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Gas mixture system (GMS) was developed, created and installed at Uragan-2M (U-2M) device. GMS is based on already known gas mixing method  successive puffing. It is implemented through successive puffing of several gases from separate high pressure cylinders into working volume. A number of experiments were carried out to create a He+H2 gas mixture with different percentages. The results of measurements of the He+H2 percentage in the GMS and the U-2M vacuum chamber are in good agreement each to other. This system allows you to change the pressure of the mixture in the U-2M chamber at a constant percentage of gases in the mixture.

For the Uragan-2M stellarator, a glow discharge cleaning (GDC) system is developed. An overview of the GDC system design is presented. The first experimental studies of GDC in an argon atmosphere have been carried out. The dependence of the breakdown voltage on the argon pressure is determined. The current-voltage characteristics of the gas discharge were measured as a function of the working gas pressure also in presence of a magnetic field.

Features of the recent Uragan-2M campaign are reviewed together with some theoretical advances. They include experiments with B4C limiter, studies of various 1…20 kHz oscillations, development of a new in-situ diagnostics for wall conditions, i.e. the thermal desorption probe, the improved numerical model of RF plasma production in stellarators in the ion cyclotron and electron-cyclotron frequency ranges, a new positive-definite form of time-harmonic Maxwell’s equations and plasma start-up studies.

The measuring complex with the cryogenic nitrogen trap [1] was created to monitor the gas composition in the stellarator Uragan-2M chamber. The complex provides several gas sampling options for the research: directly from the vacuum chamber, and condensed gas from the cryogenic trap chamber after its being heated. A new measuring cryogenic trap with its own valves was developed to implement the second method. It is necessary to provide such a state of the internal vacuum surfaces of the complex so that the background gas emission from the walls of the measuring vacuum chamber does not lead to the measurement errors in order to obtain more accurate mass spectral data. The heating of the chamber walls and continuous RF discharge at frequencies of 6…8 MHz and the power of 1 kW without a magnetic field was planned to used for this purpose. Two RF antennas, rod and planar, were designed.

The method and device have been developed and used for operative estimation of impurity level, outgassing rate and molecular layers number on high vacuum chamber surfaces of magnetic confinement fusion devices in situ. The method is based on the thermal desorption of gases into a vacuum vessel from the surface of a special metal probe during its heating up to temperature of 300 °C. To investigate and use this method, the probe was designed, manufactured and installed into the vacuum vessel of the Uragan-2 M stellarator. The technique was tested after applying VHF/RF cleaning discharges in different scenarios. A decrease of the released gas amount from the surface by more than one order of magnitude was recorded. The mass-spectrometer registered the atomic masses 18 u (H2O), 28 u (CO + N2) and 44 u (CO2), as the main gases desorbed from the probe surface during its heating. Heavy hydrocarbon masses (mainly 58 u) were also registered. The method had also been tested in the regime of hydrogen gas retained in the wall.

The erosion behavior of W-Pd bimetallic systems has been investigated for both hydrogen-saturated (H/Pd ∼ 0.65) and unsaturated states during impact of a steady-state nitrogen plasma from a mirror Penning discharge. An essential decrease by factors of about 2-5 in the erosion rate of W was observed for hydrogen-saturated W-Pd samples in the nitrogen ion energy range from 0.8 to 1.6 keV. Possible reasons for this erosion behavior are discussed. Isotherms and isobars of hydrogen permeability through W-Pd systems were measured in the temperature range of 573-973 K and hydrogen pressure range of 1.33 x 10 2 to 10 5 Pa. It is shown that the limiting stage of permeation process is, most likely, the diffusion in the W film. The activation energy of hydrogen permeability was determined to be ∼12 kJ/mol, this being much lower than the literature data for bulk tungsten at molecular hydrogen-driven permeation. Possible mechanisms are suggested and analyzed to explain the observed decrease in he activation energy of hydrogen penetration through W-Pd systems.

We have carried out an experimental investigation of the erosion of W - Pd bimetallic systems in different states (saturated with hydrogen and nonsaturated) under the action of the stationary nitrogen plasma of a mirror Penning discharge and have studied the kinetics of hydrogen penetration through such systems. Possible mechanisms have been suggested for the explanation of a significant decrease in the erosion rate and damages of W - Pd systems (shape changes, macroblistering, and macroflaking) induced by saturation with hydrogen to high concentrations. We have also analyzed the discovered anomalies in the behavior of the hydrogen permeability of W - Pd bimetallic systems by the measured isotherms and isobars of hydrogen permeability, the energy state of hydrogen in W - Pd systems, and the theory of diffusion in systems with a great number of closed and interconnected pores.

A study is made of a scheme providing spectrally pure, low hydrogen flows into a high-vacuum chamber through the use of a palladium membrane with a working surface of 20 cm2 and ethyl alcohol vapors (scheme combining the processes of hydrogen generation and admission). It is demonstrated that at an optimum alcohol vapor pressure and a membrane temperature of 973 K this scheme can provide specific hydrogen flows of about 5×10−2 Torr.l⧸s cm2. The hydrogen permeability is limited in this case by the processes occurring at the entrance surface of the Pd-membrane.

Simulation of sputtering experiments were carried out in steady state plasma of a mirror Penning discharge under low and high hydrogen recycling regimes. The samples for studies were Pd (99.98 purity) foils with and without hydrogen saturation of concentrations up to H/Pd = 0.65. Irradiation doses were 1018–1019 ions/cm2. No significant difference in Pd erosion behavior was found under hydrogen, helium or nitrogen plasma impact for the different recycling regimes. The absolute values of the erosion coefficient in helium and nitrogen plasmas are in sufficient agreement with ion sputtering data in literature. However, in the case of hydrogen plasma disagreement of more than an order of magnitude was observed. Possible reasons are suggested and discussed to explain such erosion behavior.

Summary form only given, as follows. Summary form only given. In order to optimise the performance of the tungsten-palladium bimetallic system, it is necessary to carry out thorough investigations of its properties under plasma impact, in particular, erosion behavior in hydrogen saturated or non-saturated states. Tungsten protective coatings on a palladium substrate were produced by a vacuum-arc method and by sputtering in a magnetron-type discharge (rodtron configuration) in an argon atmosphere, so that different W-film structures and morphologies were realized. For comparison, virgin samples of pure Pd were also investigated. In our plasma impact studies, the ion energy values were 0.8-16 keV and irradiation doses were 10/sup -18/-10/sup 20/ ions/cm/sup 2/. Erosion coefficient values were measured by a weight loss method. It was shown that the erosion coefficient depends weakly on ion energy for both Pd and W-Pd systems and its value (1.3 at /ion for Pd and 0.2 at /ion for W) is in good agreement with literature data. For hydrogen saturated W-Pd systems, a new kind of radiation damage was observed caused by inhomogeneous adhesion of relatively thick W-films and the changes of sample form from flat to convex. For W-films made by vacuum-arc sputtering, the erosion coefficient value is near to that for bulk tungsten, and does not change to dose about 4.10/sup 19/ ion/cm/sup 2/. For further dose increase, sputtering rate increases up to typical values for bare palladium due to full film disruption. In the case of W-coatings made in a magnetron-type discharge, the erosion coefficient increases monotonically with exposure time. Mechanisms are suggested and discussed to explain such erosion behavior.