Monitoring of absolute mirror alignment at COMPASS RICH-1 detector

M. Alexeev, R. Birsa, F. Bradamante, A. Bressan, M. Chiosso, P. Ciliberti, S. Dalla Torre, O. Denisov, V. Duic, A. Ferrero, M. Finger, M. Finger, J. Ch Gayde, M. Giorgi, B. Gobbo, S. Levorato, A. Maggiora, A. Martin, G. Menon, D. PanzieriG. Pesaro, J. Polak, E. Rocco, G. Sbrizzai, P. Schiavon, M. Slunecka, F. Sozzi, L. Steiger*, M. Sulc, S. Takekawa, F. Tessarotto

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The gaseous COMPASS RICH-1 detector uses two spherical mirror surfaces, segmented into 116 individual mirrors, to focus the Cherenkov photons onto the detector plane. Any mirror misalignment directly affects the detector resolution. The on-line Continuous Line Alignment and Monitoring (CLAM) photogrammetry-based method has been implemented to measure the alignment of individual mirrors which can be characterized by the center of curvature. The mirror wall reflects a regular grid of retroreflective strips placed inside the detector vessel. Then, the position of each mirror is determined from the image of the grid reflection. The images are collected by four cameras. Any small mirror misalignment results in changes of the grid lines' positions in the image. The accuracy limits of the CLAM method were checked by laser interferometry and are below 0.1 mrad.

Original languageEnglish
Pages (from-to)208-211
Number of pages4
JournalNuclear Instruments and Methods in Physics Research. Section A
Volume766
DOIs
Publication statusPublished - 1 Dec 2014

Bibliographical note

RICH2013 Proceedings of the Eighth International Workshop on Ring Imaging Cherenkov Detectors Shonan, Kanagawa, Japan, December 2-6, 2013

Keywords

  • Cherenkov radiation
  • Mirror alignment
  • Photogrammetry
  • RICH

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