Modulators for heavy-ion recirculating induction linacs

We have begun a two-year study on the problem of designing high-power pulse modulators for the induction cavities of a recirculating heavy-ion linac driver for inertial fusion. Recent studies have shown the potential of a recirculator for major cost reduction. However, important issues exist including beam stability and control, and severe tolerances. We are addressing the need for efficient, cost-effective modulators. Our example conceptual design uses a 3 ms, linearly rising dipole field and constant energy/turn for 96 turns. The modulator pulses must vary in duration and spacing by a factor of 4. For each 264 kV module we propose to use 50–100 Metglas cores, each driven by a number recently developed, solid-state, on-off switches. Several circuit methods are being studied, including delayed triggering of groups of switches and selective charging of pulse networks. Here we report on initial circuit studies and on preliminary experiments to characterize promising switches and related components. Plans are underway to assemble a scaled accelerating module and simulate an ion beam with a separte high-voltage modulator.