Impact ionization from silica aerogel

Silica (SiO2) aerogel samples with densities of 0.008, 0.05, and 0.13 g/cm(3) were exposed to iron microparticles having speeds of v = 3-83 km/s. Negative and positive charge carriers from the impact ionization were separated by an electric field and collected. The collected charges, Q(-) and Q(+), normalized to the mass, m, of the projectile as a function of v are presented. (C) 1997 Published by Elsevier Science Ltd.