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Title: Multi-device studies of pedestal physics and confinement in the I-mode regime

Abstract

This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier together with L-mode-like particle and impurity transport and no Edge Localized Modes (ELMs). The regime has been demonstrated on the Alcator C-Mod, ASDEX Upgrade and DIII-D tokamaks, over a wide range of device parameters and pedestal conditions. Dimensionless parameters at the pedestal show overlap across devices and extend to low collisionality. When they are matched, pedestal temperature profiles are also similar. Pedestals are stable to peeling ballooning modes, consistent with lack of ELMs. Access to Imode is independent of heating method (neutral beam injection, Ion Cyclotron and/or Electron Cyclotron Resonance Heating). Normalized energy confinement H98,y2 ≥ 1 has been achieved for a range of 3 ≤ q95 ≤ 4.9 and scales favourably with power. Changes in turbulence in the pedestal region accompany the transition from L-mode to I-mode. The L-I threshold increases with plasma density and current, and with device size, but has a weak dependence on toroidal magnetic field BT. The upper limit of power for I-modes, which is set by I-H transitions, increases with BT and the power range is largest on Alcator C-Mod at B > 5 T. Finally, issues formore » extrapolation to ITER and other future fusion devices are discussed.« less

Authors:
 [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [3];  [6];  [2];  [2];  [3];  [1];  [9];  [6];  [3];  [1];  [1];  [3] more »;  [10];  [11];  [1];  [11];  [12];  [3];  [1];  [1];  [1];  [1];  [3];  [10] « less
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  2. General Atomics, San Diego, CA (United States)
  3. Max-Planck-Institut fur Plasmaphysik, Garching (Germany)
  4. Univ. of Texas, Austin, TX (United States)
  5. Max-Planck-Institut fur Plasmaphysik, Garching (Germany); EUROfusion - Programme Management Unit, Garching (Germany)
  6. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  7. Univ. of California San Diego, La Jolla, CA (United States); Univ. of York, York (United Kingdom)
  8. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  9. ITER Organization, St. Paul Lez Durance Cedex (France)
  10. Univ. of Wisconsin, Madison, WI (United States)
  11. Univ. of California, Los Angeles, CA (United States)
  12. Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne (Switzerland)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES)
Contributing Org.:
Alcator C-Mod, ASDEX Upgrade and DIII-D Teams
OSTI Identifier:
1373884
Alternate Identifier(s):
OSTI ID: 1260287; OSTI ID: 1375941
Grant/Contract Number:  
FC02-04ER54698; FC02-99ER54512-CMOD; SC0012469; FG02-94ER54235; AC52-07NA27344; AC02-09CH11466; FG02-89ER53296; FG02-08ER54999; FG02-08ER54984
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 56; Journal Issue: 8; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; FEC 2014; tokamak; I-mode; pedestal; threshold

Citation Formats

Hubbard, A. E., Osborne, T., Ryter, F., Austin, M., Barrera Orte, L., Churchill, R. M., Cziegler, I., Fenstermacher, M., Fischer, R., Gerhardt, S., Groebner, R., Gohil, P., Happel, T., Hughes, J. W., Loarte, A., Maingi, R., Manz, P., Marinoni, A., Marmar, E. S., McDermott, R. M., McKee, G., Rhodes, T. L., Rice, J. E., Schmitz, L., Theiler, C., Viezzer, E., Walk, J. R., White, A., Whyte, D., Wolfe, S., Wolfrum, E., and Yan, Z. Multi-device studies of pedestal physics and confinement in the I-mode regime. United States: N. p., 2016. Web. https://doi.org/10.1088/0029-5515/56/8/086003.
Hubbard, A. E., Osborne, T., Ryter, F., Austin, M., Barrera Orte, L., Churchill, R. M., Cziegler, I., Fenstermacher, M., Fischer, R., Gerhardt, S., Groebner, R., Gohil, P., Happel, T., Hughes, J. W., Loarte, A., Maingi, R., Manz, P., Marinoni, A., Marmar, E. S., McDermott, R. M., McKee, G., Rhodes, T. L., Rice, J. E., Schmitz, L., Theiler, C., Viezzer, E., Walk, J. R., White, A., Whyte, D., Wolfe, S., Wolfrum, E., & Yan, Z. Multi-device studies of pedestal physics and confinement in the I-mode regime. United States. https://doi.org/10.1088/0029-5515/56/8/086003
Hubbard, A. E., Osborne, T., Ryter, F., Austin, M., Barrera Orte, L., Churchill, R. M., Cziegler, I., Fenstermacher, M., Fischer, R., Gerhardt, S., Groebner, R., Gohil, P., Happel, T., Hughes, J. W., Loarte, A., Maingi, R., Manz, P., Marinoni, A., Marmar, E. S., McDermott, R. M., McKee, G., Rhodes, T. L., Rice, J. E., Schmitz, L., Theiler, C., Viezzer, E., Walk, J. R., White, A., Whyte, D., Wolfe, S., Wolfrum, E., and Yan, Z. Tue . "Multi-device studies of pedestal physics and confinement in the I-mode regime". United States. https://doi.org/10.1088/0029-5515/56/8/086003. https://www.osti.gov/servlets/purl/1373884.
@article{osti_1373884,
title = {Multi-device studies of pedestal physics and confinement in the I-mode regime},
author = {Hubbard, A. E. and Osborne, T. and Ryter, F. and Austin, M. and Barrera Orte, L. and Churchill, R. M. and Cziegler, I. and Fenstermacher, M. and Fischer, R. and Gerhardt, S. and Groebner, R. and Gohil, P. and Happel, T. and Hughes, J. W. and Loarte, A. and Maingi, R. and Manz, P. and Marinoni, A. and Marmar, E. S. and McDermott, R. M. and McKee, G. and Rhodes, T. L. and Rice, J. E. and Schmitz, L. and Theiler, C. and Viezzer, E. and Walk, J. R. and White, A. and Whyte, D. and Wolfe, S. and Wolfrum, E. and Yan, Z.},
abstractNote = {This paper describes joint ITPA studies of the I-mode regime, which features an edge thermal barrier together with L-mode-like particle and impurity transport and no Edge Localized Modes (ELMs). The regime has been demonstrated on the Alcator C-Mod, ASDEX Upgrade and DIII-D tokamaks, over a wide range of device parameters and pedestal conditions. Dimensionless parameters at the pedestal show overlap across devices and extend to low collisionality. When they are matched, pedestal temperature profiles are also similar. Pedestals are stable to peeling ballooning modes, consistent with lack of ELMs. Access to Imode is independent of heating method (neutral beam injection, Ion Cyclotron and/or Electron Cyclotron Resonance Heating). Normalized energy confinement H98,y2 ≥ 1 has been achieved for a range of 3 ≤ q95 ≤ 4.9 and scales favourably with power. Changes in turbulence in the pedestal region accompany the transition from L-mode to I-mode. The L-I threshold increases with plasma density and current, and with device size, but has a weak dependence on toroidal magnetic field BT. The upper limit of power for I-modes, which is set by I-H transitions, increases with BT and the power range is largest on Alcator C-Mod at B > 5 T. Finally, issues for extrapolation to ITER and other future fusion devices are discussed.},
doi = {10.1088/0029-5515/56/8/086003},
journal = {Nuclear Fusion},
number = 8,
volume = 56,
place = {United States},
year = {2016},
month = {7}
}

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    Works referencing / citing this record:

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    Access and sustainment of naturally ELM-free and small-ELM regimes
    journal, September 2018


    Scaling laws from theory-based modeling for different regimes in the DEMO fusion reactor
    journal, July 2019


    Effects of zonal flows on transport crossphase in dissipative trapped-electron mode turbulence in edge plasmas
    journal, July 2019


    Scale selection and feedback loops for patterns in drift wave-zonal flow turbulence
    journal, August 2019

    • Guo, Weixin; Diamond, Patrick H.; Hughes, David W.
    • Plasma Physics and Controlled Fusion, Vol. 61, Issue 10
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    Up/down impurity density asymmetries in C-Mod plasmas
    journal, September 2018


    I-mode investigation on the Experimental Advanced Superconducting Tokamak
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    Radiative heat exhaust in Alcator C-Mod I-mode plasmas
    journal, March 2019


    Verification of GENE and GYRO with L-mode and I-mode plasmas in Alcator C-Mod
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