Investigation on Discharge Modes of Low Power DC Arcjet.

In the regime of low power DC arcjet, a research how to stabilize the operation modes was conducted in the Institute of Space and Astronautical Science (ISAS) using a 2-dimension-like DC arcjet for internal visualization, designated as ISAS-VAJ. As the results, an intermediate-voltage operation mode was newly found between the conventional low-voltage and the high-voltage mode. In the new intermediate-voltage mode, it was observed that the electron density and the ionization features were locally enhanced in the upstream region of the nozzle. It was also found that these localized features turned to be relaxed just after the formation, and the operation mode transferred to a high-voltage mode. Applying Kuriki model to this phenomenon, the operation mode and the transition were understood in view of the conditions for arc column formation. A proposal to stabilize the operation mode was made to be applied to ISAS-VAJ by adding a second-cathode in the upstream region of the nozzle. Initiating high voltage pulsed discharges on it, the operation mode was successfully transferred from a low-voltage to a stable high-voltage mode.