System Design of a Magnetically Levitated Internal Coil Device Mini-RT

Abstract

Mahajan-Yoshida proposed an idea for confining high-beta plasma utilizing a fast plasma flow in a toroidal direction. In addition, Hasegawa considered a dipole fusion reactor. Here, the authors introduce a “Mini-RT" internal coil device, in which a superconducting coil is levitated in a vacuum vessel and plasma is confined by a dipole magnetic field, to explore a new high-beta plasma for fusion research. The conductor of the floating coil (R_C= 0.15 m, I_C= 50 kA) is Bi-2223 tape that is cooled by cold helium gas to 20 K. By controlling the coil current of the levitation coil located at the top of the vacuum chamber, a few hours of levitation can be obtained for plasma experiments. It is possible to produce various magnetic configurations with a combination of vertical field coils. Several issues related to interaction with plasma produced around the floating coil have been taken into account for designing the floating coil; for example, clearance of the magnetic surface at the torus inner region, heat load to the floating coil caused by the plasma and so on.