Novel silicon photomultipliers suitable for dual-mirror small-sized telescopes of the Cherenkov telescope array

Abstract

Many of the characteristics of Silicon Photomultipliers (SiPMs), such as high Photon Detection Efficiency (PDE), are well matched to the requirements of the cameras of the Small-Sized Telescopes (SSTs) proposed for the Cherenkov Telescope Array. In fact, compared to a single mirror, the double mirror Schwarzschild-Couder configuration provides a much better Point Spread Function over a large field of view. It allows better correction of aberrations at large off-axis angles and facilitates the construction of compact telescopes. Moreover, the small plate scale of the dual-mirror SSTs allows the use of SiPM detectors despite their small pixel sizes. These sensors have two further advantages compared to the Photo Multipliers Tubes: the low cost and the possibility to observe in very high Night Sky Background (NSB) light level without any damage. However, one area in which SiPM performance has required improvement is Optical Cross-Talk (OCT), where multiple avalanches are induced by a single impinging photon. OCT, coupled with the typical NSB rate of 25 MCnts/s per pixel during Cherenkov observations, can place severe constraints on the triggering capability of the cameras. This paper describes the performance of novel Low Voltage Reverse (LVR) 2 nd and 3 rd generation Multi-Pixel Photon Counters manufactured by Hamamatsu Photonics. These are designed to have both enhanced PDE and reduced OCT. Two 7 × 7 mm 2 S14520 LVR2 MPPCs with 75 μm micro-cells are tested and compared with detectors of the same pixel size with 50 μm micro-cells. A comparative analysis of a 3 × 3 mm 2 S14520 LVR2 device and an S14520 LVR3 device is also carried out, demonstrating that the LVR3 gives better photon detection in the 240 -380 nm wave-length range. Finally, the effect of an infrared filter on the OCT is analysed.

Feasibility Study of a New Cherenkov Detector for Improving Volcano Muography

“…The number of p.e., Npe, is random generated from the Poisson distribution with mean parameter Nph and takes into account the photon detection efficiency (PDE) and the fill factor f of the SiPM, as Npe=monospacepoissrnd(Nph)×PDE×f, where monospacepoissrnd()λ is the MATLAB function to extract random number from Poisson distribution with mean parameter λ. PDE and f are set equal to 0.5 and 0.74 respectively, taking as reference the performance of novel SiPMs manufactured by Hamamatsu Photonics [26], which are likely candidates to be used for the first prototype of the Cherenkov-tag detector. The digitization procedure adds also a Gaussian noise to the signal, with mean and sigma equal to 1 both, in order to mimic the dark current rate of the SiPM.…”

Characterization method to achieve simultaneous absolute PDE measurements of all pixels of an ASTRI Mini-Array camera tile

“…A set of calibrated neutral density filters are used in front of the SiPM to attenuate the signal and avoid working with a luminous level that could saturate the detector, while having sufficient current signal detected by the photodiode. The apparatus allows PDE measurements in the spectral range of 280 -850nm by using 18 pulsed light sources (details are given in [1]).…”

“…As stated above, the main element of the front-end electronics for SiPM characterization is the Cherenkov Imaging Telescope Integrated Read-Out Chip (CITIROC) [17], produced by WEEROC 1 . The chip has been selected as the frontend electronics for the ASTRI camera.…”

“…In these measurements, the number of pulses per unit time in monochromatic light conditions are compared to the light level recorded at the same time, by a reference NIST photodetector. The used technique was discussed in detail in [1], [12], [18]. This technique is insensitive to the optical cross-talk, as we measure the probability of detecting 0 photons and derive the average assuming the Poisson statistics.…”

“…The array will give important results either in terms of scientific return or in terms of technological challenges. These telescopes have a relatively small plate scale that can be covered by SiPMs with sizes ranging from 6 × 6 mm 2 to 7×7 mm 2 [1].…”