Progress of indirect drive inertial confinement fusion in the United States

Abstract

Indirect drive converts high power laser light into x-rays using small high-Z cavities called hohlraums. X-rays generated at the hohlraum walls drive a capsule filled with deuterium–tritium (DT) fuel to fusion conditions. Recent experiments have produced fusion yields exceeding 50 kJ where alpha heating provides ~3× increase in yield over PdV work. Closing the gaps toward ignition is challenging, requiring optimization of the target/implosions and the laser to extract maximum energy. The US program has a three-pronged approach to maximize target performance, each closing some portion of the gap. The first item is optimizing the hohlraum to couple more energy to the capsule while maintaining symmetry control. Novel hohlraum designs are being pursued that enable a larger capsule to be driven symmetrically to both reduce 3D effects and increase energy coupled to the capsule. The second issue being addressed is capsule stability. Seeding of instabilities by the hardware used to mount the capsule and fill it with DT fuel remains a concern. Work reducing the impact of the DT fill tubes and novel capsule mounts is being pursed to reduce the effect of mix on the capsule implosions. There is also growing evidence native capsule seeds such as a micro-structure may be playing a role on limiting capsule performance and dedicated experiments are being developed to better understand the phenomenon. The last area of emphasis is the laser. As technology progresses and understanding of laser damage/mitigation advances, increasing the laser energy seems possible. This would increase the amount of energy available to couple to the capsule, and allow larger capsules, potentially increasing the hot spot pressure and confinement time. The combination of each of these focus areas has the potential to produce conditions to initiate thermo-nuclear ignition.

Observations of Brillouin scattering process in Particle-In-Cell simulations for laser pulse interacting with magnetized overdense plasma

“…The interaction between a high-intensity laser beam and a plasma can result in a variety of complex phenomena, including the generation of high-energy particles [8][9][10], the production of X-rays [11,12]. It also has the potential for aiding laser fusion [13][14][15][16][17][18][19][20][21][22][23][24]. The problem of ignition in the context of laser fusion requires ion heating.…”

A cylindrical implosion platform for the study of highly magnetized plasmas at LMJ

“…This increases the fusion yields as it inhibits the thermal energy transport and reduces the loss of alpha particles from the hotspot 1,[4][5][6] . Additionally, magnetized implosions may be less vulnerable to hydrodynamic instabilities 7,8 that could lead to disadvantageous mixing of the hot and cold parts of the target 9 , a crucial issue to reach ignition at the National Ignition Facility (NIF) 10 .…”

Collisional redistribution of hydrogen line radiation in low- and moderate-density magnetized plasmas

“…One main advantage of these functions is that they involve analytical expressions or integrals that can be evaluated numerically within a reasonable CPU time; applications include inertial fusion [7] and related research works in astrophysics (e.g., see Refs. [8][9][10] for reviews), laboratory plasma experiments [11,12], and general transport theory [13,14]. In each of these domains, the radiation field is investigated based on a numerical solving of the radiative transfer equation and redistribution functions occur therein through an integral scattering term.…”