Investigation of light ion fusion reactions with plasma discharges

TL;DR

This study investigates low-energy light ion fusion reactions in plasma discharges, revealing neutron yields significantly higher than expected, possibly due to electron screening effects, with implications for stellar physics and energy technology.

Contribution

It demonstrates a novel plasma-based approach to study low-energy D-D fusion with high neutron yields and models electron screening effects in a controlled, compact setup.

Findings

Neutron yields are over 100 times higher than expected at sub-2 keV energies.

Electron screening potential of approximately 1000 eV enhances tunneling probability.

The setup allows detailed parametric studies of low-energy fusion reactions.

Abstract

The scaling of reaction yields in light ion fusion to low reaction energies is important for our understanding of stellar fuel chains and the development of future energy technologies. Experiments become progressively more challenging at lower reaction energies due to the exponential drop of fusion cross sections below the Coulomb barrier. We report on experiments where deuterium-deuterium (D-D) fusion reactions are studied in a pulsed plasma in the glow discharge regime using a benchtop apparatus. We model plasma conditions using particle-in-cell codes. Advantages of this approach are relatively high peak ion currents and current densities (0.1 to several A/cm^2) that can be applied to metal wire cathodes for several days. We detect neutrons from D-D reactions with scintillator-based detectors. For palladium targets, we find neutron yields as a function of cathode voltage that are over 100 times higher than yields expected for bare nuclei fusion at ion energies below 2 keV (center of mass frame). A possible explanation is a correction to the ion energy due to an electron screening potential of 1000+/-250 eV, which increases the probability for tunneling through the repulsive Coulomb barrier. Our compact, robust setup enables parametric studies of this effect at relatively low reaction energies.