Large-area silica aerogel for use as Cherenkov radiators with high refractive index, developed by supercritical carbon dioxide drying

TL;DR

This paper reports the development of large, high-refractive-index silica aerogel tiles with improved cracking resistance, suitable for Cherenkov radiators in next-generation particle physics detectors, achieved through optimized supercritical CO2 drying.

Contribution

It introduces a new method for producing large, crack-free silica aerogel tiles with high refractive index for Cherenkov detectors, including a scalable mass-production process.

Findings

Crack-free aerogel tiles with high optical quality achieved.

Successful mass production of uniform aerogel tiles.

Tiles meet optical and hydrophobic specifications.

Abstract

This study presents the development of large-area (18 $\times $ 18 $\times $ 2 cm$^3$), high refractive index ($n \sim $1.05) hydrophobic silica aerogel tiles for use as Cherenkov radiators. These transparent aerogel tiles will be installed in a Cherenkov detector for the next-generation accelerator-based particle physics experiment Belle II, to be performed at the High Energy Accelerator Research Organization (KEK) in Japan. Cracking has been eliminated from the prototype aerogel tiles by improving the supercritical carbon dioxide (scCO$_2$) extraction procedure when drying the wet gel tiles. Finally, a method of mass-producing aerogel tiles for the actual detector was established. It was confirmed that the experimentally manufactured aerogel tiles meet the required optical and hydrophobic characteristics and have a uniform tile density.