Influence of the Hydrogen Isotope Affinity of the Cathode Coating Material on the Neutron Production Rate in the Glow Discharge–Type Fusion Neutron Source

The glow discharge–type fusion neutron source is a compact system that generates neutrons by inducing a nuclear fusion reaction between ionized-trapped deuterium and/or tritium in the system potential well. This study aims to clarify the relationship between the neutron production rate (NPR) and the deuterium depth distribution on the cathode surface. Four units of nontransparent cathodes fabricated from stainless steel as the electrode’s base material was investigated. Two units were coated with diamond-like carbon (DLC) and titanium, which have different affinities for hydrogen isotopes, and two were uncoated units. The NPR and cathode depth profiles were determined and scanned at different operating conditions for the coated cathodes and then compared to the uncoated ones.

The results revealed that the DLC-coated cathode showed much higher NPR than the other units. The increase in NPR for the system implementing a DLC-coated cathode relative to the uncoated cathode ranged from 4.7 to 10 times. In addition, the depth profile for the nontransparent cathodes showed that the deuterium concentration on/in the DLC-coated surface was more significant by about one order of magnitude than that of the other cathodes. The increase in the NPR can be attributed to the high affinity of the DLC to capture deuterium on a cathode surface. The study suggests that DLC is a promising coating for the electrode in the neutron source at low operating conditions of less than 2 kW. In the meantime, further experimental studies are planned to find more candidate materials with better performance and higher and more stable NPR as a function of time.