Gas-Dynamic Multiple-Mirror Trap GDMT

The results on applying the technique of vortex plasma confinement in the GOL-NB facility are presented. The first experiments on optimizing the biasing the in-chamber electrodes demonstrated an improvement in the dynamics of trapping the injected fast hydrogen atoms, as well as a decrease in the fluctuations of local plasma parameters in the central trap and an increase in the plasma decay time. The geometry of in-chamber electrodes arrangement, as well as the polarity and magnitude of the supplied potentials, correspond to the theory of vortex confinement and to those in similar studies at other open traps.

Control of Plasma Potential in GOL-NB Axisymmetric Multiple-Mirror Trap

Ivanov,

Polozova,

Batkin

et al. 2023

Study of Plasma Flow Velocity in an Open SMOLA Screw Trap

Inzhevatkina,

Ivanov,

Postupaev

et al. 2024

The physics of confinement of a rotating plasma in a magnetic field with linear helical symmetry is being studied at the Institute of Nuclear Physics SB RAS on the open SMOLA trap. An indicator of the quality of confinement is the plasma flow velocity in the system. The paper describes the applied diagnostics based on the Mach probe under conditions of non-magnetized plasma, which made it possible to determine the longitudinal flow velocity in experiments. The measured longitudinal flow velocity was (0.5–5) · 106 cm/s in various operating modes of the installation. The dependence of the speed on the magnitude of the magnetic field corrugation is discussed. A reverse flow of trapped particles returning to the containment zone has been detected.

Detached Plasma Studies in GOL-NB with Extra Gas Injection

Postupaev,

Batkin,

Ivanov

et al. 2024

The magnetic system of an open trap usually includes expansion sections located between highfield magnetic mirrors and end surfaces that receive plasma. In the GOL-NB device, an arc plasma gun is located in one of the expanders, which creates a low-temperature starting plasma in the confinement area. The parameters of the surface plasma sheath affect the electrical connection of the confinement area with the walls and, thereby, affect the contribution of the line-tying effect to the plasma stability and the longitudinal energy losses from the trap. The experiments with additional hydrogen injection into the plasma gun were carried out at GOL-NB. We observed a radiating plasma formation detached from the surface, which visually corresponds to that in radiating divertors in tokamaks. In both standard and detached modes, decaying plasma existed near the receiving electrodes during the entire observation time after the discharge current was terminated. In the central trap of GOL-NB, some structures in the Fourier spectrogram of magnetic fluctuations manifest earlier in the detachment mode than in the standard mode and have lower frequencies. We associate these structures with the onset of interchange-like modes due to the loss of plasma stabilization by the line-tying to the conducting ends. The observed plasma response to the additional gas supply confirmed our understanding of the line-tying effect as the main factor stabilizing the plasma core in the initial phase of density accumulation in the central trap.