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Title: Electron critical gradient scale length measurements of ICRF heated L-mode plasmas at Alcator C-Mod tokamak

Abstract

A profile for the critical gradient scale length (Lc) has been measured in L-mode discharges at the Alcator C-Mod tokamak, where electrons were heated by an ion cyclotron range of frequency through minority heating with the intention of simultaneously varying the heat flux and changing the local gradient. The electron temperature gradient scale length (LTe−1 = |∇Te|/Te) profile was measured via the BT-jog technique [Houshmandyar et al., Rev. Sci. Instrum. 87, 11E101 (2016)] and it was compared with electron heat flux from power balance (TRANSP) analysis. The Te profiles were found to be very stiff and already above the critical values, however, the stiffness was found to be reduced near the q = 3/2 surface. The measured Lc profile is in agreement with electron temperature gradient (ETG) models which predict the dependence of Lc−1 on local Zeff, Te/Ti, and the ratio of the magnetic shear to the safety factor. The results from linear Gene gyrokinetic simulations suggest ETG to be the dominant mode of turbulence in the electron scale (k⊥ρs > 1), and ion temperature gradient/trapped electron mode modes in the ion scale (k⊥ρs < 1). The measured Lc profile is in agreement with the profile of ETG critical gradients deduced from Gene simulations.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1];  [1]; ORCiD logo [1];  [1];  [1];  [2];  [2]; ORCiD logo [2];  [2];  [2]; ORCiD logo [2];  [2]
  1. Institute for Fusion Studies, The University of Texas at Austin, Austin, Texas 78712, USA
  2. Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02129, USA
Publication Date:
Research Org.:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Texas, Austin, TX (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1540168
Alternate Identifier(s):
OSTI ID: 1432578
Grant/Contract Number:  
FC02-99ER54512; FG03-96ER54373
Resource Type:
Accepted Manuscript
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 25; Journal Issue: 4; Journal ID: ISSN 1070-664X
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
Physics

Citation Formats

Houshmandyar, S., Hatch, D. R., Horton, C. W., Liao, K. T., Phillips, P. E., Rowan, W. L., Zhao, B., Cao, N. M., Ernst, D. R., Greenwald, M., Howard, N. T., Hubbard, A. E., Hughes, J. W., and Rice, J. E. Electron critical gradient scale length measurements of ICRF heated L-mode plasmas at Alcator C-Mod tokamak. United States: N. p., 2018. Web. doi:10.1063/1.5022180.
Houshmandyar, S., Hatch, D. R., Horton, C. W., Liao, K. T., Phillips, P. E., Rowan, W. L., Zhao, B., Cao, N. M., Ernst, D. R., Greenwald, M., Howard, N. T., Hubbard, A. E., Hughes, J. W., & Rice, J. E. Electron critical gradient scale length measurements of ICRF heated L-mode plasmas at Alcator C-Mod tokamak. United States. doi:10.1063/1.5022180.
Houshmandyar, S., Hatch, D. R., Horton, C. W., Liao, K. T., Phillips, P. E., Rowan, W. L., Zhao, B., Cao, N. M., Ernst, D. R., Greenwald, M., Howard, N. T., Hubbard, A. E., Hughes, J. W., and Rice, J. E. Sun . "Electron critical gradient scale length measurements of ICRF heated L-mode plasmas at Alcator C-Mod tokamak". United States. doi:10.1063/1.5022180. https://www.osti.gov/servlets/purl/1540168.
@article{osti_1540168,
title = {Electron critical gradient scale length measurements of ICRF heated L-mode plasmas at Alcator C-Mod tokamak},
author = {Houshmandyar, S. and Hatch, D. R. and Horton, C. W. and Liao, K. T. and Phillips, P. E. and Rowan, W. L. and Zhao, B. and Cao, N. M. and Ernst, D. R. and Greenwald, M. and Howard, N. T. and Hubbard, A. E. and Hughes, J. W. and Rice, J. E.},
abstractNote = {A profile for the critical gradient scale length (Lc) has been measured in L-mode discharges at the Alcator C-Mod tokamak, where electrons were heated by an ion cyclotron range of frequency through minority heating with the intention of simultaneously varying the heat flux and changing the local gradient. The electron temperature gradient scale length (LTe−1 = |∇Te|/Te) profile was measured via the BT-jog technique [Houshmandyar et al., Rev. Sci. Instrum. 87, 11E101 (2016)] and it was compared with electron heat flux from power balance (TRANSP) analysis. The Te profiles were found to be very stiff and already above the critical values, however, the stiffness was found to be reduced near the q = 3/2 surface. The measured Lc profile is in agreement with electron temperature gradient (ETG) models which predict the dependence of Lc−1 on local Zeff, Te/Ti, and the ratio of the magnetic shear to the safety factor. The results from linear Gene gyrokinetic simulations suggest ETG to be the dominant mode of turbulence in the electron scale (k⊥ρs > 1), and ion temperature gradient/trapped electron mode modes in the ion scale (k⊥ρs < 1). The measured Lc profile is in agreement with the profile of ETG critical gradients deduced from Gene simulations.},
doi = {10.1063/1.5022180},
journal = {Physics of Plasmas},
number = 4,
volume = 25,
place = {United States},
year = {2018},
month = {4}
}

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Works referenced in this record:

Spatially resolved high resolution x-ray spectroscopy for magnetically confined fusion plasmas (invited)
journal, October 2008

  • Ince-Cushman, A.; Rice, J. E.; Bitter, M.
  • Review of Scientific Instruments, Vol. 79, Issue 10, Article No. 10E302
  • DOI: 10.1063/1.2968707