Characterization of the Pedestal in I-Mode Plasmas on Alcator C-Mod

POSTER

Abstract

I-mode is an improved energy confinement regime on C-Mod, notably featuring an edge temperature pedestal without the accompanying density pedestal found in H-mode operation. I-mode has been shown to be capable of stationary operation, with the mode sustained for $\sim 10$ energy confinement times, and to have a pedestal naturally lacking large ELMs. Combined with comparable performance to H-mode operation and weaker degradation with input power, this makes I-modes potentially favorable as a reactor regime. A full characterization using the suite of high-resolution edge diagnostics on C-Mod of the pedestal in reversed-field, lower-single-null I-modes (therefore with the ion $\nabla B$ drift away from the x-point) is presented here. The presented discharges primarily feature detailed scans of plasma current and ICRF heating power at several density values. The pedestal structure found in these I-modes is also contrasted with previous studies of the pedestal in EDA and ELMy H-modes, particularly potential scalings with $\beta_{p,ped}$ consistent with the KBM-limited pedestals found in these H-modes.

*Work supported by USDOE award DE-FC02-99ER54512.

Authors

  • J.R. Walk

    • MIT PSFC
  • J.W. Hughes

    • MIT PSFC
  • J.L. Terry

    • MIT PSFC
  • A.E. Hubbard

    • MIT PSFC
  • D.G. Whyte

    • MIT PSFC
  • A.E. White

    • MIT PSFC
  • E.S. Marmar

    • MIT PSFC
  • J.E. Rice

    • MIT PSFC
  • R.M. Churchill

    • MIT PSFC
  • C. Theiler

    • MIT PSFC
  • B. LaBombard

    • MIT PSFC
  • D. Brunner

    • MIT PSFC
  • M.L. Reinke

    • MIT PSFC
  • A. DOminguez

    • MIT PSFC
  • C. Sung

    • MIT PSFC