2005 47th Annual Meeting of the Division of Plasma Physics
Monday–Friday, October 24–28, 2005;
Denver, Colorado
Session LI1b: Magnetic Plasma Technology
3:00 PM–5:00 PM,
Wednesday, October 26, 2005
Adam's Mark Hotel
Room: Plaza Ballroom ABC
Chair: J. Reece Roth, University of Tennessee
Abstract ID: BAPS.2005.DPP.LI1b.1
Abstract: LI1b.00001 : Gas Jet Disruption Mitigation Studies on Alcator C-Mod*
3:00 PM–3:30 PM
Preview Abstract
Abstract
Author:
Robert Granetz
(MIT Plasma Science and Fusion Center)
Disruptions are a major concern for C-Mod, ITER, and future
tokamak reactors. Damage can come from several different
effects, including high instantaneous thermal loads on material
surfaces, electromagnetic loads on conducting structures due to
halo and toroidal eddy currents, and highly localized damage
from relativistic runaway electron impact. Reliable mitigation
of these problems using techniques benign to tokamak operation
are key to meeting the scientific and technological goals of
these experiments. High pressure noble gas jet injection is a
mitigation technique which potentially satisfies the operational
requirements of fast response time and reliability, while still
being benign to subsequent discharges. Previous gas jet
injection experiments on DIII-D have shown good success at
reducing the deleterious effects of disruptions. However, many
questions remain about the effectiveness of this approach on
high energy density, high pressure plasmas in high field devices
such as C-Mod and ITER. Disruption mitigation experiments using
an optimized gas jet injection system are being carried out on
C-Mod to study the physics of gas jet penetration into high
pressure plasmas, the ability of the gas jet to convert plasma
energy into radiation on timescales consistent with C-Mod's fast
quench times, and the reduction of halo currents with C-Mod's
high current density. The dependence of impurity penetration
and effectiveness on noble gas species (He, Ne, Ar), gas
pressure, and plasma pressure/energy density will also be
discussed. 3-D MHD modeling of the disruption physics with
NIMROD, incorporating data from temperature profiles taken
during the disruption quench, as well as high-speed images of
the plasma cross-section in the gas nozzle region, show that
edge cooling of the plasma triggers the growth of tearing modes,
producing a stochastic region in the core of the plasma and
rapid loss of core thermal energy. This may explain the
apparent effectiveness of the gas jet despite its limited
penetration.
*Work supported by DoE
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2005.DPP.LI1b.1