Boron/hydrocarbon plasma polymer nanofuels for green energy generation via laser-driven proton-boron fusion

Abstract

Since 2005, materials rich with hydrogen and boron have been investigated as fuels for laser-driven proton-boron (pB) fusion, which is envisioned as a neutronless alternative to classical fusion for green energy generation. However, laser energy conversion is limited by large energy losses in bulk materials. Highly porous H/B-rich materials may mitigate this issue by enhancing laser absorption, but they are not readily available and are in high demand. Performing plasma polymerization of hexane in a gas aggregation cluster source, we prepared porous, dendrite-structured, micrometer-thick layers of plasma polymerized hydrocarbon nanoparticles of 65 and 560 nm size and optionally overcoated them with sputtered boron. Variable energy positron annihilation spectroscopy and N₂ sorption analysis found the multiscale porosity in the resultant nanomaterials, which is given by free volumes in the plasma polymer matrix (with characteristic diameter of 0.4–0.6 nm) and interparticle voids (10¹–10² nm). NPs were found to retain half the amount of precursor hydrogen, as determined by ERDA. Using the TARANIS laser system (10 J per 800 fs pulse, 2 × 10¹⁹ W/cm²), the pB fusion was successfully initiated to produce energetic α-particle fluxes of up to 5.6 x 10⁸ α/sr/shot and 5 × 10⁷ α/sr/J, which is competitive with the best results obtained so far. Our plasma-based method benefits from low amounts of source materials and almost no waste, offering a sustainable route toward hybrid H/B nanofuels with tunable porosity and strong potential for improving the energy conversion efficiency in laser-driven pB fusion.