In this short note we present results of background measurements carried out with a polystyrene based cast plastic 12.0x12.0x3.0 cm^3 size scintillator counter with a wavelength shifting fibre and a multi-pixel Geiger mode avalanche photodiode readout in the Baksan underground laboratory at a depth of 200 meters of water equivalent. The total counting rate of the scintillator counter measured at this depth and at a threshold corresponding to ~0.37 of a minimum ionizing particle is approximately 1.3 Hz.
The results of a development of a scintillator counter with wavelength shifting (WLS) fibre and a multi-pixel Geiger-mode avalanche photodiode readout are presented. The photodiode has a metal-resistor-semiconductor layered structure and operates in the limited Geiger mode. The scintillator counter has been developed for the EMMA underground cosmic ray experiment.
The performance of scintillator counters with embedded wavelength-shifting fibers has been measured in the Fermilab Meson Test Beam Facility using 120 GeV protons. The counters were extruded with a titanium dioxide surface coating and two channels for fibers at the Fermilab NICADD facility. Each fiber end is read out by a 2*2 mm^2 silicon photomultiplier. The signals were amplified and digitized by a custom-made front-end electronics board. Combinations of 5*2 cm^2 and 6*2 cm^2 extrusion profiles with 1.4 and 1.8 mm diameter fibers were tested. The design is intended for the cosmic-ray veto detector for the Mu2e experiment at Fermilab. The light yield as a function of the transverse and longitudinal position of the beam will be given.
The T2K neutrino experiment at J-PARC uses a set of near detectors to measure the properties of an unoscillated neutrino beam and neutrino interaction cross-sections. One of the sub-detectors of the near-detector complex, the side muon range detector (SMRD), is described in the paper. The detector is designed to help measure the neutrino energy spectrum, to identify background and to calibrate the other detectors. The active elements of the SMRD consist of 0.7 cm thick extruded scintillator slabs inserted into air gaps of the UA1 magnet yokes. The readout of each scintillator slab is provided through a single WLS fiber embedded into a serpentine shaped groove. Two Hamamatsu multi-pixel avalanche photodiodes (MPPCs) are coupled to both ends of the WLS fiber. This design allows us to achieve a high MIP detection efficiency of greater than 99%. A light yield of 25-50 p.e./MIP, a time resolution of about 1 ns and a spatial resolution along the slab better than 10 cm were obtained for the SMRD counters.
High-time-resolution counters based on plastic scintillator with silicon photomultiplier (SiPM) readout have been developed for applications to high energy physics experiments for which relatively large-sized counters are required. We have studied counter sizes up to $120times40times5$ mm^3 with series connection of multiple SiPMs to increase the sensitive area and thus achieve better time resolution. A readout scheme with analog shaping and digital waveform analysis is optimized to achieve the highest time resolution. The timing performance is measured using electrons from a Sr-90 radioactive source, comparing different scintillators, counter dimensions, and types of near-ultraviolet sensitive SiPMs. As a result, a resolution of $sigma =42 pm 2$ ps at 1 MeV energy deposition is obtained for counter size $60times 30 times 5$ mm^3 with three SiPMs ($3times3$ mm^2 each) at each end of the scintillator. The time resolution improves with the number of photons detected by the SiPMs. The SiPMs from Hamamatsu Photonics give the best time resolution because of their high photon detection efficiency in the near-ultraviolet region. Further improvement is possible by increasing the number of SiPMs attached to the scintillator.
DANSSino is a simplified pilot version of a solid-state detector of reactor antineutrino (it is being created within the DANSS project and will be installed close to an industrial nuclear power reactor). Numerous tests performed under a 3 GW(th) reactor of the Kalinin NPP at a distance of 11 m from the core demonstrate operability of the chosen design and reveal the main sources of the background. In spite of its small size (20x20x100 ccm), the pilot detector turned out to be quite sensitive to reactor neutrinos, detecting about 70 IBD events per day with the signal-to-background ratio about unity.