Progress of neutral beam R&D for plasma heating and current drive at JAERI

Abstract

Recent progress and future plans regarding development of a high power negative ion source at the Japan Atomic Energy Research Institute (JAERI) are described. The neutral beam injection system, which is expected to play an important role not only in plasma heating but also in the plasma current drive in the fusion reactor, requires a high power negative ion source which can produce negative deuterium ion beams with current of order 20 A at energy above 1 MeV. In order to realize such a high power negative ion beam, intensive research and development has been carried out at JAERI since 1984. The negative hydrogen ion beam current of 10 A achieved in recent years almost equals the value required for the fusion reactor. With regard to the negative ion acceleration, a high current negative ion beam of 0.2 A has been accelerated up to 350 keV electrostatically. On the basis of this recent progress, two development plans have been initiated as an intermediate step towards the fusion reactor. One is to develop a 500 keV, 10 MW negative ion based neutral beam injection system for JT-60U to demonstrate the neutral beam current drive in a high density plasma. The other is to develop a 1 MeV, 1 A ion source to demostrate high current negative ion acceleration up to 1 MeV. On the basis of this research and development, an efficient and reactor relevant neutral beam injection system will be developed for an experimental fusion reactor such as the International Thermonuclear Experimental Reactor.