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.

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