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Title: Resolving broadening of ECRH deposition due to edge turbulence in DIII-D by heat deposition measurement

Abstract

Interaction between microwave power, used for local heating and mode control, and density fluctuations can produce a broadening of the injected beam, as confirmed in experiment and simulation. Increased power deposition width could impact suppression of tearing mode structures on ITER[1]. This work discusses the experimental portion of an effort to understand scattering of injected microwaves by turbulence on the DIII-D tokamak. The corresponding theoretical modeling work can be found in M.B. Thomas et. al.: Submitted to Nuclear Fusion (2017)[Author Note - this paper to be published in same journal]. In a set of perturbative heat transport experiments, tokamak edge millimeter-scale fluctuation levels and microwave heat deposition are measured simultaneously. Beam broadening is separated from heat transport through fitting of modulated fluxes[2]. Electron temperature measurements from a 500 kHz, 48-channel ECE radiometer are Fourier analyzed and used to calculate a deposition-dependent flux[3]. Consistency of this flux with a transport model is evaluated. A diffusive(∝ ∇˜ T e) and convective(∝ ˜ T e) transport solution is linearized and compared with energy conservation-derived fluxes. Comparison between these two forms of heat flux is used to evaluate the quality of ECRF deposition profiles, and a Χ 2 minimization finds a significant broadening ofmore » 1D equilibrium ray tracing calculations from the benchmarked TORAY-GA ray tracing code[4] is needed. The physical basis, cross-validation, and application of the heat flux method is presented. The method is applied to a range of DIII-D discharges and finds a broadening factor of the deposition profile width which scales linearly with edge density fluctuation level. Furthermore, these experimental results are found to be consistent with the full-wave beam broadening measured by the 3D full wave simulations in the same discharges[5].« less

Authors:
 [1];  [2];  [2];  [3];  [3];  [4];  [4];  [5];  [1];  [1];  [2]
  1. Univ. of Texas at Austin, Austin, TX (United States)
  2. Univ. of York, York (United Kingdom)
  3. General Atomics, San Diego, CA (United States)
  4. Univ. of California, Los Angeles, CA (United States)
  5. Univ. of Wisconsin, Madison, WI (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1481199
Grant/Contract Number:  
FC02-04ER54698
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Name: Nuclear Fusion
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Brookman, M. W., Thomas, M. B., Leddy, J., Petty, C. C., La Haye, R. J., Barada, K., Rhodes, T. L., Yan, Z., Austin, M. E., Gentle, K. W., and Vann, R. G. L. Resolving broadening of ECRH deposition due to edge turbulence in DIII-D by heat deposition measurement. United States: N. p., 2017. Web.
Brookman, M. W., Thomas, M. B., Leddy, J., Petty, C. C., La Haye, R. J., Barada, K., Rhodes, T. L., Yan, Z., Austin, M. E., Gentle, K. W., & Vann, R. G. L. Resolving broadening of ECRH deposition due to edge turbulence in DIII-D by heat deposition measurement. United States.
Brookman, M. W., Thomas, M. B., Leddy, J., Petty, C. C., La Haye, R. J., Barada, K., Rhodes, T. L., Yan, Z., Austin, M. E., Gentle, K. W., and Vann, R. G. L. Thu . "Resolving broadening of ECRH deposition due to edge turbulence in DIII-D by heat deposition measurement". United States. https://www.osti.gov/servlets/purl/1481199.
@article{osti_1481199,
title = {Resolving broadening of ECRH deposition due to edge turbulence in DIII-D by heat deposition measurement},
author = {Brookman, M. W. and Thomas, M. B. and Leddy, J. and Petty, C. C. and La Haye, R. J. and Barada, K. and Rhodes, T. L. and Yan, Z. and Austin, M. E. and Gentle, K. W. and Vann, R. G. L.},
abstractNote = {Interaction between microwave power, used for local heating and mode control, and density fluctuations can produce a broadening of the injected beam, as confirmed in experiment and simulation. Increased power deposition width could impact suppression of tearing mode structures on ITER[1]. This work discusses the experimental portion of an effort to understand scattering of injected microwaves by turbulence on the DIII-D tokamak. The corresponding theoretical modeling work can be found in M.B. Thomas et. al.: Submitted to Nuclear Fusion (2017)[Author Note - this paper to be published in same journal]. In a set of perturbative heat transport experiments, tokamak edge millimeter-scale fluctuation levels and microwave heat deposition are measured simultaneously. Beam broadening is separated from heat transport through fitting of modulated fluxes[2]. Electron temperature measurements from a 500 kHz, 48-channel ECE radiometer are Fourier analyzed and used to calculate a deposition-dependent flux[3]. Consistency of this flux with a transport model is evaluated. A diffusive(∝ ∇˜ Te) and convective(∝ ˜ Te) transport solution is linearized and compared with energy conservation-derived fluxes. Comparison between these two forms of heat flux is used to evaluate the quality of ECRF deposition profiles, and a Χ2 minimization finds a significant broadening of 1D equilibrium ray tracing calculations from the benchmarked TORAY-GA ray tracing code[4] is needed. The physical basis, cross-validation, and application of the heat flux method is presented. The method is applied to a range of DIII-D discharges and finds a broadening factor of the deposition profile width which scales linearly with edge density fluctuation level. Furthermore, these experimental results are found to be consistent with the full-wave beam broadening measured by the 3D full wave simulations in the same discharges[5].},
doi = {},
journal = {Nuclear Fusion},
number = ,
volume = ,
place = {United States},
year = {2017},
month = {9}
}

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