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

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.

doi:10.1063/1.5022180

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

Journal Article · Tue Apr 10 00:00:00 EDT 2018 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.5022180· OSTI ID:1540168

^[1]; Hatch, D. R. ^[1];

^[1]; Liao, K. T. ^[1];

^[1]; Rowan, W. L. ^[1]; Zhao, B. ^[1]; Cao, N. M. ^[2]; Ernst, D. R. ^[2];

^[2]; Howard, N. T. ^[2]; Hubbard, A. E. ^[2];

^[2]; Rice, J. E. ^[2]

Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center

A profile for the critical gradient scale length (L_c) 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 (L_Te^-1= |∇T_e|/T_e) profile was measured via the B_T-jog technique and it was compared with electron heat flux from power balance (TRANSP) analysis. The T_e 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 L_c profile is in agreement with electron temperature gradient (ETG) models which predict the dependence of L_c^-1 on local ,Z_eff, T_e/T_i, 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_⊥ρ_s > 1), and ion temperature gradient/trapped electron mode modes in the ion scale (k_⊥ρ_s > 1). Finally, the measured L_c profile is in agreement with the profile of ETG critical gradients deduced from GENE simulations.

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Research Organization:: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Univ. of Texas, Austin, TX (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

Grant/Contract Number:: FC02-99ER54512; FG03-96ER54373

OSTI ID:: 1540168

Alternate ID(s):: OSTI ID: 1432578

Journal Information:: Physics of Plasmas, Vol. 25, Issue 4; ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 3 works

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Cited By (2)

Variable location channels to improve efficiency and precision for direct ∇ T _e measurements and high spatial resolution T _e -profile measurements using electron cyclotron emission Houshmandyar, S.; Austin, M. E.; Brookman, M. W. Review of Scientific Instruments, Vol. 89, Issue 10 https://doi.org/10.1063/1.5035429	journal	October 2018
Helical core formation and evolution during current ramp-up in the high-field tokamak Alcator C-Mod Wingen, A.; Wilcox, R. S.; Delgado-Aparicio, L. F. Physics of Plasmas, Vol. 26, Issue 2 https://doi.org/10.1063/1.5083055	journal	February 2019

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