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

Other · Thu Sep 07 00:00:00 EDT 2017 · arXiv.org Repository

OSTI ID:1481199

Brookman, M. W. ^[1]; Thomas, M. B. ^[2]; Leddy, J. ^[2]; Petty, C. C. ^[3]; La Haye, R. J. ^[3]; Barada, K. ^[4]; Rhodes, T. L. ^[4]; Yan, Z. ^[5]; Austin, M. E. ^[1]; Gentle, K. W. ^[1]; Vann, R. G. L. ^[2]

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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)

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 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].

• Research Organization: General Atomics, San Diego, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: FC02-04ER54698
• OSTI ID: 1481199
• Journal Information: arXiv.org Repository, Vol. 2017; ISSN 9999-0017
• Publisher: Cornell University
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY