On the parasitic absorption in FWCD experiments in JET ITB plasmas

T. Hellsten, M. Laxåback, T. Bergkvist, T. Johnson, F. Meo, F. Nguyen, C.C. Petty, M. Mantsinen, G. Matthews, J.-M. Noterdaeme, Tuomas Tala, D. Van Eester, P. Andrew, P. Beaumont, V. Bobkov, M. Brix, J. Brzozowski, L.-G. Eriksson, C. Giroud, E. JoffrinV. Kiptily, J. Mailloux, M-L. Mayoral, I. Monakhov, R. Sartori, A. Staebler, E. Rachlew, E. Tennfors, A. Tuccillo, A. Walden, K. D. Zastrow, JET-EFDA Contributors

Research output: Contribution to journalArticleScientificpeer-review

14 Citations (Scopus)

Abstract

Fast wave current drive (FWCD) experiments have been performed in JET plasmas with electron internal transport barriers produced with LHCD. Because of a large fraction of parasitic absorption, owing to weak single pass damping, the inductive nature of the plasma current and the interplay between the RF-driven current and the bootstrap current only small changes are seen in the central current profiles. The measured difference in the central current density for co- and counter-current drive is larger than the response expected from current diffusion calculations, but smaller than the driven currents, suggesting a faster current diffusion than that given by neo-classical resistivity. A large fraction of the power is absorbed by cyclotron damping on residual 3He ions while a significant fraction appears not to have been deposited in the plasma. The strong degradation of heating and current drive occurs simultaneously with strong increases in the Be II and C IV line intensities in the divertor. The degradation depends on the phasing of the antennas and increases with reduced single pass damping which is consistent with RF-power being lost by dissipation of rectified RF-sheath potentials at the antennas and walls. Asymmetries in direct electron heating, lost power and production of impurities, fast ions and gamma-rays are seen for co- and counter-current drive. These differences are consistent with the differences in the absorption on residual 3He ions owing to the RF-induced pinch. Effective direct electron heating, comparable to the indirect electron heating with H-minority heating, occurs for dipole phasing of the antennas without producing a significant fast ion pressure and with low impurity content in the divertor plasma.
Original languageEnglish
Pages (from-to)706 - 720
Number of pages15
JournalNuclear Fusion
Volume45
Issue number7
DOIs
Publication statusPublished - 2005
MoE publication typeA1 Journal article-refereed

Fingerprint

heating
antennas
damping
ions
counters
electrons
degradation
impurities
plasma currents
minorities
sheaths
cyclotrons
dissipation
asymmetry
gamma rays
current density
dipoles
electrical resistivity
profiles

Keywords

  • JET
  • plasma
  • fusion energy
  • fusion reactors
  • ITER
  • Tokamak
  • internal transport barriers

Cite this

Hellsten, T., Laxåback, M., Bergkvist, T., Johnson, T., Meo, F., Nguyen, F., ... JET-EFDA Contributors (2005). On the parasitic absorption in FWCD experiments in JET ITB plasmas. Nuclear Fusion, 45(7), 706 - 720. https://doi.org/10.1088/0029-5515/45/7/020
Hellsten, T. ; Laxåback, M. ; Bergkvist, T. ; Johnson, T. ; Meo, F. ; Nguyen, F. ; Petty, C.C. ; Mantsinen, M. ; Matthews, G. ; Noterdaeme, J.-M. ; Tala, Tuomas ; Van Eester, D. ; Andrew, P. ; Beaumont, P. ; Bobkov, V. ; Brix, M. ; Brzozowski, J. ; Eriksson, L.-G. ; Giroud, C. ; Joffrin, E. ; Kiptily, V. ; Mailloux, J. ; Mayoral, M-L. ; Monakhov, I. ; Sartori, R. ; Staebler, A. ; Rachlew, E. ; Tennfors, E. ; Tuccillo, A. ; Walden, A. ; Zastrow, K. D. ; JET-EFDA Contributors. / On the parasitic absorption in FWCD experiments in JET ITB plasmas. In: Nuclear Fusion. 2005 ; Vol. 45, No. 7. pp. 706 - 720.
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title = "On the parasitic absorption in FWCD experiments in JET ITB plasmas",
abstract = "Fast wave current drive (FWCD) experiments have been performed in JET plasmas with electron internal transport barriers produced with LHCD. Because of a large fraction of parasitic absorption, owing to weak single pass damping, the inductive nature of the plasma current and the interplay between the RF-driven current and the bootstrap current only small changes are seen in the central current profiles. The measured difference in the central current density for co- and counter-current drive is larger than the response expected from current diffusion calculations, but smaller than the driven currents, suggesting a faster current diffusion than that given by neo-classical resistivity. A large fraction of the power is absorbed by cyclotron damping on residual 3He ions while a significant fraction appears not to have been deposited in the plasma. The strong degradation of heating and current drive occurs simultaneously with strong increases in the Be II and C IV line intensities in the divertor. The degradation depends on the phasing of the antennas and increases with reduced single pass damping which is consistent with RF-power being lost by dissipation of rectified RF-sheath potentials at the antennas and walls. Asymmetries in direct electron heating, lost power and production of impurities, fast ions and gamma-rays are seen for co- and counter-current drive. These differences are consistent with the differences in the absorption on residual 3He ions owing to the RF-induced pinch. Effective direct electron heating, comparable to the indirect electron heating with H-minority heating, occurs for dipole phasing of the antennas without producing a significant fast ion pressure and with low impurity content in the divertor plasma.",
keywords = "JET, plasma, fusion energy, fusion reactors, ITER, Tokamak, internal transport barriers",
author = "T. Hellsten and M. Lax{\aa}back and T. Bergkvist and T. Johnson and F. Meo and F. Nguyen and C.C. Petty and M. Mantsinen and G. Matthews and J.-M. Noterdaeme and Tuomas Tala and {Van Eester}, D. and P. Andrew and P. Beaumont and V. Bobkov and M. Brix and J. Brzozowski and L.-G. Eriksson and C. Giroud and E. Joffrin and V. Kiptily and J. Mailloux and M-L. Mayoral and I. Monakhov and R. Sartori and A. Staebler and E. Rachlew and E. Tennfors and A. Tuccillo and A. Walden and Zastrow, {K. D.} and {JET-EFDA Contributors}",
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pages = "706 -- 720",
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Hellsten, T, Laxåback, M, Bergkvist, T, Johnson, T, Meo, F, Nguyen, F, Petty, CC, Mantsinen, M, Matthews, G, Noterdaeme, J-M, Tala, T, Van Eester, D, Andrew, P, Beaumont, P, Bobkov, V, Brix, M, Brzozowski, J, Eriksson, L-G, Giroud, C, Joffrin, E, Kiptily, V, Mailloux, J, Mayoral, M-L, Monakhov, I, Sartori, R, Staebler, A, Rachlew, E, Tennfors, E, Tuccillo, A, Walden, A, Zastrow, KD & JET-EFDA Contributors 2005, 'On the parasitic absorption in FWCD experiments in JET ITB plasmas', Nuclear Fusion, vol. 45, no. 7, pp. 706 - 720. https://doi.org/10.1088/0029-5515/45/7/020

On the parasitic absorption in FWCD experiments in JET ITB plasmas. / Hellsten, T.; Laxåback, M.; Bergkvist, T.; Johnson, T.; Meo, F.; Nguyen, F.; Petty, C.C.; Mantsinen, M.; Matthews, G.; Noterdaeme, J.-M.; Tala, Tuomas; Van Eester, D.; Andrew, P.; Beaumont, P.; Bobkov, V.; Brix, M.; Brzozowski, J.; Eriksson, L.-G.; Giroud, C.; Joffrin, E.; Kiptily, V.; Mailloux, J.; Mayoral, M-L.; Monakhov, I.; Sartori, R.; Staebler, A.; Rachlew, E.; Tennfors, E.; Tuccillo, A.; Walden, A.; Zastrow, K. D.; JET-EFDA Contributors.

In: Nuclear Fusion, Vol. 45, No. 7, 2005, p. 706 - 720.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - On the parasitic absorption in FWCD experiments in JET ITB plasmas

AU - Hellsten, T.

AU - Laxåback, M.

AU - Bergkvist, T.

AU - Johnson, T.

AU - Meo, F.

AU - Nguyen, F.

AU - Petty, C.C.

AU - Mantsinen, M.

AU - Matthews, G.

AU - Noterdaeme, J.-M.

AU - Tala, Tuomas

AU - Van Eester, D.

AU - Andrew, P.

AU - Beaumont, P.

AU - Bobkov, V.

AU - Brix, M.

AU - Brzozowski, J.

AU - Eriksson, L.-G.

AU - Giroud, C.

AU - Joffrin, E.

AU - Kiptily, V.

AU - Mailloux, J.

AU - Mayoral, M-L.

AU - Monakhov, I.

AU - Sartori, R.

AU - Staebler, A.

AU - Rachlew, E.

AU - Tennfors, E.

AU - Tuccillo, A.

AU - Walden, A.

AU - Zastrow, K. D.

AU - JET-EFDA Contributors, null

PY - 2005

Y1 - 2005

N2 - Fast wave current drive (FWCD) experiments have been performed in JET plasmas with electron internal transport barriers produced with LHCD. Because of a large fraction of parasitic absorption, owing to weak single pass damping, the inductive nature of the plasma current and the interplay between the RF-driven current and the bootstrap current only small changes are seen in the central current profiles. The measured difference in the central current density for co- and counter-current drive is larger than the response expected from current diffusion calculations, but smaller than the driven currents, suggesting a faster current diffusion than that given by neo-classical resistivity. A large fraction of the power is absorbed by cyclotron damping on residual 3He ions while a significant fraction appears not to have been deposited in the plasma. The strong degradation of heating and current drive occurs simultaneously with strong increases in the Be II and C IV line intensities in the divertor. The degradation depends on the phasing of the antennas and increases with reduced single pass damping which is consistent with RF-power being lost by dissipation of rectified RF-sheath potentials at the antennas and walls. Asymmetries in direct electron heating, lost power and production of impurities, fast ions and gamma-rays are seen for co- and counter-current drive. These differences are consistent with the differences in the absorption on residual 3He ions owing to the RF-induced pinch. Effective direct electron heating, comparable to the indirect electron heating with H-minority heating, occurs for dipole phasing of the antennas without producing a significant fast ion pressure and with low impurity content in the divertor plasma.

AB - Fast wave current drive (FWCD) experiments have been performed in JET plasmas with electron internal transport barriers produced with LHCD. Because of a large fraction of parasitic absorption, owing to weak single pass damping, the inductive nature of the plasma current and the interplay between the RF-driven current and the bootstrap current only small changes are seen in the central current profiles. The measured difference in the central current density for co- and counter-current drive is larger than the response expected from current diffusion calculations, but smaller than the driven currents, suggesting a faster current diffusion than that given by neo-classical resistivity. A large fraction of the power is absorbed by cyclotron damping on residual 3He ions while a significant fraction appears not to have been deposited in the plasma. The strong degradation of heating and current drive occurs simultaneously with strong increases in the Be II and C IV line intensities in the divertor. The degradation depends on the phasing of the antennas and increases with reduced single pass damping which is consistent with RF-power being lost by dissipation of rectified RF-sheath potentials at the antennas and walls. Asymmetries in direct electron heating, lost power and production of impurities, fast ions and gamma-rays are seen for co- and counter-current drive. These differences are consistent with the differences in the absorption on residual 3He ions owing to the RF-induced pinch. Effective direct electron heating, comparable to the indirect electron heating with H-minority heating, occurs for dipole phasing of the antennas without producing a significant fast ion pressure and with low impurity content in the divertor plasma.

KW - JET

KW - plasma

KW - fusion energy

KW - fusion reactors

KW - ITER

KW - Tokamak

KW - internal transport barriers

U2 - 10.1088/0029-5515/45/7/020

DO - 10.1088/0029-5515/45/7/020

M3 - Article

VL - 45

SP - 706

EP - 720

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 7

ER -

Hellsten T, Laxåback M, Bergkvist T, Johnson T, Meo F, Nguyen F et al. On the parasitic absorption in FWCD experiments in JET ITB plasmas. Nuclear Fusion. 2005;45(7):706 - 720. https://doi.org/10.1088/0029-5515/45/7/020