2D imaging of helium ion velocity in the DIII-D divertor

Samuell, C. M.; Porter, G. D.; Meyer, W. H.; Rognlien, T. D.; Allen, S. L.; Briesemeister, A.; Mclean, A. G.; Zeng, L.; Jaervinen, A. E.; Howard, J.

doi:10.1063/1.5017999

Title: 2D imaging of helium ion velocity in the DIII-D divertor

Journal Article · 25 April 2018 · Physics of Plasmas

DOI: https://doi.org/10.1063/1.5017999 · OSTI ID:1568884

^[1]; Porter, G. D. ^[1]; Meyer, W. H. ^[1]; Rognlien, T. D. ^[1]; Allen, S. L. ^[1];

^[2]; Mclean, A. G. ^[1]; Zeng, L. ^[3]; Jaervinen, A. E. ^[1];

^[4]

Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Univ. of California, Los Angeles, CA (United States)
Australian National Lab. Canberra, ACT (Australia)

Two-dimensional imaging of parallel ion velocities are compared to fluid modeling simulations to understand the role of ions in determining divertor conditions and benchmark the UEDGE fluid modeling code. Pure helium discharges are used so that spectroscopic He+measurements represent the main-ion population at small electron temperatures. Electron temperatures and densities in the divertor match simulated values to within about 20-30% establishing the experiment/model match as being at least as good as those normally obtained in the more regularly simulated deuterium plasmas. He⁺ brightness (HeII) comparison indicates that the degree of detachment is captured well by UEDGE, principally due to the inclusion of E x B drifts. Tomographically inverted Coherence Imaging Spectroscopy (CIS) measurements are used to determine the He⁺ parallel velocities which display excellent agreement between model and experiment near the divertor target where He⁺ is predicted to be the main-ion species and where electron-dominated physics dictates the parallel momentum balance. Upstream near the X-point where He⁺ is a minority species and ion-dominated physics plays a more important role, there is an underestimation of the flow velocity magnitude by a factor of 2-3. Lastly, these results indicate that more effort is required to be able to correctly predict ion momentum in these challenging regimes.

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Research Organization:: General Atomics, San Diego, CA (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA)

Grant/Contract Number:: FC02-04ER54698; AC52-07NA27344; AC05-00OR22725

OSTI ID:: 1568884

Alternate ID(s):: OSTI ID: 1434565; OSTI ID: 1491642

Report Number(s):: LLNL-JRNL-744602; TRN: US2100333

Journal Information:: Physics of Plasmas, Vol. 25, Issue 5; ISSN 1070-664X

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

Country of Publication:: United States

Language:: English

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