Implementation of βN Control in the National Spherical Torus Experiment

Simultaneous feedback control of plasma rotation and stored energy on NSTX-U using neoclassical toroidal viscosity and neutral beam injection

A model-based feedback system is presented enabling the simultaneous control of the stored energy through β_n and the toroidal rotation profile of the plasma in National Spherical Torus eXperiment Upgrade device. Actuation is obtained using the momentum from six injected neutral beams and the neoclassical toroidal viscosity generated by applying three-dimensional magnetic fields. Based on a model of the momentum diffusion and torque balance, a feedback controller is designed and tested in closed-loop simulations using TRANSP, a time dependent transport analysis code, in predictive mode. Promising results for the ongoing experimental implementation of controllers are obtained.

Magnetic diagnostics for equilibrium reconstruction and realtime plasma control in NSTX-Upgrade

This paper describes aspects of magnetic diagnostics for realtime control in National Spherical Torus Experiment-Upgrade (NSTX-U). The sensor arrangement on the upgraded center column is described. New analog and digital circuitry for processing the plasma current Rogowski data are presented. An improved algorithm for estimating the plasma vertical velocity for feedback control is presented.