Ignition criteria for x-ray fast ignition inertial confinement fusion

Abstract

The derivation of the ignition energy for fast ignition inertial confinement fusion is reviewed and one-dimensional simulations are used to produce a revised formula for the ignition energy of an isochoric central hot-spot, which accounts for variation in the radius of the hot-spot rh as well as the density ρ. The required energy may be as low as 1 kJ when ρrh≈0.36 g cm−2, T≈20 keV, and ρ≥700 g cm−2. Although there are many physical challenges to creating these conditions, a possible route to producing such a hot-spot is via a bright source of non-thermal soft x-rays. Further one-dimensional simulations are used to study the non-thermal soft x-ray heating of dense DT and it is found to offer the potential to significantly reduce hydrodynamic losses as compared to particle driven fast ignition due to the hotspot being heated supersonically in a layer-by-layer fashion. A sufficiently powerful soft x-ray source would be difficult to produce, but line emission from laser-produced-plasma is the most promising option.

Formation of hot spots at end-on pre-compressed isochoric fuels for fast ignition

“…The formula is subsequently modified to the widely used form of E ig = 140 ( ρ 100 g cm −3 ) − 1.85 kJ by 2D simulations and the ignition window in the energy, power and intensity space is discussed [19]. Recent studies claim the ignition energy can be as low as 1 kJ when ρr h ≈ 0.36 g cm −2 , T ≈ 20 keV, ρ ⩾ 700 g cm −2 with non-thermal soft x-rays as the heating source [20,21]. Most previous studies on the isochoric fast ignition model assumed hot spots in the spherical center of the fuel.…”