Experimental analysis of the ICRF waves coupling in EAST

Zhang, Junhui; Liu, J.; Cheng, Yan; Qin, Chengming; Zhao, Yanping; Mao, Yuzhou; Yuan, Shuai; Wang, L.; Ju, S. Q.; Chen, G.; Wan, B. N.; Gong, Xianzu; Qian, J.; Zhang, Taiping; Li, J. G.; Song, Yuntao; Yang, Yong; Chen, Zhiwen; Wang, J. H.; Lin, Y.; Taylor, G.; Wukitch, S.J.; Noterdaeme, Jean-Marie; Hosea, J.; Kumazawa, R.; Seki, T.; Saito, Kenji; Kasahara, Hiroshi

doi:10.1088/1741-4326/aa69ca

Cited by 33 publications

(34 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…All show deleterious impact of ICRH power. While no influence of LHWs on ICRF was noticed in L-mode, on the contrary in H-mode, LHWs were found to have some positive effects [8,4]. Density gradient being stiff, in H-mode, Fig.…”

Section: Resultsmentioning

confidence: 99%

Characterization of the mutual influence of Ion Cyclotron and Lower Hybrid Range of frequencies systems on EAST

et al. 2017

View full text Add to dashboard Cite

Abstract. Waves in the Ion Cyclotron (ICRF) and Lower Hybrid (LH) Range of Frequencies are efficient techniques respectively to heat the plasma and drive current. Main difficulties come from a trade-off between good RF coupling and acceptable level of impurities release. The mutual influence of both systems makes such equilibrium often hard to reach [1]. In order to investigate those interactions based on ScrapeOff Layer (SOL) plasma parameters, a new reciprocating probe was designed allying a three tips Langmuir probe with an emissive wire. The emissive filament provides a precise measure of plasma potential [2], which can be used to calibrate Langmuir probe's results. This paper reports on experimental results obtained on EAST, where there are two ICRF antennas and two LH launchers. Among others diagnostics, the new reciprocating probe enabled to evidence the deleterious influence of ICRF power on LHWs coupling in Lmode plasmas. In areas connected with an active ICRF antenna, SOL potentials increase while densities tend to decrease, respectively enhancing impurities release and deteriorating LHWs coupling. This phenomenon has mostly been attributed to RF sheath; the one that forms on top of Plasma Facing Components (PFCs) and causes ExB density convections [3]. From those experiments it seems ICRF has a strong influence on magnetically connected areas, both in the near field -influencing ICRF waves coupling -and in farther locations such as in front of LH grills. Moreover, influence of ICRF on LH system was observed both in L and H modes. Those results are consistent with RF sheath rectification process. Concerning the influence of LHWs on ICRF coupling, nothing was observed in L-mode. Besides during Hmode experiments, LHWs have been identified as having a mitigating effect on ELMs [4], which on average lowers the pedestal, increasing edge densities to the profit of ICRF waves coupling.

show abstract

Section: Resultsmentioning

confidence: 99%

Characterization of the mutual influence of Ion Cyclotron and Lower Hybrid Range of frequencies systems on EAST

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Mostly to simplify the analysis of the edge diagnostics data, but also because EAST ICRF system [13] does not have very strong load resilience, operations in H-mode are not appropriate to the present study which is performed in L-mode. The EAST ICRF antenna loading can be estimated by two different methods respectively based on voltage/current probes [13] and voltage probe arrays [14]. In this paper we will use the second technique which often gives more accurate results; for each shot, the maximum voltage V max is measured with voltage probe arrays in different points of each transmission lines of characteristic impedance Z 0 as shown on Fig.…”

Section: Presentation Of East Parameters and Diagnostics Used In Thismentioning

confidence: 99%

Optimization of discharges with ion cyclotron range of frequencies using local gas injection in EAST

et al. 2019

Self Cite

View full text Add to dashboard Cite

In view of improving Ion Cyclotron Range of Frequencies (ICRF) wave coupling in EAST (Experimental Advanced Superconducting Tokamak) necessary to obtain high-power discharges, two series of experiments in L-mode were devoted to the use of local gas injection as a tool to increase density in front of the antennas.During the first session, the quantity of deuterium simultaneously puffed from five different poloidal positions on each side of one ICRF antenna was gradually increased. Steady gas puffing on this antenna (~8.10 20 e/s) increased antenna coupling resistance by 100%, but puffing more gas did not provoke any further improvement.Plasma central electron density was not kept constant when using local puff but kept increasing during the discharges. During the second session, the global density was well-controlled and remained constant, the distance between the separatrix and the first wall was increased by 2cm allowing, the gas to spread better, and puffing more gas this time lead to better wave coupling. The same amount of gas was then puffed from three different locations and changes in SOL (Scrape-Off Layer) parameters were measured from several locations. Extensive analysis of the edge diagnostics made it possible to observe an electron density increase and a temperature decrease caused by the ionization of neutrals in the SOL. Heat loads on the divertor targets were slightly mitigated by gas injection, which is favorable from the perspective of long pulse scenario development. Injection at mid-plane led to the best results with the highest coupling simultaneously achieved for both antennas and smallest heat loads on the divertor target (below 1MW/m²). As far as wave coupling efficiency is concerned, most experimental trends were also successfully reproduced by antenna modelling with the RAPLICASOL finite element code with experimental density profiles from reflectometry as the main input.

show abstract

“…In order to study the ICRF coupling, some important experiments [13] including changing plasma position…”

Section: Icrf Coupling and Heating On Eastmentioning

confidence: 99%

Recent progress of RF-dominated experiments on EAST

et al. 2017

Self Cite

View full text Add to dashboard Cite

Abstract. The research of EAST program is mostly focused on the development of high performance steady state scenario with ITER-like poloidal configuration and RF-dominated heating schemes. With the enhanced ITER-relevant auxiliary heating and current drive systems, the plasma profile control by coupling/integration of various combinations has been investigated, including lower hybrid current drive (LHCD), electron cyclotron resonance heating (ECRH) and ion cyclotron resonance heating (ICRH). The 12 MW ICRH system has been installed on EAST. Heating and confinement studies using the Hydrogen Minority Heating scheme have been investigated. One of the importance challenges for EAST is coupling higher power into the core plasma, experiments including changing plasma position, electron density, local gas puffing and antenna phasing scanning were performed to improve ICRF coupling efficiency on EAST. Results show that local gas injection and reducing the k|| can improve the coupling efficiency directly. By means of the 4.6 GHz and 2.45 GHz LHCD systems, H-mode can be obtained and sustained at relatively high density, even up to ne ~ 4.5 × 10 19 m -3, where a current drive effect is still observed. Meanwhile, effect of source frequency (2.45GHz and 4.6GHz) on LHCD characteristic has been studied on EAST, showing that higher frequency improves penetration of the coupled LH (lower hybrid) power into the plasma core and leads to a better effect on plasma characteristics. Studies demonstrate the role of parasitic effects of edge plasma in LHCD and the mitigation by increasing source frequency. Experiments of effect of LH spectrum and plasma density on plasma characteristics are performed, suggesting the possibility of plasma control for high performance. The development of a 4MW ECRH system is in progress for the purpose of plasma heating and MHD control. The built ECRH system with 1MW source power has been successfully put into use on EAST in 2015. H-mode discharges with L-H transition triggered by ECRH injection were obtained and its effects on the electron temperature, particle confinement and the core MHD stabilities were observed. By further exploring and optimizing the RF combination for the sole RF heating and current drive regime, fully non-inductive H-mode discharges with V loop~0 V has progressed steadily in the 2016 campaign. The overview of the significant progress of RF dominated experiments is presented in this paper.

show abstract

Experimental analysis of the ICRF waves coupling in EAST

Cited by 33 publications

References 16 publications

Characterization of the mutual influence of Ion Cyclotron and Lower Hybrid Range of frequencies systems on EAST

Characterization of the mutual influence of Ion Cyclotron and Lower Hybrid Range of frequencies systems on EAST

Optimization of discharges with ion cyclotron range of frequencies using local gas injection in EAST

Recent progress of RF-dominated experiments on EAST

Contact Info

Product

Resources

About