Development of a Large Bucket Plasma Source

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Abstract
A large bucket-type plasma source has been developed for a neutral beam injector. An ion current density of 0.25 A/cm2 in a hydrogen plasma was achieved with a density uniformity of better than ∼10% over an area of 15×60 cm2 at about 100 kW of arc power in pulsed operation for 1s. Plasma density profiles and the discharge voltage-current characteristics, etc., were studied by varying the geometrical parameters of a tungsten filament i.e., the disposition, number, diameter, and shape. The profile was affected by the filament disposition and the gas pressure. A measure of the gap length between filaments to generate a dense uniform (< 10%) plasma was roughly 14-22 cm. An experimental scaling relation of the arc power is discussed; the arc power for the same plasma density appears to increase with an increase in the total loss-area in various sources.