Powerful 160-keV neutral deuterium beam injector for application in fusion research

A 160‐keV neutral deuterium beam injector has been developed for plasma heating in JET (Joint European Torus) fusion experiment. This injector has been reliably operated at 5.9‐MW extracted deuterium ion beam power (37‐A, 160‐keV ion beam) and 5‐s pulse duration. The neutral beam power was 1.75 MW corresponding to an overall neutral injector power efficiency of 30%. The beam divergence was 0.6°. The ion beam was accelerated with a three‐grid multiaperture system (aperture diameter φ=11 mm). The accelerating gap length was 24 mm. The extracted deuterium ion current density amounted to 150 mA/cm2. Grid and source body power loadings were acceptable for quasi‐steady‐state operation.