Absorption and scattering lengths of high density silica aerogels with n = 1.07

Charged particle identification at the PANDA experiment will be performed over a wide range of momenta by Čerenkov detectors. One option to identify higher momentum charged particles under small polar angles could be the use of silica aerogels as radiator. Simultaneously, an aerogel Čerenkov counter is being designed for the Kaos spectrometer at the Mainz Microtron MAMI for the discrimination between kaons and pions of momenta ≥ 1GeV/c. For the simulation of such detectors, the optical properties of the aerogel are needed as input data. We have measured the wavelength dependence of the transmittance (T ) and reflectivity (R) of high density aerogel with n ≈ 1.07, made by Chiba U. in Japan. The characteristic absorption length (Λabs) and scattering length (Λscat) were extracted by fitting Λabs and Λscat to T .