Transport efficiency studies for light-ion inertial confinement fusion

Abstract

The proposed Laboratory Microfusion Facility (LMF) will require {ge} 10 MJ of 30 MeV lithium ions to be transported and focused onto high-gain, high-yield inertial confinement fusion targets. The light-ion LMF approach used a multimodular system with individual ion extraction diodes as beam sources. Several transport schemes are being considered to deliver the individual ion beams to the centrally located target. Previous work examined the effect of time-of-flight bunching on energy transport efficiency, {eta}{sub t}, under realistic constraints on diode operation, beam transport, and packing. Target design considerations suggest that the instantaneous power efficiency, {Gamma}{sub t}, be maximized near peak power. Because of time-of-flight bunching, peak power occurs at the end of the power pulse for LMF designs. This work examined the effect of power efficiency tuning on {eta}{sub t} for three transport schemes. Results indicate that tuning the power pulse to maximize {Gamma}{sub t}, at about three-quarters through the pulse provides high power efficiency at the end of the pulse while still maintaining high {eta}{sub t}. In addition to power efficiency tuning, effects on {eta}{sub t} from variations of the diode impedance model and the diode voltage waveform are also examined.