Photon and neutron production as in-situ diagnostics of proton-boron fusion

TL;DR

This paper proposes using photon and neutron yields as in-situ diagnostics to verify proton-boron fusion reactions in ultra-high-intensity laser experiments, aiding optimization of fusion yield.

Contribution

It introduces a method to diagnose plasma conditions by analyzing photon and neutron yields, specifically verifying the proton-boron fusion reaction through parallel reaction ratios.

Findings

Computed photon-to-alpha yield ratios as functions of plasma parameters.

Identified promising photon-producing reactions for plasma diagnostics.

Highlighted the importance of measuring cross sections for parallel reactions.

Abstract

Short-pulse, ultra high-intensity lasers have opened new regimes for studying fusion plasmas and creating novel ultra-short ion beams and neutron sources. Diagnosing the plasma in these experiments is important for optimizing the fusion yield but difficult due to the picosecond time scales, 10s of micron-cubed volumes and high densities. We propose to use the yields of photons and neutrons produced by parallel reactions involving the same reactants to diagnose the plasma conditions and predict the yields of specific reactions of interest. In this work, we focus on verifying the yield of the high-interest aneutronic proton-boron fusion reaction $^{11}{B}(p,2\alpha){}^4{He}$, which is difficult to measure directly due to the short stopping range of the produced $\alpha$s in most materials. We identify promising photon-producing reactions for this purpose and compute the ratios of the photon yield to the $\alpha$ yield as a function of plasma parameters. In beam fusion experiments, the ${}^{11}{C}$ yield is an easily-measurable observable to verify the $\alpha$ yield. In light of our results, improving and extending measurements of the cross sections for these parallel reactions are important steps to gaining greater control over these laser-driven fusion plasmas.