Beam physics design strategy for a high-current rf linac

Abstract

The high average beam power of an rf linac system for transmutation of nuclear waste puts very stringent requirements on beam quality and beam control. Fractional beam losses along the accelerator must be kept at extremely low levels to assure ‘‘hands‐on’’ maintenance. Hence, halo formation and large‐amplitude tails in the particle distribution due to beam mismatch and equipartitioning effects must be avoided. This implies that the beam should ideally be in near‐perfect thermal equilibrium from injection to full energy‐in contrast to existing rf linacs in which the transverse temperature, T⊥, is higher than the longitudinal temperature, T∥. The physics and parameter scaling for such a system will be reviewed using the results of recent work on high‐intensity bunched beams. A design strategy for a high‐current rf linac with equilibrated beam will be proposed.