Light-Trap: A SiPM Upgrade for Very High Energy Astronomy and Beyond

TL;DR

This paper introduces a novel SiPM-based pixel with a wavelength shifter that enhances light collection, reduces cost, and improves sensitivity for high-energy gamma-ray astronomy, demonstrated through simulations, lab tests, and field deployment.

Contribution

It presents a new SiPM pixel design with a wavelength shifter that increases detection area and sensitivity, addressing limitations of traditional SiPMs in gamma-ray telescopes.

Findings

Enhanced light collection efficiency demonstrated in simulations.

Lab measurements confirm improved sensitivity and background rejection.

Field tests with a MAGIC telescope cluster validate the prototype performance.

Abstract

With the development of the Imaging Atmospheric Cherenkov Technique (IACT), Gamma-ray astronomy has become one of the most interesting and productive fields of astrophysics. Current IACT telescope arrays (MAGIC, H.E.S.S, VERITAS) use photomultiplier tubes (PMTs) to detect the optical/near-UV Cherenkov radiation emitted due to the interaction of gamma rays with the atmosphere. For the next generation of IACT experiments, the possibility of replacing the PMTs with Silicon photomultipliers (SiPMs) is being studied. Among the main drawbacks of SiPMs are their limited active area (leading to an increase in the cost and complexity of the camera readout) and their sensitivity to unwanted wavelengths. Here we propose a novel method to build a relatively low-cost pixel consisting of a SiPM attached to a PMMA disc doped with a wavelength shifter. This pixel collects light over a much larger area than a single standard SiPM and improves sensitivity to near-UV light while simultaneously rejecting background. We describe the design of a detector that could also have applications in other fields where detection area and cost are crucial. We present results of simulations and laboratory measurements of a pixel prototype and from field tests performed with a 7-pixel cluster installed in a MAGIC telescope camera.