Advanced Tokamak Research at the DIII-D National Fusion Facility
in Support of ITER
Developing a reliable energy system that is economically and
environmentally sustain-able is the long-term goal of Fusion Energy
Sciences research. The leading candidate for magnetically confining
fusion plasmas is the tokamak, a doughnut-shaped vessel in which a
strong, helical magnetic field guides the charged particles around it.
The DIII-D tokamak research program emphasizes development of integrated
scenarios for burning plasma experiments and investigation of elements
in those scenarios that are critical for the success of future devices
such as ITER. One such element is advanced tokamak research that seeks
to provide a scientific basis for steady-state high performance operation
in future fusion devices. These regimes require high plasma pressure to
maximize fusion output and to maximize the self-driven plasma current.
Achieving these conditions requires integrated, simultaneous control of
the plasma current and pressure profiles, and active control of large-scale
(on the order of the machine) plasma stability, using a diverse set of
control techniques. A sophisticated digital plasma control system allows
integrated control of these elements during experimental operation.
Steady-state operation requires replacing the inductively driven plasma
current using other sources. In DIII–D, the approach primarily relies on
self-driven bootstrap current and electron cyclotron current drive (ECCD).
Active suppression of large-scale instabilities is accomplished using both
nonaxisymmetric magnetic field coils and through plasma rotation. Using these
and other techniques, fully noninductive plasmas have been obtained and
sustained for time scales on the order of a current relaxation time. These
experimental efforts are supported by a closely coupled effort in integrated
simulation. These calculations are used both to plan and interpret experiments,
with the results being used to further improve the physics based models
themselves. In this way, our predictive capability is continually improving,
with the goal being a set of models taking into account the complex nonlinear
interactions in a fusion device that can be applied to future experiments
in DIII–D, ITER and elsewhere. Experimental and simulation progress in AT
research including the usage of
FusionGrid, and its implications for ITER and other next-step devices, will
be illustrated by results of recent experiment and simulation efforts. The
anticipated future direction of this research, using simulation, experiment,
and computational grids, will also be discussed.
Work at the DIII-D National Fusion Facility is supported by
the US DOE Office of Fu-sion Energy Sciences under Cooperative