New improved Sum-Trigger system for the MAGIC telescopes

TL;DR

The paper presents a new automatic Sum-Trigger system for MAGIC telescopes that enhances low-energy gamma-ray detection, improves calibration, and expands observational capabilities for pulsars, AGNs, and GRBs.

Contribution

A fully automatic, improved Sum-Trigger system with a novel analog delay line and larger trigger area for MAGIC telescopes, enabling better low-energy gamma-ray detection.

Findings

Successful functionality tests of the prototype.

Enhanced sensitivity in 20-100 GeV energy range.

Ready for installation on MAGIC telescopes.

Abstract

In 2007 a prototype of a new analog Sum-Trigger was installed in the MAGIC I telescope, which lowered the trigger threshold from 55 GeV to 25 GeV and led to the detection of pulsed gamma radiation from the Crab pulsar. To eliminate the need for manual tuning and maintenance demanded by that first prototype, a new setup with fully automatic calibration was designed recently. The key element of the new circuit is a novel, continuously variable analog delay line that enables the temporal equalization of the signals from the camera photo sensors, which is crucial for the efficient detection of low-energy showers. A further improvement is the much larger trigger area consisting of a fully revised configuration of overlapping summing patches. The new system will be installed on both telescopes, MAGIC I and II, enabling stereo observation in Sum-Trigger mode. This will significantly improve the sensitivity in the very low energy regime of 20 to 100 GeV, which is essential in particular for detailed pulsar studies, as well as the observation of high-redshift AGNs and distant GRB events. Here we like to present the results of functionality tests of a fully working prototype and the basic design of the final system.