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December 1999-January 2000

In December, 1999, JT-60U had been halted to replace a part of armor tiles inside the vacuum vessel. In January, 2000, the pumping system resumed to evacuate the vessel. After finishing the vacuum leak test, JT-60U carried out the coil excitation test in preparation to plasma discharges in the coming months. During this maintenance period of JT-60U, the experimental plan in 2000 has been discussed. The discussion has been continuing, but the strong subjects are as follows.

DIRECTIONS (under discussion)

(1) Aim at improving the integrated performance i) to meet "high density and high confinement" required for ITER-FEAT and ii) to demonstrate "high beta and high confinement" in steady-state, with the use of a newly introduced centrifugal pellet injector and ECRF reinforced from 1 MW to 3 MW.
(2) Continue enhancing the understandings on tokamak plasma for reliable predictions of fusion plasma.

High Performance Demonstration

(1) "High density and high confinement": H-factor ~1.7 at ne/nGR = 0.8, by pellet fuelling with keeping recycling low. Operations at high Ip ( > 2 MA) will be also explored for the purpose (high Ip enables high ne operations, resulting in low Zeff).
(2) Long sustainment of "high beta and high confinement" on the high βp H-mode and the reversed shear plasma bases.
2-1) High βp H-mode: Full current drive at Ip > 1.5 MA with βN~2.5 and H89~2.5 with the use of N-NBI and ECRF.
2-2) Reversed shear with H-mode edge: Access to higher βN (~2.5) with the help of wall stabilization and pressure profile control by ECH.

Core Plasma Physics Research

(1) Physics of internal transport barrier; ITB structure, conditions for ITB formation, etc.
(2) Electron heating dominant plasma with low fuelling; NNB- and/or ECRF-heated H-mode and reversed shear plasmas
(3) MHD and energetic particle physics

  • Onset of NTM and stabilization by ECCD
  • Wall stabilization effects and resistive wall modes
  • Destabilization conditions of Alfvén eigenmodes by N-NBI
  • Transport and loss of N-NB fast ions by MHD modes

Divertor and Edge Plasma Physics Research

(1) Physics of confinement degradation at high density
(2) Demonstrate efficient helium exhaust (τHeE<5) in ELMy H-mode and reversed shear plasmas
(3) Compilation of the ELM database on heat and particle flux
(4) Mechanism of Impurity generation and transport
(5) Physics of SOL plasma
(6) Effective fuelling with the pellet injector