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Proceedings Paper

Stability Of Compact Recirculating Accelerators
Author(s): Thomas P. Hughes; Brendan B. Godfrey
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Paper Abstract

Beam stability in high-current recirculating accelerators using magnetic beam transport is investigated. We focus on three instabilities which have the potential for causing beam disruption: the three-wave, negative-mass and beam breakup instabilities. The three-wave instability is a parametric instability caused by strong-focusing fields like the helical quadrupole in the SLIA (Spiral Line Induction Accelerator). We have obtained approximate analytic expressions for the growth rate and the convection velocity of this instability. A simple numerical simulation code E3WAVE has been written to model the linear behavior of the instability. Its results confirm the analytic results in the appropriate limits. We have used E3WAVE to make predictions for the SLIA experiments presently under way. We also have investigated the short-wavelength negative-mass instability modes, which interact resonantly with cavity modes of the drift-tube. Particle simulations show that the main nonlinear effect of the instability is to create an energy spread on the beam, rather than leading directly to current loss. We have made progress in minimizing the beam breakup instability without resorting to ion focusing. By adding ferrite in the induction gaps to increase damping, and by using gaps that are considerably wider than usual, with correspondingly higher voltage, growth can be reduced to several e-foldings during a typical acceleration cycle.

Paper Details

Date Published: 25 July 1989
PDF: 6 pages
Proc. SPIE 1061, Microwave and Particle Beam Sources and Directed Energy Concepts, (25 July 1989); doi: 10.1117/12.951830
Show Author Affiliations
Thomas P. Hughes, Mission Research Corporation (United States)
Brendan B. Godfrey, Mission Research Corporation (United States)

Published in SPIE Proceedings Vol. 1061:
Microwave and Particle Beam Sources and Directed Energy Concepts
Howard E. Brandt, Editor(s)

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