No Arabic abstract
We report on the energy, timing, and pulse-shape discrimination performance of cylindrical 5 cm diameter x 5 cm thick and 7 cm diameter x 7 cm thick {it trans}-stilbene crystals read out with the passively summed output of three different commercial silicon photo-multiplier arrays. Our results indicate that using the summed output of an 8x8 array of SiPMs provides performance competitive with photo-multiplier tubes for many neutron imaging and correlated particle measurements: for the 5x5 cm crystal read out with SensLs ArrayJ-60035_64P-PCB, which had the best overall properties, we measure the energy resolution as 13.6$pm$1.8% at 341 keVee, the timing resolution in the 100--400 keVee range as 277$pm$34 ps, and the pulse-shape discrimination figure-of-merit as 2.21$pm$0.03 in the 230--260 keVee energy range. These results enable many scintillator-based instruments to enjoy the size, robustness, and power benefits of silicon photo-multiplier arrays as replacement for the photo-multiplier tubes that are predominantly used today.
In neutrino experiments, hemispherical photomultiplier tubes (PMTs) are often used to cover large surfaces or volumes to maximize the photocathode coverage with a minimum number of channels. Instrumentation is often coarse, and neutrino event reconstruction and particle identification (PID) is usually done through the morphology of PMT hits. In future neutrino experiments, it may be desirable to perform PID from a few hits, or even a single hit, by utilizing pulse shape information. In this report, we study the principle of pulse shape PID using a single 10-inch hemispherical PMT in a spherical glass housing for future neutrino telescopes. We use the Fermilab Test Beam Facility (FTBF) MTest beamline to demonstrate that with pulse shape PID, statistical separation is possible to distinguish 2 GeV electrons from 8 GeV pions, where the total charge deposition is ~20 PE in our setup. Such techniques can be applied to future neutrino telescopes focusing on low energy physics, including the IceCube-Upgrade.
We report radiation hardness tests performed at the Frascati Neutron Generator on silicon Photo-Multipliers, semiconductor photon detectors built from a square matrix of avalanche photo-diodes on a silicon substrate. Several samples from different manufacturers have been irradiated integrating up to 7x10^10 1-MeV-equivalent neutrons per cm^2. Detector performances have been recorded during the neutron irradiation and a gradual deterioration of their properties was found to happen already after an integrated fluence of the order of 10^8 1-MeV-equivalent neutrons per cm^2.
The goal of Double Chooz experiment is a precise measurement of the last unknown mixing angle theta_13 using two identical detectors placed at far and near sites from Chooz reactor cores. The detector is optimized for reactor-neutrino detection using specially developed 10-inch PMTs. We developed two types of measurement systems and evaluated 400 PMTs before the installation. Those PMTs fulfill our requirements, and a half of those have been installed to the far detector in 2009. The character and performance data of the PMTs are stored in a database and will be referenced in analysis and MC simulation.
Silicon Photo-Multipliers (SiPMs) are semiconductor-based photo-detectors with performances similar to the traditional Photo-Multiplier Tubes (PMTs). An increasing number of experiments dedicated to particle detection in colliders, accelerators, astrophysics, neutrino and rare-event physics involving scintillators are using SiPMs as photodetectors. They are gradually substituting PMTs in many applications, especially where low voltages are required and high magnetic field is present. Hamamatsu Photonics K.K., one of leading producers of photo-detectors, in the last year introduced the S14160 series of SiPMs with improved performances. In this work, a characterization of these devices will be presented in terms of breakdown voltages, pulse shape, dark current and gain. Particular attention has been dedicated to the analysis of the parameters as function of temperature.
Muon beam monitoring is indispensable for indirectly monitoring accelerator-produced neutrino beams in real time. Though Si photodiodes and ionization chambers have been successfully used as muon monitors at the T2K experiment, sensors that are more radiation tolerant are desired for future operation. We have investigated the electron-multiplier tube (EMT) as a new sensor for muon monitoring. Secondary electrons produced by the passage of muons at dynodes are multiplied in the tube and produce signal. Two prototype detectors were installed at the T2K muon monitor location, and various EMT properties were studied based on in situ data taken with the T2K muon beam. The signal size is as expected based on calculation, and the EMTs show a sufficiently fast time response for bunch-by-bunch beam monitoring. The spill-by-spill intensity resolution is 0.4%, better than the required value (1%). Signal linearity within $pm$1% is achieved at proton beam powers up to 460 kW (with +250 kA focusing horn operation). A gradual signal decrease was observed during the initial exposure, due to the stabilization of dynode materials, before the response became stable within $pm$1%. This work demonstrates that EMTs are a good candidate for future muon monitoring at T2K, and may also have other more general applications.