Beam matter interaction physics for fast ignitors

The fast ignitor scheme for achieving inertial fusion energy precompresses the DT fuel to more than 1000 times the solid state density with nanosecond laser pulses. It then employs a picosecond 10-100-PW laser pulse to deposi t with very high efficiency the energy necessary to achieve the ignition te mperature of approx. 4 keV. In this way the necessary driver energy for ine rtial fusion energy reactors is reduced from the megajoule level to the 100 -kJ level. In this article, we present results relevant to the development of the fast ignitor scheme that have been achieved in recent years by Austr alian teams in collaboration with international teams. The topics that are specifically addressed are: (1) forces and relativistic mechanisms of laser interaction with the electrons in the intense picosecond beams; (2) electr on and ion emission from the focused beam into the precompressed plasma, in cluding double layer effects and collective stopping power; and (3) the ene rgy of the picosecond beam, which when nearly uniformly deposited into the precompressed DT-fuel can achieve the conditions for high-gain volume ignit ion. Positive results are derived for volume ignition scheme from considera tions of recent high neutron gain laser fusion experiments. (C) 1999 Publis hed by Elsevier Science S.A. All rights reserved.