Determination of spatial energy deposition in e-beam-pumped laser cells by pressure measurements

Abstract

A significant fraction of the energy deposited by electron beams in gases results in heating of the gas, which causes a transient pressure rise in the cell. When the pressure rise is uniform across the height and length of the cell, but varies across the depth, one-dimensional unsteady flow theory applies. Then a fast-response pressure measurement at the back wall of the cell can be interpreted to give the initial spatial pressure distribution. We describe the relationship between time and space coordinates for both low and medium levels of excitation in the cell. Experiments are discussed which illustrate the application of this technique. Analytical predictions using the SANDYL 3-D electron scattering code show basic agreement with the experimental results, but indicate some areas for improvements in the calculations. Intermediate-response pressure measurements are shown to be inadequate to determine the local deposition when the deposition varies markedly across the cell.