Plasma characterization of a test setup of RF-driven negative ion source by a Langmuir probe system

To study the plasma properties in a test setup of RF-driven negative ion source at HUST, a Langmuir probe system has been built in-house and applied to the source. It allows for fast, multiple acquisition of the probe I-V characteristics in a diagnosis shot of several hundred milliseconds and it is also capable of evaluating the I-V data automatically. The analysis software incorporates various methods for determination of the ion density, and the analysed results are compared. Measurements of the plasma parameters at the driver center for hydrogen discharges with the transmitted RF power of 4-20 kW and source pressure of 0.2-0.8 Pa have been carried out. Besides, the distribution of the plasma parameters along the central axis of the setup has been investigated. The plasma generated in the driver exhibits non-Maxwellian electron energy distribution with density of 1016−1017m−3 and effective electron temperature of 6-9 eV at low pressure.