Long pulse operation of the KAMABOKO III negative ion source.

The target performance for the KAMABOKO ion source on the MANTIS test bed in Cadarache is to accelerate a beam of D- with a current density of 200 A/m² and < 1 extracted electron per accelerated D-ion, at an injected power ranging between 1 and 2 kW per liter of source volume, at a source pressure of 0.3 Pa. For ITER, a continuous neutral beam must be assured for pulse lengths of 500 s, but beams of up to 3600 s are also envisaged. During the last campaign, continuous beam pulses of duration up to 1000 s were demonstrated both in hydrogen and in deuterium. In this article, the source performance, the effect of the plasma grid temperature for long pulse operation, and the limits of the present experimental setup are described. Additionally, the effect of changing the strength of the magnetic filter in the ion source on the extracted ion and electron currents and the beam transmission is reported. [ABSTRACT FROM AUTHOR]