Charge neutralisation processes for a rotating relativistic electron beam

Abstract

An experiment was carried out to study the initial phase of propagation of a rotating relativistic electron beam, where charge neutralisation processes are important. Wall probes were used to measure the beam potential as a function of axial distance from the cusp, external magnetic field and background pressure. A potential well as found to be formed in the central region of the chamber. The well was found to vary with the external magnetic field and was maximum at B₀=200 gauss. From the measurement of the potential, the charge neutralisation factor was estimated. External magnetic field was found to play a dominant role in the charge neutralisation process. Higher axial magnetic field was found to provide better radial force balance for the rotating beam during the charge neutralisation phase.