BEAMLINE PERFORMANCE OF 500 KEV NEGATIVE ION-BASED NBI SYSTEM FOR JT-60U

Construction of the 500 keV negative-ion-based NBI system (N-NBI) with its maximum capability of 10 MW and 10 s for NE current drive and pla sma core heating in high-density plasmas in JT-60 was completed in Mar ch 1996. The neutral beam injection into JT-60 with N-NBI has been per formed since then. One of the key issues in the injection was how to c ontrol the bending magnetic held for residual ion beams. In N-NBI for JT-60, a stray magnetic field from the tokamak was actively used for b ending of the residual ion beams. Combination of the stray magnetic fi eld from JT-60 and the magnetic field of the deflecting coils was cont rolled sufficiently to successfully deposit residual ion beams at a co nstant point on the ion dump surface. The deposited positive and negat ive beam profiles on the ion dump were measured with an array of therm ocouples brazed on the dump surface. This report describes the perform ance test of bending the residual ion beams and the measurement of the heat load on the ion dump for JT-60 N-NBI experiments. (C) 1998 Publi shed by Elsevier Science S.A. All rights reserved.