Achievement of high fusion triple product, steady-state sustainment and real-time NTM stabilization in high- _pELMy H-mode discharges in JT-60U

Abstract

This paper reports results on the progress in steady-state high-βp ELMy H-mode discharges in JT-60U. A fusion triple product, nD(0)τETi(0), of 3.1 × 1020 m−3 s keV under full non-inductive current drive has been achieved at Ip = 1.8 MA, which extends the record value of the fusion triple product under full non-inductive current drive by 50%. A high-beta plasma with βN ∼ 2.7 has been sustained for 7.4 s (∼60τE), with the duration determined only by the facility limits, such as the capability of the poloidal field coils and the upper limit on the duration of injection of neutral beams. Destabilization of neoclassical tearing modes (NTMs) has been avoided with good reproducibility by tailoring the current and pressure profiles. On the other hand, a real-time NTM stabilization system has been developed where detection of the centre of the magnetic island and optimization of the injection angle of the electron cyclotron wave are done in real time. By applying this system, a 3/2 NTM has been completely stabilized in a high-beta region (βp ∼ 1.2, βN ∼ 1.5), and the beta value and confinement enhancement factor have been improved by the stabilization.

Research and Development of 2-frequency (110/138 GHz) FADIS for JT-60SA ECHCD system

“…Local current generation by Electron Cyclotron Current Drive (ECCD) has been used to suppress Neoclassical Tearing Mode (NTM) activities in many tokamaks such as the JT-60U [1][2][3], the ASDEX-U [4], the DIII-D [5]. In the JT-60U experiments, active NTM suppression was demonstrated by local ECCD with several stabilization techniques such as real-time steering of the launcher mirror [1] and preemptive stabilization [2].…”

“…In the JT-60U experiments, active NTM suppression was demonstrated by local ECCD with several stabilization techniques such as real-time steering of the launcher mirror [1] and preemptive stabilization [2]. Synchronous switched injection for mode rotation of the NTM magnetic island has been proposed as a more effective suppression method relative to the continuous injection.…”

Fast polarizers installation for ECRH and ECE in TCV

“…These systems are under continual development and further improvements are sought, e.g. real-time control [6]. In recent years, the ECRH system of the Tokamak-à-Configuration-Variable (TCV) at the CRPP/EPFL has benefited from developments in real-time feedback control of some parameters such as launcher injection angle, gyrotron power and modulation, with promising results in the control of targeted plasma instabilities [7].…”

Advanced Tokamak Research in JT-60U and JT-60SA

“…In JT-60U, NTM stabilization has been performed since the installation of the first 110 GHz gyrotron in 1999 [7], and stabilization by real-time mirror steering [8], preemptive stabilization [9] and simulation with the TOPICS code [10][11][12] have been performed.…”