抄録
TOKASTAR-2 is a small tokamak-helical hybrid device which can generate tokamak and helical configurations independently. In tokamak discharge experiment, the conductive shell was installed to increase plasma current by controlling the displacement of ohmically heated (OH) plasma. The suppression of the vertical displacement was demonstrated, but the OH plasma was still located slightly above the mid plane. To compensate this displacement, the balance between up and down vertical field coil currents should be adjusted. In addition, the construction of additional helical field coils is planned to form closed vacuum magnetic surfaces. The magnetic field line tracing analysis was carried out to determine the detailed shape and location of additional helical field coils. From the simulation, it was clarified that the location of magnetic surfaces and the averaged value of rotational transform can be controlled by adjusting coil current ratios.
