A differentially pumped hollow cathode constricted anode plasma source for the production of negative ions

摘要

The negative ion source for Neutral Beam heating system of ITER is required to deliver 40 A of D"/H"negative ion cxairent though 0.2 m~2 grid. This demands high density (?5×10~(18)/m~3) plasma in front of the extraction grid at low operating pressure of 0.3 Pa pressure. The existing negative ion sources for neutral beams injection heating (NBI) are based on tungsten filament type Kamaboko-III source and the advanced RF modular type ion source [1]. These sources rely on Caesium for efficient surface production of negative ions. However Cs can migrate into the extractor region along with negative ions and can lead to the divergence of the beam, dumping enormous power on to walls of the acceleration chamber. Therefore Cs free negative ion source for ITER NBI and future fusion devices is a high priority of research.