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Title: The effect of electron cyclotron heating on density fluctuations at ion and electron scales in ITER baseline scenario discharges on the DIII-D tokamak

Abstract

Experiments simulating the ITER Baseline Scenario on the DIII-D tokamak show that torque-free pure electron heating, when coupled to plasmas subject to a net co-current beam torque, affects density fluctuations at electron scales on a sub-confinement time scale, whereas fluctuations at ion scales change only after profiles have evolved to a new stationary state. Modifications to the density fluctuations measured by the Phase Contrast Imaging diagnostic (PCI) are assessed by analyzing the time evolution following the switch-off of Electron Cyclotron Heating (ECH), thus going from mixed beam/ECH to pure neutral beam heating at fixed β N . Within 20 ms after turning off ECH, the intensity of fluctuations is observed to increase at frequencies higher than 200 kHz; in contrast, fluctuations at lower frequency are seen to decrease in intensity on a longer time scale, after other equilibrium quantities have evolved. Non-linear gyro-kinetic modeling at ion and electron scales scales suggest that, while the low frequency response of the diagnostic is consistent with the dominant ITG modes being weakened by the slow-time increase in flow shear, the high frequency response is due to prompt changes to the electron temperature profile that enhance electron modes and generate a larger heat fluxmore » and an inward particle pinch. These results suggest that electron heated regimes in ITER will feature multi-scale fluctuations that might affect fusion performance via modifications to profiles.« less

Authors:
; ; ; ; ; ; ; ; ; ; ;
Publication Date:
DOE Contract Number:  
FG02-94ER54235; FC02-04ER54698
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center; General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1880302
DOI:
https://doi.org/10.7910/DVN/5FVDQ1

Citation Formats

Marinoni, A., Pinsker, R. I., Porkolab, M., Rost, J. C., Davis, E. M., Burrell, K. H., Candy, J., Staebler, G. M., Grierson, B. A., McKee, G. R., Rhodes, T. L., and DIII-D Team. The effect of electron cyclotron heating on density fluctuations at ion and electron scales in ITER baseline scenario discharges on the DIII-D tokamak. United States: N. p., 2018. Web. doi:10.7910/DVN/5FVDQ1.
Marinoni, A., Pinsker, R. I., Porkolab, M., Rost, J. C., Davis, E. M., Burrell, K. H., Candy, J., Staebler, G. M., Grierson, B. A., McKee, G. R., Rhodes, T. L., & DIII-D Team. The effect of electron cyclotron heating on density fluctuations at ion and electron scales in ITER baseline scenario discharges on the DIII-D tokamak. United States. doi:https://doi.org/10.7910/DVN/5FVDQ1
Marinoni, A., Pinsker, R. I., Porkolab, M., Rost, J. C., Davis, E. M., Burrell, K. H., Candy, J., Staebler, G. M., Grierson, B. A., McKee, G. R., Rhodes, T. L., and DIII-D Team. 2018. "The effect of electron cyclotron heating on density fluctuations at ion and electron scales in ITER baseline scenario discharges on the DIII-D tokamak". United States. doi:https://doi.org/10.7910/DVN/5FVDQ1. https://www.osti.gov/servlets/purl/1880302. Pub date:Mon Dec 03 00:00:00 EST 2018
@article{osti_1880302,
title = {The effect of electron cyclotron heating on density fluctuations at ion and electron scales in ITER baseline scenario discharges on the DIII-D tokamak},
author = {Marinoni, A. and Pinsker, R. I. and Porkolab, M. and Rost, J. C. and Davis, E. M. and Burrell, K. H. and Candy, J. and Staebler, G. M. and Grierson, B. A. and McKee, G. R. and Rhodes, T. L. and DIII-D Team},
abstractNote = {Experiments simulating the ITER Baseline Scenario on the DIII-D tokamak show that torque-free pure electron heating, when coupled to plasmas subject to a net co-current beam torque, affects density fluctuations at electron scales on a sub-confinement time scale, whereas fluctuations at ion scales change only after profiles have evolved to a new stationary state. Modifications to the density fluctuations measured by the Phase Contrast Imaging diagnostic (PCI) are assessed by analyzing the time evolution following the switch-off of Electron Cyclotron Heating (ECH), thus going from mixed beam/ECH to pure neutral beam heating at fixed β N . Within 20 ms after turning off ECH, the intensity of fluctuations is observed to increase at frequencies higher than 200 kHz; in contrast, fluctuations at lower frequency are seen to decrease in intensity on a longer time scale, after other equilibrium quantities have evolved. Non-linear gyro-kinetic modeling at ion and electron scales scales suggest that, while the low frequency response of the diagnostic is consistent with the dominant ITG modes being weakened by the slow-time increase in flow shear, the high frequency response is due to prompt changes to the electron temperature profile that enhance electron modes and generate a larger heat flux and an inward particle pinch. These results suggest that electron heated regimes in ITER will feature multi-scale fluctuations that might affect fusion performance via modifications to profiles.},
doi = {10.7910/DVN/5FVDQ1},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2018},
month = {12}
}

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