Investigations of LHW-plasma coupling and current drive at high density related to H-mode experiments in EAST

Ding, Bojiang; Li, Y.C.; Zhang, L.; Li, M.H.; Wei, W.; Kong, E. H.; Wang, M.; Xu, Handong; Wang, S.L.; Xu, G. S.; Zhao, Liang; Hu, Haiping; Jia, H.; Cheng, Min; Yang, Yilin; Liu, L.; Zhao, Hengyu; Peysson, Y.; Decker, J.; Goniche, M.; Amicucci, L.; Cesario, R.; Tuccillo, A. A.; Baek, Seung Gyou; Parker, R.; Bonoli, P. T.; Paoletti, F.; Yang, Cheng; Shan, Jiafang; Liu, F.K.; Zhao, Yanping; Gong, Xianzu; Hu, Liqun; Gao, Xiang; Wan, Baonian; Li, J.G.

doi:10.1088/0029-5515/55/9/093030

Cited by 46 publications

(40 citation statements)

References 55 publications

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“…17 The current drive efficiency has been observed to be a function of edge parameters through the use of lithiation. 18 The strong discrepancy in current drive efficiency between limited and diverted discharges on C-Mod is also consistent with the hypothesis that interaction between the wave and edge plasma is playing a significant role.…”

Section: à3supporting

confidence: 78%

Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

et al. 2016

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For the first time, the power deposition of lower hybrid RF waves into the edge plasma of a diverted tokamak has been systematically quantified. Edge deposition represents a parasitic loss of power that can greatly impact the use and efficiency of Lower Hybrid Current Drive (LHCD) at reactor-relevant densities. Through the use of a unique set of fast time resolution edge diagnostics, including innovative fast-thermocouples, an extensive set of Langmuir probes, and a Ly a ionization camera, the toroidal, poloidal, and radial structure of the power deposition has been simultaneously determined. Power modulation was used to directly isolate the RF effects due to the prompt (t < s E ) response of the scrape-off-layer (SOL) plasma to Lower Hybrid Radiofrequency (LHRF) power. LHRF power was found to absorb more strongly in the edge at higher densities. It is found that a majority of this edge-deposited power is promptly conducted to the divertor. This correlates with the loss of current drive efficiency at high density previously observed on Alcator C-Mod, and displaying characteristics that contrast with the local RF edge absorption seen on other tokamaks. Measurements of ionization in the active divertor show dramatic changes due to LHRF power, implying that divertor region can be a key for the LHRF edge power deposition physics. These observations support the existence of a loss mechanism near the edge for LHRF at high density (n e > 1:0 Â 10 20 (m À3 )). Results will be shown addressing the distribution of power within the SOL, including the toroidal symmetry and radial distribution. These characteristics are important for deducing the cause of the reduced LHCD efficiency at high density and motivate the tailoring of wave propagation to minimize SOL interaction, for example, through the use of high-field-side launch. Published by AIP Publishing. [http://dx

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Section: à3supporting

confidence: 78%

Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

et al. 2016

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“…Similar results (Ding et al. 2013 a , b , 2015) have also been reported in EAST. Some possible mechanisms, including collisional absorption (CA) (Bonoli & Englade 1986), parametric instabilities (PI) (Liu & Tripathi 1986; Cesario et al.…”

Section: Lhcd Capability At High Densitysupporting

confidence: 87%

“…In order to obtain the scientific goal of EAST (a long pulse and high performance), two LHCD systems have been developed and exploited on EAST, operating, respectively, at 2.45 GHz (4 MW) (Ding et al. 2011, 2015) and 4.6 GHz (6 MW) (Ding et al. 2013 a , b ).…”

Section: Introductionmentioning

confidence: 99%

Studies of challenge in lower hybrid current drive capability at high density regime in experimental advanced superconducting tokamak

Ding

et al. 2017

J. Plasma Phys.

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Aiming at a fusion reactor, two issues must be solved for the lower hybrid current drive (LHCD), namely good lower hybrid wave (LHW)-plasma coupling and effective current drive at high density. For this goal, efforts have been made to improve LHW-plasma coupling and current drive capability at high density in experimental advanced superconducting tokamak (EAST). LHW-plasma coupling is improved by means of local gas puffing and gas puffing from the electron side is taken as a routine way for EAST to operate with LHCD. Studies of high density experiments suggest that low recycling and high lower hybrid (LH) frequency are preferred for LHCD experiments at high density, consistent with previous results in other machines. With the combination of 2.45 GHz and 4.6 GHz LH waves, a repeatable high confinement mode plasma with maximum density up to 4.5 × 10 19 m −3 was obtained by LHCD in EAST. In addition, in the first stage of LHCD cyclic operation, an alternative candidate for more economical fusion reactors has been demonstrated in EAST and further work will be continued.

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“…LHCD is applied for achieving long pulse plasmas and H-mode alone or with ICRF heating together on EAST. Coupling and power deposition at high density of H-mode and L-mode plasmas are main issues for the present EAST experiments [9,10]. Recent experiments focused on effect of local gas puffing from electron-and ion-side of the LHW antenna on coupling improvement with and without Li conditioned wall.…”

Section: Experiments On Lhcd and Icrf Heating 21 Lhcd Coupling And Ementioning

confidence: 99%

Progress of long pulse and H-mode experiments in EAST

Wan¹,

Li²,

Guo³

et al. 2013

Nucl. Fusion

143

118

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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.

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Investigations of LHW-plasma coupling and current drive at high density related to H-mode experiments in EAST

Cited by 46 publications

References 55 publications

Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

Lower hybrid wave edge power loss quantification on the Alcator C-Mod tokamak

Studies of challenge in lower hybrid current drive capability at high density regime in experimental advanced superconducting tokamak

Progress of long pulse and H-mode experiments in EAST

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