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

Abstract

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.

Authors:

^[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)

Publication Date:: Wed Jan 31 00:00:00 EST 2018

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

Sponsoring Org.:: USDOE

OSTI Identifier:: 1422574

Alternate Identifier(s):: OSTI ID: 1418890

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

Resource Type:: Accepted Manuscript

Journal Name:: Physics of Plasmas

Additional Journal Information:: Journal Volume: 25; Journal Issue: 1; Journal ID: ISSN 1070-664X

Publisher:: American Institute of Physics (AIP)

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY

Citation Formats


                    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., and Traverso, P. J. Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements.  United States: N. p., 2018. 
Web.  doi:10.1063/1.5013347.

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                    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. Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements.  United States.  https://doi.org/10.1063/1.5013347

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                    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., and Traverso, P. J. Wed .  
"Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements".  United States.  https://doi.org/10.1063/1.5013347.  https://www.osti.gov/servlets/purl/1422574.

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@article{osti_1422574,

  title        = {Determination of current and rotational transform profiles in a current-carrying stellarator using soft x-ray emissivity measurements},

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

  abstractNote = {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.},

  doi          = {10.1063/1.5013347},

  journal      = {Physics of Plasmas},

  number       = 1,

  volume       = 25,

  place        = {United States},

  year         = {Wed Jan 31 00:00:00 EST 2018},

  month        = {Wed Jan 31 00:00:00 EST 2018}

}

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Figures / Tables:

FIG. 1: Rendering of the last closed flux surface of a CTH plasma. Poloidal slices (highlighted in grey) indicate the toroidal locations of SXR cameras used for 3D equilibrium reconstructions.

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Works referenced in this record:

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Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements
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Physics of Plasmas, Vol. 22, Issue 12
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Design and initial operation of a two-color soft x-ray camera system on the Compact Toroidal Hybrid experiment
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Works referencing / citing this record:

Sawtooth oscillation behavior with varying amounts of applied stellarator rotational transform
journal, March 2019

Herfindal, J. L.; Maurer, D. A.; Hartwell, G. J.
Physics of Plasmas, Vol. 26, Issue 3
DOI: 10.1063/1.5080242

Figures / Tables found in this record:

Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.

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

Abstract

Citation Formats

Figures / Tables:

Tomography of quasi-static deformations of constant-emission surfaces of high-beta plasmas in ASDEX journal, March 1986

Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements journal, December 2015

Design and initial operation of a two-color soft x-ray camera system on the Compact Toroidal Hybrid experiment journal, November 2014

Separation of β̄ p and ℓ i in tokamaks of non-circular cross-section journal, October 1985

First measurement of poloidal-field-induced Faraday rotation in a tokamak plasma journal, December 1978

Tangential soft x-ray imaging for shape and current profile measurements journal, March 2003

Determination of current distribution in a tokamak journal, January 1982

Why beta p and l i cannot be separately measured in a near circular tokamak journal, November 1993

Equilibrium reconstruction of plasma profiles based on soft x-ray imaging in DIII-D journal, December 2008

The interpretation of tokamak magnetic diagnostics journal, July 1991

Magnetic analysis of non-circular cross-section tokamaks journal, June 1982

Determination of current distribution in JET from soft X-ray measurements journal, May 1989

Studies of Internal Disruptions and m = 1 Oscillations in Tokamak Discharges with Soft—X-Ray Tecniques journal, November 1974

Discrepancies between soft x-ray emissivity contours and magnetic flux surfaces in Alcator C-Mod journal, March 1996

Tomographic imaging of MHD activity in tokamaks by combining diode arrays and a tangentially viewing pinhole camera journal, August 1988

Three-dimensional free boundary calculations using a spectral Green's function method journal, December 1986

The multichannel motional Stark effect diagnostic on TFTR journal, October 1992

Magnetic diagnostics: General principles and the problem of reconstruction of plasma current and pressure profiles in toroidal systems journal, June 2001

Current distribution modification measurements in the PBX-M tokamak journal, October 1993

Design, Construction, and Operation of the Compact Toroidal Hybrid journal, May 2017

MOMCON: A spectral code for obtaining three-dimensional magnetohydrodynamic equilibria journal, February 1986

Current distribution measurement in a tokamak by FIR polarimetry (invited) journal, August 1986

V3FIT: a code for three-dimensional equilibrium reconstruction journal, July 2009

Application of x-ray imaging to current profile measurements in the PEGASUS experiment journal, January 1999

Current profile measurements with motional Stark effect polarimeter in the JT-60U tokamak journal, March 1997

Sawtooth oscillation behavior with varying amounts of applied stellarator rotational transform journal, March 2019

Tomography of quasi-static deformations of constant-emission surfaces of high-beta plasmas in ASDEX
journal, March 1986

Non-axisymmetric equilibrium reconstruction of a current-carrying stellarator using external magnetic and soft x-ray inversion radius measurements
journal, December 2015

Design and initial operation of a two-color soft x-ray camera system on the Compact Toroidal Hybrid experiment
journal, November 2014

Separation of β̄ _p and ℓ _i in tokamaks of non-circular cross-section
journal, October 1985

First measurement of poloidal-field-induced Faraday rotation in a tokamak plasma
journal, December 1978

Tangential soft x-ray imaging for shape and current profile measurements
journal, March 2003

Determination of current distribution in a tokamak
journal, January 1982

Why beta _p and l _i cannot be separately measured in a near circular tokamak
journal, November 1993

Equilibrium reconstruction of plasma profiles based on soft x-ray imaging in DIII-D
journal, December 2008

The interpretation of tokamak magnetic diagnostics
journal, July 1991

Magnetic analysis of non-circular cross-section tokamaks
journal, June 1982

Determination of current distribution in JET from soft X-ray measurements
journal, May 1989

Studies of Internal Disruptions and $m = 1$ Oscillations in Tokamak Discharges with Soft—X-Ray Tecniques
journal, November 1974

Discrepancies between soft x-ray emissivity contours and magnetic flux surfaces in Alcator C-Mod
journal, March 1996

Tomographic imaging of MHD activity in tokamaks by combining diode arrays and a tangentially viewing pinhole camera
journal, August 1988

Three-dimensional free boundary calculations using a spectral Green's function method
journal, December 1986

The multichannel motional Stark effect diagnostic on TFTR
journal, October 1992

Magnetic diagnostics: General principles and the problem of reconstruction of plasma current and pressure profiles in toroidal systems
journal, June 2001

Current distribution modification measurements in the PBX-M tokamak
journal, October 1993

Design, Construction, and Operation of the Compact Toroidal Hybrid
journal, May 2017

MOMCON: A spectral code for obtaining three-dimensional magnetohydrodynamic equilibria
journal, February 1986

Current distribution measurement in a tokamak by FIR polarimetry (invited)
journal, August 1986

V3FIT: a code for three-dimensional equilibrium reconstruction
journal, July 2009

Application of x-ray imaging to current profile measurements in the PEGASUS experiment
journal, January 1999

Current profile measurements with motional Stark effect polarimeter in the JT-60U tokamak
journal, March 1997

Sawtooth oscillation behavior with varying amounts of applied stellarator rotational transform
journal, March 2019