Edge density modification with rf on TFTR and DIII-D

Hanson, G. R.; England, A.C.; Wilgen, J. B.; Baity, F. W.; Batchelor, D. B.; Carter, M. D.; Hoffman, D. J.; Murakami, M.; Rasmussen, D. A.; Ryan, P. M.; Swain, D. W.; Rogers, J. H.; Wilson, J. R.; Majeski, R.; Schilling, G.; Doyle, E. J.; Kim, K. W.

doi:10.1063/1.49506

Cited by 3 publications

(2 citation statements)

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“…The former will reduce the local density and the the latter can generate density convection in the SOL. Some of the important results of the effects of ICRF-related parameters on LHW coupling from other tokamaks correlated with experiments presented in this paper are edge plasma density convection during ICRH on Tore Supra [29], understanding the spatial structure of RF-induced SOL modifications [18], effect of ICRF induced density modifications on LHW coupling at JET [19] and edge density modification with RF powers on TFTR and DIII-D [31]. In the JET experiment, the density modification in SOL during ICRF power is successfully measured by a Li beam, including the case with different ICRF phasing.…”

Section: Brief Description Of Rf Sheath Physicssupporting

confidence: 64%

Study and optimization of lower hybrid wave coupling in the experimental advanced superconducting (EAST) tokamak

Kong

Ding

Zhang

et al. 2013

Plasma Phys. Control. Fusion

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The results presented in this paper are an extension of our recent (Kong et al 2012 Plasma Phys. Control. Fusion 54 105003) studies on lower hybrid wave (LHW) coupling. By optimizing the shape of the LH grill, the misalignment between the poloidal limiter (PL) and the LH grill is nearly eliminated and the coupling of LHW is improved, especially on the top row, although some discrepancies are still present in the case with low edge density. Density modifications both by LHW and ion cyclotron range of frequency (ICRF) power are studied in EAST. Experimental results show that the edge density modification in front of the LH grill during LHW power depends mainly on the competition between ponderomotive force (PMF) and the ionization of neutral gas, provided by gas puffing and edge recycling. However, the local edge density during ICRF power can be reduced rapidly. Furthermore, such a modification is more obvious with higher ICRF power and the relevant mechanism of density modification by ICRF power can be related to RF sheaths. In addition, another analogous effect of RF sheaths on the coupling of LHW is also investigated, i.e. the density convection induced by E r × B drift. The changes in LHW coupling associated with different ICRF antennas are discussed and it is shown that in some cases the coupling on the lower rows of the LH grill is improved possibly due to magnetic connection between ICRF antennas and the LH grill. The local coupling of LHW can be improved by gas puffing from gas introduction modules (GIM) on both sides of the launcher, but it is difficult to judge which one is more beneficial due to errors in measurements. Experimental results with gas (D 2 ) injection during ICRF power clearly show that the coupling of LHW on the upper rows will be first improved by gas injection on the electron side and the coupling on the lower rows will be effectively improved by gas injection on the ion side. The results are consistent with the mapping of field lines.

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Section: Brief Description Of Rf Sheath Physicssupporting

confidence: 64%

Study and optimization of lower hybrid wave coupling in the experimental advanced superconducting (EAST) tokamak

Kong

Ding

Zhang

et al. 2013

Plasma Phys. Control. Fusion

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“…1,2 The density profiles, though, can be affected by the high power waves, 3,4 so LHRF coupling and scrape-off layer (SOL) density profiles are inherently interdependent. An X-mode reflectometer installed adjacent to the LH launcher ( Fig.…”

Section: Introductionmentioning

confidence: 99%

First results of the SOL reflectometer on Alcator C-Mod

Lau

Hanson

Lin

et al. 2012

Review of Scientific Instruments

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A swept-frequency X-mode reflectometer has been built on Alcator C-Mod to measure the scrape-off layer (SOL) density profiles adjacent to the lower hybrid launcher. The reflectometer system operates between 100 and 146 GHz at sweep rates from 10 μs to 1 ms and covers a density range of ∼10(16)-10(20) m(-3) at B(0) = 5-5.4 T. This paper discusses the analysis of reflectometer density profiles and presents first experimental results of SOL density profile modifications due to the application of lower hybrid range-of-frequencies power to L-mode discharges. Comparison between density profiles measured by the X-mode reflectometer and scanning Langmuir probes is also shown.

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Analysis of RF sheath interactions in TFTR

D’Ippolito¹,

Myra²,

Rogers³

et al. 1998

Nucl. Fusion

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New theoretical and experimental tools are applied to the analysis of ICRF antenna-edge plasma interactions in the Tokamak Fusion Test Reactor (TFTR) tokamak. A new numerical method for computing the three-dimensional rf sheath voltage distribution is used, and the quantitative predictions of rf sheath theory are compared with measurements of the edge density profile obtained by microwave reflectometry and with titanium impurity concentration data. It is shown that the local density depletion at the antenna is consistent with density pump-out by strong E × B convection into the Faraday screen. Modeling of the Faraday screen impurity influx shows that the calculated Ti impurity concentration based on this direct influx agrees with the measured concentration for π phasing. It is also shown that screening of impurity neutrals by ionization in the SOL is a large effect and increases with rf power. At high power over many shots, a fraction of the metal impurities migrates around the machine and is deposited on the limiters, providing a secondary source of titanium. The data shows that the central Ti concentration is strongly dependent on antenna phasing. Possible explanations for this phasing dependence are discussed.

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Edge density modification with rf on TFTR and DIII-D

Cited by 3 publications

References 0 publications

Study and optimization of lower hybrid wave coupling in the experimental advanced superconducting (EAST) tokamak

Study and optimization of lower hybrid wave coupling in the experimental advanced superconducting (EAST) tokamak

First results of the SOL reflectometer on Alcator C-Mod

Analysis of RF sheath interactions in TFTR

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