Recent Results of LHCD Experiments in EAST

Ding, Bingjun; Kong, E. H.; Li, Miaohui; Qin, Yongliang; Zhang, Lei; Peysson, Y.; Wang, Mao; Xu, Handong; Hu, Huaichuan; Huang, Yiyun; Xu, G. S.; Shan, Jiafang; Liu, Fukun; Zhao, Yanping; Gao, Xiang; Wan, Baonian; Li, Jiangang

doi:10.1088/1009-0630/13/2/05

Cited by 15 publications

(12 citation statements)

References 12 publications

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“…At present, EAST is equipped with a 2 MW LHCD heating system at a frequency of 2.45 GHz, three 1.5 MW ICRH systems with frequency in the range 20-100 MHz and more than 20 plasma diagnostics. The power spectrum for the launched lower hybrid wave can be adjusted in the range 1.85 N peak 2.6 [26], with N peak denoting the peak value of parallel refraction of the launched wave. All the discharges involved in this study used deuterium as the working gas.…”

Section: Methodsmentioning

confidence: 99%

Particle and power deposition on divertor targets in EAST H-mode plasmas

Wang

Guo

et al. 2012

Nucl. Fusion

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The effects of edge-localized modes (ELMs) on divertor particle and heat fluxes were investigated for the first time in the Experimental Advanced Superconducting Tokamak (EAST). The experiments were carried out with both double null and lower single null divertor configurations, and comparisons were made between the H-mode plasmas with lower hybrid current drive (LHCD) and those with combined ion cyclotron resonance heating (ICRH). The particle and heat flux profiles between and during ELMs were obtained from Langmuir triple-probe arrays embedded in the divertor target plates. And isolated ELMs were chosen for analysis in order to reduce the uncertainty resulting from the influence of fast electrons on Langmuir triple-probe evaluation during ELMs. The power deposition obtained from Langmuir triple probes was consistent with that from the divertor infra-red camera during an ELM-free period. It was demonstrated that ELM-induced radial transport predominantly originated from the low-field side region, in good agreement with the ballooning-like transport model and experimental results of other tokamaks. ELMs significantly enhanced the divertor particle and heat fluxes, without significantly broadening the SOL width and plasma-wetted area on the divertor target in both LHCD and LHCD + ICRH H-modes, thus posing a great challenge for the next-step high-power, long-pulse operation in EAST. Increasing the divertor-wetted area was also observed to reduce the peak heat flux and particle recycling at the divertor target, hence facilitating long-pulse H-mode operation. The particle and heat flux profiles during ELMs appeared to exhibit multiple peak structures, and were analysed in terms of the behaviour of ELM filaments and the flux tubes induced by modified magnetic topology during ELMs.

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Section: Methodsmentioning

confidence: 99%

Particle and power deposition on divertor targets in EAST H-mode plasmas

Wang

Guo

et al. 2012

Nucl. Fusion

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“…LHCD (see for example [1][2][3][4] and references therein), we will point to some previous results relevant to the present work in which LH power was used in non-conventional ways to facilitate changes in the plasma. On JFT-2M LH was found to improve confinement, with the improvements attributed to changes in edge potentials and reductions in ExB convection 5 .…”

Section: Introductionmentioning

confidence: 79%

Improved confinement in high-density H-modes via modification of the plasma boundary with lower hybrid wavesa)

et al. 2015

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Injecting Lower Hybrid Radio Frequency (LHRF) waves into Alcator C-Mod's high-density H-mode plasmas has led to enhanced global energy confinement by increasing pedestal temperature and pressure gradients, decreasing the separatrix density, modifying the pedestal radial electric field and rotation, and decreasing edge turbulence. These experiments indicate that edge LHRF can be used as an actuator to increase energy confinement via modification of boundary quantities. H 98 -factor increases of up to ~35% (e.g. H 98 from 0.75 to 1.0) are seen when moderate amounts of LH power (P LH /P tot~0 .15) are applied to H-modes of densities n e~3 x10 20 m -3 , corresponding to values ~0.5 of the Greenwald density. However, the magnitude of the improvement is reduced if the confinement quality of the target Hmode plasma is already good (i.e. H 98 target~1 ). Ray-tracing modeling and accessibility calculations for the LH waves indicate that they do not penetrate to the core. The LHRF power appears to be deposited in plasma boundary region, with a large fraction of the injected power increment appearing promptly on the outer divertor target. There is no evidence that the LH waves are driving current in these plasmas. The LHRF-actuated improvements are well correlated with suppressed pedestal density fluctuations in the 100-300 kHz range. There is also a correlation between the improved confinement and a drop in separatrix density, a correlation that is consistent with previous H-mode results with no LHRF.

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“…2014GB101001 and 2014GB101002) field B t =3.5 T, plasma current I p =1 MA, major/minor radii R/a=1.85 m/0.45 m, and elongation κ up to 1.9. A 2 MW heating power LHCD system at a frequency of 2.45 GHz was equipped on EAST, with the power spectrum for launched waves in the range of 1.85≤ N peak ≤2.6 [7] , where the N peak denoted the peak values of parallel refraction of lower hybrid waves. All the discharges discussed in this paper used deuterium as the working gas, with lithium coating wall conditions.…”

Section: Methodsmentioning

confidence: 99%

Study of Divertor Heat Patterns Induced by LHCD L-Mode Plasmas Using an Infra-Red Camera System on EAST

Zhang

Gan

Gong

et al. 2015

Plasma Sci. Technol.

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Divertor heat patterns induced by Lower Hybrid Current Drive (LHCD) L-mode plasmas are investigated using an infra-red (IR) camera system on an Experimental Advanced Superconducting Tokamak (EAST). A two-dimensional finite element analysis code DFlux is used to compute heat flux along the poloidal divertor target and corresponding quantities. Outside the Origin Strike Zone (OSZ), a Second Peak Heat Flux (SPHF) zone, where the heat flux is even stronger than that at the OSZ, appears on the lower-outer (LO) divertor plates with LHCD and disappears immediately after switching off the LHCD. The main heat-flux shifts from the SPHF zone towards the OSZ when the divertor configuration converts from double null to lower single null, indicating that the growth of the SPHF zone is apparently affected by a plasma magnetic configuration. The heat patterns on the LO divertor plates are observed to be different from that on the lower-inner (LI) targets as the SPHF zone appears only on the LO divertor target. It is also found that the heat flux at the SPHF zone was obviously enhanced after the Supersonic Molecule Beam Injection (SMBI) pulse.

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Recent Results of LHCD Experiments in EAST

Cited by 15 publications

References 12 publications

Particle and power deposition on divertor targets in EAST H-mode plasmas

Particle and power deposition on divertor targets in EAST H-mode plasmas

Improved confinement in high-density H-modes via modification of the plasma boundary with lower hybrid wavesa)

Study of Divertor Heat Patterns Induced by LHCD L-Mode Plasmas Using an Infra-Red Camera System on EAST

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