A discharge optimizer for tokamak operations with application to ITER*

A discharge optimizer has been developed to enhance and facilitate tokamak operations, reduce control errors, and save experimental time and operation cost. Prior to and/or between discharges, the optimizer calculates the set of feedforward currents for the central solenoid and poloidal-field coils to provide to the plasma-control system. Such a set of currents is critical to achieve and sustain a particular plasma scenario. Shot-to-shot modifications can be requested by the operator to vary the desired plasma shape, position, and total plasma current. In addition, power supply limits are taken into account for machine protection and control performance. Boundaries on plasma parameters (such as plasma internal inductance, normalized beta, or total plasma current) can also be imposed in order to ensure plasma stability. The optimizer is based on a model of the electromagnetic plasma response which is obtained by solving a perturbed Grad-Shafranov (GS) equation. This first-principles model is provided by the General Atomics Tokamak System Toolbox (GA TokSys). Due to the model-based nature of the optimizer, it is machine and scenario independent and tuning is not needed, so it can be easily ported between different devices. The optimizer has been tested in existing experimental devices as well as in ITER simulations.