Control of the vertical instability of the plasma in the SUNIST spherical tokamak is studied. A proportional-derivative （PD） position controller is employed in a control system which consists of a massless plasma, active coils and a passive conducting vessel. Stability conditions axe determined and the feedback control with different combinations of both active and passive coils, available on SUNIST, is emphasized. The simulation results are also discussed.
A method for the reconstruction of the plasma boundary in the sino-united spherical tokamak （SUNIST） based on the outer plasma magnetic diagnostics is reported. In SUNIST, the magnetic flux loop integral signals were measured recently and the plasma boundary could be reconstructed well with a current filament （CF） model by setting 2 to 8 current filaments. There are three additional filament positional parameters in addition to the filament current to minimize the square root error in the CF model. The plasma configuration obtained with the CF method is consistent with the visible plasma image from the CCD camera. The average difference in the minor radii for the plasma boundary, by applying the CF model and EFIT code, is below 6 mm.
