FACT – Performance of the First Cherenkov Telescope Observing with SiPMs
August 21, 2017
August 03, 2018
The First G-APD Cherenkov Telescope (FACT) is pioneering the usage of silicon photo mul-
tipliers (SiPMs also known as G-APDs) for the imaging atmospheric Cherenkov technique. It
is located at the Observatorio Roque de los Muchachos on the Canary island of La Palma. Since
first light in October 2011, it is monitoring bright TeV blazars in the northern sky. By now, FACT
is the only imaging atmospheric Cherenkov telescope operating with S I PMs on a nightly basis.
Over the course of the last five years, FACT has been demonstrating their reliability and excel-
lent performance. Moreover, their robustness allowed for an increase of the duty cycle including
nights with strong moon light without the need for UV-filters.
In this contribution, we will present the performance of the first Cherenkov telescope using solid
state photo sensors, which was determined in analysis of data from Crab Nebula, the so called
standard candle in gamma-ray astronomy. The presented analysis chain utilizes modern data
mining methods and unfolding techniques to obtain the energy spectrum of this source. The
characteristical results of such an analysis will be reported providing, e. g., the angular and energy
resolution of FACT, as well as, the energy spectrum of the Crab Nebula. Furthermore, these
results are discussed in the context of the performance of coexisting Cherenkov telescopes.
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