Review of JT-60U experimental results in 1997

The JT-60U experiments in 1997 focused mainly on the steady-state tokamak research with the newly installed W-shaped pumped divertor and the negative ion based neutral beam (NNB) in addition to the existing profile and shape control techniques developed in JT-60U. In particular, the research on divertor physics was accelerated under the new divertor system with many of fine diagnostics: Detachment characteristics, pumping control, impurity control, recycling characteristics, etc. in the W-shaped divertor were investigated in detail. The main purpose of confinement and stability studies in 1997 was to improve steadiness of high confinement plasmas with the new divertor. Researches progressed also for the formation conditions of the internal and the surface transport barriers in the high-βp mode, the reversed shear mode and the H-mode. Toward the advanced feedback controls of multiple parameters, the JT-60U started new feedback controls of central line density and divertor neutral gas pressure in addition to the existing controls of off-axis line density, radiation power and neutron production rate. The JT-60U team also carefully studied characteristics of halo current during disruptions. Optimization of NNB operation progressed steadily and injection power increased up to 4.2MW. The NNB-driven current was identified directly from the internal magnetic measurement and driven current profile was confirmed to be consistent with the ACCOME calculation. The current profile control with LHCD successfully sustained the internal transport barrier in reversed shear plasmas. Continuous TAE modes were observed with NNB for the first time as beam-driven TAE modes. (J.P.N.)