Cadarache 1 MeV negative ion accelerator development for application in thermonuclear fusion research

Additional plasma heating in the new generation of large magnetic fusion devices like ITER requires deuterium atom beams of about 1 MeV at a total neutral power of >50 MW based on negative ions. At Cadarache, ITER relevant research is performed regarding the development of a 1 MeV high beam current density (10-20 mA/cm/sup 2/) electrostatic accelerator (SINGAP). The SINGAP experiment consists of the acceleration to 1 MeV of a substantial D current (100 mA) in a simplified accelerating electrode structure. This is composed of only two acceleration stages: a pre-acceleration to 60 keV in a multi-aperture structure for ion extraction and electron suppression, and a post-acceleration stage to 1 MeV. The particular feature of the SINGAP accelerator is that the post-accelerator by means of an electrostatic lens merges the 60 keV beamlets into a single beam and accelerates the merged beam to 1 MeV in a single gap. Subjects of the study are the voltage holding at 1 MV with large electrode areas (about 60 m/sup 2/) and insulators in vacuum in the presence of an intense ion beam and radiation. The first experimental results of SINGAP are very encouraging. Up to now, H/sup -/ beams of 40 mA have been accelerated to 915 keV.