Field test of the hybrid photodetector R9792U-40 on the MAGIC camera

TL;DR

This paper reports on a field test of a high-efficiency hybrid photodetector installed in the MAGIC telescope, highlighting its potential to enhance observational sensitivity despite some operational challenges.

Contribution

First field test of the R9792U-40 hybrid photodetector in a real telescope environment demonstrating its advantages and limitations.

Findings

High quantum efficiency (>50%) at 500 nm

Significantly reduced after-pulsing probability

Operational challenges with photocathode voltage and lifetime

Abstract

The hybrid photodetector (HPD) R9792U-40 has very high peak quantum efficiency ($>50$% at 500 nm), excellent charge resolution and very low after-pulsing probability (500 times less than that of currently used photomultipliers (PMTs)). These features will improve the sensitivity, the energy resolution and the energy threshold of the MAGIC telescope. On the other hand, its high photocathode voltage (-8 to -6 kV), relatively short photocathode lifetime, and relatively large temperature dependence of the gain need to be taken care of. In February 2010, 6 HPDs were installed in a corner of the MAGIC-II camera for a field test. Here we report the results of the field test and our future plans.