Transport and pulse shaping of relativistic electron beam in low-pressure gases

An equation of motion for the transport of a relativistic electron beam in low-pressure gas in the presence of an external magnetic field has been obtained taking into account self-fields of the beam and charge neutralization. A simplified form of the equation applicable for the case without magnetic field has been integrated using the fourth-order Runge-Kutta method to study the transport of a 1 MeV, 20 kA, 50 ns beam in various gases in the pressure range 10-3 to 1 torr. The results of the charge transport calculations indicate beam front erosion and pulse shortening at low pressures. At higher pressures in the range 10-1 to 1 torr, full charge neutralization occurs and the beam pulse is transported without distortion. The pulse shape and electron energy distribution for transport in argon are given as a function of pressure. (author)