IBEX magnetic field extraction and propagation experiments of intense high-energy electron beams

Abstract
We have investigated the extraction and propagation of intense relativistic electron beams from an immersed foilless diode into a magnetic field-free region. It was established experimentally that under matching conditions, the extracted beam propagates into and through the axially varying magnetic field region with minor perturbation of the equilibrium. The independent variables of the experiment were beam current, beam radius, magnetic field strength, and gas pressure in the field-free region. The accelerator used was IBEX. [J. J. Ramirez, J. P. Corley, and M. G. Mazarakis, in Proceedings of the Fifth International Conference on High-Power Particle Beams, San Francisco (Physics International, San Leandro, CA, 1983), p. 256.] The propagation of the extracted beam was studied up to 60 cm downstream from the extraction foil. A strong, fast growing filamentation instability was observed after extraction. Time-resolved measurements of the beam current, net current, and current distribution were performed by using segmented Faraday cups. Time-integrated measurements of beam rotation and emittance were also recorded. The observed beam parameters and equilibrium radii before and after extraction are compared with theory and numerical calculations.

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