Development of transparent silica aerogel over a wide range of densities
  We have succeeded in developing hydrophobic silica aerogels over a wide range of densities (i.e. refractive indices). A pinhole drying method was invented to make possible producing highly transparent aerogels with entirely new region of refractive indices of 1.06-1.26. Obtained aerogels are more transparent than conventional ones, and the refractive index is well controlled in the pinhole drying process. A test beam experiment was carried out in order to evaluate the performance of the pinhole-dried aerogels as a Cherenkov radiator. A clear Cherenkov ring was successfully observed by a ring imaging Cherenkov counter. We also developed monolithic and hydrophobic aerogels with a density of 0.01 g/cm^3 (a low refractive index of 1.0026) as a cosmic dust capturer for the first time. Consequently, aerogels with any refractive indices between 1.0026 and 1.26 can be produced freely. 
Makoto Tabata, Ichiro Adachi, Yoshikazu Ishii, Hideyuki Kawai,   Takayuki Sumiyoshi, Hiroshi Yokogawa
physics.ins-det astro-ph.EP astro-ph.IM hep-ex nucl-ex