Effect of secondary beam neutrals on MSE: Experiment

POSTER

Abstract

It has been conjectured that the anomalous results obtained previously during beam-into-gas calibrations of the Motional Stark Effect (MSE) diagnostic on Alcator C-Mod are caused by the `secondary' beam neutrals - the neutrals that ionize following collisions with the torus gas and then re-charge exchange at a random gyro angle. Based on this conjecture, the C- Mod diagnostic neutral beam (DNB) was pivoted toroidally to impart a non-zero parallel beam velocity. In this new configuration, spectroscopic measurements and beam-into-gas calibrations confirm that the beam-into-gas anomaly is caused by the secondary beam neutrals. In addition, we report initial results from the beam-into-plasma calibration using plasma edge sweeping and plasma current ramping.

*Work supported by the U.S. Department of Energy, Grant No. DE-FC02-99ER54512, DE-AC02-76CH03073, and ED-FG03-96ER54373

Authors

  • J. Ko

    • Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA, USA
    • MIT PSFC

  • Steve Scott

    • Princeton Plasma Physics Laboratory
    • Princeton Plasma Physics Laboratory, Princeton, NJ, USA
    • PPPL

  • W.L. Rowan

    • Fusion Research Center, University of Texas, Austin, TX, USA
    • The University of Texas at Austin, Fusion Research Center
    • Fusion Research Center, Univ. of Texas
    • FRC UT AUSTIN
    • The University of Texas at Austin

  • Bob Granetz

    • Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA, USA

  • Ian Hutchinson

    • MIT
    • Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA, USA

  • Howard Yuh

    • Nova Photonics
    • Nova Photonics, Inc.
    • Nova Photonics, Inc., NJ, USA