Speaker
Description
Abstract: Cesium injection is an effective and relatively mature method to improve the negative ion yield of negative ion sources. Cesium deposition on the component surface of negative ion based neutral beam injector (NNBI) accelerators is one of the key factors affecting insulation performance. At present, the correlation between cesium deposition amount and inter-electrode insulation level has not been fully investigated. This is one of the reasons why conservative cesium injection schemes or alternative methods for improving negative ion yield are adopted in the NNBI. The Institute of Plasma Physics, Chinese Academy of Sciences has recently conducted experimental research on DC voltage holding under cesium deposition in vacuum. The ultimate goal of this study is to establish the Paschen curve of negative ion accelerator electrodes under cesium deposition in hydrogen atmosphere. A vacuum chamber with a diameter of 1 m and height of 1.5 m serves as the main experimental facility for this research. A thermostatically controlled cesium crucible and a film thickness monitor were used for cesium evaporation and deposition thickness measurement, respectively. The experiments were first carried out without cesium injection to calibrate the electrode breakdown voltage under normal conditions. Subsequently, the system was evacuated to the ultimate vacuum achievable by the pump set, and the inter-electrode breakdown voltage was measured at different cesium deposition thicknesses. Then, the vacuum chamber was filled with hydrogen at various pressures, and the breakdown voltage was investigated under different gas pressures. Finally, the electrodes were heated to induce redistribution of the deposited cesium. Variations in cesium deposition thickness and the voltage holding performance during electrode heating were recorded.
| Email address | bo.liu@ipp.ac.cn |
|---|---|
| Funding Agency | Comprehensive Research Facility for Fusion Technology Program of China |
| Classification/Track | Negative ion based neutral beam injector |
| Visitor's Visa | yes |
| Classification | H- and D- sources for fusion, accelerators and other applications |