IBIS: A hollow-cathode multipole boundary ion source

The plasma production and containment system for a high-power continuously operating magnetic multipole ion source has been designed and constructed. Preliminary tests on this system prior to high voltage extraction of large beams indicate advantageous performance for neutral-beam injection applications. The source has produced 80 A to the extractor region at 0.33 A/cm2 with a discharge of 330 A at 80 V. Density uniformity is better than 1% over a 16-cm diameter, dropping to −4% at 18 cm, with plasma noise of less than 3%. Gas utilizaion efficiency and atomic (H+) species output are anticipated to be high due to a source length of 40 cm. This quiet efficient performance is attributed to the use of a hollow-tube LaB6 cathode and an improved magnetic multipole confinement system.