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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. Furthermore, 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:
 [1];  [2];  [1];  [1];  [1];  [2];  [2];  [2];  [3];  [4];  [5]
  1. MIT Plasma Science and Fusion Center, Cambridge, MA (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  4. Univ. of Wisconsin, Madison, WI (United States)
  5. Univ. of California, Los Angeles, CA (United States)
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1374055
Alternate Identifier(s):
OSTI ID: 1374558
Grant/Contract Number:  
FG02-94ER54235; FC02-04ER54698
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 12; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ITER; ETG; Phase Contrast; turbulence; ECH

Citation Formats

Marinoni, Alessandro, Pinsker, Robert I., Porkolab, Miklos, Rost, J. C., Davis, E. M., Burrell, Keith H., Candy, Jeff, Staebler, Gary M., Grierson, B. A., McKee, George R., and Rhodes, Terry L. 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., 2017. Web. doi:10.1088/1741-4326/aa8333.
Marinoni, Alessandro, Pinsker, Robert I., Porkolab, Miklos, Rost, J. C., Davis, E. M., Burrell, Keith H., Candy, Jeff, Staebler, Gary M., Grierson, B. A., McKee, George R., & Rhodes, Terry L. 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:10.1088/1741-4326/aa8333.
Marinoni, Alessandro, Pinsker, Robert I., Porkolab, Miklos, Rost, J. C., Davis, E. M., Burrell, Keith H., Candy, Jeff, Staebler, Gary M., Grierson, B. A., McKee, George R., and Rhodes, Terry L. Tue . "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:10.1088/1741-4326/aa8333. https://www.osti.gov/servlets/purl/1374055.
@article{osti_1374055,
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, Alessandro and Pinsker, Robert I. and Porkolab, Miklos and Rost, J. C. and Davis, E. M. and Burrell, Keith H. and Candy, Jeff and Staebler, Gary M. and Grierson, B. A. and McKee, George R. and Rhodes, Terry L.},
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. Furthermore, these results suggest that electron heated regimes in ITER will feature multi-scale fluctuations that might affect fusion performance via modifications to profiles.},
doi = {10.1088/1741-4326/aa8333},
journal = {Nuclear Fusion},
number = 12,
volume = 57,
place = {United States},
year = {Tue Aug 01 00:00:00 EDT 2017},
month = {Tue Aug 01 00:00:00 EDT 2017}
}

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