Internal Magnetic Fluctuations via Cross-Polarization Scattering System during enhanced D<sub>α</sub> high confinement mode on DIII-D Tokamak

POSTER

Abstract

Cross-polarization scattering (CPS) enables localized measurements of magnetic fluctuations in fusion plasmas via orthogonal polarization scattering of electromagnetic radiation. This work presents results of internal magnetic fluctuation measurements during enhanced Dα high confinement mode (EDA H-mode) on the DIII-D tokamak.

Near the plasma edge, quasi-coherent density modes (QCMs) in both electron and ion diamagnetic directions (in lab frame, measured by DBS) were observed, with frequencies ~1100 kHz and -300 kHz, and poloidal wavenumber kθ ≈ 13 cm−1. In contrast, magnetic fluctuation measured by CPS shows only a single QCM mode in the electron diamagnetic direction, with frequency ~ 600 kHz and kθ ≈ 6.5 cm−1. These observations suggest the electron diamagnetic mode is electromagnetic (e.g., MTM, KBM, interchange mode), while the ion diamagnetic mode is electrostatic (possibly drift wave, ITG, etc.)1,2.

Perpendicular velocity fluctuation at ~40 kHz is detected by both DBS and CPS systems, and via fast magnetic coils and interferometer, indicating consistent results. 3D ray-tracing code GENRAY is used for systematic analysis of optimized measurements condition for DBS and CPS.

*This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award(s) DE-FC02-04ER54698 and DE-SC0019352.

Publication: 1. LaBombard, Brian, et al. "New insights on boundary plasma turbulence and the quasi-coherent mode in Alcator C-Mod using a Mirror Langmuir Probe." Physics of Plasmas 21.5 (2014).
2. Grenfell, G., et al. "The multi-faced nature of the quasicoherent mode in EDA H-mode." Nuclear Fusion 64.10 (2024): 104002.

Presenters

  • Ruihai Tong

    • University of California, Los Angeles

Authors

  • Ruihai Tong

    • University of California, Los Angeles

  • Rongjie Hong

    • University of California, Los Angeles

  • Terry L Rhodes

    • University of California, Los Angeles

  • Lei Zeng

    • University of California, Los Angeles
    • University of California Los Angeles

  • Satyajit Chowdhury

    • University of California, Los Angeles

  • Julius Damba

    • University of California, Los Angeles

  • Neal A Crocker

    • University of California, Los Angeles

  • Ravi Dhaliwal

    • University of California, Los Angeles