Scintillator counters with multi-pixel avalanche photodiode readout for the ND280 detector of the T2K experiment

Abstract

The Tokai-to-Kamioka (T2K) experiment is a second generation long baseline neutrino oscillation experiment which aims at a sensitive search for the ν e appearance. The main design features of the T2K near neutrino detectors located at 280 m from the target are presented. Scintillator counters developed for the T2K near detectors are described. Readout of the counters is provided via WLS fibers embedded into S-shape grooves in a scintillator and viewed from both ends by multi-pixel avalanche photodiodes operating in a limited Geiger mode. A description, operational principles and the results of tests of photosensors with a sensitive area of 1.1 mm 2 are presented. A time resolution of 1.5 ns, a spatial resolution of 9.9-12.4 cm, and a MIP detection efficiency of more than 99% were obtained for scintillator detectors in a beam test.

Background and muon counting rates in underground muon measurements with a plastic scintillator counter based on a wavelength shifting fibre and a multi-pixel avalanche photodiode readout

“…The muon peak in the spectrum corresponds to ∼61 pe. The observed shift in the muon peak position in comparison to the spectrum registered in the surface laboratory is due to an increase of the photodiode gain and photon detection efficiency because of the temperature decrease [4,5]. As can be seen in Fig.…”

“…each. We refer to [4][5][6] for more details on MRS APD. The operating voltage of the photodiode used in the measurements was 52.5 V providing a photon detection efficiency (PDE) of ∼20% at λ=515 nm at room temperature (22°C).…”

Optimization of light yield by injecting an optical filler into the co-extruded hole of the plastic scintillation bar

“…Different optical glues such as epoxy, silicon and synthetic (based on rubber) have been used for optical coupling. Epoxy glues (for example BC-600 [8]) are often used for gluing WLS fibers on the edge of scintillation bars or into grooves on strips or on tiles in many experiments such as [4], [6], [7], [14], [15] and epoxy Araldite 2020 (corporation Huntsman) is also used elsewhere. Silicone based optical glue SUREL SL-1 [12] (St. Petersburg, Russia) was used for Belle II end-cup KLM detector [16].…”

The T2K Side Muon Range Detector (SMRD)

“…A key feature of the individual SMRD counters is the usage of a serpentine-shaped fiber. The design results in near uniform response across the surface of the scintillation counter [8] and minimize the number of photosensors and electronics channels compared to more conventional designs with multiple straight fibers. Extruded polystyrene scintillators (1.5% PTP, 0.01% POPOP) have been produced by Uniplast, a company in Vladimir, Russia.…”