Fast-electron Maintaining a High Shock-Ignition Gain with a Significant Decrease in the Laser Pulse Energy

The effect of energy transfer by laser-accelerated fast electrons on thermonuclear gain of a shock-ignited ICF target at different powers and durations of the high-intensity part of the laser pulse (spike) responsible for igniting shock wave generation has been investigated on the basis of hydro-kinetic numerical simulations. The key result of these studies is that the fast-electron energy transfer is able to provide a great contribution to igniting shock wave pressure to maintain a high thermonuclear gain with a significant decrease in the energy of the igniting part of the laser pulse. Calculations were performed for the 2nd harmonic Nd-laser pulse in order to justify shock-ignition experiments at the Megajoule-class facility, which is currently under construction in Russia. Spike energy conversion to fast electron energy and its temperature were selected in the ranges, which are discussed in the literature. It has been found that fast electrons with a temperature of 50–70 keV, whose energy contains 20%–40% of spike energy, make such a large contribution to the pressure of the igniting shock wave that the gain factor retains its value of 70–80 with spike energy decrease by 1.5–2 times.