Stable beam transport may be the limiting factor in the development of a new generation of high current linear induction accelerators. In this paper we analyze several important beam stability topics, including radial oscillations induced by an accelerating gap, the diocotron, resistive wall, and cyclotron maser instabilities, and the transverse beam breakup and imge displacement instabilities. At present image displacement appears to represent the most serious limitation to high current beam transport in linear accelerator structures.

Radial oscillations of hollow, relativistic electron beams have been observed on Sandia’s RADLAC I, a multistage high-current linear induction accelerator. These oscillations, which arise because the presence of the accelerating gaps prevents radial force balance, can be responsible for poor beam quality and low current-transport efficiency. The method of magnetic field shaping to suppress oscillations is investigated. Two analytical models are formulated to derive nonuniform fields necessary to maintain force balance in a single-gap geometry. Particle code simulations have been made to test beam propagation in contoured fields. Field shaping does suppress oscillations and is not sensitive to fluctuations in beam and gap parameters.

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