Recent activities on negative ion beams at JAERI

Recent results from the negative-ion source experiments and design works of negative-ion-based NBI (neutral beam injection) systems for the JAERI (Japan Energy Research Institute) tokamak (JT-60U) and the FER (Fusion Experimental Reactor) are presented together with a description of the long-range R&D program. A 50-keV, 7.8-A negative-hydrogen-ion beam has been produced successfully for a duration of 100 ms using a cesium-supplied volume source which has 253 extraction apertures of 11.3 mm in diameter. The maximum ion-beam current density is 30 mA/cm/sup 2/ at the source pressure of 1.3 Pa. On the basis of recent promising results from the negative-ion sources, injection of a 500-keV, 10-MW deuterium beam into the JT-60U plasmas in 1994 to heat the core plasma and to drive the plasma current is proposed.<
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