Measurements of ICRF loading on DIII-D with and without a faraday shield

D. W. Swain; R. I. Pinsker; F. W. Baity; M. D. Carter; J. S. DeGrassie; E. J. Doyle; G. R. Hanson; K. W. Kim; R. A. Moyer; C. C. Petty

doi:10.1088/0029-5515/37/2/I06

Measurements of ICRF loading on DIII-D with and without a faraday shield

D. W. Swain, R. I. Pinsker, F. W. Baity, M. D. Carter, J. S. DeGrassie, E. J. Doyle, G. R. Hanson, K. W. Kim, R. A. Moyer, C. C. Petty

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Abstract

Measurements of radiofrequency (RF) loading on the Doublet III D shape (DIII-D) tokamak using a fast wave ion cyclotron antenna with and without a Faraday shield present indicate that the loading resistance seen by the antenna is significantly higher at low values of RF power (P ≤ 20 kW with no Faraday shield) than is predicted by standard fast wave antenna coupling theory. Measurements of the density profile in the plasma edge region allow a direct comparison of calculated and measured loading. At high power, the calculated fast wave loading agrees with the measurements. The high loading observed at low power can be explained by direct losses in an RF enhanced sheath. The density value at the current strap of ≈4 × 10¹⁰ cm^-3 needed to give the observed loading behaviour is in agreement with the measured density values in the plasma scrape-off region, extrapolated to the current strap location using a simple Bohm diffusion model.

Original language	English
Pages (from-to)	211-224
Number of pages	14
Journal	Nuclear Fusion
Volume	37
Issue number	2
DOIs	https://doi.org/10.1088/0029-5515/37/2/I06
State	Published - Feb 1997

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@article{4b15009bb21d4b119c2405065f376837,

title = "Measurements of ICRF loading on DIII-D with and without a faraday shield",

abstract = "Measurements of radiofrequency (RF) loading on the Doublet III D shape (DIII-D) tokamak using a fast wave ion cyclotron antenna with and without a Faraday shield present indicate that the loading resistance seen by the antenna is significantly higher at low values of RF power (P ≤ 20 kW with no Faraday shield) than is predicted by standard fast wave antenna coupling theory. Measurements of the density profile in the plasma edge region allow a direct comparison of calculated and measured loading. At high power, the calculated fast wave loading agrees with the measurements. The high loading observed at low power can be explained by direct losses in an RF enhanced sheath. The density value at the current strap of ≈4 × 1010 cm-3 needed to give the observed loading behaviour is in agreement with the measured density values in the plasma scrape-off region, extrapolated to the current strap location using a simple Bohm diffusion model.",

author = "Swain, {D. W.} and Pinsker, {R. I.} and Baity, {F. W.} and Carter, {M. D.} and DeGrassie, {J. S.} and Doyle, {E. J.} and Hanson, {G. R.} and Kim, {K. W.} and Moyer, {R. A.} and Petty, {C. C.}",

year = "1997",

month = feb,

doi = "10.1088/0029-5515/37/2/I06",

language = "English",

volume = "37",

pages = "211--224",

journal = "Nuclear Fusion",

issn = "0029-5515",

publisher = "IOP Publishing Ltd.",

number = "2",

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TY - JOUR

T1 - Measurements of ICRF loading on DIII-D with and without a faraday shield

AU - Swain, D. W.

AU - Pinsker, R. I.

AU - Baity, F. W.

AU - Carter, M. D.

AU - DeGrassie, J. S.

AU - Doyle, E. J.

AU - Hanson, G. R.

AU - Kim, K. W.

AU - Moyer, R. A.

AU - Petty, C. C.

PY - 1997/2

Y1 - 1997/2

N2 - Measurements of radiofrequency (RF) loading on the Doublet III D shape (DIII-D) tokamak using a fast wave ion cyclotron antenna with and without a Faraday shield present indicate that the loading resistance seen by the antenna is significantly higher at low values of RF power (P ≤ 20 kW with no Faraday shield) than is predicted by standard fast wave antenna coupling theory. Measurements of the density profile in the plasma edge region allow a direct comparison of calculated and measured loading. At high power, the calculated fast wave loading agrees with the measurements. The high loading observed at low power can be explained by direct losses in an RF enhanced sheath. The density value at the current strap of ≈4 × 1010 cm-3 needed to give the observed loading behaviour is in agreement with the measured density values in the plasma scrape-off region, extrapolated to the current strap location using a simple Bohm diffusion model.

AB - Measurements of radiofrequency (RF) loading on the Doublet III D shape (DIII-D) tokamak using a fast wave ion cyclotron antenna with and without a Faraday shield present indicate that the loading resistance seen by the antenna is significantly higher at low values of RF power (P ≤ 20 kW with no Faraday shield) than is predicted by standard fast wave antenna coupling theory. Measurements of the density profile in the plasma edge region allow a direct comparison of calculated and measured loading. At high power, the calculated fast wave loading agrees with the measurements. The high loading observed at low power can be explained by direct losses in an RF enhanced sheath. The density value at the current strap of ≈4 × 1010 cm-3 needed to give the observed loading behaviour is in agreement with the measured density values in the plasma scrape-off region, extrapolated to the current strap location using a simple Bohm diffusion model.

UR - http://www.scopus.com/inward/record.url?scp=0031071861&partnerID=8YFLogxK

U2 - 10.1088/0029-5515/37/2/I06

DO - 10.1088/0029-5515/37/2/I06

M3 - Article

AN - SCOPUS:0031071861

SN - 0029-5515

VL - 37

SP - 211

EP - 224

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 2

ER -

Measurements of ICRF loading on DIII-D with and without a faraday shield

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