# The Light-Trap: A novel concept for a large SiPM-based pixel for Very High Energy gamma-ray astronomy and beyond

## TL;DR

The paper introduces the Light-Trap, a cost-effective SiPM-based pixel with enhanced light collection and sensitivity for VHE gamma-ray astronomy, demonstrating improved performance over standard SiPMs through laboratory measurements and simulations.

## Contribution

It presents a novel Light-Trap pixel design combining a SiPM with a wavelength-shifting disk to increase collection area and sensitivity, addressing limitations of traditional SiPMs in large-scale experiments.

## Key findings

- Light-Trap covers 20 times larger area than the SiPM itself.
- Laboratory measurements confirm increased sensitivity to near-UV light.
- Simulations show potential performance improvements for gamma-ray detection.

## Abstract

Among the main disadvantages of using silicon photomultipliers (SiPMs) in large experiments are their limited physical area (increasing the cost and the complexity of the readout of a camera) and their sensitivity to unwanted wavelengths. This explains why photomultiplier tubes (PMTs) are still selected for the largest cameras of present and future Very High Energy (VHE) gamma-ray telescopes. These telescopes require photosensors that are sensitive to the fast and dim optical/near-UV Cherenkov radiation emitted due to the interaction of gamma rays with the atmosphere. Here we introduce a low-cost pixel consisting of a SiPM attached to a PMMA disk doped with a wavelength-shifting material, which collects light over a much larger area than standard SiPMs, increases sensitivity to near-UV light and improves background rejection. We also show the measurements performed in the laboratory with a proof-of-concept \textit{Light-Trap} pixel that is equipped with a 3$\times$3~mm$^2$ SiPM collecting light only in the 300-400~nm band, covering an area $\sim$20 times larger than that of the same SiPM itself. We also present results from simulations performed with Geant4 to evaluate its performance. In addition to VHE astronomy, this pixel could have other applications in fields where detection area and cost are critical.