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.
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.
The performance of Lu3Al5O12:Ce (LuAG:Ce) and Y3Al5O12:Ce (YAG:Ce) scintillators were compared under γ‐ray excitation using photomultiplier tube (PMT) readout. Light yield non‐proportionality and ...energy resolution were measured with a Photonis XP5500B PMT. The energy resolution, obtained in this work for 662 keV γ‐rays, was 6.7 and 7.0%, respectively, for LuAG:Ce and YAG:Ce detectors. A fast component in the scintillation decay of LuAG:Ce crystal is faster than that of 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 583 and 660 ps, respectively, for LuAG:Ce‐ and YAG:Ce‐based detectors in coincidence experiment together with a BaF2 scintillation detector. Normalized coincidence time resolution was also discussed in terms of a number of photoelectrons and decay time of the light pulse.
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.
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.
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.
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.
A detailed study of the scintillation light pulse shape in CsI(Tl) at room temperature as a function of incoming photon energy in 6-662 keV energy range is presented. Three samples of CsI(Tl) of ...different amount of Tl dopant (0.01, 0.06 and 0.25 mol%) were used in measurements. A delayed coincidence single photon counting method was applied to measure the decay times in the microsecond range. Three-exponential function was fitted to the time spectra to describe the light pulse shape, which resulted in three components of tau 1 = 730 plusmn 30 ns (fast), tau 2 = 3.2 plusmn 0.3 mus (slow) and tau 3 = 16 plusmn 2 mus (tail). The intensity of the second component was found to be sensibly independent of photon energy, whereas the intensities of the first and third ones varied with the energy of absorbed photon in low energy region. For a given crystal the most intense fast component was measured for 6-keV X-rays from 55 Fe at the cost of decreasing intensity of the slowest one. Furthermore, the intensity of the fast component depends on Tl concentration and reaches its maximum value for the 0.06 mol% doping, close to the well-know optimal concentration of 0.1 mol%.
Abstract
This report presents a concept of constructing a detector
dedicated for detection of muons observed during measurements
carried out at the MPD (Multi-Purpose Detector) detector that is
...currently under construction at the NICA facility, Russia, Dubna. It
has been proposed to design and build an additional detector that
will complement the current MPD set and increase its measurement
capabilities. The main goal of this project is to provide
information from cosmic muons that pass the MPD detector in both
in-beam and off-beam experiments. Hence, the detector is called the
MPD COsmic Ray Detector (MCORD).The conceptual design of MCORD is
proposed by a Polish consortium NICA-PL comprising several Polish
scientific institutions.
The data from cosmic ray muons could be used as a trigger for
calibration of other detection systems comprising the MPD
detector. Large surface covered by the MCORD offers also possibility
for efficient registration of muons generated in expanding
atmospheric showers induced by distant sources. Moreover, beyond
some energy threshold, observation of muons originating from decays
of collision products will also be possible. In this report examples
of the MCORD functionality as a part of the MPD detector are
presented.
The MCORD is designed as a universal, fast triggering system built
as a modular reconfigurable construction. The detection system will
be based on plastic scintillators equipped with wavelength shifting
fibers, and silicon photomultipliers (SiPM) will be used for
scintillation readout. The online analysis of received signals will
be performed using digital FPGA modules. Due to the modular design,
the same system (its small part) can be used for both laboratory
testing of other MPD sub-detectors, and the calibration of these
detectors after placing them inside the MPD in off-beam mode. The
full detector will support these systems as an additional trigger,
calibrator, and muon identifier during the normal operation of the
MPD detector with the beam. Thanks to its unique construction, it
will expand the possibilities of collecting scientific data of the
MPD detector with astrophysical observations.
The publication will show the assumptions of the mechanical
structure and electronic systems of the planned detector. The
installation site of the detector as part of the MPD detector will
be described in detail. In the following, the results of simulations
made in preparation for this project will be presented. In
particular, simulations with the CORSIKA code present angular
distributions of particles in cosmic showers in the Dubna city
region. Since muons dominate the cosmic ray showers, the MPD
detector response to expected cosmic muon flux was also
simulated. The results provide information about the muon cut-off
thresholds depending on the MPD detector composition during the
installation campaign. Simulations of muon events that could be used
for MPD subsystems calibration were also performed. The results
shown for various configuration of MCORD detector modules will
enable the estimation of the time necessary to perform such tests in
the future.
Simulations with UrQMD model shows the muon abundances due to
beam-beam collisions. Approximately 90% of muons are created from
pions, whereas the number of muons that reach the MCORD detector is
10 times greater than the number of pions. The MPD detector response
was also simulated under the influence of a stream of various
particles, especially muons. It shows energy dependence of muon
transmission coefficient for MPD with and without ECal
assembled. Assuming requirement for muon transmission above 95%,
the muon cut-off thresholds are 1.6 GeV and 2.0 GeV, respectively.
MCORD detector performance evaluation is also reported. In the case
when we used scintillators with one fiber with a diameter of 1 mm,
the time resolution of about 1.0 ns was recorded, which corresponds
to the positional accuracy (σ
x
) of 7.1 cm. The results of
laboratory tests show that application of a 2 mm diameter WLS fiber
instead of the previously used 1 mm diameter fiber improves the
time resolution to 0.80 ns.
Experimental research on light response of CsI:Tl, that was performed in the last 30 years, have shown that spectrometry parameters of this crystal are influenced by existence of slow scintillation ...components and could be improved by increasing the peaking time. In this study authors analysed and discussed the non-proportionality, number of photoelectrons and energy resolution (with their intrinsic, statistical and noise contributions) as a function of light pulse integration time (adequately to the peaking time known from analogue readouts). The study of light responses of CsI:Tl crystal after interaction with gamma radiation was performed by acquisition of raw single scintillation signals using a photomultiplier and a high class digital oscilloscope. The analysis was performed off-line using Python scripts. The crystal was excited using X-ray and gamma-ray sources with energies from 22 keV up to 835 keV at 293 K (＋20 °C). The data was processed with integration time up to 150μs, which was not achievable so far with analogue electronics commonly used in gamma-ray spectrometry with scintillation detectors. This study considers the problem of the energy resolution as good as other spectrometry parameters improvement using a digital light pulse processing.
