TRANSP-based Optimization Towards Tokamak Scenario Development
W.P. Wehner, E. Schuster, M.D. Boyer, F.M. Poli
Fusion Engineering and Design, 146 (2019) 547–550.
Abstract
|
|
An optimization approach that incorporates the predictive transport
code TRANSP is proposed for tokamak scenario development. Optimization
methods are often employed to develop open-loop control strategies to
aid access to high performance tokamak scenarios. In general, the
optimization approaches use control-oriented models, i.e. models that
are reduced in complexity and prediction accuracy as compared to
physics-oriented transport codes such as TRANSP. In the presented
approach, an optimization procedure using the TRANSP code to simulate
the tokamak plasma is considered for improved predictive capabilities.
As a test case, the neutral beam injection (NBI) power is optimized to
develop a control strategy that maximizes the noninductive current
fraction during the ramp-up phase for NSTX-U. Simulation studies towards
the achievement of noninductive ramp-up in NSTX-U have already been
carried out with the TRANSP code. The optimization-based approach
proposed in this work is used to maximize the noninductive current
fraction during ramp-up in NSTX-U, de- monstrating that the scenario
development task can be automated. An additional test case considers
optimization of the current ramp rate in DIII-D for obtaining a
stationary plasma characterized by a flat loop voltage profile in the
flattop phase.