This paper presents the results of the proton irradiation of silicon photomulipliers (SiPMs) by mono-energetic 170 MeV protons with fluence up to 4.6×109 particles/cm2. In our work, three types of ...silicon photodetectors from Hamamatsu with areas 3×3 mm2 and different subpixel sizes of 25×25 μm2, 50×50 μm2, and 75×75 μm2 were used. The changes in the SiPM dark count rate (DCR) spectrum before and after irradiation in temperatures in the range of 20ˆC to −65ˆC are presented. The influence of the DCR changes on the energy resolution of the 662 keV gamma line from the 137Cs for a non-irradiated GAGG:Ce (1%) scintillator is investigated. The time period of usability of the SiPM detector irradiated by protons in cosmic space was estimated.
▶ Pt–Rh–Pd activity in methanol adsorption/oxidation depends on surface composition. ▶ Pt–Rh–Pd real surface area/composition can be estimated by cyclic voltammetry. ▶ Methanol adsorbate structure is ...more similar to adsorbed CO
2 rather than CO. ▶ High surface rhodium content contributes in low methanol dehydrogenation rate.
Methanol adsorption and electrooxidation have been studied on Pt–Rh–Pd alloys using cyclic voltammetry and chronoamperometry. Pt–Rh–Pd electrodes were prepared by a potentiostatic electrodeposition on a gold wire from chloride solutions. Alloy bulk composition was determined by SEM/EDAX measurements. Alloy surface composition was estimated adapting Rand and Woods's method for homogenous binary noble metal alloys utilizing the potential of surface oxide reduction peak. Electrode real surface area was calculated from the charge due to surface oxide formation/reduction. Methanol was oxidized both in stripping voltammetric experiments and continuously under potentiostatic conditions from 1
M CH
3OH/0.5
M H
2SO
4 solution. The values of electron per site, surface coverage and oxidation potential were used for the characterization of methanol adsorption products. The comparison of these results with analogous data for CO
2 and CO adsorption has revealed high similarity between CO
2 and methanol adsorption products, both consisting of mainly linearly and bridge-bonded CO species, however, with a higher contribution from bridge-bonded CO in the case of methanol. Current densities obtained during continuous methanol oxidation were the highest for Pt–Rh–Pd alloys with initial bulk composition 30.6% Pt, 23.7% Rh, 45.7% Pd, being of the same order as for pure Pt electrode.
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 properties of cesium-zirconium hexachloride (Cs2ZrCl6) were investigated by γ-ray spectrometry and the Compton Coincidence Technique. The tested cylindrical sample had 20 mm ...diameter and 12 mm height. The crystal shows a high light output of 40 900 photons per MeV as measured by a spectroscopy type photomultiplier with 20 μs pulse integration time under γ-ray excitation at room temperature. A small deviation from linear response as a function of energy deposited in γ-ray absorption or Compton scattering processes, combined with a high light yield, results in good energy resolution equal to 4.3 % at 662 keV and 2.3 % at 2.6 MeV. Due to long lasting scintillation decay the sample properties were studied at different shaping time constants in an analogue spectroscopy chain or using different integration time gates when employing a digital analyzer.
In this paper, five detectors (EJ-270 — single plastic scintillator, EJ-309B5 — single liquid scintillator, and 3 phoswich detectors: EJ-276+GS20, GS20+EJ-276, EJ-309+GS20) were studied in terms of ...simultaneous detection of gamma-rays and slow and fast neutrons. The measurements were carried out in a mixed field of neutron and gamma radiation from an intense (∼106 neutrons/s/4π) PuBe source. The PuBe neutron source was placed in an 18 cm diameter paraffin ball in order to increase the number of slow neutron detections. This paper covers the measurements of the neutron/gamma discrimination, photoelectron yield and analysis of the light pulse shapes originating from events related to gamma-rays, slow neutrons and fast neutrons. Sensitivity to slow neutrons is also briefly discussed. A comparison of n/γ discrimination for all of the tested detectors shows excellent performance of all phoswich detectors. Phoswich configurations tested within the scope of this study allow unambiguously resolve all three types of radiation and show superior performance in comparison with single loaded plastic or liquid scintillators.
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.
Study of MPPC damage induced by neutrons Mianowski, S.; Baszak, J.; Gledenov, Y.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2018, Letnik:
906
Journal Article
Recenzirano
This paper presents the results of neutron irradiation of two types of Multi-Pixel Photon Counter (MPPC). The measurements were taken at the National Centre for Nuclear Research (NCBJ), Poland and ...the Joint Institute for Nuclear Research (JINR), Russia. Two types of neutron source were used: PuBe with a continuous energy spectrum up to 11 MeV, and mono-energetic 4.8 MeV neutrons produced in a (d,d) reaction. For both sources, fluence in the range of 1010 n/mm2 was achieved. A series of MPPC tests were performed after each irradiation. The changes in MPPC properties, such as current–voltage (I–V) characteristics, breakdown voltage and energy resolution of 662 keV from the 137Cs gamma line for a Gd3Al2.6Ga2.4O12:Ce (1%) scintillator as a function of neutron fluence are presented.
The light response of cesium iodide crystals was measured at temperatures of 303 K (30 °C) to 203 K (−70 °C) and for gamma sources with energies from 17 keV to 835 keV. Two different methods were ...used to determine the properties of the CsI:Tl crystals. The first used classic analogue spectrometry equipment to check the dependence of energy resolution, intrinsic resolution, and non-proportionality parameters as a variations in temperature, excitation energy, and integration time. The second method registered the light pulses from the PMT without integrating or shaping circuits. At the current stage of the research, the authors have decided to maintain the thesis about the existence of three decay components in CsI:Tl crystals that was employed in previous studies - the light pulse decays were analyzed under this assumption. We observed that the light pulses slowed with a decrease in temperature. When the crystals were cooled from 303 K to 203 K, the fitted decay times increased significantly by factors of two to four. The non-proportionality of the three fitted components was also determined and it was found that the first and second (fast and slow components) exhibited positive non-proportionality while the third (tail component) presented a negative trend for non-proportionality at temperatures of 303 K–203 K. It was found that using sufficiently long integration times, to include compensating trends of all decay components, the light response of CsI:Tl could be proportional.
A custom design cryostat was constructed to study the temperature dependence of relative light yield and non-proportionality trends of scintillators between −182 °C and ＋152 °C. CsI:Tl crystal ...response to γ-rays and X-rays was investigated between 14 keV and 662 keV. Scintillation light was detected by a SiPM device, which was installed on a copper frame separated from the crystal and the cooling rod to enable operating the device at room temperature. The scintillation efficiency of CsI:Tl is peaked at about room temperature. The light yield of CsI:Tl at temperature close to liquid nitrogen boiling point is reduced by a factor of 15 in comparison to room temperature conditions. The non-proportionality of CsI:Tl scintillation response is high at low temperatures and is getting more proportional with increasing temperature.
Evolution of spectroscopic properties of two types of Multi-Pixel Photon Counters (MPPC) during neutron irradiation is reported. In such experiments the change of MPPCs characteristics is a serious ...issue. A series of neutron irradiation tests were performed at the National Centre for Nuclear Research (NCBJ, Poland) and Joined Institute for Nuclear Research (JINR, Russia). Two types of neutron sources were used: PuBe with continous energy spectrum up to 11 MeV and mono-energetic 4.8 MeV neutrons produced in (d,d) reaction. For both cases the fluence in the range of 10 10 n/cm 2 was achived.
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