Flat Thomson Temperature Profiles in SPECTOR with Li-coated walls

SPECTOR is built as a small spherical tokamak device, (R = 12 cm, a = 8.5 cm, B₀ = 0.3 T, I_pl = 220 kA) supplied with Li-coated walls. It can generate the relatively dense (n_e ~ 1x10²⁰ m^-3) and hot (T_e = 300 – 400 eV) plasma. The plasma current is induced by injecting helicity, using a magnetized coaxial Marshall gun. The machine is fueled by a brief initial gas pulse into the gun prior to the plasma breakdown. The radial profiles of electron temperature and the density have been measured by the Thomson laser scattering at 6 radially resolved points. Flat or nearly flat  radial profiles with a hot edge (up to T_e = 300 eV) have been observed when no gas was injected after the plasma formation, and the plasma was continuously losing particles. The low recycling mode was established in the deuterium plasma. The experiments with helium plasma did not show flat T_e profiles, since helium ions were poorly retained by the lithium-coated wall, and the low recycling mode likely did not establish.