Modeling Snowflake Divertors in MAST-U Tokamak

Khrabry, A. I.; Soukhanovskii, V. A.; Rognlien, T. D.; Umansky, M. V.; Moulton, D.; Harrison, J. R.

doi:10.1088/1741-4326/ac3364

Title: Modeling Snowflake Divertors in MAST-U Tokamak

Abstract

We report that in a snowflake (SF) divertor, two magnetic field nulls are placed close to each other, creating four strike points (SPs) compared to two in a standard X-point divertor. In preparation for MAST-U experiments, magnetic configurations with the standard and SF divertors with various locations and separation distances of the nulls were modeled using the two-dimensional multi-fluid code UEDGE with a full plasma transport model featuring charge-state-resolved sputtered carbon impurities. The complex interplay of the plasma transport and magnetic configurations was comprehensively studied using a simple model for the theoretically predicted fast plasma mixing driven by the 'churning' mode instability in the two-null SF region. The modeling results show that (1) all SF-plus configurations and SF-minus configuration with closely located nulls produce the same plasma parameters and heat fluxes at the same SPs; (2) SF divertors approach the outer and inner SP detachment conditions at lower upstream density w.r.t. the standard divertor; (3) heat flux profiles at primary SPs are substantially broadened and peak values are reduced in SF configurations w.r.t. SN divertors; this broadening becomes more pronounced with the fast plasma mixing increase.

Authors:

^[1];

^[1]; Rognlien, T. D. ^[1]; Umansky, M. V. ^[1]; Moulton, D. ^[2];

^[2]

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Culham Centre for Fusion Energy, Abingdon (United Kingdom)

Publication Date:: Thu Dec 02 00:00:00 EST 2021

Research Org.:: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

Sponsoring Org.:: USDOE National Nuclear Security Administration (NNSA); RCUK Energy Programme; EURATOM

OSTI Identifier:: 1860701

Report Number(s):: LLNL-JRNL-822879
Journal ID: ISSN 0029-5515; 1035485; TRN: US2305421

Grant/Contract Number:: AC52-07NA27344; EP/P012450/1

Resource Type:: Accepted Manuscript

Journal Name:: Nuclear Fusion

Additional Journal Information:: Journal Volume: 62; Journal Issue: 1; Journal ID: ISSN 0029-5515

Publisher:: IOP Science

Country of Publication:: United States

Language:: English

Subject:: 70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats


                    Khrabry, A. I., Soukhanovskii, V. A., Rognlien, T. D., Umansky, M. V., Moulton, D., and Harrison, J. R. Modeling Snowflake Divertors in MAST-U Tokamak.  United States: N. p., 2021. 
Web.  doi:10.1088/1741-4326/ac3364.

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                    Khrabry, A. I., Soukhanovskii, V. A., Rognlien, T. D., Umansky, M. V., Moulton, D., & Harrison, J. R. Modeling Snowflake Divertors in MAST-U Tokamak.  United States.  https://doi.org/10.1088/1741-4326/ac3364

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                    Khrabry, A. I., Soukhanovskii, V. A., Rognlien, T. D., Umansky, M. V., Moulton, D., and Harrison, J. R. Thu .  
"Modeling Snowflake Divertors in MAST-U Tokamak".  United States.  https://doi.org/10.1088/1741-4326/ac3364.  https://www.osti.gov/servlets/purl/1860701.

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@article{osti_1860701,

  title        = {Modeling Snowflake Divertors in MAST-U Tokamak},

  author       = {Khrabry, A. I. and Soukhanovskii, V. A. and Rognlien, T. D. and Umansky, M. V. and Moulton, D. and Harrison, J. R.},

  abstractNote = {We report that in a snowflake (SF) divertor, two magnetic field nulls are placed close to each other, creating four strike points (SPs) compared to two in a standard X-point divertor. In preparation for MAST-U experiments, magnetic configurations with the standard and SF divertors with various locations and separation distances of the nulls were modeled using the two-dimensional multi-fluid code UEDGE with a full plasma transport model featuring charge-state-resolved sputtered carbon impurities. The complex interplay of the plasma transport and magnetic configurations was comprehensively studied using a simple model for the theoretically predicted fast plasma mixing driven by the 'churning' mode instability in the two-null SF region. The modeling results show that (1) all SF-plus configurations and SF-minus configuration with closely located nulls produce the same plasma parameters and heat fluxes at the same SPs; (2) SF divertors approach the outer and inner SP detachment conditions at lower upstream density w.r.t. the standard divertor; (3) heat flux profiles at primary SPs are substantially broadened and peak values are reduced in SF configurations w.r.t. SN divertors; this broadening becomes more pronounced with the fast plasma mixing increase.},

  doi          = {10.1088/1741-4326/ac3364},

  journal      = {Nuclear Fusion},

  number       = 1,

  volume       = 62,

  place        = {United States},

  year         = {Thu Dec 02 00:00:00 EST 2021},

  month        = {Thu Dec 02 00:00:00 EST 2021}

}

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