Development of a scintillation track detector based on multichannel photodetectors. A.F. Yanin, I.M. Dzaparova, E.A. Gorbacheva, A.N. Kurenya, V.B. Petkov. The matrices of silicon photomultipliers (SiPM) are promising multi-channel photosensors for scintillation detectors. They can be used to construct tracks of the passage of relativistic particles inside the detectors. The snapshots of the events inside the scintillator were taken for the two SiPM matrices arrangements. In the first variant both matrices are placed on the surface of the plastic scintillator. In the second variant an optical system with Fresnel lens was used. It is expected that the proposed method of detecting particles may be useful in the creation of new large detectors to neutrino astrophysics and geophysics.

Variants of SiPM matrices

Matrix - ArrayC-60035-64P-PCB (firm SensL) PCB - ABL-ARRAYB64PH Operation amplifiers SiPM – 8x8 = 64; One SiMP – 18980 pixels; Output impedance - 100 Ω; Maximum output - 50 mA current; Duration of the leading edge - 15÷20 ns; Duration of output - ≤ 200 ns pulse; The polarity of the output pulses is negative; Quantum efficiency - 31÷41%; High gain factor (106); Immunity to magnetic fields. Connectors Matrix

Scheme of experiment with direct contact of matrices with a scintillator 2

General scheme for studying the properties of individual SiPM matrices. - Initially, a trigger was formed from these SIPM

Electric circuit functional formation of the trigger +VCC Number of inputs – 128 С* - Adjustment of the duration of the signal GATE – 210 ns Amp – amplifier Comp – comparator The gain for each input is 0.5

Variants of the formation of triggers. MicroSM has a Peltier cooler MicroSM (series MiniSM)  

An electrical functional the information collection system Data collection from the scintillation detector with these matrices as photodetectors is carried out by means of a multichannel measuring system MIMS-32, created on the basis of 32-chanical charge-digital converters (QDC) V792 of the VME standard, serially produced by CAEN (Italy).

Images of events for a detector with a plastic scintillator measuring 59 x 59 x 50 mm3 with direct contact. c)  Horizontal matrices a b 1 2  Vertical matrices Wide tracks are possible a) b) c) c If the track passes close to the surface of the scintillator, it is narrow d) e) f) g)

Sketch of prototype scintillation detector with silicon photomultipliers using Fresnel lenses Mode 3D Direction of the muon

Illustration of the construction of the object and its image Lens B a) The main points of the lens b) Оbject A-B is behind a double focal length (point A) B´ B´ B B c) Object A-B is located between the points f and 2f d) Оbject A-B is behind a double focal length (point A and B)

Depth of focus D с

Depth of focus for scintillator size 118x118x118 mm The size of a structure decreases when the image sharpens down

photomultipliers using Fresnel lenses. Working variant of a prototype of a scintillation detector with silicon photomultipliers using Fresnel lenses. The optical system implemented by Fresnel lenses, allowed us to obtain a projection of the events is much clearer. To reduce the dimensions of the detector, can reduce the focal length using two lenses. A matrix is located on the doubled focal distance f of from the center of the scintillator.

Diagram of an experiment to confirm track events

Typical tracks of muons and other charged particles Features: narrower trajectories than direct contact of matrices with a scintillator. The difference in brightness between neighboring SiPM along the trajectory is greater. Track with good focus Track with bad focus

Prospective variants of track detectors: a) using truncated cones of rectangular cross-section with a reflective inner coating; b) the same, plus optical fiber. Option a) can be printed on a 3D printer in conjunction with the matrix mounts. These options allow the development of track detectors of large volumes.

Filtering of temperature noise by means of time coincidence of signals with small amplitudes. Dark counting speed ~ 1 MHz This option may allow you to work with signals commensurate with noise. FPGA - Field Programmable Gate Array.

Conclusions: By direct contact of the matrix with the scintillator, there is a limit on the size of the detector. The use of the optical system removes this restriction. This improves the ratio signal/noise We used a Fresnel lens made ​​of optical acrylic with a threefold increase in the size of A4 . Such  mass production of lenses are available , inexpensive, and can have a large size . The depth of sharpness of the optical system suffices, that light track on a matrix had a width less size one SiPM, that confirm the brought pictures over with the use of the optical system. The experiments with optic were performed with a detector the size of 50x59x59 mm3 . We plan to increase the size of the scintillator to 120x120x120 mm3 . There are good opportunities for improving track detectors using truncated cones (variants a and c).

Calibration of the entire tract including SIPM, amplifiers, delay lines, adapters and QDC

Spectra of energy deposition SiPM from a scintillator 500x500x50 mm3