The test and calibration system for the Elementary Cells of the Cherenkov Camera in the PBR Mission

TL;DR

The paper addresses calibrating large SiPM-based focal planes for space-based Cherenkov telescopes under harsh thermal and radiation conditions. It presents a dedicated test and calibration system for 32 EC units (2048 channels) using an $(8\times8)$ Hamamatsu SiPM matrix, with $I$-$V$ and photon-counting measurements across $-40 \le T \le 30^{\circ}\mathrm{C}$ at fixed $V_{\rm{ov}}$, plus climate-chamber integration and automated data acquisition. Key contributions include a detailed protocol to extract $V_{\rm{bd}}$, $R_q$, $G$, $DCR$, and $p_{\rm{CT}}$ for all channels, validation on the first EC, and development of end-to-end hardware/software pipelines (LED driver, CAEN DT5202 FERS, LabView, Janus, Notion). Significance lies in enabling mass testing and reliable calibration of a 2048-pixel focal surface for space-borne Cherenkov detection in the POEMMA/PBR program, advancing readiness for future missions.

Abstract

The development of detectors using Silicon Photo-Multipliers for acquisition of fast light signals coming from Cherenkov and fluorescence emissions started by particle showers in the terrestrial atmosphere is the main goal of the Italian ASI/INFN Agreement n.2021-8-HH.2-2022, named "ASI/INFN_EUSO-SPB2", in view of the next generation of telescopes in balloon-borne and space-based experiments. A survey of performances of different Silicon Photo-Multipliers available on the market has been performed to identify the best sensors for space applications, where high thermal excursions and environmental radiation must be mainly taken into account in contrast to ground-based experiments. In particular, a characterization protocol for Silicon Photo-Multiplier qualification has been specified to Hamamatsu S13161-3050AE-08 sensor ($8 \times 8$) array in the $30 \, \textrm{C}^{\circ}$ down to $-40 \, \textrm{C}^{\circ}$ temperature range. The protocol specifies measurements of break-down voltage, quenching resistance, gain, dark count rate and the probability of cross-talk. These parameters have been measured as a function of temperature at fixed over-voltage. Based on these previous measurements, a dedicated set-up is under completion for performing massive tests to validate and calibrate 32 Silicon Photo-Multipliers (Hamamatsu S13361-3050 series, 64 channels each), composing the (2048 pixels, $12^{\circ} \times 6^{\circ}$ field of view) Focal Surface of the Cherenkov Camera that will fly on the POEMMA-Balloon with Radio mission. The technical details and description of this system and the procedural steps implemented are reported, preliminary measurements on the first Elementary Cell are also shown.

Figures (5)

• Figure 1: Left: the experimental set-up for measuring the SiPM $(I-V)$ curves at different temperatures. Right: the experimental set-up for measuring the SiPM multi-peak spectrum at different temperatures.
• Figure 2: From left to right: an artistic view of the Focal Surface; different components of an Elementary Cell.
• Figure 3: Above: matrix scheme and geometrical dimensions of the Hamamatsu SiPM S13161-3050AE-08 model (top, side and bottom views). Below, on the left: gain, probability of cross-talk and photon-detection efficiency as function of the over-voltage at room temperature; on the right: a table reporting electrical and optical characteristics.
• Figure 4: Left: the block diagram of the experimental set-up used for measuring the SiPM $(I-V)$ curves at different temperatures. Right: the block diagram of the experimental set-up used for measuring the SiPM multi-peak spectra at different temperatures.
• Figure 5: Left: the Elementary Cell inside the climate chamber joined to a custom 3D-printed light-tight box, placed on a designated base, illuminated by means of an optical fiber (in red) and connected with the instrumentation outside through Samtec cables (in blue); centre: multi-peak spectrum (at LED on) measured for a given channel of the first EC at fixed V$_{bias}$ at different temperatures; right: dark count spectrum (at LED off) measured for the same given channel, at fixed temperature ($25^{\circ} \,\textrm{C}$) for different V$_{bias}$.