56th Annual Meeting of the APS Division of Plasma Physics
Volume 59, Number 15
Monday–Friday, October 27–31, 2014;
New Orleans, Louisiana
Session JI1: ITER Physics
2:00 PM–5:00 PM,
Tuesday, October 28, 2014
Room: Acadia
Chair: Chuck Greenfield, General Atomics
Abstract ID: BAPS.2014.DPP.JI1.2
Abstract: JI1.00002 : Impurity transport experiments in Alcator C-Mod to address high priority R and D for ITER*
2:30 PM–3:00 PM
Preview Abstract
Abstract
Author:
Matthew Reinke
(University of York)
The decision to start ITER operation in the non-active phase (H/He plasmas)
with a W divertor has brought increased attention to physics issues related
to high Z impurity transport and control. Lack of impurity control would
lead to the radiative collapse of plasmas by W accumulation and increased
disruptivity, which is detrimental to ITER operation. Prediction of plasma
contamination by high Z impurities in ITER and its control requires
understanding of W production and transport in the SOL through the edge
transport barrier (in H-mode) and into the core plasma in conditions as
similar as possible to those in ITER.
Experiments in Alcator C-Mod have been carried out to understand these
physics processes and their control in electron heated (ICRH$+$LHCD) L-mode
and H-mode plasmas without significant core particle or momentum sources as
in ITER. Core transport of impurities injected by laser blow off in L-modes
shows that, in the absence of sawteeth, W develops stationary peaked
profiles (for 100s of ms vs. $\tau_{\mathrm{E}} =$ 14 ms) while lower Z
impurities (e.g. Ar) do not. Sawteeth are observed to be very effective in
flushing out W on timescales of the sawtooth period ($=$10 ms) in these
L-mode plasmas. Injection of Ca shows that the impurity diffusivity in the
core plasma decreases by a factor of 10 in H-mode with respect to L-mode and
that an inwards pinch is necessary at the H-mode edge to match observed
increases in impurity confinement time in H-mode, up a factor of 5-50
compared to L-mode. Initial results of impurity transport in He L-mode
plasmas show similar results to D plasmas. The results of these and other
ongoing C-Mod experiments (including impurity transport and impurity peaking
control by heating sources (magnitude, fast particle population, radial
location, etc.) in H-mode plasmas with ITER-like peaked density profiles and
T$_{\mathrm{e}} =$ T$_{\mathrm{i}}$ ) will be described and consequences
for ITER impurity transport control will be drawn.
Supported by the US DOE under DoE Contract No. DE-FC02-99ER54512
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.DPP.JI1.2