Natural Divertor Spherical Tokamak Plasmas with bean shape and ergodic limiter

The former spherical tokamak (ST) MEDUSA (Madison EDUcation Small Aspect.ratio tokamak, R\textless 0.14m, a\textless 0.10m, B$_{T}$\textless 0.5T, I$_{p}$\textless 40kA, 3ms pulse) [1] is being recommissioned in Costa Rica Institute of Technology. The main objectives of the MEDUSA-CR project are training and to clarify several issues in relevant physics for conventional and mainly STs, including beta studies in bean-shaped ST plasmas [2], transport, heating and current drive via Alfv\'{e}n wave, and natural divertor STs with ergodic magnetic limiter [2,3]. We report here improvements in the self-consistency of these equilibrium comparisons and a preliminary study of their MHD stability beta limits.\\[4pt] [1] G. D. Garstka, PhD thesis, University of Wisconsin at Madison, September 1997\\[0pt] [2] C. Ribeiro et al., Proc. 25$^{\mathrm{th}}$ Symposium on Fusion Engineering, San Francisco, US, June 2013\\[0pt] [3] C. Ribeiro et al., Proc. 39$^{\mathrm{th}}$ EPS Conf. Contr. Fusion and Plasma Phys., vol. 36F, P1.091, Stockholm, Sweden, July 2012\\[0pt] [4] J. J. E. Herrera-Velazquez, E. C. Alarcon, and C. Ribeiro, 24$^{\mathrm{th}}$ IAEA Fusion Energy Conference, TH-p2-28, San Diego, US, 8-12 October 2012