Energy and wavelength scaling of shock-ignited inertial fusion targets

Abstract

In inertial fusion shock ignition, separation of the stages of fuel compression and hot spot creation introduces some degree of design flexibility. A lower implosion velocity can be compensated for by a more intense ignition pulse. Flexibility increases with target (and driver) size and allows for a compromise between energy gain and risk reduction. Having designed a reference ignition target, we have developed an analytical model for (up)-scaling targets as a function of laser energy, while keeping under control parameters related to hydro-and plasma instabilities. Detailed one-dimensional simulations confirm the model and generate gain curves. Options for increasing target robustness are also discussed. The previous results apply to UV laser light (with wavelength λ = 0.35 µm). We also show that our scaling model can be used in the design of targets driven by green laser light (λ = 0.53 µm).

Influence of laser induced hot electrons on the threshold for shock ignition of fusion reactions

“…First, we investigate in Sec. IV a pure-DT design from the HiPER project 25 . This target is expected to see its performances significantly degraded by the presence of LPI-HEs, as the DT is not an efficient material to stop the LPI-HE flux.…”

Low initial aspect-ratio direct-drive target designs for shock- or self-ignition in the context of the laser Megajoule

“…An exhaustive description of different scaling is done in [97] where discrepancy is highlighted between models and numerical fits concerning the ignition criteria: J s = (gR)hTh = const or J s a v. The self-consistent model developed in [97] integrating the return shock propagation in the shell and the change of shell adiabat at stagnation leads to the following minimum kinetic energy scaling for ignition: 39 , similar to the one used in recent literature [119] and proposed by Hermann etal [117]: E Kmin a v -5.89±o.i2 a i.88±o.o5 p -o.77±o.i2_ Inthese scalings, ignition is not occurring at the same energy than Ek^ but when target gain G = £xh/-Et.min = 1 (G is defined as the ratio of the capsule thermonuclear yield £xh over the capsule absorbed energy E^mm), achieved at lower kinetic energy than Ek,ihr-Thus, figure 13 compares these energies for both A.…”

Focus on high energy density physics

“…Despite its limitations, hydrodynamic modeling can provide an important understanding of some aspects of HED systems. In the present collection, we see this in two papers directly motivated by inertial confinement fusion, one of which concerns the use of lowdensity foams to create smoother pressure on the surface of a fusion target [14], and the other of which directly addresses one of the approaches to the ignition of fusion targets, known as shock ignition [15]. Other papers concern the behavior of flowing material, in which the kinetic and electromagnetic behavior of the particles is important [16] and in which collisionless dynamics becomes dominant [17] and might be observable in experiments [18].…”

“…Magnetic fields are ubiquitous in HED systems, and several of the above papers concern dynamical systems in which they can become important [5,6,15,16,18]. Three other papers are more directly focused on magnetic fields, although in very different contexts.…”