Development of long-pulse neutral beam injectors for JT-60SA

Kojima, Atsushi; Hanada, Masaya; JT-60NBI Group

30-34 MW neutral deuterium beams are injected to JT-60SA plasmas by using neutral beam injectors with 24 positive ion sources for 12 units and 2 negative ion sources for 1 unit. As for the positive NBI, 2MW, 30s injections has already achieved with temperature increase of cooling water saturated. A beam duct for Re-ionization loss is required to be cooled additionally. The existing power supplies are applicable by enhancing the heat tolerance. Long pulse injections with higher stray magnetic field than JT-60U could be carried out by masking partial apertures whose beamlets missed the beam damp. As for the negative NBI, productions of 500keV, 3A, 0.8s and 350keV, 3MW, 30s beams has been achieved so far. Recently the database for vacuum insulation has been obtained to achieve stable acceleration of 500keV beams. Long pulse production of the negative ions are planned by constructing the new test stand of the negative ion source with temperature-controlled plasma grid.