Electron-beam Calibration of Aerogel Tiles for the HELIX RICH Detector

TL;DR

This paper details the calibration process of aerogel radiator tiles for the HELIX RICH detector using an electron beam, ensuring precise refractive index measurements for accurate cosmic-ray particle identification.

Contribution

It introduces a novel calibration apparatus and method to measure the refractive index of aerogel tiles with high precision for the HELIX RICH detector.

Findings

Achieved refractive index measurement precision of O(10^{-4})

Validated calibration method with electron beam tests

Ensured uniformity of aerogel tiles for detector performance

Abstract

The HELIX cosmic-ray detector is a balloon-borne instrument designed to measure the flux of light isotopes in the energy range from 0.2 GeV/n to beyond 3 GeV/n. It will rely on a ring-imaging Cherenkov (RICH) detector for particle identification at energies greater than 1 GeV/n and will use aerogel tiles with refractive index near 1.15 as the radiator. To achieve the performance goals of the experiment it is necessary to know the refractive index and its position dependence over the lateral extent of the tiles to a precision of O(10$^{-4}). In this paper we describe the apparatus and methods developed to calibrate the HELIX tiles in an electron beam, in order to meet this requirement.