To match the large power long pulse neutral beam injectors for HL-2A Tokarnak,a circular magnetic multipole line-cusp ion source(namely a bucket ion source)has been designed.The arc chamber of this ion source is a water-cooled,stainless-steel cylinder 26cm in diameter,4mm thick,and 24cm long.So far,many arc discharge experiments on this ion source have demonstrated that the plasma density has been 0.24A/cm^2,for 3 seconds duration, within 5%—7% plasma uniformity,and 3 seconds maximum pulse.Arc discharge characteristics,such as the gas pressure dependence and filaments arrangements dependence have been studied experimentally and theoretically in this paper.
