Plasma shape control options for edge physics studies on HBT-EP

The cross-sectional shape of tokamak discharges strongly influences plasma stability and confinement. Control of the plasma's outer shape is critical to divertor optimization and can improve diagnostic access to the scrape-off-layer (SOL). HBT-EP demonstrated the capability of creating fully diverted plasmas by energizing a ``zero-net-turn'' poloidal field coil-system located on the high-field side of HBT-EP.[1]  As compared to limited discharges, the inner x-point modified the kink mode's poloidal structure while keeping the plasma's response to resonant magnetic perturbations unchanged. Shaped plasmas are predicted to modify the multi-mode behavior of kink modes[2] and are necessary to control the helicity of driven SOL currents for feedback studies.[3] In this poster, we discussion options for new HBT-EP poloidal field coils and power supplies that will provide improved outer boundary control and give flexibility to explore novel edge physics and control techniques.

[1] P.J. Byrne, Dissertation (2017); https://doi.org/10.7916/D8R78SJ0.

[2] D.A. Maurer, et al., Plasma Phy Contr Fus, 53, 074016 (2011).

[3] J.P. Levesque, et al., Nuc Fusion, 57, 086035 (2017).