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

• The Belle II A-RICH counter requires transparent silica aerogel Cherenkov radiators.
• Required refractive index of hydrophobic aerogel tiles is approximately 1.05.
• Mass production of large-area (18 cm × 18 cm × 2 cm), crack-free aerogel tiles is vital.
• A method for producing aerogel tiles satisfying all requirements is established.
• Crack-free aerogel tiles are ensured by pressure control in the supercritical drying.

This study presents the development of large-area (18 cm × 18 cm × 2 cm), high refractive index (n ∼ 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 (scCO2) 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.

Figure optionsDownload as PowerPoint slide