Scintillation properties of praseodymium doped LuAG have been investigated. The crystal is a dense (6.7 g/cm 3 ) scintillator with a short decay time around 20 ns and wavelength emission spectrum ...peaked at 310 nm. The tested sample was 10 mm times 10 mm times 5 mm cuboid, polished on all surfaces. The dopant concentration amounts to 0.23 mo1%. A light yield of 16000plusmn1600 ph/MeV was measured using high sensitivity (13.7 muA/1mF) Photonis photomultiplier (PMT) XP5500B. High quantum efficiency of this PMT (35%) allowed us to register 5600plusmn400 phe/MeV using 12 mus shaping time in the spectroscopy amplifier. The measured energy resolution was equal to 5.0plusmn0.1%. Response of LuAG:Pr to gamma-rays was found to be proportional over wide energy range. Deviation from proportionality does not exceed 10% at 16.6 keV. This results in good intrinsic energy resolution of LuAG:Pr amounting to 3.0plusmn0.3%, measured with 662 keV gamma-rays from 137 Cs.
A comparative study of the neutron–γ discrimination performance of a liquid scintillator detector BC501A coupled to four different 5in. photomultiplier tubes (ET9390kb, R11833-100, XP4512 and R4144) ...was carried out. Both the Charge Comparison method and the Integrated Rise-Time method were implemented digitally to discriminate between neutrons and γ rays emitted by a 252Cf source. In both methods, the neutron–γ discrimination capabilities of the four photomultiplier tubes were quantitatively compared by evaluating their figure-of-merit values at different energy regions between 50keVee and 1000keVee. Additionally, the results were further verified qualitatively using time-of-flight to distinguish γ rays and neutrons. The results consistently show that photomultiplier tubes R11833-100 and ET9390kb generally perform best regarding neutron–γ discrimination with only slight differences in figure-of-merit values. This superiority can be explained by their relatively higher photoelectron yield, which indicates that a scintillator detector coupled to a photomultiplier tube with higher photoelectron yield tends to result in better neutron–γ discrimination performance. The results of this work will provide reference for the choice of photomultiplier tubes for future neutron detector arrays like NEDA.
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.
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.
Scintillation properties of CsI:In single crystals Gridin, S.; Belsky, A.; Moszynski, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2014, Letnik:
761
Journal Article
Recenzirano
Scintillation properties of CsI:In single crystals have been investigated. Scintillation yield of CsI:In measured with the 24μs integration time is around 27,000ph/MeV, reaching the saturation at ...0.005mol% of the activator. However, luminescence yield of CsI:In is close to CsI:Tl scintillation crystals, which is around 60,000ph/MeV. This difference is explained by the presence of an ultra-long afterglow in CsI:In scintillation pulse. Thermoluminescence studies revealed a stable trap around 240K that is supposed to be related to millisecond decay components. The best measured energy resolution of (8.5±0.3)% was achieved at 24μs peaking time for a CsI sample doped with 0.01mol% of In. Temperature stability of CsI:In radioluminescence intensity was found to be remarkably high. Its X-ray luminescence yield remains stable up to 600K, whereafter thermal quenching occurs. The latter property gives CsI:In a potential to be used in well logging applications.
This paper presents the results of the fast neutron irradiation (En > 0.5 MeV) of an EJ-276 scintillator performed in the MARIA research reactor with fluence up to 5.3 × 1015 particles/cm2. In our ...work, four samples with size φ 25.4 mm × 5 mm were tested. The changes in the light yield, emission and absorption spectrum and neutron/gamma discrimination using PuBe source before and after irradiation are presented. The figure of merit in neutron/gamma discrimination based on the charge integration method for different neutron fluences and different short gate integration times are determined.
The scintillation characteristics of Lu1.95Y0.05SiO5:Ce (LYSO:Ce) and Lu0.7Y0.3AlO3:Ce (LuYAP:Ce) single crystals were compared for γ-ray detection. The values of scintillation decay time and ...coincidence time resolution were evaluated. The scintillation decay of LYSO:Ce exhibits approximately a single-exponential component with decay time of 39ns, whereas for LuYAP:Ce an intensity of the fast component with decay time of 21ns is reduced (∼42%) and followed by a high intensity of slower components. The coincidence time resolution for 511keV annihilation quanta of 234 and 894ps was obtained, respectively, for LYSO:Ce and LuYAP:Ce detectors in coincidence experiment using a BaF2-based detector. The time resolution was also discussed in terms of a number of photoelectrons and decay time of the scintillation pulse.
The absorption, luminescence, and scintillation characteristics of cerium‐doped lutetium‐yttrium perovskite (LuxY1−x AlO3:Ce; x = 0, 0.3, 0.7) single crystals were investigated. The values of light ...yield, scintillation decay time, and coincidence time resolution were evaluated. At 662 keV γ‐rays (137Cs source), the light yield of 30 700 ph MeV−1 obtained for YAlO3:Ce is much higher than that of 16 200 and 10 600 ph MeV−1 obtained for Lu0.3Y0.7AlO3:Ce and Lu0.7Y0.3AlO3:Ce, respectively. Scintillation decays are dominated by a fast component with decay time value of 16–20 ns, which nearly coincides with the photoluminescence decay time value of 17.5 ns. In scintillation decays the intensity of the fast component becomes reduced and the content of slower components considerably increased with increasing lutetium content in the crystals. The coincidence time spectra for 511 keV annihilation quanta were measured in coincidence experiment using a BaF2‐based detector and time resolution was also discussed in terms of a number of photoelectrons and decay time of the scintillation pulse. The photofraction for all the crystals under 662 keV γ‐ray excitation was also evaluated and discussed.
A series of oligoesters based on a rigid triphenyl-diyne core is described. The molecules were readily synthesized from key intermediates, and retained good solubility properties. One of the ...compounds displayed modest ion transport activity in vesicles, was capable of forming highly conducting single channels in planar bilayers and exhibited an irregular non-linear current-voltage response. All the reported molecules had minimal aqueous fluorescence while being highly fluorescent in less-polar media including lipid vesicles; their partitioning into the membrane could be monitored by a significant blue-shift and increase in fluorescence intensity, as well as a decreased extent of quenching in vesicles over that in water. The combined data indicated that the compounds are highly aggregated in aqueous solution, which limits their membrane partitioning and ion transport activity, in agreement with mechanisms proposed for other 'simple' oligoester channels.
The intrinsic energy resolution and nonproportionality of the light yield as a function of gamma ray energies, in the energy range of 14 keV to 1.33 MeV, were studied for small BGO (Bi/sub 4/Ge/sub ...3/O/sub 12/) crystals at room and liquid nitrogen (LN/sub 2/) temperatures. The study showed that the intrinsic resolution of BGO and the light yield nonproportionality as a function of energy do not depend on the crystal temperature. High light outputs of 14000/spl plusmn/300 electron-hole pairs and energy resolution of 6.5% /spl plusmn/ 0.2% for 662keV gamma rays were measured with the 9 mm diameter, 4 mm thick crystals, coupled to large area avalanche photodiodes and cooled down to LN/sub 2/ temperature. Special attention was paid to analyzing the energy resolution of the escape peaks, which were well separated from the full-energy peaks due to the good energy resolution of BGO at LN/sub 2/ temperatures and the energy of bismuth KX-rays. The intrinsic energy resolution of the BGO crystal for escape peaks does not show deviations from analysis of total energy absorption photopeaks. This is in spite of the fact that the contributions of X-rays and Auger electron cascade in creation of escape peaks are much smaller than in full-energy peaks. In the small volume crystal, mainly electrons produced in the photoelectric absorption create the escape peaks.
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