High-Resolution Laser-Pulse Method for Measuring Charge Distributions in Dielectrics

Abstract

A laser-induced pressure-pulse method for measuring the charge distribution in (10 to 100 \ensuremath{\mu}m thick) dielectric samples with a resolution of about 4 \ensuremath{\mu} m is described. A short ( ns) energetic light pulse from a neodymium-doped yttrium aluminum garnet laser is applied to a specially coated surface of the sample. The recoil due to ablation of material from the coating generates a pressure pulse (\ensuremath{\sim}2 ns) which propagates through the sample. The charge distribution is evaluated by measuring the electrode currents from 25- and 75-\ensuremath{\mu}m polymers charged with corona and electron-beam methods.