Runaway electron x-ray emission during the startup of MST tokamak plasmas

POSTER

Abstract

Energetic electron emission has been observed during the startup (∼0-10 ms) of reproducible tokamak plasmas (Ip = 40-60 kA, ne < 0.05-0.2 x 1019 m-3) produced at the Madison Symmetric Torus (MST). The multi-energy soft x-ray (ME-SXR) pinhole camera provides brightness measurements of the bremsstrahlung radiation given off by the suprathermal runaway electrons (RE’s) with space (Δr/a≈2%), time (∼1 ms), and energy resolution. Motivated by an ITPA Joint Analysis task, the effects of prefill gas pressure, applied electric field, and current ramp-up rate on the startup of MST tokamak plasmas were investigated with a specific focus on the RE emission. Resonant magnetic perturbations (RMPs) with m=1, 2, and 3 fields were applied with different amplitudes, phases, and times to explore the suppression of these RE’s during startup. Preliminary results suggest that RE acceleration is decreased at sufficiently high pressures, but the consistent presence of RE emission indicates that RE generation is a robust feature of MST tokamak plasma startup. A new gating capability was tested using the versatile PILATUS3 detector to improve the time-resolution of the x-ray measurement from 0.5 kHz to 2 kHz and 4 kHz, providing a more complete picture of the RE emission during the breakdown and startup of the plasma.

*This work was supported by the U.S. DOE-OFES, under Contract No. DE-AC02-09CH11466, and L.F.D A's 2015 DOE Early Career Award Research Program. The experiments were conducted at the Wisconsin Plasma Physics Laboratory (WiPPL), a research facility supported by the DOE-OFES, under Contract No. DE- SC0018266, with major facility instrumentation developed with the support from the NSF, under Award No. PHY 0923258. The MST Tokamak Thermal Quench Program is funded under DOE-OFES, Award No. DE- SC0020245.

Presenters

  • Courtney L Johnson

    • Princeton University
    • Princeton Plasma Physics Laboratory

Authors

  • Courtney L Johnson

    • Princeton University
    • Princeton Plasma Physics Laboratory

  • Luis F Delgado-Aparicio

    • Princeton Plasma Physics Laboratory

  • Aubrey Houser

    • University of Wisconsin-Madison

  • Noah C Hurst

    • University of Wisconsin - Madison
    • UW-Madison

  • Patrick D VanMeter

    • University of Wisconsin - Madison

  • Diego Del-Castillo-Negrete

    • Oak Ridge National Lab

  • minglei yang

    • Oak Ridge National Laboratory

  • Brett E Chapman

    • University of Wisconsin - Madison
    • UW-Madison

  • Novimir A Pablant

    • Princeton Plasma Physics Laboratory
    • PPPL
    • PPPL, Princeton University, P.O. Box 451, Princeton, New Jersey 08543, USA

  • Kenneth W Hill

    • PPPL
    • Princeton Plasma Physics Laboratory

  • Manfred L Bitter

    • Princeton Plasma Physics Laboratory

  • Oulfa Chellai

    • Princeton Plasma Physics Laboratory

  • Tullio Barbui

    • Princeton Plasma Physics Laboratory

  • John P Wallace

    • University of Wisconsin - Madison

  • Karsten J McCollam

    • University of Wisconsin - Madison
    • University of Wisconsin-Madison

  • Cary B Forest

    • University of Wisconsin - Madison
    • University of Wisconsin-Madison