Assessing Proton-Boron Fusion Feasibility under non-Thermal Equilibrium Conditions: Rider's Inhibition Revisited

TL;DR

This study revisits Rider's 1997 analysis on proton-boron fusion feasibility under non-thermal conditions, showing that bremsstrahlung losses prevent net energy gain in most scenarios, but high electron temperatures could potentially enable net energy production.

Contribution

The paper provides updated simulations with new fusion cross-sections to evaluate non-thermal proton-boron fusion, confirming Rider's conclusions and exploring conditions for potential net energy gain.

Findings

Recirculating power exceeds fusion power output in most conditions.

Increasing electron temperature reduces bremsstrahlung losses but still prevents net gain.

At around 140 keV electron temperature, bremsstrahlung losses match electron-ion transfer, enabling potential net energy gain.

Abstract

Compared to the D-T reaction, the neutron-free proton-boron (p-$^{11}$B) fusion has garnered increasing attention in recent years. However, significant Bremsstrahlung losses pose a formidable challenge in p-$^{11}$B plasmas in achieving $Q>1$ in thermal equilibrium. The primary aim of this study is to corroborate Todd H. Rider's seminal work in the 1997 Physics of Plasmas, who investigated the feasibility of sustaining p-$^{11}$B fusion under non-thermal equilibrium conditions. Employing a series of simulations with new fusion cross-section, we assessed the minimum recirculating power that must be recycled to maintain the system's non-thermal equilibrium and found that it is substantially greater than the fusion power output, aligning with Rider's conclusions, whether under the conditions of non-Maxwellian electron distribution or Maxwellian electron distribution, reactors reliant on non-equilibrium plasmas for p-$^{11}$B fusion are unlikely to achieve net power production without the aid of highly efficient external heat engines. However, maintaining the ion temperature at 300 keV and the Coulomb logarithm at 15, while increasing the electron temperature beyond 23.33 keV set by Rider, leads to diminished electron-ion energy transfer and heightened Bremsstrahlung radiation. When the electron temperature approaches approximately 140 keV, this progression ultimately leads to a scenario where the power of Bremsstrahlung loss equals the power of electron-ion interactions, yet remains inferior to the fusion power. Consequently, this results in a net gain in energy production.