Recent progress of the LHD experimental research

In the third campaign (07.13.99 - 12.14.99) of the LHD experiments, NBI (≤4.2 MW), ICRF (≤1.4 MW) and ECRH ((≤ 0.9 MW) were used to heat the plasma. Carbon tiles were installed as divertor plates, resulting in a significant reduction in the concentration of metal (Fe) impurities. The maximum field used in the experiment was 2.9 T. Upgrading of the key hardware system led to (i) higher central electron temperature [Te(0) = 4.4 keV at the average electron density = 5.3 x 1018 cm-3 and the absorbed power Pabs = 1.8 MW], (ii) higher confinement time [τe = 0.3 s at = 6.5 x 1019 m-3 and Pabs = 2.0 MW], (iii) higher diamagnetic stored energy [Wpdia = 0.88 MJ], and (iv) higher diamagnetic average beta [<β>dia = 2.4% at the magnetic field B = 1.3 T]. The edge transport barrier enhances confinement significantly [50% higher than the ISS (International Stellarator Scaling) 95 scaling]. ICRF heating was found to be as efficient as NBI heating. Long pulse discharges (80 sec NBI shot, 68 sec ICRF shot) were achieved without difficulty. (J.P.N.)