Investigation Of Thickness Dependent Scintillator Photosensor Interface Reflection Coefficients For Improved Light Yield Calculations In Inorganic Scintillators

Radiation scintillation detectors are used in numerous fields including low and high energy physics (HEP) experiments, medical imaging (MI), space exploration, well-logging, and homeland security. Since they can be manufactured with vastly different properties for virtually any type of radiation detection application, they are ubiquitous in scientific research and industry. For a given application, scintillation detectors are chosen based on their properties such as their efficiency, energy resolution (ER), and time resolution. Light yield (LY) is one of the most important properties of scintillators in characterizing their performance under irradiation. It has a direct correlation with the energy and time resolutions of scintillators since a larger number of light photons produced in scintillators translates to a larger number of light photons detected by photosensors, which improves both energy and time resolutions. Excellent energy and time resolutions of scintillators are critical in various applications such as radioisotope identification and positron emission tomography - time of flight (PET-TOF). LY is also an important parameter in simulation studies where the goal is to either characterize already existing detectors and compare simulation results to experimental observations or investigate novel configurations involving scintillators. In the latter case, LY plays a critical role in the optimization of new detection systems. Although the importance of LY is well known in the field of radiation detection, its accurate measurement is not straightforward. Any measurement of LY is bound to have large uncertainties due to various physical processes involved in its estimation. Accurate measurement of scintillator LYs necessitates accurate knowledge of numerous properties of both the scintillators and the photosensors that are used to convert the scintillation light into electronic signal. These properties include but not limited to the surface conditions and bulk properties of scintillators, the photodetection efficiency of photosensors, the single-photoelectron response (SPER) of photosensors and the light reflection properties between scintillators and photosensors. Consequently, there are large differences in reported LY values even for widely used scintillators such as thallium-activated sodium-iodide (NaI(Tl)) and cerium-activated lutetium-yttrium oxyorthosilicate (LYSO:Ce3+), as any major change in the aforementioned quantities has an impact on the estimated LY. One of the approaches to determine the scintillator LYs is to measure their light outputs (LO) as a function of scintillator thickness and fit an analytical model function to the data set to extrapolate the LO for a point scintillator. Since this method does not require relatively sophisticated equipment such as integrating spheres, electron monochromators or electron collimators, it can be carried out in most radiation detection laboratories. However, the model functions need to be as realistic as possible, and they need to contain all the relevant physics to make LY estimations accurate. In this thesis, two new analytical light transport model (LTM) functions for cuboid scintillators are derived, and it is demonstrated that they make LY estimations more accurate. These two analytical LTM functions are called the extended 2D-model and the 3D-model. The 3D-model is shown to estimate the LO of scintillators as accurately as Monte Carlo (MC) simulations, which makes full-scale MC simulations in cuboid scintillators needless in certain applications. One of the most important quantities that affect LY estimations is the scintillator-photosensor interface reflection coefficient (SPIRC). SPIRC is the observed reflection coefficient of the scintillator-photosensor boundary averaged over photon angles and energies and is typically considered a constant. Since scintillation emission contains photons of various wavelengths, and scintillators have wavelength dependent surface and bulk properties, it is not straightforward to reliably estimate SPIRCs. Moreover, SPIRC is dependent on the optical coupling methods employed in radiation measurements, which are typically dry (air) coupling and grease coupling. In this thesis, two new experimental methods (the single-PMT setup and the dual-PMT setup) are suggested and tested to estimate the SPIRCs in different optical coupling configurations. Furthermore, a new hypothesis is put forward regarding the SPIRC dependency on scintillator thickness. It is hypothesized through MC simulations that SPIRC decreases with increasing scintillator thickness as a result of change in the scintillation photons' angular distribution on the scintillator-photosensor interface (SPI). This hypothesis is tested with three different inorganic scintillation crystals by employing the two new experimental methods, and the SPIRC dependency on scintillator thickness is experimentally observed by evaluating the extended 2D-model and the 3D-model for LYSO:Ce3+ and cerium-activated gadolinium-aluminum-gallium garnet (GAGG:Ce3+) inorganic scintillators. The SPIRC dependency on scintillator thickness is observed by the 3D-model with more than 2[sigma] confidence for both LYSO:Ce3+ and GAGG:Ce3+ scintillators in the single-PMT setup. The SPIRC dependency on scintillator thickness is observed with more than 3[sigma] confidence for GAGG:Ce3+ scintillators in the dual-PMT setup. Consequently, it is suggested that the measurements should consider thickness-dependent SPIRCs (TD-SPIRC) to make accurate LY estimations.

This second open access volume of the handbook series deals with detectors, large experimental facilities and data handling, both for accelerator and non-accelerator based experiments. It also covers applications in medicine and life sciences. A joint CERN-Springer initiative, the "Particle Physics Reference Library" provides revised and updated contributions based on previously published material in the well-known Landolt-Boernstein series on particle physics, accelerators and detectors (volumes 21A, B1,B2,C), which took stock of the field approximately one decade ago. Central to this new initiative is publication under full open access

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This book describes the fundamentals of particle detectors as well as their applications. Detector development is an important part of nuclear, particle and astroparticle physics, and through its applications in radiation imaging, it paves the way for advancements in the biomedical and materials sciences. Knowledge in detector physics is one of the required skills of an experimental physicist in these fields. The breadth of knowledge required for detector development comprises many areas of physics and technology, starting from interactions of particles with matter, gas- and solid-state physics, over charge transport and signal development, to elements of microelectronics. The book's aim is to describe the fundamentals of detectors and their different variants and implementations as clearly as possible and as deeply as needed for a thorough understanding. While this comprehensive opus contains all the materials taught in experimental particle physics lectures or modules addressing detector physics at the Master's level, it also goes well beyond these basic requirements. This is an essential text for students who want to deepen their knowledge in this field. It is also a highly useful guide for lecturers and scientists looking for a starting point for detector development work.

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"Radiation detection is key to experimental nuclear physics as well as underpinning a wide range of applications in nuclear decommissioning, homeland security and medical imaging. This book presents the state-of-the-art in radiation detection of light and heavy ions, beta particles, gamma rays and neutrons. The underpinning physics of different detector technologies is presented, and their performance is compared and contrasted. Detector technology likely to be encountered in contemporary international laboratories is also emphasized. There is a strong focus on experimental design and mapping detector technology to the needs of a particular measurement problem. This book will be invaluable to PhD students in experimental nuclear physics and nuclear technology, as well as undergraduate students encountering projects based on radiation detection for the first time. Part of IOP Series in Nuclear Spectroscopy and Nuclear Structure." -- Prové de l'editor.

Handbook of Radioactivity Analysis is written by experts in the measurement of radioactivity. The book describes the broad scope of analytical methods available and instructs the reader on how to select the proper technique. It is intended as a practical manual for research which requires the accurate measurement of radioactivity at all levels, from the low levels encountered in the environment to the high levels measured in radioisotope research. This book contains sample preparation procedures, recommendations on steps to follow, necessary calculations, computer controlled analysis, and high sample throughput techniques. Each chapter includes practical techniques for application to nuclear safety, nuclear safeguards, environmental analysis, weapons disarmament, and assays required for research in biomedicine and agriculture. The fundamentals of radioactivity properties, radionuclide decay, and methods of detection are included to provide the basis for a thorough understanding of the analytical procedures described in the book. Therefore, the Handbook can also be used as a teaching text. Includes sample preparation techniques for matrices such as soil, air, plant, water, animal tissue, and surface swipes Provides procedures and guidelines for the analysis of commonly encountered na

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