Pulse shape discrimination in scintillators is one of the most popular ways of recognizing events due to neutrons or gamma rays. Presently, n-γ discrimination is done mainly using two methods, charge ...comparison or zero-crossing. The aim of the study is to compare digital implementation of both algorithms using the same experimental data. For this purpose special application was developed in LabView environment which analyze the data digitized by Tektronix oscilloscope TDS5104B. The software allows optimization of each algorithm depending on the properties of the recorded pulse. The comparison is based on values of Figure of Merit and their relation to the light pulse characteristics. Both methods are used in measurements with XP5500B photomultiplier and Stilbene scintillator. Additionally the analysis of the detectors based on two types of Hamamatsu silicon photomultipliers (12×12mm2 and 24×24mm2) is presented. The results are compared with an analog zero-crossing system based on NDE202 NIM module.
The main aim of this work was characterization of the newest MPPC arrays (with 12×12mm and 24×24mm active area) made using through silicon via (TSV) technology in gamma-ray spectrometry with five ...different scintillators: CsI:Tl, NaI:Tl, LSO/LYSO, BGO, LaBr3. The results of the study are compared with that obtained previously with the older sample of the 12×12mm MPPC array made as a monolithic device. TSV MPPC array with the size of 24×24mm is one of the first commercially available SiPM with so large active area and with the dead space between channels minimized to only 0.2mm. Moreover in these devices Hamamatsu introduced resistors made with a new type of material. Such a change allowed lowering of crosstalks and afterpulses. These improved TSV MPPC arrays can be commercially used for scintillation light readout of "large" crystals with diameter of 1×1inch or 2×2inch, suitable for gamma spectrometry. Such combination may allow replacement of PMTs in monitoring handheld devices. The presented studies with MPPCs were carried out in the two main experimental conditions: direct illumination of the SiPM using a LED pulser and measurements with scintillators. The first method allowed the measurements of basic parameters of MPPCs such as breakdown voltage and excess noise factor (ENF). The second method allowed the measurements of the full scintillation detector parameters, such as: optimum operating voltage, number of photoelectrons (number of fired APD cells), photon detection efficiency (PDE), linearity and energy resolution.
Spectroscopic performance of 4 types of large detectors consisting of 3 different scintillators (LaBr 3 , NaI(Tl) and BGO) coupled to large MPPC array are presented. The measurements are made with ...S12642-1616PB-50(X) Hamamatsu TSV MPPC array having a 50x50 µm 2 cell size and effective active area of 48x48 mm 2 (16x16 channels). In all measurements the common readout of all channels is used. The results obtained with MPPC, such as energy resolution and linearity, are compared with measurements of the same crystals on classic photomultiplier. Also the possible optimization of data acquisition electronics is presented.
The aim of this work is to provide the characteristics of MPPC as a part of neutron detector based on scintillators with n/γ discrimination capabilities. Measurements presented in the work cover: ...characterization of n/γ discrimination properties by means of Figure of Merit (FOM); comparison of scintillation light pulse shape measured with MPPC and PMT (rise time and fall time) and its influence on the ZC method; estimation of the number of photoelectrons per energy unit (phe/MeV) done by Bartolaccini method.
Effective dead time of APD cells of SiPM Grodzicka, M.; Moszynski, M.; Szczesniak, T. ...
2011 IEEE Nuclear Science Symposium Conference Record,
2011-Oct.
Conference Proceeding
The linear response of the silicon photomultiplier (SiPM) device depends on the number of APD cells, their effective dead time and is related to a width of the detected light pulses or a decay time ...of a scintillation crystal. The aim of this work was determination of the effective dead time of APD cells on the basis of the measured linear response of the SiPM for light pulses of different width. A closer analysis of the SiPM response to the light pulses shorter than the effective dead time of pixels, made possible evaluation of a number of fired pixels (or number of photoelectrons) in cases when a single photoelectron peak was not well defined. This analysis also allows determination of the position of the single photoelectron peak, necessary in case of measurements of the number of photoelectrons for light pulses with various widths. Measurements were done with SiPMs manufactured by three companies: Hamamatsu, Zecotek and SensL.
Time jitter of silicon photomultipliers Szczesniak, T.; Moszynski, M.; Grodzicka, M. ...
2012 IEEE Nuclear Science Symposium and Medical Imaging Conference Record (NSS/MIC),
2012-Oct.
Conference Proceeding
Time jitter, it means timing distribution of a detector response to single photons is one of the key parameters describing the timing resolution capabilities of any photodetector. In this work, the ...time jitter measurements of silicon photomultipliers (SiPMs) with active area from 1 to 36 mm2 are presented. These measurements were made using fast picosecond laser PicoQuant LDH P C-405 with wavelength of 405 nm and pulse width below 70 ps. The measurements were done with Hamamatsu Multi-Pixel Photon Counters (MPPCs) with micropixel size of 50 μm (050C). Additional data were also recorded when only a part of an active area of the tested MPPCs was illuminated. The MPPC output was fed into fast amplifier MiniCircuits ERA-4SM+ with 4GHz bandwidth and then further amplified by NIM modules and processed by constant fraction discriminator. In each experiment the noise component was measured and subtracted from the raw timing data. The aim of the study was to understand the influence of the SiPM's capacitance and rise time on the time jitter and also to distinguish differences resulting from the electronics optimization from those due to physical effects connected with an active or illuminated area of a detector.
The aim of this work is to provide the characteristics of MPPC arrays with an active area of 6x6 mm 2 in gamma-ray spectrometry with 5x5x5mm 3 CsI:TI scintillator at a wide temperature range. The ...measurements presented in this work covered: characteristics of breakdown voltage, selection of MPPC optimum operating voltage, verification of excess noise factor, measurement of energy resolution and the number of photoelectrons per 1 MeV. All measurements were carried out as a function of temperature and compared with similar results obtained previously with CsI:TI crystal coupled to a Large Area Photodiode (LAAPD).
Presently, a majority of studies concerning application of silicon photomultipliers (SiPMs) in positron emission tomography detectors are focused on scintillators containing lanthanum (LaBr 3 ) or ...lutetium (LSO, LYSO, LFS). However, the modules with the well known BGO in combination with SiPM light readout are also interesting due to unique features of SiPMs. In this work the two types of detectors, based on BGO and LSO scintillators are compared in terms of requirements for positron emission tomography scanners. The presented studies are performed with two Hamamatsu Multi Pixel Photon Counter (MPPC) arrays of 2×2 channels, with total area of 6×6 mm 2 and micro-pixel size of 25 μm (S10985-025C) and 50 μm (S10985-050C). The measurements of a number of photoelectrons, energy resolution at 511 keV and 22 Na time resolution are reported for various sizes of scintillators, including 3×3 mm 2 pixels and single crystals covering the whole MPPC active area. The paper is more focused on optimization of the system with BGO since its performance in combination with SiPM light readout is less known. The aim of this work is to show advantages of a SiPM based detector, especially in combination with BGO, in respect to the block detectors where classic photomultipliers are used.
CaF2(Eu): An "Old" scintillator revisited Plettner, C; Pausch, G; Scherwinski, F ...
IEEE Nuclear Science Symposuim & Medical Imaging Conference,
2010-Oct.
Conference Proceeding
Homeland security applications demand high performance Compton-camera systems, with high detector efficiency, good nuclide identification and able to operate in-field conditions. A low-Z scintillator ...has been proposed and studied as a promising candidate for use in the scattering plane of a scintillator-based Compton camera: CaF 2 (Eu). All the relevant properties for the application of this scintillator in a mobile Compton camera system have been addressed: the energy resolution and the non-linearity at room temperature and in the temperature range of -20°C to +55°C, the photoelectron yield and the relative light yield in the relevant temperature range. A new method of inferring the relative light output of scintillators as a function of temperature has been proposed.
The Wide-Angle Compton Coincidence (WACC) technique was adapted to measure the electrons produced in cadmium zinc telluride (CZT) detector by Compton scattered gamma rays of 662 keV energy emitted by ...a 137 Cs source. The measurements were carried out with a 4 × 4 pixel anode array build on a 5 mm thick CZT crystal with 1.1 mm pitch. A High Purity Germanium (HPGe) detector operating in coincidence mode measured energy of the scattered photons. The coincidence pulse height data from the CZT and HPGe detectors were recorded in a list mode. The CZT electron spectra were determined by subtracting the energy of the scattered photons from the incident photon energy. The scattering angle was determined by selecting a narrow energy window in the collected HPGe spectra. The CZT electron linearity and resolution were measured in the energy range of 100 keV-300 keV corresponding to the scattering angle range of 31°-66°.
