DIII-D Research Advancing the Scientific Basis for Burning Plasmas and Fusion Energy
W.M. Solomon et al.
57 (2017) 102018 (18pp)
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Abstract
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The DIII-D tokamak has addressed key issues to advance the physics basis
for ITER and future steady-state fusion devices. In work related to
transient control, magnetic probing is used to identify a decrease in
ideal stability, providing a basis for active instability sensing.
Improved understanding of 3D interactions is emerging, with RMP-ELM
suppression correlated with exciting an edge current driven mode. Should
rapid plasma termination be necessary, shattered neon pellet injection
has been shown to be tunable to adjust radiation and current quench rate.
For predictive simulations, reduced transport models such as TGLF have
reproduced changes in confinement associated with electron heating. A
new wide-pedestal variant of QH-mode has been discovered where increased
edge transport is found to allow higher pedestal pressure. New dimensionless
scaling experiments suggest an intrinsic torque comparable to the beam-driven
torque on ITER. In steady-state-related research, complete ELM suppression
has been achieved that is relatively insensitive to q95, having a weak
effect on the pedestal. Both high-qmin and hybrid steady-state plasmas
have avoided fast ion instabilities and achieved increased performance
by control of the fast ion pressure gradient and magnetic shear, and use
of external control tools such as ECH. In the boundary, experiments have
demonstrated the impact of E × B drifts on divertor detachment and divertor
asymmetries. Measurements in helium plasmas have found that the radiation
shortfall can be eliminated provided the density near the X-point is used
as a constraint in the modeling. Experiments conducted with toroidal rings
of tungsten in the divertor have indicated that control of the strike-point
flux is important for limiting the core contamination. Future improvements
are planned to the facility to advance physics issues related to the
boundary, transients and high performance steady-state operation.
