R&D on an Innovative Silicon Photomultiplier-based Calibration System for the T2K Scintillator Tracker Detector

The T2K collaboration decided to upgrade the ND280 to collect enough statistics to search for CP violation. In order to reduce the neutrino oscillation systematic uncertainties, a new highly granular, fully active scintillator detector SuperFGD with a light readout interface based on Sil- icon Photomultipliers (SiPM) is introduced. As the SiPMs characteristics depend on voltage and temperature, a calibration system to achieve consistent measurements across all channels and to monitor the SiPM performance as a function of time is crucial. The conceptual design is similar to the technique proposed for the CALICE collaboration – notched fibres. To show the feasibil- ity of the LED-based calibration system with notched fibres on a wavelength shifting (WLS) fibre readout system, the light-yield of two notched squared 1 × 1 mm2 fibres with double cladding, clear Saint-Gobain and WLS Kuraray, were measured obtaining satisfactory results with the light yield relatively uniform along the fibre. Furthermore, a possible integration in the SuperFGD mechanical box was demonstrated.