Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D

M. A. Van Zeeland; W. W. Heidbrink; R. Nazikian; M. E. Austin; C. Z. Cheng; M. S. Chu; N. N. Gorelenkov; C. T. Holcomb; A. W. Hyatt; G. J. Kramer; J. Lohr; G. R. McKee; C. C. Petty; R. Prater; W. M. Solomon; D. A. Spong

doi:10.1088/0029-5515/49/6/065003

Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D

M. A. Van Zeeland, W. W. Heidbrink, R. Nazikian, M. E. Austin, C. Z. Cheng, M. S. Chu, N. N. Gorelenkov, C. T. Holcomb, A. W. Hyatt, G. J. Kramer, J. Lohr, G. R. McKee, C. C. Petty, R. Prater, W. M. Solomon, D. A. Spong

Plasma Theory and Modeling

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Abstract

Neutral beam injection into reversed magnetic shear DIII-D plasmas produces a variety of Alfvénic activity including toroidicity and ellipticity induced Alfvén eigenmodes (TAE/EAE, respectively) and reversed shear Alfvén eigenmodes (RSAE) as well as their spatial coupling. These modes are studied during the discharge current ramp phase when incomplete current penetration results in a high central safety factor and strong drive due to multiple higher order resonances. It is found that ideal MHD modelling of eigenmode spectral evolution, coupling and structure are in excellent agreement with experimental measurements. It is also found that higher radial envelope harmonic RSAEs are clearly observed and agree with modelling. Some discrepancies with modelling such as that due to up/down eigenmode asymmetries are also pointed out. Concomitant with the Alfvénic activity, fast ion (FIDA) spectroscopy shows large reductions in the central fast ion profile, the degree of which depends on the Alfvén eigenmode amplitude. Interestingly, localized electron cyclotron heating (ECH) near the mode location stabilizes RSAE activity and results in significantly improved fast ion confinement relative to discharges with ECH deposition on axis. In these discharges, RSAE activity is suppressed when ECH is deposited near the radius of the shear reversal point and enhanced with deposition near the axis. The sensitivity of this effect to deposition power and current drive phasing as well as ECH modulation are presented.

Original language	English
Article number	065003
Journal	Nuclear Fusion
Volume	49
Issue number	6
DOIs	https://doi.org/10.1088/0029-5515/49/6/065003
State	Published - 2009

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Van Zeeland, M. A., Heidbrink, W. W., Nazikian, R., Austin, M. E., Cheng, C. Z., Chu, M. S., Gorelenkov, N. N., Holcomb, C. T., Hyatt, A. W., Kramer, G. J., Lohr, J., McKee, G. R., Petty, C. C., Prater, R., Solomon, W. M., & Spong, D. A. (2009). Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D. Nuclear Fusion, 49(6), Article 065003. https://doi.org/10.1088/0029-5515/49/6/065003

@article{78723d9f350241af98e69517a8729a47,

title = "Measurements, modelling and electron cyclotron heating modification of Alfv{\'e}n eigenmode activity in DIII-D",

abstract = "Neutral beam injection into reversed magnetic shear DIII-D plasmas produces a variety of Alfv{\'e}nic activity including toroidicity and ellipticity induced Alfv{\'e}n eigenmodes (TAE/EAE, respectively) and reversed shear Alfv{\'e}n eigenmodes (RSAE) as well as their spatial coupling. These modes are studied during the discharge current ramp phase when incomplete current penetration results in a high central safety factor and strong drive due to multiple higher order resonances. It is found that ideal MHD modelling of eigenmode spectral evolution, coupling and structure are in excellent agreement with experimental measurements. It is also found that higher radial envelope harmonic RSAEs are clearly observed and agree with modelling. Some discrepancies with modelling such as that due to up/down eigenmode asymmetries are also pointed out. Concomitant with the Alfv{\'e}nic activity, fast ion (FIDA) spectroscopy shows large reductions in the central fast ion profile, the degree of which depends on the Alfv{\'e}n eigenmode amplitude. Interestingly, localized electron cyclotron heating (ECH) near the mode location stabilizes RSAE activity and results in significantly improved fast ion confinement relative to discharges with ECH deposition on axis. In these discharges, RSAE activity is suppressed when ECH is deposited near the radius of the shear reversal point and enhanced with deposition near the axis. The sensitivity of this effect to deposition power and current drive phasing as well as ECH modulation are presented.",

author = "{Van Zeeland}, {M. A.} and Heidbrink, {W. W.} and R. Nazikian and Austin, {M. E.} and Cheng, {C. Z.} and Chu, {M. S.} and Gorelenkov, {N. N.} and Holcomb, {C. T.} and Hyatt, {A. W.} and Kramer, {G. J.} and J. Lohr and McKee, {G. R.} and Petty, {C. C.} and R. Prater and Solomon, {W. M.} and Spong, {D. A.}",

year = "2009",

doi = "10.1088/0029-5515/49/6/065003",

language = "English",

volume = "49",

journal = "Nuclear Fusion",

issn = "0029-5515",

publisher = "IOP Publishing",

number = "6",

}

Van Zeeland, MA, Heidbrink, WW, Nazikian, R, Austin, ME, Cheng, CZ, Chu, MS, Gorelenkov, NN, Holcomb, CT, Hyatt, AW, Kramer, GJ, Lohr, J, McKee, GR, Petty, CC, Prater, R, Solomon, WM & Spong, DA 2009, 'Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D', Nuclear Fusion, vol. 49, no. 6, 065003. https://doi.org/10.1088/0029-5515/49/6/065003

TY - JOUR

T1 - Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D

AU - Van Zeeland, M. A.

AU - Heidbrink, W. W.

AU - Nazikian, R.

AU - Austin, M. E.

AU - Cheng, C. Z.

AU - Chu, M. S.

AU - Gorelenkov, N. N.

AU - Holcomb, C. T.

AU - Hyatt, A. W.

AU - Kramer, G. J.

AU - Lohr, J.

AU - McKee, G. R.

AU - Petty, C. C.

AU - Prater, R.

AU - Solomon, W. M.

AU - Spong, D. A.

PY - 2009

Y1 - 2009

N2 - Neutral beam injection into reversed magnetic shear DIII-D plasmas produces a variety of Alfvénic activity including toroidicity and ellipticity induced Alfvén eigenmodes (TAE/EAE, respectively) and reversed shear Alfvén eigenmodes (RSAE) as well as their spatial coupling. These modes are studied during the discharge current ramp phase when incomplete current penetration results in a high central safety factor and strong drive due to multiple higher order resonances. It is found that ideal MHD modelling of eigenmode spectral evolution, coupling and structure are in excellent agreement with experimental measurements. It is also found that higher radial envelope harmonic RSAEs are clearly observed and agree with modelling. Some discrepancies with modelling such as that due to up/down eigenmode asymmetries are also pointed out. Concomitant with the Alfvénic activity, fast ion (FIDA) spectroscopy shows large reductions in the central fast ion profile, the degree of which depends on the Alfvén eigenmode amplitude. Interestingly, localized electron cyclotron heating (ECH) near the mode location stabilizes RSAE activity and results in significantly improved fast ion confinement relative to discharges with ECH deposition on axis. In these discharges, RSAE activity is suppressed when ECH is deposited near the radius of the shear reversal point and enhanced with deposition near the axis. The sensitivity of this effect to deposition power and current drive phasing as well as ECH modulation are presented.

AB - Neutral beam injection into reversed magnetic shear DIII-D plasmas produces a variety of Alfvénic activity including toroidicity and ellipticity induced Alfvén eigenmodes (TAE/EAE, respectively) and reversed shear Alfvén eigenmodes (RSAE) as well as their spatial coupling. These modes are studied during the discharge current ramp phase when incomplete current penetration results in a high central safety factor and strong drive due to multiple higher order resonances. It is found that ideal MHD modelling of eigenmode spectral evolution, coupling and structure are in excellent agreement with experimental measurements. It is also found that higher radial envelope harmonic RSAEs are clearly observed and agree with modelling. Some discrepancies with modelling such as that due to up/down eigenmode asymmetries are also pointed out. Concomitant with the Alfvénic activity, fast ion (FIDA) spectroscopy shows large reductions in the central fast ion profile, the degree of which depends on the Alfvén eigenmode amplitude. Interestingly, localized electron cyclotron heating (ECH) near the mode location stabilizes RSAE activity and results in significantly improved fast ion confinement relative to discharges with ECH deposition on axis. In these discharges, RSAE activity is suppressed when ECH is deposited near the radius of the shear reversal point and enhanced with deposition near the axis. The sensitivity of this effect to deposition power and current drive phasing as well as ECH modulation are presented.

UR - http://www.scopus.com/inward/record.url?scp=67649407423&partnerID=8YFLogxK

U2 - 10.1088/0029-5515/49/6/065003

DO - 10.1088/0029-5515/49/6/065003

M3 - Article

AN - SCOPUS:67649407423

SN - 0029-5515

VL - 49

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 6

M1 - 065003

ER -

Measurements, modelling and electron cyclotron heating modification of Alfvén eigenmode activity in DIII-D

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