Transparent tiles of silica aerogels for high-energy physics

TL;DR

This paper reviews recent technological advances in producing transparent silica aerogel tiles with controlled refractive indices for use as photon radiators in Cherenkov counters, enhancing particle detection in high-energy physics experiments.

Contribution

It introduces new fabrication techniques for large-area, crack-free silica aerogel tiles with improved transparency and tunable refractive indices for scientific instrumentation.

Findings

Enhanced transparency of silica aerogels with controlled refractive indices

Development of crack-free large-area aerogel tiles

Applications in high-energy physics detectors

Abstract

Silica aerogels are important to be used as photon radiators in Cherenkov counters for high-energy-physics experiments because of their optical transparency and intermediate refractive indices between those of gases and liquids or solids. Cherenkov counters that employ silica aerogels as radiators and photodetectors are often used to identify subatomic charged particles (e.g., electrons, protons, and pions) with momenta on the order of sub-GeV/$c$ to GeV/$c$; they are also used to measure particle velocities in accelerator-based particle- and nuclear-physics experiments and in space- and balloon-borne experiments in the field of cosmic-ray physics. Recent studies have demonstrated that it is important for the design of Cherenkov counters that the transparent silica-aerogel tiles comprise solid material with recently improved transparency and a refractive index that can be controlled between 1.003 and 1.26 by varying the bulk density in the range of 0.01$-$1.0 g/cm$^3$. Additionally, a technique for fabricating large-area silica-aerogel tiles without cracking has been developed. In this chapter, we describe advances in the technologies for producing silica aerogels with high optical performances to be used in scientific instruments. We further discuss the principles underlying the operation of detectors based on the Cherenkov effect. We also review applications of silica aerogels in specific high-energy-physics experiments.