The conceptual design of Formosa Integrated Research Spherical Tokamak

The preliminary plasma parameters for the new FIRST (Formosa Integrated Research Spherical Tokamak) device have been determined. The fixed boundary equilibrium is calculated using the CHEASE [1] and stability properties of the equilibrium are checked using the DCON code [2]. Low-n ideal external kink modes are stabilized with a close-fitting ideal wall placed near the plasma. The design parameters are chosen based on the scans while varying the plasma elongation and triangularity. The eventual parameters that meet the missions of FIRST are as follows: the major radial R₀=45cm, the plasma minor radius a=32 cm (aspect ratio 1.4), the plasma elongation κ=2.4 and the triangularity δ=0.5. A monotonic safety factor profile is assumed to achieve high beta of β=38% and β_N= 8. The low-n ideal external kinks, internal modes, and ballooning modes are all stable. Other physics properties of the reference equilibrium will also be examined and reported.



[1] H. Lütjens, A. Bondeson & O. Sauter, Computer Physics Communications 97 (1996).

[2] A. H. Glasser, Physics of Plasmas 23, 072505 (2016).