July 29, 2015 to August 6, 2015
World Forum
Europe/Amsterdam timezone

The Optical system for the Large Size Telescope of the Cherenkov Telescope Array

Aug 1, 2015, 3:30 PM
Mississippi Foyer (World Forum)

Mississippi Foyer

World Forum

Churchillplein 10 2517 JW Den Haag The Netherlands
Board: 87
Poster contribution GA-IN Poster 2 GA


Dr Masaaki Hayashida (Institute for Cosmic-Ray Research, University of Tokyo)


The Large Size Telescope (LST) of the Cherenkov Telescope Array (CTA) is designed to achieve a threshold energy of 20 GeV. The LST optics is composed of one parabolic primary mirror 23 m in diameter and 28 m focal length. The reflector dish is segmented in 198 hexagonal, 1.51 m flat to flat mirrors. The total effective reflective area, taking into account the shadow of the mechanical structure, is about 368 m$^2$. The mirrors have a sandwich structure consisting of a glass sheet of 2.7 mm thickness, aluminum honeycomb of 60mm thickness, and another glass sheet on the rear, and have a total weight about 47 kg. The mirror surface is produced using a sputtering deposition technique to apply a 5-layer coating, and the mirrors reach a reflectivity of ~94% on average at 370 nm. The mirror facets are actively aligned during operations by an Active Mirror Control system, using actuators, CMOS cameras and a reference laser. Each mirror facet carries a CMOS camera, which measures the position of the light spot of the optical axis reference laser on the target of the telescope camera. The two actuators and the universal joint of each mirror facet are respectively fixed to three neighboring joints of the dish space frame, via specially designed Interface Plate. In this contribution, we will overview the design and validation of each component in the optical system for the LST prototype.
Registration number following "ICRC2015-I/" 81
Collaboration CTA

Primary author

Dr Masaaki Hayashida (Institute for Cosmic-Ray Research, University of Tokyo)


Achim Vollhardt (Universitaet Zuerich (CH)) Akira Okumura (Nagoya University) Arno Gadola (Universität Zürich) Christopher Jablonski (MPI for Physics) Dieter Horns (Univ. Hamburg) Hideaki Katagiri (Ibaraki University) Holger Wetteskind (Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut) (D) Koji Noda (Max-Planck-Institute for Physics) Masahiro Teshima (Max-Planck-Institute) Michi Chikawa (Unknown) Mika Kagaya (Iberaki University) Momoko Ogino (ICRR) Norihito CHO (Ibaraki University) Robert Stadler (MPI for Physics) Satoshi Fukami (ICRR) Stefan Steiner (Universitaet Zuerich (CH)) Takayuki Saito (Kyoto University) Tatsuo Yoshida (Ibaraki University) Ulisses Barres de Almeida (CBPF) Ulrich Straumann (Universitaet Zuerich (CH)) Yoshitaka Hanabata (ICRR) tokonatsu yamamoto (Konan University)

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