Study on influence on plasma under current-generated magnetic filter using Langmuir probe in HUST negative ion source

Abstract

Abstract The current-generated magnetic filter is widely used in negative ion sources to bring down electron temperature and optimize source operation. The effect of the current-generated magnetic filter on plasma generation and transport is important. The axial distribution of cesium-free plasma parameters under different magnetic filter configurations was measured by a movable Langmuir probe at HUST negative ion source. Abnormal changes of plasma parameters are discovered at the driver exit. When the magnetic filter field penetrates into the driver, plasma density inside the driver increase, and the high-density high-temperature region of plasma expands outside of the driver. And the radiofrequency power coupling is also influenced by the magnetic filter. These experimental phenomena indicate that a new magnetic filter configuration is required to optimize source operation.