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Register a new userA Position and Pulse Shape Discriminant p-Terphenyl Detector Module
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We present the development of a neutron detector array module made with $textit{para}$-terphenyl, a bright, fast, n/$gamma$ discriminating crystalline organic scintillator. The module is comprised of 2 cm $times$ 2 cm $times$ 2 cm $textit{p}$-terphenyl crystals that have been optically coupled together to create a $textit{pseudo-bar}$ module. While only relying on two photo detectors, the module is capable of distinguishing interactions between up to eight crystals. Furthermore, the module retains the $textit{p}$-terphenyls pulse shape discrimination (PSD) capability. Together this makes the pseudo-bar module a promising position-sensitive neutron detector. Here we present characteristics of the pseudo-bar module - its timing resolution as well as its pulse shape and position discrimination capabilities, and briefly discuss future plans for utilizing an array of pseudo-bar modules in a useful neutron detector system.
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In this work, two particular properties of the position-sensitive, thick silicon detectors (known as the E detectors) in the High Resolution Array (HiRA) are investigated: the thickness of the dead layer on the front of the detector, and the overall thickness of the detector itself. The dead layer thickness for each E detector in HiRA is extracted using a measurement of alpha particles emitted from a $^{212}$Pb pin source placed close to the detector surface. This procedure also allows for energy calibrations of the E detectors, which are otherwise inaccessible for alpha source calibration as each one is sandwiched between two other detectors. The E detector thickness is obtained from a combination of elastically scattered protons and an energy-loss calculation method. Results from these analyses agree with values provided by the manufacturer.
The 2x3 channel pseudo Vertex Position Detector (pVPD) in the STAR experiment at RHIC has been upgraded to a 2x19 channel detector in the same acceptance, called the Vertex Position Detector (VPD). This detector is fully integrated into the STAR trigger system and provides the primary input to the minimum-bias trigger in Au+Au collisions. The information from the detector is used both in the STAR Level-0 trigger and offline to measure the location of the primary collision vertex along the beam pipe and the event start time needed by other fast-timing detectors in STAR. The offline timing resolution of single detector channels in full-energy Au+Au collisions is ~100 ps, resulting in a start time resolution of a few tens of picoseconds and a resolution on the primary vertex location of ~1 cm.
In this study, we evaluate and compare the pulse shape discrimination (PSD) performance of multipixel photon counters (MPPCs, also known as silicon photomultiphers - SiPMs) with that of a typical photomultiplier tube (PMT) when testing using CsI(Tl) scintillators. We use the charge comparison method, whereby we discriminate different types of particles by the ratio of charges integrated within two time-gates (the delayed part and the entire digitized waveform). For a satisfactory PSD performance, a setup should generate many photoelectrons (p.e.) and collect their charges efficiently. The PMT setup generates more p.e. than the MPPC setup does. With the same digitizer and the same long time-gate (the entire digitized waveform), the PMT setup is also better in charge collection. Therefore, the PMT setup demonstrates better PSD performance. We subsequently test the MPPC setup using a new data acquisition (DAQ) system. Using this new DAQ, the long time-gate is extended by nearly four times the length when using the previous digitizer. With this longer time-gate, we collect more p.e. at the tail part of the pulse and almost all the charges of the total collected p.e. Thus, the PSD performance of the MPPC setup is improved significantly. This study also provides an estimation of the short time-gate (the delayed part of the digitized waveform) that can give a satisfactory PSD performance without an extensive analysis to optimize this gate.
A prototype of a position sensitive photo-detector with 5.6 x 5.6 cm2 detection area readout with 64 Hamamatsu MPPCs (S10931-100P) with 3 x 3 mm2 active area each has been built and tested. The photo-sensors are arranged in a 8 x 8 array with a quadratic mirror light guide on top. The module is currently readout by in-house developed preamplifier boards but employing existing ASIC chips optimized for SiPM readout is also planned. Such a device is one of the candidates to be used for photon detection in the PANDA DIRC detectors.
A software package for modeling segmented High-Purity Segmented Germanium detectors, AGATAGeFEM, is presented. The choices made for geometry implementation and the calculations of the electric and weighting fields are discussed. Models used for charge-carrier velocities are described. Numerical integration of the charge-carrier transport equation is explained. Impact of noise and crosstalk on the achieved position resolution in AGATA detectors are investigated. The results suggest that crosstalk as seen in the AGATA detectors is of minor importance for the position resolution. The sensitivity of the pulse shapes to the parameters in the pulse-shape calculations is determined, this as a function of position in the detectors. Finally, AGATAGeFEM has been used to produce pulse-shape data bases for pulse-shape analyses of experimental data. The results with the new data base indicate improvement with respect to those with the standard AGATA data base.
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