Determination of charge distribution volume in electron irradiated insulators by scanning electron microscope

The scanning electron microscope mirror image method is developed to measure the charge distribution volume in insulators. An electrostatic potential expression is derived by assuming the dipolar approximation and hemispheroid distribution. Dielectric samples with different relative permittivities are employed in charging experiments to justify our approach. The proposed method is employed to measure the radius of the charge distribution volume in polymethylmethacrylate samples irradiated by electron beams with energy ranging from 25 to 39 keV. Experimental results achieved are in good agreement with those obtained through the use of other experimental techniques and Monte Carlo simulation. The strength of the present method is in its ability to quantitatively give the total trapped charge and its distribution in the electron irradiated insulators in a single experiment.