Annual report of Naka Fusion Research Establishment for the period from April 1, 1992 to March 31, 1993

Research and development activities at Naka Fusion Research Establishment, JAERI, are reported for the period from April 1, 1992 to March 31, 1993. The main objectives of JT-60U experiments in FY1992 were to improve plasma confinement properties and to study non-inductive current drive. High-βp H-mode performance obtained in March 1993 was highlighted, in particular, a world-record fusion-triple-product of 1.1 x 1021 m-3 · s · keV, and record values for JT-60 of neutron yield rate of 5.6 x 1016 s-1, stored energy of 8.3 MJ, and H-factor of 3.6. The JFT-2M continued to study divertor biasing and ergodic limiter experiments, and disruption control by ECH. The study in Plasma Theory and Computation focused on scaling laws of the thermal energy confinement and the bootstrap current, the iron temperature gradient instability, the MHD stability, the rotation damping by external magnetic error field, and the burning plasma of D-3He fusion. As for the fusion engineering research, the vacuum technology advanced the development of a high resolution quadrupole mass spectrometer, etc. The super-conducting Demo Poloidal Coil achieved pulsed operation with 7 T in 0.5 s, and newly developed conductors made of Nb3Al and Nb3Sn showed 40 kA at 12 T and 82 kA at 13.6 T, respectively. A high energy H- beam of 350 kV, 0.17 A was produced with a current density of 10 mA/cm2. Much effort was made in developing the ECH gyrotron with an output power of 460 kW at 120 GHz for 100 ms. The main progress in the Tritium Systems Test Assembly (a US/Japan collaboration) was continuous loop run for 25 days. The developed plasma facing components posed no problem under a heat flux of 20 MW/m2 for 30 s over 1000 thermal cycles. (J.P.N.)