Scaling of energy confinement time in the Globus-M spherical tokamak

The paper is devoted to an energy confinement study at the Globus-M spherical tokamak (ST). Experiments were performed in single null divertor configuration with elongation as high as 1.8-1.9 for variable plasma current and fixed toroidal magnetic field. The confinement time (tau(E)) dependence on density for ohmic-heated (OH) deuterium plasma is presented. It was found that tau(E) rises linearly with plasma current in H-mode with pure ohmic heating. Pronounced electron and ion heating was achieved in discharges with neutral beam injection at a moderate density level. The dependence of tau(E) on absorbed power was weak.