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The spiral line recirculating induction accelerator (SLIA) is a compact, lightweight electron accelerator, designed to produce high current (> 1 kA), high energy 50 MeV) and moderate to high quality electron beams with macropulse widths up to several micro-seconds. The SLIA is an open-ended spiral configuration in which the electron beam recirculates in independent transport lines 20) passing through a common ferrite core accelerating section with high gain/pass (- 10 MeV), The concept differs from the spiral line accelerator studied at NBS by Wilson and Leiss in that a toroidal field threads the transport lines for space charge confinement and suppression of instabilities. A strong focussing field (2, = 2 stellarator) is used in the bends to provide tolerance to field errors and an energy bandwidth desirable with high gain/pass. The accelerator can be designed to produce effective accelerating gradients in the 50 MV/m range for compactness and yet be amenable to long pulse trains at high current. A modulated pulse train is applied to the accelerating cells to provide an accelerating field while the beam is present and to reset the cores during the recirculation period of the beam. Reuse of the core material significantly reduces system weight. The modulated pulse traip (tens of MHz) is made feasible by developments in branched magnetic switching by Birx'.. By using the ferromagnetic induction technology developed at LLNL for ATA, the SLIA can provide the necessary input power to rapidly accelerate high current beams using state-of-the-art technology for relatively near-term applications. An experimental (PSI) and theoretical (SAIC) program is underway to investigate key physics issues regarding energy bandwidth, control of emittance growth, and suppression of the growth of collective instabilities. A nominal 1 MeV, 1 kA, 100 ns beam is injected into a transport line with a 180° bend of 0.5 m radius. The program is intended to provide the information required for scaling to a multipass induction cavity experiment to study the beam breakup instability and complete a proof-of-principle demonstration.
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