pp eta-prime w celu wyznaczenia szerokości naturalnej mezonu eta-prime z pomiarów wykonanych układem detekcyjnym COSY-11
Author: Eryk Czerwiński
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2006
Symulacja kwazi-swobodnej reakcji nn->d pi- w oddziaływaniu deuteronu z deuteronem
Author: Izabela Drągowska
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2006
Bremsstrahlung radiation in the deuteron - proton collision
Author: Joanna Przerwa
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2004
Despite the fact that Bremsstrahlung radiation has been observed many years ago, it is still the subject of interest of many theoretical and experimental groups. Due to the high sensitivity of the NN --> NNgamma reaction to the nucleon-nucleon potential, Bremsstrahlung radiation is used as a tool to investigate details of the nucleon-nucleon interaction. Such investigations can be performed at the cooler synchrotron COSY in the Research Centre Juelich, by dint of the COSY-11 detection system. For the first time at the COSY--11 experiment signals from gamma - quanta were observed in the time-of-flight distribution of neutral particles measured with the neutral particle detector. In this thesis the results of the identification of Bremsstrahlung radiation emitted via the dp --> dpgamma reaction in data taken with a proton target and a deuteron beam are presented and discussed. The time resolution of the neutral particle detector and its timing calibration are crucial for the identification of the dp --> dpgamma reaction. Therefore, methods of determining the relative timing between individual modules - constituting the neutron detector - and of the general time offset with respect to the other detector components are described. Furthermore the accuracy of the momentum determination of the registered neutron which defines the precision of the event reconstruction was extracted from the data.
Eta and Eta-prime meson production in the quasi-free proton-neutron collisions at the COSY-11 facility
Author: Rafał Czyżykiewicz
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2002
Both, the structure of the eta meson as well as its production mechanism are
still under strong discussion and debate. The most possible hypothesis concerning
the explanation of the almost three times larger mass for this meson observed
experimentally relative to the theoretically calculated mass is a gluonium admixture
to the eta-prime wave function. This gluonium admixture should reflect itself in the
production yield of the eta-prime meson in proton-neutron collisions. Since the production
of eta-prime meson through the gluonium exchange is isospin independent, the ratio
R(eta) = (pn->pn eta)/(pp->pp eta) close to threshold is expected to be R(eta-prime) = 1,
after corrections for initial and final state interactions.
The close to threshold eta-prime production in proton-proton collisions has already
been investigated at the COSY-11 facility. Cross section values in the threshold
region have been measured. However, until now no data have been taken for the
eta-prime meson production in the proton-neutron collision.
In order to investigate the eta-prime production in proton-neutron collisions at the
COSY synchrotron, the COSY-11 facility has been equipped with two new subsystems,
namely the neutron detector and the spectator counter. The optimization
of the topography for these additional detectors, the selection of the most suitable
beam momentum and a discussion for the method of luminosity determination for
the quasi-free pn->pn eta (eta-prime) reactions are presented in this thesis. Rates for the
production of eta and eta-prime mesons in proton-neutron collisions at COSY-11 have been
estimated. For the calculations a special fast program has been written.
Response function of the trigger scintillation detector for the COSY-11 installation
Author: Paweł Moskal
Supervisor: prof. Lucjan Jarczyk
abstract
Defence year: 1993
The aim of this work is to test the response of a scintillation detector to ionizing particles. This counter, consisting of sixteen detection modules, will serve as a trigger of the whole COSY-11 detection system. Thus the time resolution as well as a signal amplitude variation with respect to a hit position is of a special interest. The former because this detector will be used as a start counter for the time of flight measurement, the latter as it will provide energy loss measurements of the registered particles.
The work is divided into two parts. In the first one the main stages of a signal production by scintillation counters are considered. In the second one the first chapter presents measurements of the characteristics
of the photomultiplier, whereas the second one contains a description of the experimental set-ups as well as the method of data evaluation. The final chapter in turn presents the main characteristics of the considered detector.
Evaluation of the NEMA characteristics for the Modular J-PET scanner
Author: Faranak Tayefi Ardebili
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2024
This study aim is to evaluate the performance characteristics of the Modular Jagiellonian Positron Emission Tomograph (Modular J-PET) in accordance with the recognized standards established by the National Electrical Manufacturers Association (NEMA) for Positron Emission Tomography (PET) scanners. The Modular J-PET represents the lat-est prototype within the Jagiellonian-PET group, distinguished by its utilization of plastic scintillator strips optimized for the precise detection of back-to-back gamma quanta arising from electron-positron annihilations. The Modular J-PET comprises 24 individual mod-ules arranged in a symmetrical 24-sided polygon circumscribing a circular configuration with a diameter of 73.9 cm. Each module is constructed from 13 scintillator strips, aligned adjacently, each measuring 50 cm in length and possessing a cross-sectional dimension of 6 mm × 24 mm. Dual-ended scintillation light readout is accomplished through analog Silicon Photomultipliers (SiPMs).Data collected during the experimentation phase were subjected to analysis employing software known as the J-PET Framework. The average system sensitivity of the ModularJ-PET was determined to be 0.768?0.003 cps/kBq in the center with the peak sensitivity of 2.1 cps/kBq. The system sensitivity has improved by sixfold compared to the first generation of the J-PET prototype with 192 strips.Radial spatial resolution for TOF image reconstruction methods was found to be 4.92?0.56 mm,7.38?0.49 mm, and 6.94?0.38 mm at positions 1 cm, 10 cm, and 20 cm from the detector center, respectively. Tangential spatial resolution for TOF image reconstruction methods was determined as 7.38?0.51 mm,7.37?0.10 mm, and 14.67?0.31 mm at the same positions, while axial spatial resolution was calculated as 30.73?0.52 mm,30.73?0.64 mm, and 31.96?0.29 mm. It is worth noting that the tangential and radial spatial resolution values of the Modular J-PET detector align closely with those of commercialPET devices. Future enhancements are anticipated in axial spatial resolution through anextended axial field of view scanner and the application of wavelength shifting (WLS)techniques. The determination of the scattered fraction based on single-scatter randoms background (SSRB) algorithms yielded a value of 41.68?0.19 [%], which is consistent with that observed in commercial PET devices. To validate the experimental findings,GATE simulations were conducted.The simulations included spatial resolution assessments using a sodium source, as wellas evaluations of sensitivity and scatter fraction involving a phantom conforming to NEMA standards. The simulations indicated that the Modular J-PET achieves a system sensitivity of 1.324?0.032 cps/kBq at the center of the detector?s field of view and 1.313?0.001 cps/kBq at a 10 cm offset from the tomograph center. The peak sensitivity at the center of the detector?s filed of view to be 2.9 cps/kBq across various multiplicity cuts. Fur-thermore, the scatter fraction, computed utilizing SSRB algorithms, was established at(40.25?2.3)%. Radial spatial resolution for TOF image reconstruction methods was found to be 4.80?0.59 mm,7.26?0.55 mm, and 6.67?0.42 mm at positions 1 cm, 10 cm, and 20 cm from the detector center, respectively. Tangential spatial resolution for TOF image reconstruction methods was determined as 7.27?0.47 mm ,7.27?0.59 mm, and 15.1?0.4 mm at the same positions, while axial spatial resolution was calculated as 29.97?0.49 mm,30.53?0.74 mm, and 31.78?0.11 mm.The Modular J-PET, characterized by its single-layer configuration with 50 cm scintillator strips, exhibits the potential for extension to an extended axial field-of-view through multi-layer arrangements. Consequently, the presented Modular J-PET prototype holds promise for the cost-effective development of a total-body J-PET system constructed from plastic scintillators.
Evaluation of Positron Emission Mammography using plastic scintillator and wavelength shifters
Author: Shivani Shivani
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2023
The thesis focuses on the design and fabrication of a specialized detector system called J-PEM (Jagiellonian Positron Emission Mammography) optimized for breast imaging. This system utilizes plastic scintillators, wavelength shifters, and photodetectors to improve spatial resolution and detection of annihilation photons.
The prototype system consists of a single module comprising two layers of plastic scintillators and one layer of wavelength shifters. Silicon Photomultipliers are used for signal readout. The use of plastic scintillators and wavelength shifters enables the achievement of a spatial resolution of approximately 5 mm, as validated by simulation studies and experimental analyses.
Despite being a single-head module, the J-PEM system demonstrates spatial resolution comparable to established imaging modalities, making it a cost-effective tool for breast cancer detection. Comparisons between different configurations suggest that employing wavelength shifters without optical separation yields superior resolution.
The J-PEM system incorporates DOI (depth of interaction) sensitivity, which indicates the potential for further enhancements through narrower wavelength shifters in future advancements. Overall, the research findings highlight the effectiveness, efficiency, and potential of the J-PEM system for improving breast cancer detection with enhanced spatial resolution.
Determination of performance characteristics of the J-PET tomograph
Author: Monika Pawlik-Niedźwiecka
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Michał Silarski
abstract
Defence year: 2023
The aim of this work was to determine the performance characteristics of the Jagiellonian Positron Emission Tomography (J-PET) detector according to the worldwide NEMA norm for PET scanners. J-PET scanner was built out of three layers of axially arranged organic scintillators and it was optimized for detection of back-to-back gamma quanta from electron-positron annihilations.
Sensitivity of the J-PET detector is equal to 0.130 ? 0.014cps/kBq and 0.0789 ? 0.0061 cps/kBq for 0 and 10 cm radial offset, respectively. Low sensitivity value comes from the sparse detector geometry.
Tangential spatial resolution is equal to 0.635 ? 0.092 cm, 0.715 ? 0.092 cm and 0.630 ? 0.092 cm for position 1, 10 and 20 cm from the detector center, respectively. Radial spatial resolution is equal to 0.280 ? 0.092 cm, 0.500 ? 0.092 cm and 0.445 ? 0.092 cm, respectively, and the axial spatial resolution is equal to 3.850 ? 0.028 cm, 3.667 ? 0.048 cm and 3.788 ? 0.053 cm. Tangential and radial spatial resolution values of the J-PET detector are of the same order as for commercial PET devices. Axial spatial resolution will be improved in the future by application of the WLS.
Obtained value of scattered fraction on the level of 35.41 ? 0.19 [%] is comparable to the commercial PET devices.
Feasibility study of lesion detection by means of Total-Body Jagiellonian Positron Emission Tomography scanner
Author: Meysam Dadgar
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2022
Metastasis as the major reason for 90 % of cancer-related deaths, occurs when cancerous cells detach from their primary tissue and spread to the other part of the body through blood vessels or the lymphatic system. Detection of these malignant lesions in their early stages can increase the patient?s survival rate by taking proper treatment strategies. Due to their low sensitivity, conventional PET scanners cannot detect metastatic lesions in the early stages.
In 2019, a new Total-Body PET (TB PET) scanner called uEXPLORER with higher sensitivity thanks to the full detector coverage along the patient?s body was constructed. The main obstacle in the worldwide utilization of this generation of scanners is their higher construction and maintenance price. Since 2013, there has been continuous research to develop a novel economic type of PET scanner named Jagiellonian Positron Emission Tomography (J-PET) based on plastic scintillators. This technology, by providing a cost-efficient solution in the construction of the Total-Body PET scanners opens possibilities for worldwide utilization of these systems and improves the survival rate of patients significantly with precise diagnosis. The research presented in this thesis evaluated the lesion detectability of Total-Body J-PET scanners by accomplishing the GATE simulation from XCAT anthropomorphic digital phantoms.
This thesis?s main aim is to investigate the lesion detectability of the Total-Body J-PET scanner and improve this feature by optimizing event selection criteria and the spatial resolution of the tomograph. The liver is the organ under study to determine the lesion detectability of Total-Body J-PET.
For the case of the presented thesis, a series of simulations with point sources and cylindrical phantoms has been performed for the determination of optimum characteristics of Total-Body J-PET. The second group of the simulations has been performed by utilization of human-grade XCAT anthropomorphic phantoms. The results of the simulations have been analyzed by Gate Output J-PET Analyzer (Goja) which has been developed by the J-PET collaboration. Due to the unique configuration of the J-PET-based scanners and their special detection principle, conventional image reconstruction software could not be compatible. In the case of the image reconstruction Quantitative Emission Tomography Iterative Reconstruction (QETIR) in collaboration with the Medisip research group from Gent, Belgium has been used.
The results showed that the Total-Body J-PET tomograph can detect centimeter-grade lesions in the various ranges of the XCAT phantoms with different body mass index (BMI). However applying acceptance angle criteria to remove the contribution of the most oblique coincidences in the image reconstruction, provided the possibility of detecting sub-centimeter (5mm) lesions in a higher number of the iterations of image reconstruction.
Rzadkie procesy atomowe w ciężkich jonach badane przy pomocy aparatury EBIT
Author: Weronika Biela-Nowaczyk
Supervisor: prof. Andrzej Warczak
abstract
Defence year: 2022
In electron-ion collisions recombination processes play a very important role. A good understanding of these processes in the laboratory enables development of theory, which is useful for plasma diagnostics. For example, recombination processes affect the state of astrophysical objects [1, 2], as well as nuclear fusion plasma [3, 4]. In many cases electron-ion interaction involves more than one electron. There, electron-electron interaction is a crucial aspect of these particular atomic reactions. This doctoral dissertation focuses on rare atomic processes both from theoretical and experimental perspectives.
In Highly Charged Ions Laboratory in the Institute of Physics of the Jagiellonian University, an electron beam ion trap (Dresden EBIT [5, 6], DREEBIT Co.) was installed in 2012. This compact room-temperature HCI-trap, equipped with an X-ray detector (XFlash 5030, Bruker Co.), opens a wide range of possibilities for studies of atomic processes associated with ion production and trapping in an EBIT [6].
The aim of this PhD dissertation is to collect experimental data and compare them with theoretical calculations done with the use of Flexible Atomic Code (FAC [7]). First examined process is called radiative recombination (RR). The capture of a free electron into a bound state of an ion is accompanied by the emission of a photon. It is worth mentioning, that a good resolution of RR spectra for bare argon ions (Ar18+) is an evidence of EBIT great research opportunities [8, 9, 10]. Secondly, resonant recombination involving more than one electron has been discussed. The most basic of these resonant processes is dielectronic recombination (DR) where a free electron is captured into a bound state of an ion with the simultaneous excitation of a core electron [11, 12, 13, 14, 15, 16, 17]. These resonantly populated excited states decay via characteristic K-shell X-ray emission. Very good resolution of the X-ray detector enabled the K-LL DR resonances to be distinguished for He- up to C-like Ar ions [8, 18, 19]. In the observed X-ray energy region, in addition to the DR, the intrashell tricelectronic recombination (intrashell TR) has been seen [8].
The last part of the presented studies is dedicated to the multishell TR, specifically to the KK TR [18]. Here, the resonant capture of a free electron to an ion-bound state transfers simultaneously two K-shell electrons to a higher atomic shell. This way, a doubly-excited K-shell state is produced and, in most cases, it decays via emission of two photons. The first transition to theempty K shell is responsible for emission of the Kh hypersatellite photon with an energy slightly higher than energy of the following Ks satellite transition. A maximum-like behavior of the intensity ratio between Kh ? and Ks ? has been reported. This behavior is a fingerprint of the investigated TR process. Finally, to the best of my knowledge, this is the first successful observation of this TR process [20].
One has to add, that the presented research analysis was supplemented with orginal methods of determination of the charge state distribution of ions in the UJ-EBIT plasma. These methods were based on the analysis of the X-ray lines profile [21].
Design and optimization of beam shaping assemblies for boron neutron capture therapy based on accelerators and DD/DT neutron generators
Author: Vahagn Ivanyan
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Michał Silarski
abstract
Defence year: 2022
The aim of this thesis was to design and optimize neutron beam shaping assemblies (BSA) for adapting neutron beams produced by Deuterium-Deuterium (DD) and Deuterium-Tritium (DT) neutron generators as well as by Cyclotron C18/18 for application in boron neutron capture therapy (BNCT). A series of GEANT4 simulations were performed in order to find a BSA design enabling formation of neutron flux meeting recommendations of the International Atomic Energy Agency (IAEA) for BNCT. Energies of neutrons produced by generators and by protons from cyclotrons are too high, and the neutron flux is too much diffused for the direct applications in BNCT. Therefore, the thermalization, as well as focusing processes need to be performed before the treatment. The design of BSA included optimization of shapes and materials for multipliers, moderators, reflectors and shielding purposes for DT and DD neutron generator were performed using computer simulations applying GEANT4 programming package. The main optimization criterion for BSA design was the maximization of the epithermal neutron flux with respect to the flux of thermal and fast neutrons and with respect to the radiation dose from gamma quanta. The simulations were performed by taking into account 2.5 MeV initial energy and 1011 n/s to 1013 n/s neutron yield of DD compact neutron generators, as well as 14.1 MeV and up to 1014 n/s neutron yield of DT neutron generators. Also, separately cyclotron C18/18 based BSA design and optimization was simulated, by selecting exact thickness and material type for the proton beam of the C18/18 cyclotron installed at A. Alikhanian National Laboratory of Armenia. For the above-mentioned purposes, nat-U, nat-W, and its 182W, 184W, 186W isotopes were discussed as first part of the moderator. It is known, that materials mixed with fluorine, such as AlF3, MgF3, AlF3 mixtures with nat-Al and other materials, can be useful to increase the number of neutrons in the epithermal energetic region from 1 eV to 10 keV and may be placed next to the first part of moderator as the second layer of the thermalization system. Before collimating the flux, filters like hydrogen borate (boric acid), cadmium, lead and other materials were placed in as filters to lower the amount of thermal neutrons. The best established version of the DD based BSA includes moderator consisting of 8 cm thick 186W, 45 cm thick mixture of 5% Fe and 95 % AlF3, 1.25 cm thick LiF, 0.5 mm Bi and 1 mm thick lead, and the 20 cm thick back and 15 cm thick side Pb reflectors with 15 cm thick lead collimator. As for DT neutron generator based BSA the best design consisted from 27 cm thick Bi, 53 cm thick FeAlF3, 3 cm thick Al, and 1 cm thick LiF moderator with 25 cm thick back and side lead reflectors and 10 cm thick lead collimator. The achieved epithermal over thermal neutron ratio was larger than 100 and comparably lower fast neutrons flux was registered from 106 initially simulated neutrons/projectiles. Thermal/epithermal neutron flux of C18/18 based BSA for BNCT as result of the GEANT4 simulation study is ~ 5?108 n/ (s?cm2), where the majority of particles are epithermal neutrons in energy range from 1 eV to 10 keV, while DD based BNCT yet needs to be revised as the highest yield of neutrons was less than needed >1013 n/s. The system resulting in epithermal neutron current over the epithermal neutron flux which should be > 0.7 is under development.
Test of T, P and CP Symmetry in the decay of ortho-Positronium using the J-PET detector
Author: Juhi Raj
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Eryk Czerwiński
abstract
Defence year: 2022
Conservation of discrete symmetries plays a fundamental role in the exploration of physics laws in the area of elementary particle physics. CP symmetry violation in the weak interaction was one of the first intriguing discoveries to the particle physics community in this domain. So far, there has not been any experimental evidence of violating discrete symmetries in the charged leptonic sector. This Ph.D. thesis reports the explored sensitivity of testing the T, P and CP symmetries in the charged leptonic sector using the versatile and novel detector, Jagiellonian- Positron Emission Tomograph (J-PET), in the decay of ortho-Positronium. A distinctive research methodology to test T, P and CP discrete symmetries in the decay of ortho-Positronium was formulated from four experiments conducted through 2017-2020 for 122 days. The achieved result showed no asymmetry within the achieved sensitivity of 7 × 10^?4.
Development of positronium imaging with the 192-strip J-PET detector
Author: Kamil Dulski
Supervisor: prof. Paweł Moskal, prof. Bożena Jasińska
abstract
Defence year: 2022
The thesis describes the basics of a new imaging technique - positronium imaging. Positronium imaging is a technique that combines the metabolic information obtained in a standard Positron Emission Tomography (PET) scan with the structural indices examined by the Positron Annihilation Lifetime Spectroscopy (PALS) technique. In particular, proof of concept of the positronium imaging, by means of the 192-strip J-PET detector is presented.
A research hypothesis was formulated which stated that it is possible to simultaneously measure the distribution of the radioisotope inside the sample and to determine the structural index (mean ortho-positronium lifetime) in each part of the sample. According to this hypothesis, it is possible to distinguish samples with a di erent structure. Therefore, positronium imaging can nd application not only in PET scans by delivering additional information, potentially improving PET diagnosis e ectiveness, but also in material research as a technique to characterize the nanostructure in every part of the large sample. In order to demonstrate that positronium imaging can be an important technique and prove the research hypothesis, comprehensive studies were carried out using the 192-strip J-PET detector. To ensure the high quality of the collected data, the J-PET detector was calibrated for time and position reconstruction, and a set of data selection conditions was developed. It was also checked how developed selection criteria and dedicated measurement simulations re ect the measurement conditions and at the same time maintain high purity of the data sample. In order to check how well the J-PET detector is able to examine the properties of positronium, an additional analysis was carried out in terms of the separation of various states and types of positronium decay. The results of the analysis shows the possibilities of the J-PET detector in the context of fundamental studies, on the example of the precise determination of the ortho-positronium decay constant.
The main part of the work focuses on testing the research hypothesis on two systems that covered two potential applications of positronium imaging - material and medical studies. The positronium image of a system composed of samples of di erent porosity shows that it is possible to distinguish the samples in terms of structure, despite the lack of visible di erences on the analogue to the standard image of annihilation density distribution. The developed method of estimating the mean o-Ps lifetime for single voxels allows to obtain quite good agreement, even for voxels with a relatively low o-Ps intensity. A clear separation in terms of structure is also presented in the positronium image from the in-vitro measurement of the human tissues. Measurement setup consisted of four samples of two types of tissue - cardiac myxoma and adipose tissue. Despite relatively low di erences in the mean lifetime of o-Ps, the positronium image of these samples also con rms the research hypothesis, successfully separating di erent types of tissues, with quite good compatibility of tissues of the same type.
Characterization of melanoma cell spheroids by means of imaging techniques and positron annihilation lifetime spectroscopy
Author: Hanieh Karimi
Supervisor: prof. Paweł Moskal, prof. Ewa Stępień
abstract
Defence year: 2022
The presented thesis is devoted to evaluating the three-dimensional (3D) spheroid characteristics using imaging techniques and examining the positron annihilation lifetime spectroscopy (PALS) as a novel biomedical approach to identify the cancer malignancy level. A 3D spheroid mimics important properties of a real tumor and may soon become a reasonable substitute for animal models and human tissue. In this thesis, the morphological analysis of spheroid cell cultures was conducted using micro-CT and compared to that of confocal microscopy. An approach is proposed that can potentially open new diagnostic opportunities to determine the characteristics of cancer cells cultured in 3D structures instead of using actual tumors. Micro-CT analysis of a spheroid showed that the spheroid size and shape differed depending on the cell line, initial cell number, and duration of culture. The micro-CT allows for high-resolution visualization of the spheroids? structure.
In this study, it was hypothesized whether the difference between the grade of malignancy of cancer cell lines can be probed by positronium biomarker. The hypothesis was tested on the 3D spheroid model. Positron annihilation lifetime spectroscopy is known as an appropriate technique to evaluate the properties of different organic and inorganic materials based on the determination of the void size within and between molecules.
To test the proposed hypothesis, the lifetime of ortho-Positronium (o-Ps) was evaluated in 3D melanoma spheroids from two melanoma cell lines differing in the stage of malignancy. Obtained results show that the o-Ps lifetime and intensity are different between 3D melanoma spheroids with different malignancy level. The presented method paves the way for the application of the
3D spheroids for the in-vitro tests of positronium biomarker. The result of the method applied to studies of positronium in melanoma cancer cells revealed that positronium is a promising biomarker that may be applied in PET diagnostics for the assessment of the degree of cancer malignancy.
Poszukiwanie jąder eta-mezonowych helu w reakcji pd -> dppi0 za pomocą układu detekcyjnego WASA-at-COSY
Author: Aleksander Khreptak
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Magdalena Skurzok
abstract
Defence year: 2021
Rozprawa doktorska poświęcona jest eksperymentalnemu badaniu możliwości powstania silnie związanego układu mezonu eta i jądra atomowego, tzw. jądra mezonowego. Pomiar reakcji pd -> dppi0 wykonano w 2014 roku przy użyciu układu detekcyjnego WASA-at-COSY w Centrum Badawczym Juelich w Niemczech. Dane zbierano podczas powolnej i ciągłej zmiany pędu wiązki w zakresie od 1.426 do 1.635 GeV/c, co odpowiada zakresowi energii dostępnej od -70 do +30 MeV. Aby wyznaczyć funkcję wzbudzenia dla tego procesu zidentyfikowano wszystkie emitowane cząstki oraz zastosowano odpowiednie kryteria selekcji wybrane na podstawie wyników symulacji Monte Carlo reakcji powstania jądra mezonowego 3He-eta i jego rozpadu poprzez wzbudzenie rezonansu N*(1535). W funkcji wzbudzenia nie zaobserwowano wąskiej struktury rezonansowej, która mogłaby zostać zinterpretowana jako sygnatura istnienia eta-mezonowego jądra helu. Dlatego też wyznaczono górną granicę całkowitego przekroju czynnego na produkcję stanu związanego 3He-eta i jego rozpad w procesie pd -> (3He-eta)związany -> dppi0. Górna granica na poziomie ufności 90% waha się od 13 do 24 nb dla zakresów energii wiązania od 0 do 40 MeV oraz szerokości od 5 do 50 MeV.
Investigations of mechanisms of particle production in proton-induced nuclear spallation
Author: Udai Singh
Supervisor: prof. Krzysztof Pysz
Auxilliary supervisor: dr Sushil Sharma
abstract
Defence year: 2021
Studies of the selected problems in understanding of nuclear spallation physics are undertaken. Among them are the description of the initial phase of proton - target nucleus collision and proceeding of the intranuclear cascade, isotropic emission of nuclear fragments of very broad mass spectrum, contribution of the nonequlibrium and equilibrium processes to the total production
cross-section and its dependence on the isotope isospin, variation of the total production cross-section related to the number and ratio of protons and neutrons of the emitted particle. New experimental distributions of the double differential production cross-sections (d^2sigma/dOmegadE) for p, d, t, pi+ and pi- in the p + Nb reaction at 3.5 GeV proton beam energy are provided. They have been measured by High Acceptance DiElectron Spectrometer (HADES) experiment. The measured energy range of hydrogen isotopes are significantly extended in comparison to the experimental data available in the literature. The new experimental spectra are confronted with the theoretical prediction of three models of intranuclear cascade - GiBUU, UrQMD, INCL++. Discrepancies of the experimental and theoretical distributions are noticed and discussed. Experimental data derived from the literature are
used for examination of nuclear mechanisms assigned to the nuclear deexcitation phenomena. The comparative analysis of the four model prediction (ABLA07, GEMINI++, GEM2, SMM) of the selected observables relevant to the isotropic nuclear fragment emission is performed. Disagreement of the model prediction and the experimental data is observed.
Design and optimization of the strip PET scanner based on plastic scintillators
Author: Paweł Kowalski
Supervisor: prof. Wojciech Wiślicki, prof. Paweł Moskal
abstract
Defence year: 2021
The novel whole-body PET system is developed by the J-PET Collaboration. It is built of relatively cheap plastic scintillator strips arranged axially in the form of a cylinder. Usage of plastic scintillators opens perspective for the cost-effective construction of the total-body PET. In order to determine properties of the scanner prototype and optimize its geometry, advanced computer simulations using the GATE software were performed.
Firstly, simulations were verified with experimental results for laboratory prototype. After that, the simulations were used to calculate the NEMA characteristics and maps of efficiency. The spatial resolution, the sensitivity, the scatter fraction and the NECR were estimated according to the NEMA norm as a function of the length of the tomograph, number of the detection layers, diameter of the tomographic chamber and for various types of the applied readout.
Simulations results were used to optimize geometry and working parameters of the JPET scanner. They were also used to compare the J-PET solution with current commercial technology.
Biomedical applications of Positron Annihilation Lifetime Spectroscopy: nanostructural characterization of normal and cancer cells and tissues
Author: Ewelina Kubicz
Supervisor: prof. Paweł Moskal, prof. Ewa Stępień
abstract
Defence year: 2020
This thesis is devoted to examining a possible biomedical application of Positron Annihilation Lifetime Spectroscopy (PALS), for the characterisation of normal and cancer cells and tissues. PALS allows to study molecular structure at the nano- and subnanometer levels, by measurement of positronium properties in intra-molecular voids.
Studies conducted in the framework of this thesis aim to test the research hypothesis that positronium can be used as a novel biomarker for cancer diagnostics. The working hypothesis assumes that cancer cells differ from normal ones, in their nanostructure and molecular interactions. These changes are significant enough to affect positronium properties to a degree observable with the PALS technique. Correlations between the cellular organisation, its relation to the cell morphology and
signalling with positronium are examined in connection with positronium properties to carcinogenesis and metastatic processes.
The proposed hypothesis is tested in two models: benign cardiac myxoma specimens and malignant melanoma cultured cell lines. In both cases, positronium properties are compared to an appropriate normal tissue and cell line. Studies are performed
for both fixed and living cells and tissues to investigate the influence of water and cell viability on the PALS signal.
Obtained results show significant differences in positronium lifetime and its production intensity between cancer and normal cells and tissues in all studied cases, regardless of hydration and fixation of specimens. Therefore, obtained results validate
the working hypothesis that positronium can be applied as a novel biomarker in cancer diagnostics.
Study of angular correlations in the ortho-positronium annihilation with the J-PET detector for the search of CPT symmetry violation
Author: Muhsin Mohammed
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Aleksander Gajos
abstract
Defence year: 2020
Testing the conservation of the CPT symmetry is one of the most important issues for modern physical science. CPT is the only combination of charge conjugation, parity, and time-reversal that is observed to be an exact symmetry of nature at the fundamental level. Several experiments are currently performed to test the symmetry in the leptonic sector, e.g. in neutrino oscillations. CPT can be tested also by using charged leptons by searching for the electric dipole moment, e.g. of the electron. In this thesis, we present a test of CPT invariance in the decays of positronium as the lightest purely leptonic bound system.
Positronium is a viable system for the investigation of possible violations of the discrete symmetries in the leptonic sector. We search for CPT-violating decay processes of positronium atoms by the Jagiellonian Positron Emission Tomograph (J-PET), using the angular correlation of S ⋅ (k1 × k2), where S is the positronium spin and k1, k2 are the momenta of the most energetic positronium decay photons. A non zero expectation value of CPT-odd angular correlation would give rise to an up/down asymmetry of the decay plane with respect to the spin orientation of the ortho-positronium atom. In the previous similar experiments, the precision of determining this kind of correlation has been limited to about 3‰. The precise experimental CPT symmetry tests with J-PET are possible thanks to a dedicated reconstruction technique of the ortho-positronium (o-Ps) into 3γ decays. The reconstruction of the o-Ps decay into three photons was used in order to determine the spin direction of the positronium atoms. Also, the identification of o-Ps decay into 3γ events as well as the reconstruction of their annihilation points was achieved using a large decay chamber with a layer of a highly porous material target silica (R60G) on its inner wall, whose setup allows for determining the o-Ps spin linear polarization without the use of external magnetic field. The measurements were performed with the J-PET by using two radioactive sources with different activities and two different kinds of annihilation chambers. We have measured the angular distribution of gamma quanta emitted in three-photons annihilation as a result of o-Ps decay.
The test of the CPT symmetry with J-PET detector resulted in the mean value of the CPT-sensitive angular correlation operator OCPT=(-5.5 ± 3.7) × 10-4, which corresponds to the CPT violation coefficient of CCPT=(-13.6 ± 9.2) × 10-4, therefore no violation has been found at the precision level of 9.2 × 10-4, which is factor of 3 better than the previous experimental results.
Near-threshold kaon pair production in proton-proton collisions
Author: Damian Gil
Supervisor: prof. Jerzy Smyrski
abstract
Defence year: 2019
Measurements of the pp -> ppK+K- reaction close to the kinematical threshold allow the studies of the K+K-, pK+ and pK- interactions in the final state. Therefore, these measurements can help to understand the nature of the f0(980) and a0(980) mesons which, according to some theoretical models, are kaonic molecules, and of the Lambda(1405) hyperon which is considered as a pK- bound state.
In the framework of the present work, measurement of the total cross section for the pp -> ppK+K- reaction at incident beam momentum of 3.316 GeV/c, corresponding to the excess energy of only 4.5 MeV, was performed.
The measurement was done at the internal proton beam of the COSY accelerator in Juelich Research Centre in Germany using the COSY-11 detection system. The integrated luminosity, determined using a coincidence measurement of the elastically scattered protons, was 1.52 pb-1. In the absence of ppK+K- events observed in the experiment, an upper limit at 95% level of confidence on the pp -> ppK+K- total cross section of 0.070 nb has been determined.
This limit lies below theoretical calculations taking into account the pp, pK- and K+K- final-state interactions and describing the experimental data available higher above the threshold. This can indicate the influence of the Coulomb interaction which was not
fully included in the theoretical calculations or absorption of kaons due to formation of the K+K- bound state.
Search for eta-mesic 3He in non-mesonic final states
Author: Oleksandr Rundel
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Magdalena Skurzok
abstract
Defence year: 2019
The eta-mesic nucleus that is the bound state of a nucleus and eta meson has been postulated theoretically in 1986 but has not been observed in the experiments yet.
In May-June 2014, the experiment devoted to the search for the bound state of the eta meson and 3He nucleus has been performed at COSY accelerator in Research Center Jülich in Germany with WASA-at-COSY facility. The excitation functions for pd->3He+2gamma, pd->3He+6gamma, pd->ppp+pi-, pd->ppn+pi0, pd->dn+pi-, pd->dp+p0, pd->pd, and pd->ppn reactions have been measured in the vicinity of the eta meson production threshold. The experiment was carried out using COSY ramped proton beam and deuterium pellet target. The beam momentum varied continuously in the range of 1.426-1.635 GeV/c corresponding to 3He-eta excess energy range from -70 to +30 MeV.
This dissertation is devoted to the search for eta mesic 3He nucleus in the non-mesonic decay channels: pd->3He+2gamma and pd->3He+6gamma reactions. The excitation functions for these processes were obtained after identification of all outgoing particles and selection of events with conditions based on the results of Monte Carlo simulations of direct decay of eta meson bound in the 3He nucleus. The integrated luminosity dependence on the excess energy, used for the excitation function normalization, was calculated based on pd->3He+eta and pd->ppn_{spectator} reactions.
The analysis of the obtained excitation functions for the pd->3He+eta indicate slightly the signal from the bound state for Gamma>20 MeV$ and B in [0;15] MeV. However, the observed indication is in the range of the systematic error. Therefore the final conclusion of this thesis is that no narrow structure that could be interpreted as eta-mesic nucleus was observed in both excitation curves. Thus, the upper limit for the total cross section of the bound state formation was estimated assuming that the eta decay branching ratios in the bound state is the same as in free space. The upper limit at the 90% confidence level varies from 2 to 15 nb
within the binding energy range from 0 to 60 MeV and the width from 2.5 to 40 MeV.
Studies of CPT symmetry violation in matter-antimatter systems
Author: Daria Kisielewska
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Eryk Czerwiński
abstract
Defence year: 2019
In this thesis systems made of quark-antiquark and lepton-antilepton were studied for CPT symmetry violation effects.
The first study was preformed in neutral K meson pairs by comparing the asymmetries constructed from the decay rates into the two CP conjugated semileptonic final states, pi- e+ nu and pi+e-ar(nu). If the CPT symmetry holds, then the asymmetry constructed for short-lived kaon (A S ) and long-lived kaon (A L ) are expected to be identical. At present, the most precise measurement of A L has been performed by the KTeV collaboration: A L = ( 3.322 pm 0.058 stat pm 0.047 syst ) 10^(-3) . The measurement of its counterpart is experimentally more difficult since it requires a very pure K S beam which can be realised only by exploiting the entangled neutral kaons pairs produced at a phi-factory. The first measurement of A S has been performed by the KLOE collaboration in 2006 using 410 pb^(-1) of integrated luminosity: A S = ( 1.5 pm 9.6 stat pm 2.9 syst ) 10^(-3) , with an accuracy dominated by the statistical uncertainty. The new measurement reported in this thesis is based on a four times
larger data sample, corresponding to an integrated luminosity of 1.63 fb^(-1) . The final value A S = ( ?4.9 pm 5.7 stat pm 2.6 syst ) 10^(-3) improves statistical accuracy by a factor of almost two with respect to the previous KLOE result. The combination of these two measurements gives A S = ( ?3.8 pm 5.0 stat pm 2.6 syst ) 10^(-3) and allows to determine the new limits on CPT violating parameters Re ( x ? ) = ( ?2.0 pm 1.4 ) 10^(-3) , and Re ( y ) = ( 1.7 pm 1.4 ) 10^(-3) . The obtained results are in agreement with CPT invariance and with statistical uncertainty almost a factor of two smaller with
respect to the former measurements.
The second part of this work comprised a demonstration of the feasibility of using the J-PET detector to test the CPT violation in correlations of momenta of photons originating from ortho-positronium annihilation and the spin of ortho-positronium.
For this purpose simulations of the o-Ps formation and its annihilation into three photons were performed taking into account distributions of photons? momenta as predicted by quantum electrodynamics and the response of the J-PET tomograph.
The results indicate that the J-PET detector has a realistic chance to improve best present limits established for CPT symmetry violations in decays of positronium by more than an order of magnitude. This can be achieved by the application
of plastic scintillators which have superior time resolution and allow to create a setup with high granularity of detection strips and low detection pile-ups, which allows to overcome the limitation on the source activity. In addition, the improved
angular resolution combined with the excellent timing, and with the possibility of triggerless registration of all events allow for suppression and monitoring of background events.
Double-strip prototype of polymer time-of-flight positron emission tomograph based on multi-level analog electronics
Author: Szymon Niedźwiecki
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2019
The aim of this work was to construct and perform tests of a proto-
type Positron Emission Tomography (PET) scanner consisting of two
detection modules. Each module consisted of a long plastic scintil-
lator strip and was read-out from both sides by fast vacuum tube
photomultipliers. Two dimensions of strips were tested: 5 x 19 x 300
mm 3 and 7 x 19 x 500 mm 3 . It was shown, that one can successfully
utilise plastic scintillators for 511 keV gamma quanta registration and
determination of e + e ? annihilation position.
The research presented in this thesis was conducted in the frame-
work of the J-PET collaboration, whose aim is the elaboration of the
cost-effective method for construction of total-body PET.
In the course of this work a R9800 Hamamatsu photomultiplier is
selected for the first prototype of the total-body J-PET scanner and
a multi-threshold constant threshold board design is decided to be
used for time of interaction and energy loss measurement. An opti-
misation method of detector parameters: voltage supplied and thresh-
old for front end-boards is provided.
The main comparison with commercial scanners was performed
for a 30 cm long prototype. The fractional energy resolution is deter-
mined to be 9% at 340 keV - which is equal to the Compton edge for
511 keV gamma quanta. The Coincidence Resolving Time (CRT) is
determined to be 280 ps and Point Spread Function (PSF) at 1 cm off
the center of tested prototype was equal to 9.8 mm and 6.7 mm for
transaxial and axial resolutions, respectively.
Result of this thesis constituted the basis for the project of the full
scale prototype with diamater of 85 cm and axial field of view of 50
cm. The author of this thesis was taking part in the costruction of the
first full scale whole-body prototype from the stage of mechanical
assembly to assistance in performing measurements similiar to the
ones as described in the thesis.
Synthesis and characterization of polystyrene scintillators and their application in positron emission tomography
Author: Łukasz Kapłon
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Andrzej Kochanowski
abstract
Defence year: 2018
The aim of the thesis was to develop polystyrene scintillator for use in the novel time of flight Jagiellonian Positron Emission Tomography (J-PET) scanner being elaborated for the whole-body imaging. To achieve this goal, polystyrene based plastic scintillators with the different chemical compositions were produced and characterized. Spectroscopic and optical properties of these polystyrene scintillators were measured. Structure of manufactured plastic scintillators were studied using two methods: powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC).
Optimization of the conditions of styrene polymerization for the production of gamma radiation detectors was conducted. As a result of the work presented in this thesis the time-temperature cycles were established: (i) for polymerization in small cylinders as well as (ii) for polymerization in the glass mold allowing to manufacture long plastic scintillator strips. This thesis presents also a new method developed for the fast quality control of plastic scintillator strips. The method was successfully applied during J-PET prototype building.
Light output, decay time, emission spectra and technical attenuation length were measured to develop best composition of polystyrene scintillator. Among the polystyrene scintillators synthesized in the framework of this thesis it was established that:
(i) polystyrene scintillator with 2% BPBD primary solute and 0.06% POPOP wavelength shifter possess the best timing properties with decay time of 1.51 ns that is in the range of the decay time of the best commercial scintillators as e.g. BC-420 (1.5 ns), BC-404 (1.8 ns) and EJ-230 (1.5 ns) used in the J-PET tomograph;
(ii) polystyrene scintillator with 2% PPO primary solute and 0.03% bis-MSB and 0.03% POPOP wavelength shifters is characterized by the best light output of over 11200 photons per megaelectronvolt (MeV) which is comparable with light output of BC-420 with value 10240 photons per MeV.
Investigations of fundamental symmetries with the electron-positron systems
Author: Aleksander Gajos
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Eryk Czerwiński
abstract
Defence year: 2018
This work concerned two experimental searches for the violation of fundamental discrete symmetries in physical systems originating from electron-positron interactions. The first study was a direct test of the symmetry under reversal in time in transitions of neutral K mesons, performed with quantum-entangled neutral kaon pairs produced in the e+e->KsKl process. Data collected by the KLOE experiment operating at the DAFNE collider in 2004-2005 were studied to select events of the KsKl->pi e nu 3pi0 and KsKl->pi+pi- pi e nu processes and compare their rates. For the Kl->3pi0 decay involving only neutral particles, a dedicated reconstruction technique based on trilateration was devised. Rates of each process identified by two time-ordered neutral kaon decays, determined as a function of a difference between kaon decays, were used to measure the asymptotic level of two T-violation sensitive ratios of double kaon decay rates, yielding the values of R2 = 1.020 +/- 0.017stat +/- 0.035syst and R4 = 0.990 +/- 0.017stat +/- 0.039syst. In agreement with expectation based on the size of the the dataset used, these results do not reach the sensitivity needed to probe T violation. However, this measurement proves that the required reconstruction and analysis of the data is feasible and prospects exist for a statistically significant test of the T symmetry with a larger dataset collected by the KLOE-2 experiment is certain systematic effects are eliminated.
The second part of this work comprised a demonstration of the feasibility of using the J-PET detector to search for non-vanishing angular correlations in the decays of ortho-positronium atoms, the lightest purely leptonic systems decaying into photons. The trilateration based reconstruction method prepared for Kl->3pi0 decay at KLOE was adapted to the ortho-positronium annihilations into three photons. Its performance was validated using Monte Carlo simulations proving it may be applied to determination of spin direction of positrons forming the positronium atoms, thus allowing for control of their polarization in the experiment. Moreover, the feasibility of identification of 3gamma events as well as reconstruction of their origin points was demonstrated using a test measurement performed with the J-PET detector.
Hit-time and hit-position reconstruction of gamma quanta in the J-PET tomography system based on a library of model signals
Author: Neha Gupta-Sharma
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Michał Silarski
abstract
Defence year: 2018
Positron Emission Tomography (PET) is an advanced nuclear medicine imaging modal-
ity. It enables to determine the diseases (like cancer, heart diseases etc) in vivo in their
earliest stage which significantly influence the health-care resources provided to the pa-
tient. However, high cost of PET scanners construction has limited their availability.
J-PET (Jagiellonian-PET) is one of the project started with the aim to build a more
economical PET modality. It is an assemble of plastic scintillators in a cylindrical fash-
ion with large longitudinal field-of-view (FOV). In the plastic scintillators gamma quanta
emitted from the patient?s body interact via Compton scattering. Therefore, amplitudes
of processed signals strongly depend not only on the hit-position but also on the energy
deposition which demands for a new reconstruction method.
The aim of this work is to develop a new reconstruction method for hit-time and
hit-position of the registered gamma quanta. The developed method is based on the eval-
uation of degree of similarity between the registered signals and model signals stored in
a database. The compared signals are expressed in the form of an array including times
determined when sampling the signal in voltage domain. As a measure of similarity the
Mahalanobis distance between the examined and model signals is used. The model signal
is referred to as a signal which shape is determined from the measured experimental data.
The hit-position and hit-time are defined as the time and position of the model signal at
most similar to the registered one. The method is optimized for number of threshold levels
with different combinations, energy loss regions and number of parameters included to
calculate the value of Mahalanobis distance. Time-of-flight resolution is used as a criterion
of optimization. The final conclusion is that the reconstruction of image will be performed
on the two-threshold levels followed by the bisection of energy region from 0.2 MeV to
0.38 MeV in two parts using Mahalanobis distance as a function of position (z) and time
shift (?t).
The method was validated on the J-PET two-strips prototype, for two sets of strips
modules: one with dimensions 5x19x300 mm3 and the second with dimensions 7x19x500 mm3 .
As a result the obtained time-of-flight resolutions for the annihilation point in the center
of the detector are equal to 325 ps (FWHM) and 414 ps (FWHM) for the modules with
dimensions of 5x19x300 mm3 and 7x19x500 mm3 , respectively. Spatial resolutions when
gamma was hitting at the center of the scintillator for module with dimensions 5x19x300
mm3 and 7x19x500 mm3 are equal to 25.2 mm (FWHM) and 32.3 mm (FWHM), respec-
tively. Spatial transverse and axial resolutions obtained from the image reconstructed by
the J-PET two-strips prototype for point-like source placed at the center of the detector
with maximum likelihood expectation maximization algorithm using two-strip module
with dimension 5x19x300 mm3 are equal to FWHM = 7.7 mm and FWHM = 20.2 mm,
respectively.
Development of novel plastic scintillators based on polyvinyltoluene for the hybrid J-PET/MR tomograph
Author: Anna Wieczorek
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Andrzej Kochanowski
abstract
Defence year: 2017
Kalibracja energetyczna i synchronizacja czasowa modularnego scyntylacyjnego systemu detekcyjnego do tomografii TOF-PET
Author: Tomasz Bednarski
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Eryk Czerwiński
abstract
Defence year: 2016
Celem tej pracy było skonstruowanie i uruchomienie pierwszego prototypu urzadzenia
do tomografii pozytonowej wykorzystujacego scyntylatory plastikowe. Wykonany
został 24-modułowy detektor, w którym scyntylatory o wymiarach
5 × 19 × 300 mm3 sa ułozone na pobocznicy walca o srednicy 360 mm. W stosunku
do obecnie dostepnych, komercyjnych skanerów, uruchomiony prototyp tomografu
PET ma około dwa razy wieksze osiowe pole widzenia i jednoczesnie o około 50 ps
(FWHM) lepsza rozdzielczosc czasowa. Dodatkowo w ramach tej pracy zostały przygotowane
i przetestowane metody synchronizacji czasowej i kalibracji energetycznej
detektora.
Uzyskana rozdzielczosc czasowa koincydencji pomiedzy modułami detekcyjnymi
dla anihilacji elektronu z pozytonem w srodku detektora to sigma = 208 ? 4 ps
(FWHM = 490 ps). Natomiast rozdzielczosc przestrzenna uproszczonej rekonstrukcji
(Rozdział 9.1) dla punktowego zródła waha sie od sigma = 26.9 ? 0.2 mm
(FWHM = 63.3 mm) do sigma = 39.6 ? 0.9 mm (FWHM = 93.3 mm) w obszarze od
centrum tomografu do 100 mm od jego osi. Wykonanie rekonstrukcji obrazu metoda
najwiekszej wiarygodnosci MLEM (z ang. Maximum Likelihood Expectation Maximization)
po dziesieciu iteracjach pozwala na otrzymanie poprzecznej rozdzielczosci
przestrzennej FWHM = 18 ? 2 mm (odpowiednio sigma = 7.6 mm) oraz rozdzielczosci
wzdłuz osi detektora FWHM = 27 ? 2 mm (odpowiednio sigma = 11.5 mm).
Osiagniete wyniki były podstawa projektu konstrukcji tomografu w pełnej skali,
tj. o srednicy wewnetrznej 800 mm, osiowym polu widzenia 500 mm i składajacego
sie ze 192 modułów detekcyjnych.
W pracy, potwierdzono, ze mozliwa jest pozytonowa tomografia emisyjna wykorzystujaca
scyntylatory plastikowe, wbrew opiniom uznanym przez prawie 40 lat.
Light and intermediate mass fragment emission from proton - nucleus collisions
Author: Mariusz Wojciechowski
Supervisor: prof. Bogusław Kamys
abstract
Defence year: 2016
Determination of the analysing power for the vec(p)p -> ppeta reaction using WASA-at-COSY detector
Author: Iryna Schätti-Ozerianska
Supervisor: prof. Paweł Moskal
Auxilliary supervisor: dr Marcin Zieliński
abstract
Defence year: 2016
The eta meson production process can be studied via measurements of the analyzing power, Ay, which may be understood as a measure of the relative deviation between the differential cross section with and without polarized beam. Spin-dependent observables such as cross sections and analyzing powers have been determined only for a small number of excess energies and with very high statistical uncertainty. Therefore, measurements of the reaction vec(p)p -> ppeta was performed at the WASA-at-COSY detector in a fixed-target experiment with beam momenta of 2026 MeV/c and 2188 MeV/c. These correspond to excess energies of 15 MeV and 72 MeV, respectively. The eta meson was identified by the techniques of missing mass and invariant mass. The invariant mass technique was mainly used to reduce background events, while the missing mass technique provided an accurate value of the number of the eta mesons as a function of the emission angle.
The angular distribution of the analyzing power was compared with existing theoretical models. Predictions of all existing models strongly disagree with the experimental results determined in the framework of this thesis.
A comparison of the obtained Ay angular distribution with a series of associated Legendre polynomials revealed negligible contribution of the Sd partial wave at Q =15 MeV. However, at Q=72 MeV, a significant interference of the Ps and Pp partial waves was observed.
Validation of Spallation Models
Author: Sushil Sharma
Supervisor: prof. Bogusław Kamys
abstract
Defence year: 2016
Search for eta-mesic helium via dd -> 3Henpi0 reaction by means of the WASA-at-COSY facility
Author: Magdalena Skurzok
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2016
This dissertation is about the search for 4He-? bound state in dd?3Hen?0 reaction with the WASA detector installed in Forschungszentrum Jülich. The experiment was carried out using a deuteron COSY beam and deuteron pellet target. The beam momentum varied continuously in each of acceleration cycle from 2.127 GeV/c to 2.422 GeV/c which corresponds to a range of excess energy Q?(-70,30)MeV.
The excitation function for the considered process was determined after identification of all outgoing particles and the application of the selection conditions based on Monte Carlo simulations of ?-mesic helium production and its decay via excitation of the N? resonance. No narrow structure of the ?-mesic helium was observed in the excitation function. The upper limit of the total cross section for the dd?(4He-?)bound?3Hen?0 process was determined on the 90% confidence level. It varies from 21 to 36 nb for the bound state width ranging from 5 MeV to 50 MeV, respectively. However, an indication for a broad state was observed. The kinematic region, where we expect the evidence of the signal from the bound state, cannot be fully described only by the combination of the considered background processes. In contrast, the experimental excitation function is very well fitted by the background contributions for the region where the signal is not expected.
A novel data acquisition system based on fast optical links and universal readout boards
Author: Grzegorz Korcyl
Supervisor: prof. Piotr Salabura
abstract
Defence year: 2015
Various scale measurement systems are composed of the sensors providing data through the data acquisition system to the archiving facility. The scale of such systems is determined by the number of sensors that require processing and can vary from few up to hundreds of thousands. The number and the type of sensors impose several requirements on the data acquisition system like readout frequency, measurement precision and online analysis algorithms. The most challenging applications are the large scale experiments in nuclear and particle physics.
This thesis presents a concept, construction and tests of a modular and scalable, tree-structured architecture of a data acquisition system. The system is composed out of two logical elements: endpoints which are the modules providing data and hubs that concentrate the data streams from the endpoints and provide connectivity with the rest of the system. Those two logical functions are realised by the base modules called Trigger Readout Board (abbr. TRB) which feature basic functionality: digitization of the signals, communication with other modules and external networks, control and monitoring mechanisms. This set of functions can be extended on the modules via a system of Add-on boards that introduce new features and allows to adapt the platform for various applications.
The key characteristics of TRB based system are: scalable, flexible, extensible and reconfigurable. The scalability of the platform is realized by the hub components, which allow to create tree structures with many layers, each opening new ports for additional endpoints, without reducing the performance of the entire system. The TRB boards are based on FPGAs, which are reconfigurable, programmable logic devices. This approach results in a possible use of the same hardware module for different functions with just a change of the firmware. It also allows to introduce new functionalities over time. Together with the Add-on system, the platform can be relatively easily adapted to various applications and extended with new elements.
The platform was developed inside the HADES Collaboration with significant contribution from the author. The HADES detector was also the largest target application and was used for extensive tests of the system. Several conducted experiments and laboratory tests described in this thesis confirm the design and allow to evaluate the system performance. The platform has also found application in various other systems, one of them being the J-PET medical imaging project also described in this thesis.
Investigation of Deuteron Disintegration
Author: Ghanshyambhai Khatri
Supervisor: prof. Stanisław Kistryn, dr Izabela Ciepał
abstract
Defence year: 2015
The Kraków-Katowice-KVI Few-Body Collaboration has provided large database of the cross sections and analyzing powers in the sector of three-nucleon (3N) systems. In this work, taking a step forward into the system composed of four nucleons (4N), the
experiment was performed with the BINA detector at KVI Groningen. The data were obtained in deuteron-deuteron collisions at 160 MeV energy. The data were firstly preanalyzed, then the energy calibration, particle identification and track reconstructions
procedures were performed. Various two- and three-body channels were identified. For the first time a detailed analysis of the data collected in the ball ? the backward part of the BINA ? was performed with respect to energy and angular resolution and
detection efficiency. The three body dd!dpn breakup reaction was extensively studied in the forward part of BINA. The differential cross section of the breakup reactions were obtained within the quasi-free scattering (QFS) region for about 150 angular
configurations. The results have been compared to the very first calculations based on the CDBonn+ potential in a single-scattering approximation (SSA). Shape of the cross-section distributions for dp=160 and dp=180 is quite well reproduced by the theoretical predictions. The results , significantly enriching the 4N database, are very important for the development of theoretical description of the 4N systems dynamics.
Study of the phi->eta e+e- dalitz decay using KLOE detector
Author: Jarosław Zdebik
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2013
In this thesis the results of the investigation of the phi -> eta e+ e- -> pi+ pi- pi0 e+ e- reaction are presented. The goal of this work is to extract the branching ratio of the phi -> eta e+ e- decay, the slope of an electromagnetic transition form factor of phi-eta mesons and a charge radius of the phi meson. For this aim the phi mesons were produced in the electron-positron collisions and the eta mesons were identified via the eta -> pi0 pi+ pi- decay channel. The measurement was performed using the KLOE detector and the electron-positron beams circulated in the DAPhiNE accelerator. The experimental data used in this thesis has been collected in 2004-2005 years. After selection of the final sample, we reconstructed around 13000 events coming from phi -> eta e+e- -> pi0 pi+ pi- e+ e- decay with less than 2% background. Thus improving the statisticscollected by previous experiments by about two orders of magnitude. The extracted values of form factor slope parameter,b , branching ratio, BR and the radius of phi meson for analyzed reaction are: b = 1.32 +/- 0.23stat +/- 0.02syst GeV-2 , BR = (1.170 +/- 0.035stat +/- 0.008syst ) * 10-4 , radius = 0.56 +/- 0.05 fm, respectively. The results for slope of transition form factor, branching ratio and the charge radius of phi meson are delivered with the biggest precision ever.
Test of charge conjugation invariance in eta->pi(0)e(+)e(-) and eta->pi(+)pi(-)pi(0) decays
Author: Marcin Zieliński
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2012
Charge conjugation C is one of the fundamental symmetries in nature which
transforms particles into antiparticles. This symmetry was studied in weak interaction
where it is fully violated, but it is poorly known in the strong and electromagnetic interactions.
Therefore, it is important to test this symmetry accurately for a better understanding of the nature
of the strong interaction and for the understanding of the significantly larger abundance of matter
over antimatter in the Universe.
To this end, in this thesis we investigated nd ???+?-?0 and ???0e+e- decays, which might violate charge conjugation symmetry.
The violation of C symmetry in nd ???+?-?0 process could manifest
itself as an asymmetry between energy spectra of charged pions, and can be studied using event density
distribution on Dalitz plot.
The ???0e+e- decay is forbidden by C symmetry in the first order of electromagnetic
interaction, and can only proceed by emission of two virtual photons with the branching ratio
on a level of 10^{-8}, as predicted in the framework of the Standard Model.
Therefore, observation of a larger branching ratio could indicate a
mechanism involving first order electromagnetic interaction violating charge conjugation.
Both decays were investigated by means of the WASA-at-COSY detector operating at the COSY synchrotron
at the Forchungszentrum Juelich in Germany. The ? meson was produced via pp?pp?
reaction at the proton beam momentum of 2.14 GeV/c which corresponds to kinetic energy of 1.4 GeV.
The measurement was done at the turn of October and November in the year 2008. In total around
5x10^7 ? mesons were collected during the two weeks of data taking.
The tagging of the ? meson was done by means of the missing mass technique
and the decay products were identified by the invariant mass reconstruction.
As a result of the analysis conducted in the framework of this thesis a Dalitz Plot distribution
for the and ???+?-?0 decay was obtained. From this distribution we extracted
asymmetry parameters sensitive to C symmetry violation for different isospin values of the final state
and we have established that all are consistent with zero within the obtained accuracy.
For the ???0e+e- decay we have not observe signal and thus we estimated an upper limit
for the branching ratio. The established upper limit amounts to BR(???0e+e-) < 3.7x10^{-5}
at the 90% confidence level. This result is more precise than previously obtained in other experiments.
We intend to continue the research, and thanks to the 20 times higher statistics of already collected data by WASA-at-COSY, the upper limit will be improved significantly.
Search for the CP symmetry violation in the decays of Ks mesons using the KLOE detector
Author: Michał Silarski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2012
The aim of this work was to determine the KS ->3pi0 decay branching ratio and a modulus of the eta_000 parameter, defined as the ratio of amplitudes for KS ->3pi0 to KL -> 3pi0 decays, which characterizes the CP symmetry violation in this decay. The measurement has been carried out with the KLOE detector operating at the phi?factory DAFNE in the Italian National Center for Nuclear Physics in Frascati. DAFNE collides the e+ and e- beams at the center of mass energy s = 1019.45 MeV. The e+e? collisions result in the phi meson creation which is almost at rest and decay predominantly to kaon pairs. The decay products are registered using the KLOE detection setup, which consists of large cylindrical drift chamber surrounded by the electromagnetic calorimeter. The detectors are placed in a magnetic field of B = 0.52 T generated
by superconducting solenoid.
The KS mesons were identified with high efficiency via registration of these KL mesons which crossed the drift chamber without decaying and then interacted with the KLOE electromagnetic calorimeter . The KS four-momentum vector was then determined using the registered position of the KL meson and the known momentum of phi. Next, the search for the KS -> 3pi0 -> 6gamma decay was carried out by the selection of events with six gamma quanta which momenta were reconstructed using time and energy measured by the electromagnetic calorimeter. To increase the signal over background ratio after identification of the KS meson and requiring six reconstructed photons a discriminant analysis was performed. It was based on kinematical fit, testing of the signal and background hypotheses and exploiting of the differences in kinematics of the KS decays into 2pi0 and 3pi0. The search for the KS ->3pi0 decay presented in this work failed to detect a signal of sufficient statistical significance. Hence, we have obtained the upper limit on the KS -> 3pi0 branching ratio at the 90% confidence level: BR(KS -> 3pi0) < 2.7*10^{-8},which is almost five times lower than the latest published result. This upper limit can be translated into a limit on the modulus of the eta_000 parameter amounting to:|eta_000| < 0.009 at the 90% confidence level. This corresponds to an improvement of the |eta_000| uncertainty by a factor of two with respect to the latest direct measurement. The upper limit on the KS ->3pi0 branching ratio determined in this work is still about one order of magnitude larger than the prediction based on the Standard Model. Hence, the search for this decay will be continued with the upgraded KLOE detector, which has realistic chances to observe the KS ->3pi0 decay for the first time in the near future.
Study of the eta -> g e+ e- decay using WASA-at-COSY detector system
Author: Małgorzata Hodana
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2012
Since the eta meson is a short-lived neutral particle, it is not possible to investigate its structure via classical methods of particle scattering. To learn about its quark wave function, one studies those decay processes of this meson in which a pair of photons is produced, where at least one of them is virtual. The virtual photons have a non-zero mass and convert into lepton-antilepton pairs. Therefore, information about the quarks' spatial distribution inside the meson can be extracted from the lepton-antilepton invariant mass distributions by comparing the empirical results with QED predictions, which are based on the assumption that the meson is a point-like particle. The deviation from the expected behavior in the leptonic mass spectrum exposes the inner structure of the meson. This deviation is characterized by a form factor.
The corresponding data were collected for the pd --> 3He eta reaction at a proton beam momentum of 1.69 GeV/c. The experiment was performed using the WASA-at-COSY detector in November 2008.
525 +/- 26 events of the eta --> g e+ e- decay channel were reconstructed. The analysis chain led to the determination of the value of the slope parameter, bp, equal to (2.27 +/- 0.73stat. +/- 0.46sys.) GeV-2, where the systematical uncertainty should be treated as an upper limit only.
The estimation of the charge radius of the eta meson has been made resulting with the value of < r(eta)^2 >^(1/2) = (0.68 +/- 0.02) fm.
@Version including minor corrections according to the comments of the referees
Search for eta-mesic 4He with the WASA-at-COSY detector
Author: Wojciech Krzemień
Supervisor: prof. Jerzy Smyrski
abstract
Defence year: 2011
We performed a search for the 4He-eta bound state via exclusive measurement of the excitation function for the dd->3Heppi- reaction, where the outgoing p-pi- pair originates from the conversion of the eta meson on a neutron inside the 4He nucleus. The measurements were performed at the Cooler Synchrotron COSY-Juelich with the WASA-at-COSY detection system.The internal deuteron beam of COSY was scattered on a pellet-type deuteron target. The data were taken during a slow acceleration of the beam from 2.185 GeV/c to 2.400 GeV/c crossing the kinematical threshold for the eta production in the dd->4He-eta reaction at 2.336 GeV/c. The corresponding excess energy in the 4He-eta system varied from -51.4 MeV to 22 MeV. Events corresponding to decays of the eta-mesic 4He were selected using cuts on the 3He momentum, p and pi- kinetic energies and the relative p-pi- angle in the center of mass system. The range of the applied cuts was inferred from simulations of decay of the 4He-eta bound state proceeding via excitation the N* resonance. The integrated luminosity in the experiment was determined using the dd->3He-n reaction and the relative normalization of the points of the dd->3Heppi- excitation function was based on the quasi-elastic proton-proton scattering. No signal of the 4He-eta bound state was observed in the excitation function. An upper limit for the cross-section for the bound state formation and decay in the process dd->(4He-eta)_bound->3Heppi- determined for the bound state width of 10, 20 and 30 MeV equals to 28, 32 and 41 nb, respectively. The measured angular and momentum distributions of the reaction products are close to those simulated under the assumption of uniform phase-space distribution.
Study of the eta meson decay into e+ e- pi+ pi- using WASA-at-COSY detector system
Author: Michał Janusz
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2010
Determination of the total width of the eta-prime meson
Author: Eryk Czerwiński
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2009
The aim of this work was to determine the total width of the eta-prime meson. The investigated meson was produced via the pp->ppeta-prime reaction in the collisions of beam protons from COSY synchrotron with protons from a hydrogen cluster target. The COSY-11 detector was used for the measurement of the four-momentum vectors of outgoing protons. The mass of unregistered meson was determined via the missing mass technique, while the total width was directly derived from the mass distributions established at five different beam momenta. Parallel monitoring of the crucial parameters (e.g. size and position of the target stream) and the measurement close-to-threshold permitted to obtain mass resolution of FWHM = 0.33 MeV/c^2.
Based on the sample of more than 2300 reconstructed pp->ppeta-prime events the determined total width of the eta-prime meson amounts to 0.226+-0.017(stat.)+-0.014(syst.) MeV, which is the most precise measurement until now.
Isospin dependence of the eta-prime meson production in collisions of nucleons
Author: Joanna Klaja
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2009
The upper limit of the total cross section for quasi-free pn -> pn eta-prime reaction has been determined in the excess energy range near the kinematic threshold. The measurement has been carried out at the COSY-11 detection setup using a proton beam and a deuteron cluster target. The identification of the eta-prime meson has been performed using the missing mass technique. The energy dependence of the upper limit of the cross section is extracted with a fixed proton beam momentum of p_beam}=3.35GeV/c and exploiting the Fermi momenta of nucleons inside the deuteron. The data cover a range of centre-of-mass excess energies from 0 to 24 MeV. The experimentally determined upper limit of the ratio R(eta-prime)=sigma(pn -> pn eta-prime) sigma(pp -> pp eta-prime), which is smaller than the ratio for the eta meson, excludes the excitation of the S_11(1535) resonance as a dominant production mechanism of the eta-prime meson in nucleon-nucleon collisions. At the same time, the determined upper limits of R(eta-prime) go in the direction of what one would expect in the glue production and production via mesonic currents. For quantitative tests of these mechanisms an order of magnitude larger statistics and a larger energy range would be required. This can be reached with the WASA-at-COSY facility.
Comparative studies of the interaction in the low energy ppeta and ppeta' systems
Author: Paweł Klaja
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2009
The COSY-11 collaboration measured the pp -> ppeta and pp -> ppeta' reactions in order to perform comparative studies of the interactions within the proton-proton-meson system. This thesis presents in detail the analysis of the pp -> ppeta' reaction which was measured at the proton beam momentum of 3.260 GeV/c. The elaboration results in differential distributions of squared invariant proton-proton (s_pp) and proton-eta' (s_peta') masses, as well as in angular distributions and the total cross section at an excess energy of 16.4 MeV. The differential distributions s_pp and s_peta' are compared to theoretical predictions and to the analogous spectra determined for the pp -> ppeta reaction. The comparison of the results for the eta and eta' meson production rather excludes the hypothesis that the enhancement observed in the invariant mass distributions is due to the meson-proton interaction. Further, the shapes of the distributions do not favour any of the postulated theoretical models.
Study of the production mechanism of the eta meson in proton-proton collisions by means of analysing power measurements
Author: Rafał Czyżykiewicz
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2006
The analysing power measurements for the p(pol)p -> pp eta reaction studied in this dissertation are used in the determination of the reaction mechanism of the eta meson production in nucleon-nucleon collisions.
Measurements have been performed in the close-to-threshold energy region at beam momenta of p(beam)=2.010 and 2.085 GeV/c, corresponding to the excess energies of Q = 10 and 36 MeV, respectively. The experiments were realised by means of a cooler synchrotron and storage ring COSY along with a cluster jet target. For registration of the reaction products the COSY-11 facility has been used. The identification of the eta meson has been performed with the missing mass method.
The results for the angular dependence of the analysing power combined with the hitherto determined isospin dependence of the total cross section for the $eta$ meson production in the nucleon-nucleon collisions, reveal a statistically significant indication that the excitation of the nucleon to the S_{11} resonance, the process which intermediates the production of the eta meson, is predominantly due to the exchange of a pi meson between the colliding nucleons.
The determined values of the analysing power at both excess energies are consistent with zero implying that the eta meson is produced predominantly in the s-wave at both excess energies.
Eta-prime meson production in the p p -> p p eta-prime reaction near threshold
Author: Paweł Moskal
Supervisor: prof. Lucjan Jarczyk
abstract
Defence year: 1998
The eta-prime meson belongs to the ground state pseudoscalar meson nonet. According
to the SU(3) classification its quark composition is similar to the structure of
the eta meson. However, due to the small pseudoscalar mixing angle (~15 degrees)
the eta-prime meson is predominantly a flavour singlet state and hence can comprise a
significant amount of gluons. A possible gluon admixture would be reflected in the
production mechanism of the eta-prime meson in the elementary proton-proton reaction,
it would modify an eta-prime-p-p coupling constant which determines the direct production
amplitude, and it would also influence the potential of the proton-eta-prime meson
interaction. These issues make the investigations of the eta-prime meson very interesting.
The total cross section for the production of the eta-prime meson in the pp-->ppeta-prime reaction
has been measured close to the kinematical threshold. The experiment has
been carried out at the cooler synchrotron COSY using the internal proton beam
and the hydrogen cluster target. The ejected charged particles were registered
using the COSY-11 detection system, which allow for an unique identification of
positively charged particles and determination of their four-momentum vectors.
Events with the creation of the eta-prime meson were identified by means of the missing
mass technique. The obtained cross sections for the eta-prime meson production are by about a factor
of fifty smaller that the cross section for the production of the eta meson at the same
center of mass excess energies. Such large difference suggests that these mesons are produced in a rather different way. Comparison of the measured cross section values with calculations based on the
effective Lagrangian approach yields an upper limit for the eta-prime-p-p coupling constant.
The analysis of the energy dependence of the total cross section for the pp-->ppeta-prime reaction suggests that either the primary production amplitude decreases very close to threshold or that the proton-eta-prime interaction is repulsive.
Study of high-energy photons polarization in Compton scattering using the J-PET detector system
Author: Kamila Kasperska
Supervisor: dr Magdalena Skurzok
abstract
Defence year: 2023
The purpose of this work is the study of the high-energy photons polarization in Compton scattering using the Jagiellonian Positron Emission Tomography scanner (J-PET), more specifically finding the distribution of an angle between incoming and scattered photons polarization planes which opens the door for the polarization studies. Although polarization itself is a well studied phenomenon, until now it was only possible to investigate it in a narrow range of energies, using optical methods. J-PET detector, due to its unique construction, allows the registration of high-energetic gamma quanta emitted by the radioactive source and
coming from the electron-positron annihilation and also their multiple scatterings. It enables to determine the direction of photons momentum vectors, thus the directions of their polarization. In this work three main types of analysis were performed, differing in the energy and origin of the incoming photons: (i) electron-positron annihilation photons, with the energy of 511 keV, (ii) already scattered photons, found between two interactions in the detector with an unknown energy, (iii) 22Ne de-excitation photons, with the energy of 1275 keV. Future measurements of the polarization will allow deeper understanding of the other phenomena,
such as quantum entanglement or testing discrete symmetries in the leptonic sector.
Application of XAD4 water solutions for positronium imaging phantom
Author: Gabriela Łapkiewicz
Supervisor: dr Szymon Niedźwiecki
abstract
Defence year: 2022
Positron Emission Tomography (PET) is a non-invasive method of medical examina- tion, that allows for early diagnosis of diseases (such as cancer) and therapeutic process monitoring. At the heart of this method is registration of gamma quanta sourcing from the direct annihilation of positron originating from ?+ decay and electron from surrounding matter.
Positrons from Beta+ decay can also bond with electrons and create a meta-stable atom called positronium. Positronium exists for a limited period of time dependent on medium properties. Measurement of lifetime of positronium is the subject matter of Positronium Annihilation Lifetime Spectroscopy (PALS).
Positronium Annihilation Lifetime Spectroscopy (PALS) is a research method that uses dependency of the lifetime of positronium on free volume sizes for examining properties and structure of the matter. New PET imaging method developed at Jagiellonian University enables measurement and imaging of the lifetime of ortho-positronium. Research conducted at Jagiellonian University shows that the ortho-positronium lifetime measurement can be applied for medical diagnostics purposes to improve specificity of PET imaging. To assess the accuracy of this new method it is essential to develop a phantom that will allow for measurement of the lifetime of ortho-positronium alongside activity concentration.
Presented in this thesis is a method for assessing mean lifetime of ortho-positronium dependency on concentration of XAD4 and water mixture using PALS technique. Within this dissertation hypothesis was tested, that adding water to XAD4 polymer will result in gradual filling of pores, with increase of water concentration in a mixture and with electron free volume decrease, mean lifetime of ortho-positronium is expected to shorten accordingly. A total of 6 samples were measured: dry XAD4, distilled water and 4 mixtures of XAD4 and water in different concentrations. Acquired lifetime spectra were analysed using PALS Avalanche program. The results of the measurements show dependency of mean lifetime of ortho-positronium on XAD4 mass percentage in water.
The presented method of controlling mean lifetime of ortho-positronium in XAD4 pores will serve in the future to prepare a phantom for assessment of precision of the positronium imaging method developed at Jagiellonian University.
Opracowanie metody oznaczania czasu życia pozytonium w mikropęcherzykach pochodzących z hodowli komórek prawidłowych beta-trzustki
Author: Julia Nizioł
Supervisor: prof. Ewa Stępień
abstract
Defence year: 2021
The phenomenon of positronium formation in biological material brings new possibilities formedical diagnostics. This thesis presents a method for determining mean positronium lifetme in microvesicles isolated from the culture of beta-pancreatic cells using low-vacuum filtration technique combined with the ultracentrifugation. The concentration of microvesicles in the prepared samples was tested with qNano particle analyzer, the operation of which is based on the TRPS (Tunable Resistive Pulse Sensing) technology. Before starting the actual measurements, Positron Annihilation Lifetime Spectrometer was adjusted accordingly, e.g. by equipping it with a thermostat which allows to precisely control the temperature in the system. A series of measurements was performed to check the temperature stability and a calibration curve was obtained, on the basis of which it is possible to accurately determine the temperature of the sample during the measurement. The positron source was additionally secured against leakage, which may occur when testing with liquid samples. Parafilm was used for this purpose, the positronium lifetime in it changes with temperature, what was taken into account in data analysis. The positronium lifetime in microvesicles cultured under normoglycemic and hyperglycemic conditions was investigated. The values were 1.80 ns and 1.77 ns respectively, thus not significantly different from the lifetime determined in the PBS buffer in which microvesicles were suspended (g = 1.80 ns). On the basis of the obtained results, it can be concluded that to conduct research with microvesicles using the presented method, it is necessary that the samples have a higher concentration of vesicles.
Simulations of absorption in the brain of gamma quanta from positronium atoms
Author: Agata Jędruszczak
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2021
Positronium imaging is a new method that can be used for PET scanning. This method allows not only to determine the location of the tumor, but also to analyze the structure of the tissue. What is important is how many gamma quanta from a positronium atom reach the detector. The main goal of this work is to study the absorption in the brain of gamma quanta from a positronium atom. The brain in this study is approximated by a sphere with water. The 3 gamma / 2 gamma ratio, a parameter that reflects the tissue structure, is determined. For this purpose, Monte Carlo simulations of positron decays into 2 gamma and 3 gamma and photon absorption in the brain and skull were performed. The simulation results were compared with theoretical calculations. The results of the percent events for which none of photons scattered in the head are as follows: 26.10 +/- 0.05% for para-positronium and 8.40 +/- 0.03% for ortho-positronium (absorption in the brain), 20.84 +/- 0.05% for para-positronium, 5.46 +/- 0,02% for ortho-positronium (absorption in the brain and in skull). The values of the 3 gamma / 2 gamma ratio from the simulation are: 0.322 +/- 0.002 for absorption in the brain and 0.262 +/- 0.002 for absorption in the brain and skull. The dependence of absorption probability of photons in the head on the location of positronium atom decay in the brain is determined.
Analiza pochodnych steroli i prenoli w próbkach pęcherzyków zewnątrzkomórkowych metodą spektrometrii masowej TOF-SIMS
Author: Agnieszka Babińska
Supervisor: prof. Ewa Stępień
Auxilliary supervisor: dr inż. Magdalena Marzec
abstract
Defence year: 2021
Niniejsza praca ma na celu przedstawienie wyników wykorzystujących spektrometrię masową jonów wtórnych z analizatorem czasu przelotu (ToF-SIMS) do analizy składu lipidowego pęcherzyków zewnątrzkomórkowych, pochodzących z ludzkich komórek beta trzustki hodowanych w warunkach hiperglikemii. ToF-SIMS jest czułą metodą spektrometryczną, stosowaną do jakościowego określania składu powierzchni. Dzięki jej zaawansowanemu rozwojowi, została zaadoptowana do badań biologicznych, gdzie wykorzystywana jest przede wszystkim do analizy lipidów oraz protein.
Zawartość prenoli i steroli w pęcherzykach zewnątrzkomórkowych komórek beta trzustki jest regulowana wieloma czynnikami środowiskowymi, jak i genetycznymi. W części eksperymentalnej, czynnikiem wywołującym widoczne zmiany składu lipidowego były warunki hiperglikemiczne.
Z przeprowadzonej jednoczynnikowej analizy wariancji ANOVA oraz testu Tukey?a wynika, iż dla wszystkich wybranych jonów dla prenoli i steroli występują istotne różnice statystyczne pomiędzy średnimi wartościami intensywności dla warunków normalnych oraz hiperglikemicznych przy p?0,05.
Przeprowadzona analiza potwierdziła, iż wykorzystana technika ToF-SIMS jest skuteczna, zaś jej zaawansowany rozwój sprawił, iż jest coraz częściej stosowana do badań biologicznych, gdzie wykorzystywana jest przede wszystkim do analizy lipidów oraz protein.
Zastosowanie promieniowania kosmicznego do kalibracji czasowej detektora J-PET
Author: Magdalena Styczeń
Supervisor: dr Eryk Czerwiński
abstract
Defence year: 2018
The aim of the study was to simulate the passage of cosmic radiation through
the J-PET detection system in order to determine the multiplicity of events with
individual scintillators depending on their orientation.
Results obtained for 10^6 generated events show double and triple multiplicity as
most common ones. Higher multiples were noted in scintillators oriented more
horizontally. Assuming a 100% probability of the reaction of the cosmic radiation
with the scintillator, it has been shown that for multiples greater than one, there
are scintillators through which up to 0.61% of the recorded cosmic radiation
passes.
The obtained results will help in the time calibration of the J-PET detector,
enabling a more accurate estimation of the probability of a given coincidence
occurring.
Badanie własności wybranych materiałów scyntylacyjnych pod kątem zastosowania w identyfikacji substancji niebezpiecznych
Author: Anna Miś
Supervisor: dr Michał Silarski
abstract
Defence year: 2018
Celem pracy było zbadanie energetycznej zdolności rozdzielczej wybranych materiałów scyntylacyjnych: jodku sodu aktywowanego talem (NaI:Tl), fuorku baru (BaF2), germanianu bizmutu (BGO), krzemianu lutetu domieszkowanego cerem (LSO:Ce) oraz bromku lantanu domieszkowanego cerem i strontem (LaBr3:Ce:Sr), które można wykorzystać do pomiaru widm aktywacyjnych. Badane były widma energetyczne standardowych źródeł promieniotwórczych kwantów gamma (22Na, 137Cs, 133Ba, 60Co). Wybrano najlepszy materiał scyntylacyjny, z którego będzie wykonany detektor kwantów gamma w urządzeniu do nieinwazyjnego wykrywania materiałów niebezpiecznych w środowisku wodnym budowanego w Instytucie Fizyki UJ w ramach projektu SABAT. Zgodnie z oczekiwaniami, okazał się nim bromek lantanu domieszkowany cerem. Ponadto, został wykonany pomiar widm energii powstałych z wewnętrznej promieniotwórczości kryształu LSO:Ce.
Aktywacja neutronowa - projekt ćwiczenia na II Pracownię Fizyczną
Author: Sabina Rachwalska
Supervisor: dr Michał Silarski
abstract
Defence year: 2018
Celem niniejszej pracy było zaprojektowanie ćwiczenia opartego na aktywacji neutronowej na II Pracownię Fizyczną Uniwersytetu Jagiellońskiego na Wydziale Fizyki Astronomii i Informatyki Stosowanej. Aktywacja neutronowa polega na aktywacji izotopów w badanej próbce. Powstałe w wyniku naświetlania neutronami promieniotwórcze izotopy emitują kwanty promieniowania gamma o charakterystycznej dla siebie energii co umożliwia ich identyfikacje, a co za tym idzie pierwotnego izotopu w próbce. Rozdział 1 zawiera informacje na temat neutronów, oddziaływania neutronów z materią, o źródłach promieniowania neutronowego oraz używanym w projektowanym ćwiczeniu źródle Am-Be. Dokładny opis teoretyczny aktywacji neutronowej znajduje się w rozdziale 2. W rozdziale 3 znajdują się informacje na temat działania promieniowania na organizmy żywe, natomiast rozdział 4 określa zasady bezpieczeństwa jakie powinny być przestrzegane podczas pracy z promieniowaniem jonizującym wraz z obliczeniami dotyczącymi grubości jaką powinna mieć parafinowa osłona źródła Am ? Be. Projektowane ćwiczenie opisane jest w rozdziale 7. Zawiera ono 3 warianty: oznaczani srebra, oznaczanie rtęci w produktach spożywczych oraz obserwowanie rozrodczości drożdży pod wpływem promieniowania neutronowego.
Badanie czasu życia pozytonium pod kątem diagnostyki nowotworowej za pomocą tomografu J-PET
Author: Zuzanna Bura
Supervisor: dr Michał Silarski
abstract
Defence year: 2018
Celem niniejszej pracy była demonstracja potencjału wykorzystania metody PALS w diagnostyce nowotworowej z wykorzystaniem nowoczesnego pozytonowego tomografu emisyjnego, rozwijanego w Instytucie Fizyki UJ. W tym celu przeprowadzono szereg pomiarów czasów życia orto-pozytonium w materiałach o różnej porowatości, za pomocą skanera J-PET, jako wstęp do dalszych badań nad wykorzystaniem PALS w diagnostyce. Metoda pozytonowej tomografii emisyjnej pozwala nie tylko na wyznaczenie lokalizacji nowotworu, ale również otwiera nowe możliwości w rozpoznawaniu ich rodzajów. Opis podstaw fizycznych tomografii PET znajduje się w rozdziale 1. W rozdziale 2 opisano ogólnie budowę skanera J-PET. Sposób pomiaru i analizy danych został przedstawiony w rozdziale 3, a podsumowanie wykonanych badań znajduje się w ostatnim rozdziale, oznaczonym jako 4.
Feasibility study of proton beam therapy range monitoring by means of the J-PET tomograph
Author: Maria Kawula
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2017
The aim of this work was to determine amount of positron emitters produced in block made of poly methyl methacrylate (PMMA) during proton beam irradiation, check detection efficiency for registartion of annihilation gamma quanta with the plastic J-PET (Jagiellonian Positron Emission Tomography) tomograph and to find spatial resolution of such a scanner. Simulations were prepared using emph{GATE} software.\Obtained numbers of most significant for imaging isotopes: $^{15}$O, $^{11}$C and $^{10}$C for proton beam with energy 175 MeV that consists of 10$^6$ protons, are respectively 1.84 $cdot 10^4$, 4.47$cdot 10^4$, 4.69$cdot 10^3$. Efficiency for registration of gamma quanta by 2.5 cm thick layer of scintilation material used in J-PET scanner is at the level of 22.7\%. Spatial resolution of point source, that emits pairs of gamma quanta with energy 511 keV and is placed at the centre of two modules system (one module consists of ten plastic strips), was defined by point spread function (PSF) in three dimensions: $z$- along detector, $x$,$y$- transve$^3$rsal to detector. For a strip size $0.6cross 2.5cross 50$ cm and the distance between modules of 20 cm results are: PSF$_{z}=1.2$ cm, PSF$_{y}=3.7$ cm, PSF$_{x}=0.1$ cm and for a strip size $0.3cross 1cross 50$ cm and distance between modules of 20 cm results are: PSF$_{z}=1$ cm, PSF$_{y}=3.1$ cm, PSF$_{x}=0.1$ cm.
Plastic scintillators as an alternative for crystals in PET - determination of the counting efficiency
Author: Julia Gnatek
Supervisor: dr Eryk Czerwiński
abstract
Defence year: 2017
The aim of this work was to experimentally check the theoretical predictions of plastic scintillators? efficiency. The BC?420 scintillators have been used in the prototype of the J-PET detector. The measurement system consisted of two BaF_2 detectors, a plastic detector, an oscilloscope, 4 photomultipliers and a sodium isotope 22Na (as a source of positrons). The assessment of the plastic scintillators? efficiency was conducted by counting the number of registered and unregistered events from 511 keV gamma ray beam.
The efficiency was determined for 6 detector depths, in particular for 1.9 cm, which is the thickness of plastic scintillators used in the J-PET system. The obtained efficiency for this setup is (11.1 +- 0.3stat +- 3.0syst)%, for events with energy deposited greater than 100 keV, while theoretical prediction is 11.6 % with negligible error.
Badania możliwości jednoczesnego dokonywania pomiarów za pomocą tomografu Jagiellonian-PET oraz tomografu komputerowego.
Author: Nikodem Krawczyk
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2015
Test of Lightguides for the J-PET Detector
Author: Dominika Alfs
Supervisor: dr Eryk Czerwiński
abstract
Defence year: 2015
The aim of this work was to test the impact of the lightguides insertion in the J-PET detection system and to choose the best of available solutions. At the two strip J-PET test system a series of measurements was performed with different combinations concerning the length of the lightguides (3 mm and 3 cm) and scintillators (3, 15 and 30 cm), shape of lightguides (trapezoidal and cylindrical, with and without a cut matching the scintillator size) and optical connection between elements (optical gel and glue). It was proven that the insertion of the thin lightguide does not spoil the time resolution and the light output. Additionally, the correlation between the time resolution and the light output was confirmed.
Wyznaczanie miejsca i czasu interakcji kwantu gamma w paskach styntylacyjnych przy użyciu metody największej wiarygodności
Author: Krzysztof Giergiel
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
Badanie właściwości detektorów scyntylacyjnych otoczonych lustrami pod kątem zastosowania w Pozytonowej Emisyjnej Tomografii
Author: Adam Ciesielski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
Synteza scyntylatorów polimerowych i ich badanie pod kątem zastosowania w obrazowaniu PET
Author: Kamil Dulski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2014
Nieorganiczne scyntylatory używane komercyjnie w Pozytonowej Emisyjnej Tomografii (PET) pomimo dobrych właściwości detekcyjnych posiadają stosunkowo wysoką cenę produkcji. Materiały polimerowe w większości są znacznie tańsze i dlatego warto rozważyć ich użycie w tomografii PET. Znalezienie materiału polimerowego, lub polimeru odpowiednio domieszkowanego, zdolnego zastąpić komercyjne scyntylatory, bez wielkiej straty na dokładności pomiaru, pozwoliłoby na zredukowanie kosztów diagnostyki PET. W tej pracy skupiono się na sprawdzeniu czy związki polimerowe domieszkowane dodatkami luminescencyjnymi, zdołają osiągnąć parametry detekcyjne porównywalne z szeroko stosowanymi materiałami scyntylacyjnymi. Ograniczono się do testów polimerów pod kątem rejestrowania promieniowania o energii zbliżonej do energii promieniowania anihilacyjnego używanego w tomografii PET.
Synteza scyntylatorów polimerowych domieszkowanych ciężkimi atomami
Author: Arkadiusz Janas
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2013
Celem niniejszej pracy jest wprowadzenie ciężkich atomów do scyntylatorów polimerowych w celu maksymalnego zwiększenia prawdopodobieństwa wystąpienia efektu fotoelektrycznego co wiąże się z zwiększeniem wydajności świetlnej scyntylatora a tym samym możliwością detekcji promieniowania jonizującego. Synteza polega na sporządzeniu roztworów o odpowiedniej ilości monomeru, inicjatora oraz związków zawierających ciężkie atomy w tym wypadku jest są to atomy ołowiu w postaci dimetakrylanu ołowiu. Przygotowany roztwór polimeryzuje poprzez polimeryzację rodnikową w masie. Scyntylatory polimerowe są najczęściej używane do celów diagnostycznych w pozytonowej emisyjnej tomografii komputerowej.
Methods of searching for the dark matter boson
Author: Krzysztof Kacprzak
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2012
Analiza izotopów promieniotwórczych w zegarkach
Author: Bartłomiej Sadowski
Supervisor: prof. Paweł Moskal
abstract
Defence year: 2011
Tarcze starych zegarków były pokrywane farbami które posiadały w swoim składzie
różne promieniotwórcze pierwiastki. Za pomoca licznika półprzewodnikowego zebralismy
widma energii kwantów gamma emitowanych z tarcz zegarków by móc na ich podstawie
okreslic rodzaj pierwiastków promieniotwórczych które wchodziły w skład farby.
Analizie poddano 4 zegarki.
Computer simulation of CMS(CERN) experiment.
Author: Iryna Ozerianska, L. Levchyk
abstract
Defence year: 2008
