Recirculating induction accelerators as drivers for heavy ion fusion*

Abstract

A two-year study of recirculating induction heavy ion accelerators as low-cost driver for inertial-fusion energy applications was recently completed. The projected cost of a 4 MJ accelerator was estimated to be about $500 M (million) and the efficiency was estimated to be 35%. The principal technology issues include energy recovery of the ramped dipole magnets, which is achieved through use of ringing inductive/capacitive circuits, and high repetition rates of the induction cell pulsers, which is accomplished through arrays of field effect transistor (FET) switches. Principal physics issues identified include minimization of particle loss from interactions with the background gas, and more demanding emittance growth and centroid control requirements associated with the propagation of space-charge-dominated beams around bends and over large path lengths. In addition, instabilities such as the longitudinal resistive instability, beam-breakup instability and betatron-orbit instability were found to be controllable with careful design.

Magnetic core studies at LBNL and LLNL

“…A recirculating induction accelerator passes the beam through each core many times, reducing the mass of cores required. [3] For a recirculator, core optimization emphasizes minimizing core energy losses more than minimizing initial cost.…”

Technologies for Advanced Induction Accelerators

“…A 1991 study 1 showed that a recirculating ion beam accelerator (or recirculator) would be a promising candidate for a cost-effective driver for inertial fusion energy. Its promise is derived from the fact that the beam passes multiple times through each accelerating component.…”

Methods used in WARP3d, a three-dimensional PIC/Accelerator code

“…or "recirculator," offers the prospect of reduced cost relative to a conventional linear accelerator because the accelerating and focusing elements are re-used many times per shot (7). A small recirculator is being developed at LLNL to explore the beam dynamics of a HIF driver in a scaled manne~the key dimensionless parameters that characterize the beam are similar lo those of a driver-scale ring but the physical scale is much smaller (8).…”