Effect of self fields on the dynamics of relativistic electron beams in a cusp magnetic field

Abstract

Experimental measurements using a long pulse relativistic electron beam of about 800 ns duration and peak energy of about 200 keV were used. Numerical calculations, for the determination of the trajectories of the beam electrons, were also carried out using a model for the self-fields based on measurements. The beam diamagnetic field, radial loss at the cusp etc. were calculated and compared with the experimental results. Axial beam diamagnetism was observed in the precusp region. The external cusp field was seen to be drastically modified by the self fields. The peak radial loss of beam electrons in the cusp region was seen to occur along the shifted cusp plane. Total radial loss in the cusp region was seen to depart from the single particle value for self fields comparable to the external field. The postcusp beam diamagnetism was also seen to be enhanced over the value estimated from the single particle description in the range of beam self fields comparable to and larger than the external field.