Engineering Design And Preliminary Experiments Of 10cm RF Ion Source

High-power and high-current neutral beam injection is a major plasma auxiliary heating method in the field of nuclear fusion research. Since radio frequency (RF) ion source have the potential advantages of nearly unlimited lifetime, high reliability and reduced maintenance, it has been chosen to heat the International Thermonuclear Experimental Reactor (ITER) fusion test device. As a member of ITER program, it is urgency to do those relevant researches.Some principal problems of RF ion source are discussed in detail. In RF ion source with a low pressure discharge there happen two processes: the space recombination and recombination on the discharge wall. The second process is usually dominant while RF discharge, therefore, it can not be negligible when decide the material of the discharge chamber. There are two methods of coupling the RF power: Capacitively Coupled and Inductively Coupled. And the method of this RF plasma source is Inductively Coupled. Furthermore, according to the mechanism of discharge, the RF discharge can be divided into the following two types: First Type of RF Discharge (Low-Pressure Discharge) and Second Type of RF Discharge (Medium or High Pressure Discharge). Since the pressure in the chamber of the High-power and high-current RF ion source is not very low, this kind of discharge is the Second Type of RF Discharge.Based on the principle of operation and guideline for design, an experimental RF ion source with 10cm in inner diameter and 12.4cm in height has been developed. Machining property and flexible assembly, vacuum seal, cooling and other factors are taken into account while designing. The 3-D modeling of the source's parts and assembly are built by CATIA which is excellent CAD software in manufacturing area. The 10cm RF ion source consists of plasma discharge vessel, RF induction coil, confinement magnetic field, cooling, diagnostics, starter filament, gas feeding and vacuum pumping system. Impedance matching network is a major part, and L matching network is chosen to provide maximum power transfer from the RF power generator to RF induction coil.In view of diagnosing electron temperature and plasma density in the vessel during discharging, Langmuir double-probe is designed. Another, an array of 9 Faraday cups in the button of the discharge vessel is used to diagnose beam current distribution. In the preliminary experiment, electron temperatures of 12.9eV and 14.8eV have been achieved respectively, when the RF ion source is operated at an RF-discharge power of 50W and 100W. Plasma densities are 1.1×101 4 / m3 and 1.8×101 4 / m3 respectively. Furthermore, beam profiles at different RF-discharge power in the 10cm RF ion source are uniform and similar with those of the ASDEX-Upgrade NBI RF ion sources. A 10cm cylindrical RF ion source is designed and tested in a low RF input power. Some common rules of designing high-power and high-current ion source are seized. Therefore, these are helpful to design larger RF ion sources in dimension.