Transport and fluctuations in high temperature spheromak plasmasa)

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https://pubs.aip.org/aip/pop/article-abstract/13/5/056105/1032750/Transport-and-fluctuations-in-high-temperature?redirectedFrom=fulltext

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https://doi.org/10.1063/1.2192469
 http://hdl.handle.net/11603/31471

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UMBC Mechanical Engineering Department

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Author/Creator ORCID

https://orcid.org/0000-0002-6830-3126

Date

2006-05-08

Type of Work

journal articles
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Citation of Original Publication

H. S. McLean, R. D. Wood, B. I. Cohen, E. B. Hooper, D. N. Hill, J. M. Moller, C. Romero-Talamas, S. Woodruff; Transport and fluctuations in high temperature spheromak plasmas. Phys. Plasmas 1 May 2006; 13 (5): 056105. https://doi.org/10.1063/1.2192469

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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract

Higher electron temperature (Tₑ>350 eV) and reduced electron thermal diffusivity (Xₑ < 10 m²/s) is achieved in the Sustained Spheromak Physics Experiment (SSPX) by increasing the discharge current = I gun and gun bias flux = Ψ gun in a prescribed manner. The internal current and q = safety factor profile derived from equilibrium reconstruction as well as the measured magnetic fluctuation amplitude can be controlled by programming the ratio λ gun =μ₀Igun / Ψ gun⁠. Varying λ gun above and below the minimum energy eigenvalue = λ FC of the flux conserver (Δ x B = λ FC B) varies the q profile and produces the m/n = poloidal/toroidal magnetic fluctuation mode spectrum expected from mode-rational surfaces with q=m/n⁠. The highest Tₑ is measured when the gun is driven with λ gun slightly less than λ FC⁠, producing low fluctuation amplitudes (<1%) and 1/2<q<2/3⁠. Transport analysis shows a reduction in Xₑ as Tₑ increases, differing from Bohm or open field line transport models where Xₑ increases with Tₑ⁠. Detailed resistive magnetohydrodynamic simulations with the NIMROD code support the analysis of energy confinement in terms of the causal link with the q profile, magnetic fluctuations associated with low-order mode-rational surfaces, and the quality of magnetic surfaces