High-Power Ion Beam Characteristics of a Magnetic Multi-Pole Line-Cusp Ion Source for the HL-2A Tokomak

A circular magnetic multi-pole line-cusp ion source with a nominal 45keV 25A hydrogen ion beam is developed for the neutral beam injector of the HL-2A tokomak. At present, this bucket ion source can produce a 40keV 20A hydrogen ion beam for less than 100ms on a test bed, and a 35keV 13A ion beam for 300ms on the injector of the HL-2A tokomak. The 1/e half-width of the ion beam power profile is about 6.0±0.2 cm at the position of 3.26m downstream from ion source, and the corresponding divergence degree is nearly 1.1. The optimum perveance matched conditions were obtained experimentally, and were in good agreement with the values from experiential equation of Uhlemann et al The maximum of optimum perveance reached 2.2×10^-6 A/V^1.5 for 38keV beam energy. An ion beam with above 60% H⁺ species fraction can be achieved, which was measured by H_α light Doppler shift spectroscopy. According to research results, a neutral beam with a total power of more than 0.6MW was successfully injected into the plasma of the HL-2A Tokomak in 2008.