Development of beam source and bushing for ITER NB system

The paper reports recent progress of R&D towards the beam source and HV bushing of the ITER Neutral Beam System. A new magnetic configuration with a “tent” magnetic filter was tested to suppress localization of fast electrons in a large negative ion source. The result was a drastic improvement of the negative ion uniformity with a beam intensity deviation less than ±4%. This fulfills the requirement of ITER (deviation ≤±5%). In a 1 MeV accelerator development, experiment of high current beam acceleration is in progress. The H− ion beams of 0.24 A has been obtained so far, at beam energy of 800 keV. Concerning the insulator rings of the HV bushing, a new cold-isostatic press method was developed to press alumina powder to the ring form. Formation and sintering of a full-scale (1.56 m in diameter) ceramic insulator ring was successfully completed without damages or cracks in the ceramic body.