Pitcher-Catcher p-B fusion Boosted by Nanowire Array

In the laser-assisted pitcher-catcher proton-boron fusion scheme, fusion probability can be increased by the laser-preheating of the boron target until the bulk electron thermal speed exceeds that of the incoming protons. The electronic stopping power is suppressed. However, laser-produced overdense plasma on the target surface impedes laser penetration, resulting in inefficient bulk target heating and low fusion yield.

In this work, we discuss the potential of using nanowire (NW) array targets to achieve efficient target heating and boost p-B fusion probability. Three-dimensional Particle-in-Cell simulation models the interaction between a a₀≈5, 35 fs, 800 nm laser pulse incident on 200 nm-diameter, 2 µm-long NWs attached on an 8 µm boron foil. The high aspect ratio of the NW array allows efficient generation of hot electrons by vacuum heating and the J×B mechanism, which in turn heats the bulk target electrons through collision. The cylindrical geometry of the NWs can enhance the laser field locally, resulting in enhanced energy gain of electrons between the NW gaps. For comparison, the NW target absorbed 65.2 % of laser energy (planar target: 11.4 %), raising the bulk electron temperature from 1.1 keV to 4 keV, doubling the fully ionized B⁺⁵ to 40%. For 675 keV protons, the stopping power drops from 61 keV/m to 25 keV/m. These results highlight the potential of using NW arrays to facilitate p-B fusion reactions.