Laser fusion with nonlinear force driven plasma blocks: Thresholds and dielectric effects

Anomalous interaction of picosecond laser pulses of terawatt to petawatt power is due to suppression of relativistic self-focusing if prepulses are cut-off by a contrast ratio higher than 10 8 , resulting in quasi-neutral directed plasma blocks with deuterium tritium ion current densities above 10 11 A/cm 2 . This is still not high enough for ignition of solid-state density deuterium tritium because the energy flux density E * has to be higher than the threshold of 4 ×10 8 J/cm 2 obtained within the theory of Chu (1972). A revision of this evaluation shows a reduction of this threshold by a factor 20 if the later discovered inhibition factors for thermal conduction because of double layer effects as well as the shorter stopping lengths of the alpha particles due to collective effects are taken into account. Under these relaxed conditions, the parameters of nonlinear force generated blocks of dielectrically increased thickness for deuterium tritium ignition with directed ions of energies near the 80 keV resonances are discussed.