Calibration of the prototype of a large-volume scintillation detector with photosensors based on silicon photomultiplier matrices

Abstract

In recent years, the staff of the Institute for Nuclear Research of the Russian Academy of Sciences (INR RAS) has been elaborating the project for a large-volume scintillation detector at the Baksan Neutrino Observatory (BNO). The detector will become a part of the global network of neutrino detectors. One of the prototypes of such a detector being developed at BNO is an acrylic sphere with a diameter of 500 mm filled with liquid scintillator. The matrices of silicon photomultipliers (SiPMs) are used as photosensors of the detector. For many years such photosensors have been used in various physical experiments. In our case, unlike other experiments, the SiPM matrices are used not only to measure the total light output from the interaction of particles in the scintillator but also to obtain images of such events. This approach will allow us to separate useful (neutrino) events from background ones and monitor supernova explosions in our Galaxy.

Two matrices of 64 SiPMs (ARRAYJ-60035-64P-PCB by the SensL company) register photons passing through the optical collector of the detector from the interaction of particles inside the sphere volume of liquid scintillator. The optical collector consists of Fresnel lenses with a diameter of 300 mm and a focal length of 120 mm. With a LED mounted on the lever, measurements of the volume viewed by the matrices were carried out. The 128-channel data acquisition system is an MDU3-GI64X2 unit (manufactured by AiT Instruments) connected to the preamp boards by a flat micro-coaxial cable. Data reading to an online computer is implemented via a USB 3.0 interface. Channels are calibrated in each measurement cycle. The charge spectrum in the detector is given, which is the total signal measured by 64 SiPMs of the matrix. The image of the event track is presented. Currently, the method for measuring and analyzing the data obtained is being worked out, and there are preparations for working with the next prototype of the detector, which is an acrylic sphere with a diameter of 1 m.