arXiv subjects

M. Panter

Publications and source records attributed to M. Panter.

23 records · Page 2Linked to original sources

arXiv2003

The optical system of the H.E.S.S. imaging atmospheric Cherenkov telescopes, Part I: layout and components of the system

H.E.S.S. -- the High Energy Stereoscopic System -- is a new system of large imaging atmospheric Cherenkov telescopes, with about 100 m^2 mirror area for each of four telescopes, and photomultiplier cameras with a large field of view (5 degr.) and small pixels (0.16 degr.). The dish and reflector are designed to provide good imaging properties over the full field of view, combined with mechanical stability. The paper describes the design criteria and specifications of the system, and the individual components -- dish, mirrors, and Winston cones -- as well as their characteristics. The optical performance of the telescope as a whole is the subject of a companion paper.

astro-ph↗

arXiv2003

The optical system of the H.E.S.S. imaging atmospheric Cherenkov telescopes, Part II: mirror alignment and point spread function

Mirror facets of the H.E.S.S. imaging atmospheric Cherenkov telescopes are aligned using stars imaged onto the closed lid of the PMT camera, viewed by a CCD camera. The alignment procedure works reliably and includes the automatic analysis of CCD images and control of the facet alignment actuators. On-axis, 80% of the reflected light is contained in a circle of less than 1 mrad diameter. The spot widens with increasing angle to the telescope axis. In accordance with simulations, the spot size has roughly doubled at an angle of 1.4 degr. from the axis. The expected variation of spot size with elevation due to deformations of the support structure is visible, but is completely non-critical over the usual working range. Overall, the optical quality of the telescope exceeds the specifications.

astro-ph↗

arXiv1998

Locating TeV Gamma-Ray Sources with Sub-Arcminute Precision: the Pointing Calibration of the HEGRA System of Imaging Atmospheric Cherenkov Telescopes

Stereoscopic viewing of TeV gamma-ray air showers with systems of Imaging Atmospheric Cherenkov Telescopes (IACTs) allows to reconstruct the origin of individual primary particles with an accuracy of 0.1 degree or better. The shower impact point can be determined within 15 meters. To actually achieve this resolution, the pointing of the telescopes of an IACT system needs to be controlled with high precision. For the HEGRA IACT system, a procedure to calibrate telescope pointing was established, using bright stars distributed over the sky as references. On the basis of these measurements, one determines parameters of a correction function which is valid for the complete hemisphere. After correction a pointing accuracy of 0.01 degree is achieved.

astro-ph↗

arXiv1998

Changes of the cosmic-ray mass composition in the 10^{14} - 10^{16} eV energy range

Changes of the cosmic-ray mass composition at the `knee' of the cosmic-ray flux spectrum near 10^{15} eV energy are investigated using data from ten Cosmic Ray Tracking (CRT) detectors and the HEGRA air-shower array on La Palma, Canary Islands. The analysis is based on the angular distribution of muons in air showers. Results can be easily expressed in terms of of primary cosmic rays. We find a rise of below 10^{15} eV, consistent with direct measurements. Simple cosmic-ray composition models are presented which are fully consistent with our results as well as the JACEE flux and composition measurements and the flux measurements of the Tibet AS-gamma collaboration.

astro-ph↗

arXiv1997

Characteristics of the Multi-Telescope Coincidence Trigger of the HEGRA IACT System

The HEGRA--collaboration is operating a system of imaging atmospheric Cherenkov telescopes to search for sources of TeV-gamma-rays. Air showers are observed in stereoscopic mode with several telescopes simultaneously. To trigger the telescope system a versatile two-level trigger scheme has been implemented, which allows a significant reduction of the energy threshold with respect to single telescopes. The technical implementation of this trigger scheme and the performance of the trigger system are described. Results include the dependence of single- and multi-telescope trigger rates on the trigger thresholds, on the orientation of the telescopes, and on the type of the primary particle.

astro-ph↗