JT-60U MONTHLY SUMMARY

March 1997


OPERATION AND CONFINEMENT PHYSICS

The main objectives of operation / confinement physics in 1997 is to contribute to (1) Sustainment of high integrated performance ( high H-factor, high-beta-N, high-bootstrap-fraction ) with QDT=0.3-0.5 under full non-inductive current drive at Ip~2MA by using high triangularity shape and NNB-CD, (2) Sustainment of high performance reversed shear enhanced mode with QDT=0.3-0.5 and (3) Sustainment of ELMy H-mode with H-factor~2 at a high density sufficient for remote radiative cooling. Other key subjects are as follows: (4) Analyses of H-mode characteristics (in particular at a high density) under the new divertor condition. (5) Development and demonstration of feedback controls for density, neutron production rate and radiation. Time response of profiles to the externally applied heating power , momentum, current and particles will be systematically analyzed not only for physics understandings but also for design study of new advanced feedback control systems. (6) Systematic study related to major disruption and halo current. (7) Detailed analyses of profile effects on confinement and stability. Formation of both internal and edge transport barriers will be studied by changing current and rotation profiles. Concerning the beta-limit, we will focus on the limit in steady-state. For sustainment of high performance reversed shear discharges, current / pressure driven ideal / resistive instabilities will be studied in detail.

CURRENT DRIVE AND HIGH ENERGY PARTICLE PHYSICS

Experiment plan in 1997 was discussed. Main experimental subjects in the field of current drive and high energy particle are the current drive and sustainment of high performance plasmas with NNB and TAE modes with NNB and/or ICRF.

Recent results from current drive with NNB, confinement of ICRF-driven protons, fast ion behavior in sawtooth crash and ICRF-driven TAE modes were presented in the Meeting of the Japan Society of Plasma Science and Nuclear Fusion Research and the Meeting of Physical Society of Japan.

DIVERTOR AND BOUNDARY PHYSICS

The main issues for divertor study in 1997 are 1) simultaneous realization of radiative divertor and good confinement of core plasmas, 2) understanding of fundamental divertor functions in the new W-shaped divertor such as heat flux reduction, deuterium and helium pumping, reduction in back flow of neutrals and impurities etc. and 3) geometrical effect of the W-shaped divertor. High density H-mode plasmas will be main targets for these studies. Reverse shear plasmas will be also studied as targets, which leads to an advanced fusion plasma concept. High triangularity configuration will be used in these experiments.

The construction of the W-shaped divertor for JT-60U is now under way. New divertor diagnostics are under installation; Ionization gauges, bolometers, reciprocating divertor Langmuir probe, horizontal Langmuir probe, divertor interferometer. The operating test of fast shutter valves for controlling divertor pumping was done. The shutter speed was about 1.3 sec for opening full aperture and 0.4 sec for 1/4 aperture. They are being installed to the divertor pumping ports.