Manipulation of High-Current Pulses for Heavy-Ion Fusion

For efficient induction-driven heavy-ion fusion, the current profile along a pulse must be modified in a non-selfsimilar manner between the accelerator and the target. In the accelerator, the pulse should have a duration of at leaat !io ns in order to make efficient use of the induction cores, and the current should by nearly uniform along the pulse to minimize the aperture. In contrsst, the optimal current proiile on target consists of a main pulse of about 10 ns preceded by a longer low-current “foot.” This pulse-shape manipulation must be carried out at the final pulse energy (5-10 GeV for 200 arm ions) in the presence of a large nonlinear longitudinal space-charge field. A straightforward method is presented here for doing the required pulse shaping. Induction-cell voltages are generated using idealized beam profiles both in the accelerator and on target, and they are verified and checked for error sensitivity using the fluid/envelope code CIRCE.