The receiver calorimeter (RC) is one of the main elements of the beam path of an atomic beam injector with ballistic focusing. A water-cooled RC developed for an injector of a focused beam of fast deuterium atoms with a beam power of more than 1 MW and pulse duration of 2 s [1] installed at the variable configuration tokamak (TCV) in Lausanne (Switzerland) is considered. The design of the RC includes receiving plates with liquid flow swirlers installed in them to enhance heat transfer and pipe-in-pipe collectors of water inlet and water outlet that provide the movement into a vacuum. These technical solutions made it possible to achieve good energy efficiency of the device with very small overall dimensions and mass flow of the coolant. The design of the main elements of the calorimeter is described. The results of simulation of the coolant flow and heat transfer and some experimental data are presented.

Flow structure of incompressible fluid in a Ranque-Hilsch vortex tube was studied experimentally. A pattern of streamlines in the whole volume of the vortex tube was constructed from the velocity distributions measured using laser Doppler anemometry. The radial distributions of the azimuthal velocity in the Ranque-Hilsch vortex tube are shown to be different from those in a vortex tube with a tangential inlet and a single central exit orifice. Based on the obtained structure of the flow, a simple qualitative model is proposed to explain the physical mechanism of the temperature separation effect.

An injector of fast deuterium atoms for plasma heating was designed and installed at the Tokamak à Configuration Variable (TCV). The neutral beam can deliver 1 MW power to the plasma in 2 s pulses. An ion beam of the injector is formed by a triode multislit ion-optical system with spherical electrodes which provide ballistic focusing. Tests at TCV revealed that the total angular divergence of the neutral beam across the slits exceeded the expected value more than twice. It was finally established that this increase in divergence was caused by the asymmetry of the chamfers at the slit edges of the plasma electrode. The redesigned shape of the slits of the plasma grid together with precise machining significantly improved the beam quality. Experimental testing proved that the neutral beam profile in the direction across the grid slits became very close to the expected value.

Operation of a plasma source with a hot disk cathode and a cylindrical hollow anode in axial magnetic field is sensitive to the cathode-to-anode diameter ratio. When the cathode edge maps along magnetic field lines to the inner anode surface, the discharge voltage is relatively low, and the plasma stream with moderate density occupies the entire cross-section of the anode bore. By contrast, when the cathode projection is fully inside the anode bore with the radial cathode-to-anode gap ∼ 1 cm, the discharge voltage jumps to much higher values exceeding 250 V. The plasma density profile becomes Gaussian-like with the width matching the cathode radius according to magnetic flux surfaces. The plasma density in the high-voltage cross-field discharge reaches 1013 cm−3, and the discharge parameters almost do not change with magnetic field up to 1.5 kG in the anode area. This plasma source is suitable for the use in linear devices for plasma-material interaction studies.

By initiating explosive charges in a cylindrical tube with one end face being plugged, vortex rings with diameters of the order of 1 m and initial velocity of motion greater than 100 m/s are obtained. Such rings emit a clearly heard acoustic signal, which is of interest for studying generation of acoustic waves by vortices and scaling mechanisms of noise generation. Vortex rings are generated due to exhaustion of a high-velocity gas jet formed after shock wave propagation over the tube. The measured vortex velocities are found to be weakly dependent on the explosive mass, i.e., as the mass increases, the fraction of energy transformed to the vortex ring energy becomes smaller.

The structure of twisted flow in a Ranque−Hilsch vortex tube is investigated experimentally by modeling gas flow with an incompressible fluid flow. The velocity field is measured with a laser Doppler anemometer in the entire volume of the vortex chamber. The streamline pattern, which gives a complete presentation of the flow structure in the Ranque−Hilsch tube, is plotted in the axial section of the chamber. The resulting streamline pattern can serve as a basis for explaining the physical mechanism of the Ranque effect.

The report presents two experiments carried out in Budker Institute for obtaining the maximum plasma beta (ratio of the plasma pressure to magnetic field pressure) in axially symmetric magnetic field. The experiments are based on injection of powerful focused neutral beams with high neutral power density in the plasma. The produced fast ion population significantly increases the plasma pressure. It the axially symmetric GDT experiment (Gas Dynamic Trap) the plasma beta exceeded 0.6 at the fast ion turning points. The CAT experiment (Compact Axisymmetric Toroid) is being prepared for obtaining a plasmoid with extremely high diamagnetism in axially symmetric magnetic field. Reversal of magnetic field in the plasmoid is possible in this experiment.

The paper describes experiment devoted to the field reversal in a mirror trap with neutral beam injection, which is planned for realization now in Budker Institute. The technical details of experimental device and expected plasma parameters are discussed. In accordance with theoretical predictions, parameters of experimental facility (neutral beam current - 240 atom A, energy of neutrals - 15 keV, magnetic field - 0.2 T, electron temperature 50 eV and target plasma density similar to 10(13)-10(14) cm(-3)) are expected to be sufficient to field reversal in the case, if anomalous ion losses are not essential.

The structure of a swirl flow in a vortex chamber is studied. Distributions of the azimuthal and axial components of velocity are obtained almost in the entire volume of the chamber. A pattern of streamlines of this flow is constructed, and the mechanism of the emergence of a reverse flow directed toward the closed end face of the chamber is identified.

A plane circular LaB6 cathode and a hollow anode are used for the arc discharge plasma production in a newly developed linear plasma device with the axially symmetric magnetic field. The cathode is heated by radiation from a graphite foil flat spiral. A separately powered magnetic coil located around the plasma source is used to vary the radial distance between the outermost magnetic field line from the cathode and the inner anode surface. The discharge geometry defines distinct operational modes: partially direct discharge and magnetic insulation. The magnetic field in the source can be varied from 0 to 2.4 kG while preserving the chosen field geometry, with the discharge voltage and current depending on the particular mode. A hydrogen plasma stream with a density of up to 1·1013 cm−3 and a diameter of about 4 cm is produced. The discharge characteristics and the plasma parameters do not change significantly between the two modes and in a relatively broad range of magnetic fields.

A plane cathode composed of close-packed hexagonal LaB6 (lanthanum hexaboride) segments is described. The 6 cm diameter circular cathode is heated by radiation from a graphite foil flat spiral. The cathode along with a hollow copper anode is used for the arc discharge plasma production in a newly developed linear plasma device. A separately powered coil located around the anode is used to change the magnetic field strength and geometry in the anode region. Different discharge regimes were realized using this coil.

A magnetic divertor incorporated into a central solenoid of GDT is considered as an alternative MHD stabilizer for axisymmetric high-β plasma. The divertor magnetic field structure can be produced by addition of several new coils to the present coil system in the region occupied by a hot-ion population. The important constraints on the divertor magnetic field are discussed. It must naturally fit into the GDT magnetic field and neutral beam geometry, should be adjustable to the plasma and allow for easy recovery of the standard operational regimes.

The results of preliminary experiments with relatively low power electron beam interacting with plasma in GDT device are discussed. The beam was injected into the device through one of the end mirrors. In the experiments, the problems related to the beam transport through the magnetic mirror were addressed.

Recent upgrade of the neutral beam system has resulted in considerable improvement of the plasma parameters in the gas dynamic trap experiment. With injection of 5 ms, 20 keV, 4.5 MW neutral beams the electron temperature approaching 250 eV was obtained. At the same time maximal plasma beta attained about 60%. Further progress in plasma temperature and pressure could only be possible with considerable increase of the magnetic field in the central solenoid and re-optimization of its profile to improve stability of high-beta plasma, as well as with extension of the neutral beam pulse. Possible steps in this direction are considered in this paper.