Fast-electron maintaining a high shock-ignition gain with a significant decrease in the laser pulse energy

Abstract

The effect of energy transfer by laser-accelerated fast electrons on thermonuclear gain of a shock- ignited ICF target at the different power and duration of 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 laser pulse. Calculations were performed for the 2nd harmonic Nd-laser pulse in order to justify shock-ignition experiments on MJ-class facility, which is under construction in Russia now. 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 so large contribution to the pressure of igniting shock wave that the gain factor retains its value of 70-80 with spike energy decrease by 1.5-2 times.

Role of hot electrons in shock ignition constrained by experiment at the National Ignition Facility

“…The deleterious effect of preheat 27 outweighs the benefit of drive support for hot electrons with a population temperature higher than 30keV or mono-energetic hot electron populations with an energy exceeding ∼ 50keV (target dependant). Conversely, there is evidence that kinetically modelled hot-electrons can provide benefit to implosion performance across a broad range of population temperatures [28][29][30] (up to 70keV). Within these simulations the LPI scattered light energy fraction is not explicitly related to the LPI hot-electron energy fraction which may explain the difference in impact of hot electrons compared to those that use simplified LPI models.…”