Progress in the development of a plasma jet source and its utilization for injection of hydrogen plasma and neutral gas jets into the Globus-M spherical tokamak are presented. The latest version of the high kinetic energy gas and plasma jet source with titanium hydride grains is described. Reproducibility of the gas jet generation was increased due to automatic loading of fresh grains into the source before every shot. It allows producing stable gas release for many discharges. Impurity radiation intensity from the plasma jet was decreased by more than 100 times by preliminary processing titanium hydrate grains and developing a new filter. The result of special experiments on two colliding jets is discussed. It was confirmed that the plasma jet recombines into a gas jet after it escapes the source edge and has a kinetic energy higher than the hydrogen ionization potential. Hydrogen plasma jet with low impurity content has a density up to 2 × 1022 m-3, a total number of accelerated particles (1-5) × 1019 and a flow velocity of ~ 200 km/s. It was used as an instrument for density control in Globus-M. Jet injection into deuterium plasma core during current plateau phase led to fast density increase in all spatial points of the plasma column including the plasma central region. Such injection allowed density doubling in the tokamak plasma. The model predictions are consistent with the experimental observations of the density raise recorded by the interferometer and Thomson scattering.
Researches on the plasma jet source and injection of hydrogen plasma and neutral gas jets into the Globus-M spherical tokamak are presented. A novel source of dense plasma with high directed velocity is designed, constructed and investigated. This is a double stage system consisting of an intense source utilizing titanium-hydride grains for neutral gas production and a conventional pulsed coaxial accelerator. Optimization of the accelerator parameters, so as to achieve a maximum possible flow velocity with a limited discharge current and a reasonable length of the coaxial electrodes is performed. The calculations are compared with the experiment. A test bed is used for investigation of the intense plasma jet generated by a plasma gun. Plasma jet parameters, among them pressure distribution across the jet, flow velocity, plasma density etc., were measured. Plasma jets with densities of up to 1022 m 3, total numbers of accelerated particles (1 5) . 1019, and flow velocities of 50 100 km/s were successfully injected into the plasma column of the Globus-M tokamak. Interferometric and Thomson scattering measurements confirmed a deep jet penetration and a fast density rise (<0.5 ms) at all spatial points up to the radius r H 0.3a. The injection did not result in plasma degradation.
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