Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

Ma, X.; Cianciosa, M. R.; Ennis, D. A.; Hanson, J. D.; Hartwell, G. J.; Herfindal, J. L.; Howell, E. C.; Knowlton, S. F.; Maurer, D. A.; Traverso, P. J.

doi:10.1063/1.5013347

Title: Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements

Journal Article · Wed Jan 31 00:00:00 EST 2018 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.5013347· OSTI ID:1422574

^[1];

^[2]; Ennis, D. A. ^[1]; Hanson, J. D. ^[1];

^[1];

^[3]; Howell, E. C. ^[1]; Knowlton, S. F. ^[1];

^[1]; Traverso, P. J. ^[1]

Auburn Univ., AL (United States). Physics Department
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Auburn Univ., AL (United States). Physics Department ; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

In this research, collimated soft X-ray (SXR) emissivity measurements from multi-channel cameras on the Compact Toroidal Hybrid (CTH) tokamak/torsatron device are incorporated in the 3D equilibrium reconstruction code V3FIT to reconstruct the shape of flux surfaces and infer the current distribution within the plasma. Equilibrium reconstructions of sawtoothing plasmas that use data from both SXR and external magnetic diagnostics show the central safety factor to be near unity under the assumption that SXR iso-emissivity contours lie on magnetic flux surfaces. The reconstruction results are consistent with those using the external magnetic data and a constraint on the location of q = 1 surfaces determined from the sawtooth inversion surface extracted from SXR brightness profiles. The agreement justifies the use of approximating SXR emission as a flux function in CTH, at least within the core of the plasma, subject to the spatial resolution of the SXR diagnostics. Lastly, this improved reconstruction of the central current density indicates that the current profile peakedness decreases with increasing external transform and that the internal inductance is not a relevant measure of how peaked the current profile is in hybrid discharges.

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Research Organization:: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC05-00OR22725; FG02-00ER54610

OSTI ID:: 1422574

Alternate ID(s):: OSTI ID: 1418890

Journal Information:: Physics of Plasmas, Vol. 25, Issue 1; ISSN 1070-664X

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

Country of Publication:: United States

Language:: English

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Cited by: 2 works

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Cited By (1)

Sawtooth oscillation behavior with varying amounts of applied stellarator rotational transform Herfindal, J. L.; Maurer, D. A.; Hartwell, G. J. Physics of Plasmas, Vol. 26, Issue 3 https://doi.org/10.1063/1.5080242	journal	March 2019

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