FIREX Project and Effects of Self-generated Electric and Magnetic Fields on Electron Driven Fast Ignition

Kunioki Mima, A. Sunahara, Hiroyuki Shiraga, H. Nishimura, H. Azechi, T. Johzaki, H. Nagatomo, C. Garcia, P. Veralde, A. Sen, S. Sharma, P. N. Guzdar
Fast ignition is a new scheme in láser fusión, in which higher energy gain with a smaller láser pulse energy is expected. A cone target has been introduced for realizing higher coupling efficiency. At ILE, Osaka University, a láser with four beams and a total output of lOUps -1 , láser for fast ignition experiment (LFEX), has been constructed and we have carried out an integrated experiment with one beam of the LFEX. Through experiments it was found that the coupling efficiency is degraded when
more » ... the láser pre-pulse is not sufficiently small. Namely, the main pulse is absorbed in the long-scale pre-plasma produced by the pre-pulse and the hot electrón energy is higher than that for a clean pulse. Furthermore, the distance between the hot electrón source and the core plasma is large. Henee, we are exploring how to overeóme the pre-pulse effects on the cone target. In this paper it is proposed that a thin foil covers the láser entrance of the cone to mitígate the pre-plasma and a double cone reduces the loss of highenergy electrons from the side wall of the cone. The simulations indicate that a higher coupling efficiency is expected for the double cone target with a thin foil at the láser entrance. Namely, the pre-pulse will be absorbed by the foil and the electromagnetic fields generated on the surface of the inner cone will confine high-energy electrons.
doi:10.1063/1.3526161 fatcat:wz2vhc7zonb2fexyyxs62arbfa