Transport dynamics of a 19-MeV, 700-kA electron beam in a 10. 8-m gas cell

Measurements and modeling show that the 19-MeV, 700-kA HERMES III electron beam can be stably transported over 10.8 m in a 65-cm diam drift cell filled with low-pressure air or N{sub 2}. A pressure of 100{plus minus}20 Torr maximizes the energy transport efficiency at 71{plus minus}2.4%. At 100 Torr, the pressure is high enough to generate a net current sufficient to produce magnetic pinch forces that contain the radial oscillations of the beam, but low enough to prevent significant loss from inelastic collisions and beam instabilities. Comparison of the model results with the measurements show that the modeling can be used to predict qualitatively beam behavior in the cell.