Abstract
Two different surface treatments (mechanical polishing, thin film deposition) were done on cathode surfaces, and the field emission current from the cathodes were measured by using MCP. In order to discuss a relationship between the breakdown voltage and pre-breakdown current in vacuum gap, breakdown voltage was measured after a field emission measurement. The V-I characteristics of field emission and breakdown voltage were influenced by surface treatment, the breakdown voltages of mechanical polished cathodes were lower than thin film deposited cathodes. It was found that the probability of breakdown was higher as the field emission current was reached at 10-11A. From atomic force microscope (AFM) measurement, there were a lot of protrusion on the cathode surface at a case of thin film deposition treatment, and we estimated by using finite element method that these protrusions, however, make field enhancement effect low. It was supposed that the breakdown voltage in vacuum gaps could be increased by thin film deposition method.
