Acceleration of 100A/m2 Negative Hydrogen Ion Beams in a 1 MeV Vacuum Insulated Beam Source.

In the ITER NB, conventional gas insulated beam source (GIBS) cannot be utilized because of the radiation-induced conductivity of the insulation gas. Thus a vacuum insulated beam source (VIBS), where the whole beam source is immersed in vacuum, has been developed at JAERI. Recently, voltage holding capability of the VIBS was drastically improved by the large stress ring, which reduces the electric field concentration at the triple junction. Up to now, a high current density H- beam of 102 A/m2 (140 mA) at 800 keV has been accelerated. The beam acceleration was quite stable and accomplished for several hundreds shots. The degradation of the voltage holding due to the beam acceleration and/or Cs seeding was not observed. Thus the development of vacuum insulated beam source has solved technical issues of high voltage insulation of 1 MV level under the presence of the H- ion beams. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]