Energy resolution of scintillation detectors Moszyński, M.; Syntfeld-Każuch, A.; Swiderski, L. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2016, Letnik:
805
Journal Article
Recenzirano
According to current knowledge, the non-proportionality of the light yield of scintillators appears to be a fundamental limitation of energy resolution. A good energy resolution is of great ...importance for most applications of scintillation detectors. Thus, its limitations are discussed below; which arise from the non-proportional response of scintillators to gamma rays and electrons, being of crucial importance to the intrinsic energy resolution of crystals. The important influence of Landau fluctuations and the scattering of secondary electrons (δ-rays) on intrinsic resolution is pointed out here. The study on undoped NaI and CsI at liquid nitrogen temperature with a light readout by avalanche photodiodes strongly suggests that the non-proportionality of many crystals is not their intrinsic property and may be improved by selective co-doping. Finally, several observations that have been collected in the last 15 years on the influence of the slow components of light pulses on energy resolution suggest that more complex processes are taking place in the scintillators. This was observed with CsI(Tl), CsI(Na), ZnSe(Te), and undoped NaI at liquid nitrogen temperature and, finally, for NaI(Tl) at temperatures reduced below 0°C. A common conclusion of these observations is that the highest energy resolution, and particularly intrinsic resolution measured with the scintillators, characterized by two or more components of the light pulse decay, is obtainable when the spectrometry equipment integrates the whole light of the components. In contrast, the slow components observed in many other crystals degrade the intrinsic resolution. In the limiting case, afterglow could also be considered as a very slow component that spoils the energy resolution. The aim of this work is to summarize all of the above observations by looking for their origin.
Silicon photomultipliers in gamma spectroscopy with scintillators Grodzicka-Kobylka, M.; Moszyński, M.; Szczęśniak, T.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2019, Letnik:
926
Journal Article
Recenzirano
In the first part of this paper the various characteristics of SiPMs that affect the use of SiPMs in gamma spectroscopy using scintillators, are reviewed. It covers SiPM gain, photon detection ...efficiency (PDE), after-pulses and cross-talk (which are responsible for the excess noise factor), dark noise, and linearity of response. In this respect the influence of the SiPMs’ effective dead time on the linearity of the response is discussed. In the second part, the optimization of SiPM operation for the best energy resolution and linearity of response is presented. Finally, a number of tests on combinations of SiPM arrays of different sizes that are coupled to different scintillators used in gamma spectroscopy are reported (such as NaI(Tl), BGO, LaBr3, and LYSO are reviewed, including 3x3 inch NaI(Tl) and BGO tests. Besides the characterization of the different SiPMs used in scintillation detection and spectroscopy, a discussion is carried out concerning their present and future application in various fields of use — covering instrumentation for homeland security, environmental study, plasma physics and others.
•The main performance parameters of SiPMs.•SiPMs in gamma spectroscopy using scintillators.•Present and future applications of SiPM arrays in gamma spectroscopy using scintillators.
The scintillation properties of LuAG:Ce and YAG:Ce crystals were compared with LYSO:Ce crystal under ¿ -ray excitation. Light yield non-proportionality and energy resolution were measured with a ...Photonis XP5500B PMT. The energy resolution, obtained in this work for 662 keV ¿ -rays, was 6.7, 7.0 and 8.7%, respectively, for LuAG:Ce, YAG:Ce and LYSO:Ce detectors. The values reflect the influence of the light yield non-proportionality on the measured energy resolution. A fast component in the scintillation decay of LuAG:Ce crystal is faster than that of the YAG:Ce crystal, whereas the relative intensity of a fast component for YAG:Ce crystal is higher than that of LuAG:Ce crystal. The coincidence time resolution, obtained in this work for 511 keV annihilation quanta, was 660, 583 and 222 ps, respectively, for YAG:Ce, LuAG:Ce and LYSO:Ce detectors in coincidence experiment together with a BaF 2 detector. Time resolution was also discussed in terms of a number of photoelectrons and decay time of the light pulse.
Temperature dependences of LaBr3(Ce), LaCl3(Ce) and NaI(Tl) scintillators Moszyński, M.; Nassalski, A.; Syntfeld-Każuch, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2006, Letnik:
568, Številka:
2
Journal Article
The purpose of this work is to present a measurement method for determining the neutron responses of various liquid organic scintillators using a time-of-flight technique in conjunction with a D–T ...neutron generator. The method is based on fast-neutron scattering on protons in a liquid-scintillator medium and on the acquisition of the neutron response of the medium as a function of the proton-recoil energy. This method can be applied to all scintillators that utilize fast-neutron elastic scattering.
According to the present knowledge, the non-proportionality of the light yield of scintillators appears to be the fundamental limitation of energy resolution. However, several observations collected ...in the last 15 years on the influence of slow components of the light pulses on energy resolution suggest more complex processes in the scintillators. The presented study of undoped CsI crystals shows a large deterioration of the intrinsic resolution of the crystal, when most of the light, including slow component was integrated. Moreover, it was confirmed by a large difference of the non-proportionality characteristics measured at short peaking time, corresponding to the integration of the fast intrinsic emission of the CsI, and that observed with a long peaking time, when the slow component was integrated.
The performance of multi pixel photon counters (MPPC) of 3 mm × 3 mm size, with 14400 and 3600 pixels, were studied by means of the signal from a laser light pulser and using the 3 mm × 3 mm × 20 mm ...LSO pixel scintillator. Special attention was paid to measure number of fired pixels, generated by the light of pulser and that of the LSO crystal, using a direct method of a comparison of the light peak position in the pulse height spectrum with that of the single photoelectron. The tests of the LSO crystal showed 1550 ± 80 fired pixels per MeV in the MPPC with 14400 pixels assuring a good linearity of the response up to about 1 MeV energy of gamma rays absorbed in the LSO crystal. Energy resolution of 14.8% for 662 keV gamma rays from 137 Cs source and a time resolution of about 850 ps for 511 keV annihilation quanta were limited by a rather low number of the fired pixels compared to the number of photoelectrons in photomultipliers.
A micro photomultiplier (microPMT or μPMT) works like a classic photomultiplier but the whole device is made directly in a silicon wafer sandwiched between two glass layers. A microPMT has dimensions ...of only 13x10x2 mm and its photocathode has a size of 3x1 mm. The aim of the work is to check usefulness of a microPMT in gamma spectrometry with scintillators and fast timing. In the first part of the study analysis of the energy resolution obtained with 3x3x1 mm LSO, BGO and CsI(Tl) scintillators is made. The recorded values for 662 keV are equal to 22.9% and 13.5% for CsI and LSO, respectively. The light pulse shapes of a single photoelectron and scintillation signal of LSO are also shown. The important part of the study is measurement of the number of photoelectrons and estimation of the excess noise factor. Only 2200 phe/MeV were obtained for LSO coupled with the tested microPMT. The calculated excess noise factor is equal to 1.4. In the second part, measurements of the time jitter and timing resolution with LSO crystal for 511 keV annihilation quanta are reported. The timing characteristics of the tested device is poor. Its time jitter equals to 1.5 ns, whereas timing resolution for 22 Na is 620 ps. All the results are compared with data obtained with classic PMTs.
In spite of the excellent performance of SiPMs in the application of time-of-flight PET detectors, the development of better photomultipliers for PET detectors is still worth considering. Fast timing ...with detectors based on the PMT light readout depends mainly on the time jitter and the quantum efficiency of the PMTs. Several studies in the past showed that a screening grid at the anode significantly improves the time resolution when measured with scintillation detectors. ADIT Co. has started a development of a 1" diameter fast PMT with the screening grid at the anode to be applied in the block detectors in TOF PET scanners. In the presented studies, we report the first comparative study of the L25, a classical PMT, with one that is equipped with a screening grid. Adding the screening grid yielded a large improvement in the time resolution, up to a factor of 1.2.
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