Characterization of a 6×6-mm² 75-μm cell MPPC suitable for the Cherenkov Telescope Array project

Abstract

This paper presents the latest characterization results of a novel Low Cross-Talk (LCT) large-area (6×6-mm²) Multi-Pixel Photon Counter (MPPC) detector manufactured by Hamamatsu, belonging to the recent LCT5 family and achieving a fill-factor enhancement and cross-talk reduction. In addition, the newly adopted resin coating is demonstrated to yield improved photon detection capabilities in the 290–350 nm spectral range, making the new LCT MPPC particularly suitable for emerging applications like Cherenkov Telescopes. For a 3×3-mm² version of the new MPPC under test, a comparative analysis of the large pixel pitch (75-µm) detector versus the smaller pixel pitch (50-µm) detector is also undertaken. Furthermore, measurements of the 6×6-mm² MPPC response versus the angle of incidence are provided for the characterized device.

Introduction

Silicon photomultipliers (SiPMs) are a relatively new class of solid-state photodetectors suitable for an increasing number of perspective applications in many scientific fields. Thanks to their outstanding characteristics in terms of photon number resolution, low operating voltage, fast dynamic response and insensitivity to magnetic fields, SiPM applications have been continuously growing over time, especially in the fields of high-energy astrophysics [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], nuclear medicine [15], [16], [17] and cosmic-ray muon detection [18], [19], [20].

The unique features presented by most commercially available detectors from the world's leading manufacturers are the result of modern semiconductor fabrication technologies. Considerable effort is presently being invested by the producers of SiPMs to further improve the global performance achieved by this class of devices [21], [22], [23], [24], [25]. In addition, the large popularity of SiPMs in the sensors community has led to a remarkable number of characterization studies and methodologies for evaluating the detector performance [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37]. The rising demand for optimal speed and single photon time resolution on one side, and for suitable integrated front-ends on the other, has also triggered research efforts for reliable analytical investigations on the dynamic response of SiPMs, allowing a detailed analytical description of the sensor behavior [38], [39], [40], [41], [42], [43], [44].

This paper presents the characterization of a newly available large-area (6×6-mm²) Multi-Pixel Photon Counter (MPPC) detector from Hamamatsu Photonics, addressing the challenge of high sensitivity and low cross-talk, especially requested in the new generation of Cherenkov telescopes as the ones adopted in the ASTRI Mini-Array Project [4] within the Cherenkov Telescope Array (CTA) Observatory [5], [6].

We also present a comparative analysis of the large pixel pitch (75-µm) detector versus the smaller pixel pitch (50-µm) device with the same active area (3×3-mm²), to compare the detector performance when increasing the pixel dimension for the same device size. Furthermore, to investigate the 6×6-mm² detector response with respect to the incident photons, measurement at several angles of incidence are provided as well.

The measurements presented here are carried out at the Catania astrophysical Observatory Laboratory for Detectors (COLD) within INAF – Osservatorio Astrofisico di Catania.