Development of high power negative ion source/accelerator for ITER-NBI

Recent progress on the development of high power negative ion sources/accelerators at JAERI is presented. A high current H^- ion beam of 18.4 A/350 keV and a D^- ion beam of 14.3 A/380 keV were obtained in the negative ion source for JT-60U N-NBI. A high energy H^- ion beam of 868 keV, 19 mA, 1 s has been accelerated in the MeV Test Facility. A D^- current density of 20 mA/cm² (1.4 A/30 keV), which is a design value of ITER-NBI, was achieved in the JAERI/CEA joint experiment at a low operating gas pressure of 0.3 Pa using JAERI KAMABOKO source. Continuous operation of the negative ion source for 139 hours, which corresponds to half year operation of the ITER-NBI, was also demonstrated in the JAERI Long Pulse Negative Ion Source. The beam optics study has showed that the accelerated negative ion beam has the minimum beam divergence of around 2-3 mrad at an optimum perveance and a beam-halo component is about 10%