NCSX Magnetic Configuration Flexibility and Robustness

Abstract

The National Compact Stellarator Experiment (NCSX) will study the physics of low-aspect ratio, high-β, quasi-axisymmetric stellarators. To achieve the scientific goals of the NCSX mission, the device must be capable of supporting a wide range of variations in plasma configuration about a reference baseline equilibrium. We demonstrate the flexibility of NCSX coils to support such configuration variations and demonstrate the robustness of performance of NCSX plasmas about reference design values of the plasma current Ip, β, and profile shapes. The robustness and flexibility calculations make use of free-boundary plasma equilibrium constructions using a combination of nonaxisymmetric modular coils and axisymmetric toroidal and poloidal field coils. The primary computational tool for the studies is STELLOPT, a free-boundary optimization code that varies coil currents to target configurations with specific physics properties.