The topological second-level trigger of the HESS phase 2 telescope

• Published in: Astroparticle physics Vol. 34; no. 7; pp. 568 - 574
• Main Authors: Moudden, Y., Barnacka, A., Glicenstein, J.-F., Venault, P., Calvet, D., Vivier, M., Fontaine, G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.02.2011
• Subjects: FPGA; HESS; Imaging atmospheric Cherenkov telescope; Real-time; Trigger; γ-Ray astronomy; γ-Ray astronomy; Imaging atmospheric Cherenkov telescope; Trigger; HESS; FPGA; Real-time
• ISSN: 0927-6505; 1873-2852
• DOI: 10.1016/j.astropartphys.2010.12.003

HESS is an array of atmospheric Cherenkov telescopes dedicated to GeV–TeV γ-ray astronomy. The original array has been in operation since the beginning of 2004. It is composed of four 12-m diameter telescopes. The installation of a fifth 28-m diameter telescope is being completed. This telescope will operate both in stereoscopic mode and in monoscopic mode i.e. without a coincident detection on the smaller telescopes. A second-level trigger system is needed to suppress spurious triggers of the 28-m telescope when operated in monoscopic mode. This paper gives the motivation and principle of the second-level trigger. The principle of operation is illustrated by an example algorithm. The hardware implementation of the second level trigger system of HESS phase 2 is described and its expected performances are then evaluated.