Ignition and high gain with ultrapowerful lasers*

TLDR

Ultrahigh‑intensity lasers could enable inertial confinement fusion capsules to ignite with only a few tens of kilojoules of laser energy, potentially achieving high gain, but the challenge shifts to producing and delivering such lasers. The authors propose a three‑phase scheme to achieve ignition. The scheme first implodes the capsule as in conventional ICF, then bores a hole through the ablated corona to bring the critical density close to the high‑density core via ponderomotive forces, and finally ignites the fuel with suprathermal electrons generated by high‑intensity laser–plasma interactions that propagate to the core. This approach dramatically eases the implosion requirements, allowing lower‑quality fabrication and relaxed beam quality and symmetry constraints.

Abstract

Ultrahigh intensity lasers can potentially be used in conjunction with conventional fusion lasers to ignite inertial confinement fusion (ICF) capsules with a total energy of a few tens of kilojoules of laser light, and can possibly lead to high gain with as little as 100 kJ. A scheme is proposed with three phases. First, a capsule is imploded as in the conventional approach to inertial fusion to assemble a high-density fuel configuration. Second, a hole is bored through the capsule corona composed of ablated material, as the critical density is pushed close to the high-density core of the capsule by the ponderomotive force associated with high-intensity laser light. Finally, the fuel is ignited by suprathermal electrons, produced in the high-intensity laser–plasma interactions, which then propagate from critical density to this high-density core. This new scheme also drastically reduces the difficulty of the implosion, and thereby allows lower quality fabrication and less stringent beam quality and symmetry requirements from the implosion driver. The difficulty of the fusion scheme is transferred to the technological difficulty of producing the ultrahigh-intensity laser and of transporting this energy to the fuel.