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 .