Mirror system of the RICH detector of the NA62 experiment

Abstract

A: A large RICH detector is used in NA62 to suppress the muon contamination in the charged pion selection by a factor 100 in the momentum range between 15 and 35 GeV/c. The detector consists of a 17 m long tank (vessel), filled with neon gas at atmospheric pressure. Cherenkov light is reflected by a mosaic of 20 spherical mirrors with 17 m focal length, placed at the downstream end, and collected by 1952 photomultipliers (PMTs) placed at the upstream end. In this paper the characterization of the mirrors before installation and the mirror support system are described. The mirror installation procedure and the laser alignment are also illustrated. K: Cherenkov detectors; Large detector systems for particle and astroparticle physics; Particle identification methods

NA62 RICH performance: measurement and optimization

“…To provide the best detector performance, RICH mirrors must be aligned as precisely as possible. The accuracy of the laser alignment performed during the installation is ∼500 μrad in terms of mirror orientation [2]. A better precision is achieved by using reconstructed tracks.…”

“…It identifies charged particles from kaon and pion decays and provides the reference time for the L0 trigger. The design and commissioning of the RICH detector are summarized in [2]. The detector layout is shown in Fig.…”

“…The RICH mirror system [2] consists of 18 hexagonal (350 mm side) and two semi-hexagonal mirrors, the latters placed in the central part. The focal length of all mirrors is = 17 m. Mirror orientation is provided by two stabilizing aluminium ribbons connected to the mirror at one end and to a piezo motor at the other end.…”

Precise Mirror Alignment and Basic Performance of the RICH Detector of the NA62 Experiment at CERN

“…The RICH detector is shown in figure 2. The core part of the detector is the mirror system [2]. It consists of 18 hexagonal (350 mm side) and two semi-hexagonal mirrors which are placed in the central part and cut to accomodate the beam pipe.…”

“…for each mirror with the accuracy of ∼500 µrad in terms of mirror orientation [2]. For a more precise alignment using reconstructed tracks a dedicated procedure has been developed.…”