Gas composition change during operation of a compact discharge fusion neutron source with a closed deuterium supply system

A compact cylindrical fusion neutron source has been developed for various applications, such as a D-T fusion neutron source for blanket neutron transport experiments for blanket development. Currently, the operation of a discharged fusion device is mostly deuterium-deuterium (D-D) fusion, in which D-2 fuel is continuously fed to the vacuum chamber and pumped out to keep its pressure constant. Deuterium-tritium (D-T) fusion operation requires a closed supply system for radioactive tritium. So, the fuel supply system has been developed using ZrCo. In this system, however, fuel D-2 gas is diluted due to light hydrogen released from the inner wall of the vacuum chamber and the surface of the electrodes, which results in a decrease of neutron production rate (NPR). Therefore, the external gas supply mode was performed to remove light hydrogen from the electrode surface before the operation of the closing system. The results of the gas analysis show that H-2 was not increased and the D-2 ratio was maintained. As a result, the neutron production rate achieved (NPR) > 10(5) n/s, and the dependency of the NPR on the voltage was similar to that of the external supply mode. These results indicate that removing light hydrogen from the electrode surface is effective to suppress fuel gas dilution.

Automated summary

A compact cylindrical fusion neutron source has been developed for various applications, such as a D-T fusion neutron source for blanket neutron transport experiments. The external gas supply mode is effective in removing light hydrogen from the electrode surface, thereby suppressing fuel gas dilution.