Progress of long pulse and H-mode experiments in EAST

Abstract

Significant progress has been made in EAST since last IAEA FEC on both technology and physics fronts, particularly towards high performance, long pulse plasma discharges. The following key results have been achieved under a strongly lithium coated wall condition: fully steady-state long pulse diverted plasma entirely driven by Lower Hybrid Current Drive (LHCD) over 400 s, and stationary H-mode discharges over 30s with a combination of LHCD and Ion Cyclotron Resonant Heating (ICRF). H-modes with various type of ELMs have been realized at an H factor of H IPB98(y,2) ranged from 0.7 to over unity, providing great opportunities for H-mode physics study. New and exciting physics with dominant RF heating has been emerged, such as new findings on LHCD-induced 3D edge magnetic topology and its effect on manifestation in the heat and particle flux and influence on ELMy characteristics; the role of zonal flows limit cycle for the L-H transition or the occurrence of the I-phase; and new small Edge Localized Mode (ELM) regime, etc. Various means for mitigating ELMs have also been demonstrated to facilitate long pulse operation, including SMBI, as well as innovative solid Li granule injection.

Study on the L–H transition power threshold with RF heating and lithium-wall coating on EAST

“…In order to demonstrate high performance, long pulse plasma and in preparation for ITER, the carbon wall is being replaced by a metal wall step by step. The full carbon wall in the 2010 campaign (C wall) was replaced by molybdenum in the main chamber and carbon in the divertor in the 2012 campaign (Mo/C wall) [2]. EAST now routinely uses lithium coating as a main wall conditioning technique [3].…”

New Edge Coherent Mode Providing Continuous Transport in Long-Pulse H-mode Plasmas

“…We have discovered a new edge coherent mode (ECM) near the local electron diamagnetic frequency in the steep-gradient pedestal region, existing continuously throughout a long-pulse H-mode regime with a record pulse length over 30 s, recently achieved in the EAST superconducting tokamak (R 0 ¼ 1.9 m, a ¼ 0.44 m, B t ¼ 1.5-2.5 T) [11,12]. This Letter demonstrates, for the first time, that the ECM is able to provide sufficient particle and energy exhaust across the pedestal in H modes in the absence of ELMs, by direct probing the ECM-driven radial fluxes inside the separatrix using a new diamond-coated reciprocating probe array [13], which allows ELM-less operation in stationary H-mode conditions up to 60 times the energy confinement time [14].…”

“…(18b) in [17], n G ¼ I p =πa 2 is the Greenwald density and I p (0.28-0.6 MA) is the plasma current. These H-mode plasmas are achieved in a lowrecycling regime due to extensive lithium wall coating [11,12], with combined lower hybrid current drive (LHCD) and ion cyclotron resonant frequency (ICRF) hydrogen minority heating with central deposition in deuterium plasmas, at a power of P LHCD ¼ 1-2 MW and …”

Development of an integrated energetic neutral particle measurement system on experimental advanced full superconducting tokamak

“…Significant progress, on both the technological and physical fronts towards high-performance long-pulse plasma discharges, has been achieved in recent years. 8,9 Aggressive upgrade plans have been established and will enhance EAST operation and research capabilities drastically in the near future.…”