Annual report of the Naka Fusion Research Establishment for the period of April 1, 1985 to March 31, 1986

Research and development activities of the Naka Fusion Research Establishment for the period of April 1985 to March 1986 are described. The JT-60 tokamak machine was completed in April 1985 after a seven-year construction period, and the first plasma operation was achieved on April 8, 1985. Initial experiments with Joule-heated plasmas were performed for three months from April to June 1985 and confirmed tokamak discharges of sufficient plasma current and density as required for additional heating in the divertor configuration. In JFT-2M experiments on beam and ICRF heated plasmas, H-mode discharges with good confinement characteristics were achieved in open divertor configurations. The Doublet III device had been modified into D-III D with a large deeshaped cross-section. The first plasma was obtained in February 1986. The development of a numerical tokamak code TRITON-II was continued. Plasma-surface interaction studies and vacuum technology development were continued. In the study of plasma heating technology, programmable control of the neutral beam energy was demonstrated in a proto-type injector unit. Negative hydrogen ion beams of 25 keV, 0.1 A were extracted by using multiaperture extraction grid. Research was also carried out on improvements of RF coupling system with emphasis on RF breakdown phenomena in a pill box type ceramic window. In the development of superconducting magnets, generation of a 12T magnetic field was demonstrated by the Test Module Coils. The fabrication of the Demonstration Poloidal Coil was started. Preliminary tritium tests on JAERI's proto-type Pd-diffuser and ceramic electrolysis cell had been successfully carried out in the TSTA at LANL. The design study of the Fusion Experimental Reactor was continued. A wide range of scoping studies was also made to evaluate cost/benefits effects. INTOR design studies were concentrated on tokamak innovations. (J.P.N.)