Equilibrium Reconstruction using Soft X-Ray Chordal Diagnostics on the Compact Toroidal Hybrid Experiment

Equilibrium reconstructions using the V3FIT [1] code will be presented for current carrying plasmas on the Compact Toroidal Hybrid (CTH) torsatron experiment (R = 0.75 m, a $\sim $ 0.2 m, B $\le $ 0.7 T, ne $\le $ 10$^{19}$ m$^{-3}$, Te $\le $ 250 eV). The reconstruction input data set includes the Soft X-Ray (SXR) chord signals normally used for tomographic reconstructions. Four cameras, each consisting of a 20-channel AXUV-20EL photo-diode array view the CTH plasma through 2$\mu $m Be foil. Three cameras view the plasma at one symmetry plane ($\varphi $ =36$^{\circ})$ while the fourth views the plasma at another symmetry plane ($\varphi $ =0$^{\circ})$, one-half field period away. When observed, sawtoothing provides additional constraints to reconstructions. The reconstructions assume uniform SXR emissivity on a flux surface. The SXR signals provide additional data inputs to V3FIT, which has primarily used magnetic data to fit the equilibrium. \\[4pt] [1] J. Hanson, S. Hirshman, S. Knowlton, L. Lao, E. Lazarus, J. Shields, Nucl. Fusion, \textbf{49} (2009) 075031