Timing Resolution Of Scintillation Detectors Research Articles

Luminescence rise time in self-activated PbWO4 and Ce-doped Gd3Al2Ga3O12 scintillation crystals

The time resolution of scintillation detectors of ionizing radiation is one of the key parameters sought for in the current and future high-energy physics experiments. This study is encouraged by the necessity to find novel detection methods enabling a sub-10-ps time resolution in scintillation detectors and is focused on the exploitation of fast luminescence rise front. Time-resolved photoluminescence (PL) spectroscopy and thermally stimulated luminescence techniques have been used to study two promising scintillators: self-activated lead tungstate (PWO, PbWO4) and Ce-doped gadolinium aluminum gallium garnet (GAGG, Gd3Al2Ga3O12). A sub-picosecond PL rise time is observed in PWO, while longer processes in the PL response in GAGG:Ce are detected and studied. The mechanisms responsible for the PL rise time in self-activated and doped scintillators are under discussion.

Analytical calculation of the lower bound on timing resolution for PET scintillation detectors comprising high-aspect-ratio crystal elements

Excellent timing resolution is required to enhance the signal-to-noise ratio (SNR) gain available from the incorporation of time-of-flight (ToF) information in image reconstruction for positron emission tomography (PET). As the detector’s timing resolution improves, so does SNR, reconstructed image quality, and accuracy. This directly impacts the challenging detection and quantification tasks in the clinic. The recognition of these benefits has spurred efforts within the molecular imaging community to determine to what extent the timing resolution of scintillation detectors can be improved and develop near-term solutions for advancing ToF-PET. Presented in this work, is a method for calculating the Cramér–Rao lower bound (CRLB) on timing resolution for scintillation detectors with long crystal elements, where the influence of the variation in optical path length of scintillation light on achievable timing resolution is non-negligible. The presented formalism incorporates an accurate, analytical probability density function (PDF) of optical transit time within the crystal to obtain a purely mathematical expression of the CRLB with high-aspect-ratio (HAR) scintillation detectors. This approach enables the statistical limit on timing resolution performance to be analytically expressed for clinically-relevant PET scintillation detectors without requiring Monte Carlo simulation-generated photon transport time distributions. The analytically calculated optical transport PDF was compared with detailed light transport simulations, and excellent agreement was found between the two. The coincidence timing resolution (CTR) between two mm LYSO:Ce crystals coupled to analogue SiPMs was experimentally measured to be ps FWHM, approaching the analytically calculated lower bound within 6.5%.

The main characteristics of polystyrene scintillators produced at the institute of high-energy physics and detectors on their basis

The results of measurements of the main characteristics of polystyrene scintillators, which were developed using new technologies at the Institute of High-Energy Physics (IHEP), are presented. Scintillators are used in a number of experiments both on the IHEP accelerator and on facilities of foreign physical centers (CERN, FNAL, BNL, DESY). Specific features of the operation of detectors that use “scintillator-wavelength shifting fiber” systems are considered. The efficiencies of various reflecting surfaces, the light yield, and the time resolution of scintillation detectors were measured.

The lower bound on the timing resolution of scintillation detectors

The timing performance of scintillation detectors is ultimately limited by photon counting statistics. In fact, photon counting statistics form a dominant contribution to the overall timing resolution of many state-of-the-art detectors. A common approach to investigate this contribution is to calculate the variance in the registration times of individual scintillation photons within the photosensor. However, in general the single-photon variance is not equal to the intrinsic limit on the timing resolution, since in principle one can make use of the timing information carried by all photons detected. In this work, the Cramér–Rao lower bound on the timing resolution of a scintillation detector, based on the information contained in the full set of registered photons, is calculated. The results appear to be in good agreement with trends observed in the literature. Furthermore, it is shown that the timestamp obtained from any single scintillation photon never yields the optimum timing resolution for realistic scintillation detectors. Yet, it appears that the intrinsic timing resolution limit can be approached closely by making use of the timestamps from a relatively small number of photons emitted during the initial part of the scintillation pulse.

Light transport contribution to the timing characteristics of scintillation detectors

A Monte Carlo simulation of the light transit time in scintillation detectors is described, with the wavelength dependencies of different interaction processes being taken into account. The simulation results presented give an estimate of the contribution of light transport to the timing resolution of scintillation detectors.

Measurement of coincidence timing resolution of scintillation detectors compared to semiconductor detectors to image three-photon positron annihilation

The coincidence timing resolution is a critical parameter for triple coincidence to measure the three photon positron annihilation yield. The yield is inversely proportional to the concentration of oxygen which acts as a quenching agent within the tissue and, therefore, provides important information about the state of the cancerous tumor. A comparison between scintillation and semiconductor detectors with respect to their timing properties for triple coincidence measurements and imaging was carried out. The coincidence timing resolution for example for HPGe detectors was found to vary between 35.4±0.02 and 42.8±0.02 ns. A comparison of all detector characteristics with respect to HPGe is presented.