Experimental approach of the interaction between a sub-microscopic cathode tip and the plasma

The interaction between electrical arc and cathode represents a crucial problem in the conception of arc jet thrusters, circuit breakers, and plasma torch or arc heaters. At the cathode surface, the current and energy transfers are controlled by the current emitting site (cathodic spot). Theories and experimental observations, at macroscopic and mesoscopic scale, deal with the erosion of the cathodic surface. Under micrometer range, theories refer to the arc root to describe the erosion of the surface. The works presented here propose an original method to evaluate the arc-cathode interaction at micrometric scale. A nanotechnology is used in order to control the roughness of the electrode surface and to deposit the microscopic tip. After discharge, the influence of the tip in the cathodic erosion process is studied. Scanning Electron Microscopy images show that a good reproducibility of the erosion zone is obtained by using this experimental method.