Production of a New Generation of Silica Aerogel and its Application for the KEK B-factory Experiment

Low-refractive index silica aerogel is the most convenient radiator for threshold-type Cherenkov counters, which is used for particle identification in high-energy physics experiments. For the BELLE detector at the KEK B-Factory, we have produced about 2 m of hydrophobic silica aerogels of n = 1.01 1.03 using a new production method. The particle identification capability of the aerogel Cherenkov counters was tested and 3 σ pion/proton separation has been achieved at 3.5 GeV/c. Radiation hardness of the aerogels was confirmed up to 9.8 Mrad. Thanks to the improved transparency, aerogels prepared by the two-step method can be used as radiators for not only threshold-type, but also for Ring Imaging-type Cherenkov counters. The newly developed aerogels will be used extensively for particle identification devices in future high-energy physics experiments.