Study of transparent silica aerogel with high refractive index

Optical quality of silica aerogel with refractive index values greater than 1.06 has been remarkably improved by introducing a new fabrication technique, called “pinhole drying method”. This technique allows to produce ultra-high index aerogel up to 1.26 with excellent transparency. The transmission length of the aerogel tile with index of 1.06, obtained with the new method, was found to be doubled compared to that with conventional production. To evaluate the optical performance as a Cherenkov radiator, a prototype RICH counter was built and a test beam experiment was carried out. A clear Cherenkov ring has been observed and significant increase in the detected light yield has been confirmed.