# Developing a silica aerogel radiator for the HELIX ring-imaging Cherenkov system

## TL;DR

This paper details the successful fabrication and initial testing of silica aerogel Cherenkov radiators for the HELIX cosmic-ray detector, demonstrating promising optical quality and suitability for balloon-borne experiments.

## Contribution

It introduces a new production process for high-quality silica aerogel tiles specifically designed for Cherenkov detectors in cosmic-ray observation.

## Key findings

- 40 out of 48 tiles are crack-free
- 8 of 16 tiles are flight-qualified based on optical tests
- Water-jet trimming successfully adapted tiles for support structure

## Abstract

This paper reports the successful fabrication of silica aerogel Cherenkov radiators produced in the first batches from a 96-tile mass production performed using pin-drying technique in our laboratory. The aerogels are to be used in a ring-imaging Cherenkov detector in the spectrometer of a planned balloon-borne cosmic-ray observation program, HELIX (High Energy Light Isotope eXperiment). A total of 36 transparent, hydrophobic aerogel tiles with a high refractive index of 1.16 and dimensions of 10 cm $\times $ 10 cm $\times $ 1 cm will be chosen as the flight radiators. Thus far, 40 out of the 48 tiles fabricated were confirmed as having no tile cracking. In the first screening, 8 out of the first 16 tiles were accepted as flight-qualified candidates, based on basic optical measurement results. To fit the aerogel tiles into a radiator support structure, the trimming of previously manufactured prototype tiles using a water-jet cutting device was successful.