Commissioning of the plasma central column for the PROTO-SPHERA spherical tokamak

PROTO-SPHERA is the first plasma project with a simply connected configuration, namely not requiring other objects inside the plasma. This is obtained by a hydrogen plasma arc, shaped as a screw pinch, acting as the central column of a spherical torus with minimal aspect ratio. The reduced size and complexity of the configuration can lead to several physical and engineering advantages, providing relevant contributions to the magnetic plasma confinement methods. Moreover, due to the limited costs and requirements, the set-up is attractive for replication and developments also on an industrial scale with many potential applications. This paper describes the initial activities of the PROTO-SPHERA project, with emphasis on the electrical tests and commissioning performed to implement the plasma central column. In particular, an intermediated experiment classified as MULTI-PINCH was designed to investigate the breakdown conditions and the pinch stability.