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Title: Measurements, modelling and electron cyclotron heating modification of Alfven eigenmode activity in DIII-D

Abstract

Neutral beam injection into reversed magnetic shear DIII-D plasmas produces a variety of Alfvenic activity including toroidicity and ellipticity induced Alfven eigenmodes (TAE/EAE, respectively) and reversed shear Alfven 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 Alfvenic activity, fast ion (FIDA) spectroscopy shows large reductions in the central fast ion profile, the degree of which depends on the Alfven 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 depositionmore » near the axis. The sensitivity of this effect to deposition power and current drive phasing as well as ECH modulation are presented.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [3];  [7];  [6];  [3];  [6];  [8];  [6];  [1];  [3];  [9]
  1. General Atomics
  2. University of California, Irvine
  3. Princeton Plasma Physics Laboratory (PPPL)
  4. University of Texas, Austin
  5. National Cheng Kung University, Tainan, Taiwan
  6. General Atomics, San Diego
  7. Lawrence Livermore National Laboratory (LLNL)
  8. University of Wisconsin, Madison
  9. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1015754
DOE Contract Number:  
DE-AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 49; Journal Issue: 6; Journal ID: ISSN 0029--5515
Country of Publication:
United States
Language:
English

Citation Formats

Van Zeeland, Michael, Heidbrink, W., Nazikian, Raffi, Austin, M. E., Cheng, C Z, Chu, M. S., Gorelenkov, Nikolai, Holcomb, C T, Hyatt, A. W., Kramer, G., Lohr, J. T., Mckee, G. R., Petty, C C., Prater, R., Solomon, W. M., and Spong, Donald A. Measurements, modelling and electron cyclotron heating modification of Alfven eigenmode activity in DIII-D. United States: N. p., 2009. Web. doi:10.1088/0029-5515/49/6/065003.
Van Zeeland, Michael, Heidbrink, W., Nazikian, Raffi, Austin, M. E., Cheng, C Z, Chu, M. S., Gorelenkov, Nikolai, Holcomb, C T, Hyatt, A. W., Kramer, G., Lohr, J. T., Mckee, G. R., Petty, C C., Prater, R., Solomon, W. M., & Spong, Donald A. Measurements, modelling and electron cyclotron heating modification of Alfven eigenmode activity in DIII-D. United States. https://doi.org/10.1088/0029-5515/49/6/065003
Van Zeeland, Michael, Heidbrink, W., Nazikian, Raffi, Austin, M. E., Cheng, C Z, Chu, M. S., Gorelenkov, Nikolai, Holcomb, C T, Hyatt, A. W., Kramer, G., Lohr, J. T., Mckee, G. R., Petty, C C., Prater, R., Solomon, W. M., and Spong, Donald A. 2009. "Measurements, modelling and electron cyclotron heating modification of Alfven eigenmode activity in DIII-D". United States. https://doi.org/10.1088/0029-5515/49/6/065003.
@article{osti_1015754,
title = {Measurements, modelling and electron cyclotron heating modification of Alfven eigenmode activity in DIII-D},
author = {Van Zeeland, Michael and Heidbrink, W. and Nazikian, Raffi and Austin, M. E. and Cheng, C Z and Chu, M. S. and Gorelenkov, Nikolai and Holcomb, C T and Hyatt, A. W. and Kramer, G. and Lohr, J. T. and Mckee, G. R. and Petty, C C. and Prater, R. and Solomon, W. M. and Spong, Donald A},
abstractNote = {Neutral beam injection into reversed magnetic shear DIII-D plasmas produces a variety of Alfvenic activity including toroidicity and ellipticity induced Alfven eigenmodes (TAE/EAE, respectively) and reversed shear Alfven 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 Alfvenic activity, fast ion (FIDA) spectroscopy shows large reductions in the central fast ion profile, the degree of which depends on the Alfven 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.},
doi = {10.1088/0029-5515/49/6/065003},
url = {https://www.osti.gov/biblio/1015754}, journal = {Nuclear Fusion},
issn = {0029--5515},
number = 6,
volume = 49,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 2009},
month = {Thu Jan 01 00:00:00 EST 2009}
}