Accession Number:

ADA142822

Title:

Longitudinal and Transverse Instabilities in a High Current Modified Betatron Electron Accelerator.

Descriptive Note:

Interim rept.,

Corporate Author:

NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s):

Report Date:

1984-05-17

Pagination or Media Count:

25.0

Abstract:

In this paper we derive a general dispersion relation which describes the longitudinal and transverse instabilities on an intense non neutral electron beam in a modified betatron field configuration. In a modified betatron, the usual betatron fields are supplemented by a strong toroidal stabilizing magnetic field. The negative mass kink, longitudinal resistive wall and transverse resistive wall instabilities have been analyzed in the new field configuration for an intense, non neutral, confined electron ring. Our model includes self field effects as well as induced field effects due to the image charges and currents on the toroidal chamber walls. The electron ring, which is assumed to have an energy spread, is taken to be located near the center of a toroidal chamber of finite conductivity. All the instabilities examined here are shown to significantly reduced by the presence of the strong toroidal magnetic field. In the limit of low beam current and no toroidal magnetic field our results reduce to the usual expressions. We find an unstable hybrid mode of oscillation which is a coupled azimuthal and longitudinal mode and exists at beam energies below the transition energy. The negative mass kink instability associated with and ultra high current approximately 10 kA modified betatron electron accelerator is analyzed and evaluated in some detail. Growth rate curves are given for various ranges of system parameters, including electron beam energy spread. It is found that with a moderate energy spread on a 10 kA injected electron beam, the negative mass kink instability can be stabilized.

Subject Categories:

  • Particle Accelerators

Distribution Statement:

APPROVED FOR PUBLIC RELEASE