Preparation of Silica Aerogel and Its Application in the Tass0 Cerenrov Counters

The Cerenkov counters in TASS0 consist of 3 elements, one filled with aerogel and two with Freon 114 and CO2. The 1700 liters of aerogel cover an area of 11.8m2 with a thickness of 13.5 to 18 cm. Most cells are filled with an index of refraction between 1.023 and 1.026. In a running period of 2 months after installation = 3.9 + 0.2 photoelectrons were observed. The mean valu: over 17 months is = 3.0 + 0.2. The aerogel was manufactured at DES9 with a rate of up to 90 l/week. The dimensions of the samples are 17 x 17 x 2.3 cm3. The refractive index of 986 pieces with n around 1.025 is distributed with u = 0.0013. The transmission length for light with 12 438 nm is A = 2.64 cm with aA = 0.22 cm. For 100 samples with n = 1.017, A = 3.8 with op = 0.6 was found. In recent investigations the transmission length for aerogel with n = 1.025 could be improved to h = 5.1 cm.