Validation of conducting wall models using magnetic measurements

Hanson, Jeremy M.; Bialek, James M.; Turco, Francesca; King, J.; Navratil, Gerald A.; Turnbull, Alan

doi:10.1088/0029-5515/56/10/106022

Title: Validation of conducting wall models using magnetic measurements

Journal Article · Tue Aug 16 00:00:00 EDT 2016 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/56/10/106022· OSTI ID:1354790

Hanson, Jeremy M. ^[1]; Bialek, James M. ^[1]; Turco, Francesca ^[1]; King, J. ^[2]; Navratil, Gerald A. ^[1]; Turnbull, Alan ^[2]

Columbia Univ., New York, NY (United States)
General Atomics, San Diego, CA (United States)

The impact of conducting wall eddy currents on perturbed magnetic field measurements is a key issue for understanding the measurement and control of long-wavelength MHD stability in tokamak devices. As plasma response models have growth in sophistication, the need to understand and resolve small changes in these measurements has become more important, motivating increased fidelity in simulations of externally applied fields and the wall eddy current response. In this manuscript, we describe thorough validation studies of the wall models in the MARS-F and VALEN stability codes, using coil–sensor vacuum coupling measurements from the DIII-D tokamak. The valen formulation treats conducting structures with arbitrary threedimensional geometries, while mars-f uses an axisymmetric wall model and a spectral decomposition of the problem geometry with a fixed toroidal harmonic n. The vacuum coupling measurements have a strong sensitivity to wall eddy currents induced by timechanging coil currents, owing to the close proximities of both the sensors and coils to the wall. Measurements from individual coil and sensor channels are directly compared with valen predictions. It is found that straightforward improvements to the valen model, such as refining the wall mesh and simulating the vertical extent of the DIII-D poloidal field sensors, lead to good agreement with the experimental measurements. In addition, couplings to multi-coil, n = 1 toroidal mode perturbations are calculated from the measurements and compared with predictions from both codes. Lastly, the toroidal mode comparisons favor the fully three-dimensional simulation approach, likely because this approach naturally treats n > 1 sidebands generated by the coils and wall eddy currents, as well as the n = 1 fundamental.

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Research Organization:: Columbia Univ., New York, NY (United States); General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE Office of Nuclear Energy (NE)

Grant/Contract Number:: FC02-04ER54698; FG02-95ER54309; FG02-04ER54761

OSTI ID:: 1354790

Alternate ID(s):: OSTI ID: 1295983

Journal Information:: Nuclear Fusion, Vol. 56, Issue 10; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 7 works

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Identification of multiple eigenmode growth rates in DIII-D and EAST tokamak plasmas Wang, Z. R.; Logan, N. C.; Munaretto, S. Nuclear Fusion, Vol. 59, Issue 2 https://doi.org/10.1088/1741-4326/aaf671	journal	January 2019

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