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Results of many-year-long studies of high-power quasi-stationary acceleration and compression systems whose channel is a magnetoplasma analogue of the Laval nozzle are summarized. Double-stage quasi-stationary plasma accelerators with channels made of rod electrodes or complicated magnetoplasma transformers are described. Results are presented from experimental studies of acceleration and compression systems. It is shown that, in the optimal operating regime corresponding to the proper choice of the initial and boundary conditions, plasmadynamic devices are able to generate plasma streams with parameters close to the theoretical limit for given experimental conditions. A unique set of parameters of the generated streams were achieved: the density of the accelerated stream of up to 1016 cm–3 at a maximum velocity of (4–4.2) × 107 cm/s and the density of the compressed stream of up to 1019 cm–3 at a plasma temperature of 60–100 eV. The total energy content in the accelerated plasma streams reaches 0.9–0.95 MJ at an accelerating channel efficiency of 0.8–0.9. The generation time of accelerated stream amounts to 150–200 particle flight times along the channel of the plasmadynamic device, while the lifetime of the compression region reaches 20–30 particle flight times.

The features of plasma energy transfer to material surfaces during plasma–surface interactions (PSIs) in the presence of a strong magnetic field are investigated within the recently developed quasi-stationary plasma accelerator, QSPA-M. This novel PSI test-bed facility can reproduce edge localized mode (ELM) impacts, both in terms of heat load and particle flux to the surface, and provide plasma transportation in an external magnetic field, which mimics the divertor conditions. Investigations of energy transfer to the material surface have been performed for varied plasma heat load and external magnetic field values. Calorimetry, optical emission spectroscopy and high-speed imaging were applied for PSI characterization. For perpendicular plasma incidence, it has been shown that the transient plasma layer is formed in front of the surface by the stopped head of the plasma stream even for rather small plasma heat loads, which do not result in surface melting. The plasma density in this near-surface layer is much higher than in the impacting stream. It leads to the arisen screening effect for energy transfer to the surface. For B = 0, the thickness of the screening layer is less than 3 cm, but it increases to 15 cm when B = 0.8 T. The shielding effect due to the formation of a dense plasma layer in front of the exposed surface should be favorable for material performance, being important for decreasing the overall erosion of plasma-facing components during a large number of repetitive ELMs.

Processes occurring in a plasma flow generated by a magnetoplasma compressor (MPC) during the formation of the compression zone are discussed. The paper presents results of measurements of the spatial distribution of the electric current in the plasma flow, the temporal and spatial (along the flow) distributions of the plasma density, and the profiles of the velocity of individual flow layers along the system axis. The spatial distribution of the electromagnetic force in the flow is analyzed. It is shown that the plasma flow is decelerated when approaching the compression zone and reaccelerated after passing it. In this case, the plasma flow velocity decreases from ν = (2–3) × 107 cm/s at the MPC output to ν < 106 cm/s in the region of maximum compression and then again increases to 107 cm/s at a distance of 15–17 cm from the MPC output. In some MPC operating modes, a displacement of the magnetic field from the compression zone and the formation of toroidal electric current vortices in the plasma flow after passing the compression zone were detected.

Results from experimental studies of extreme UV (EUV) radiation from the compression zone of a magnetoplasma compressor (MPC) operating with xenon are presented. Two MPC operating modes that differ in the method of xenon injection into the discharge were studied. It is shown that EUV radiation in the wavelength range of 5–80 nm is emitted from the compression zone. In the MPC operating mode with local xenon injection directly into the compression zone surrounded by helium plasma, the radiation power reaches it peak value of 16–18 kW in the wavelength range of 12.2–15.8 nm.

Results from experimental studies of a compact magnetoplasma compressor designed for operation with heavy gases are presented. The integral characteristics of the discharge and the energy contents and other parameters of the generated xenon plasma streams are determined.

The paper presents the investigations of parameters of xenon plasma streams generated by magnetoplasma compressor (MPC) of compact geometry with conical-shaped electrodes and pulsed gas supply. Discharge characteristics and dynamics of the plasma streams, generated by MPC in different operation modes are analyzed. First results of Xe plasma radiation measurements in EUV wave range, obtained with AXUV diodes are presented.

The paper presents energy characteristics of the plasma streams generated with quasi‐steady‐state plasma accelerator QSPA Kh‐50 and the main features of plasma interaction with tungsten surfaces in dependence on plasma heat loads. The samples of pure sintered tungsten of EU trademark have been exposed to hydrogen plasma streams. The experiments were performed with up to 450 pulses (pulse duration of 0.25 ms) and the surface heat loads in the range of (0.45 – 1.2) MJ/m2. A threshold character of morphological changes on the melt tungsten surface with the pulses number is demonstrated. The number of initial exposures without formation of corrugations and pits is about 200, which does not depend on the target heat load magnitude. Further increase of the exposures results in the corrugation structures becoming dominant. The melt layer disintegrates into a set of droplets remaining at the surface. Such evolution seems to be driven by the surface tension forces within the fine cells of crack network. Finally a stabilization of the surface pattern occurs. The onset of intensive evaporation at molten tungsten surface under the repetitive heat loads has also been studied. The evaporation can result in enhanced mass losses: increase of the heat load from 0.75 to 1.1 MJ/m2 rises mass losses for one order of magnitude and causes bubble structures at the surface. Due to evaporation, the erosion crater grows with the rate of 0.04 μm/pulse. It was obtained, that for ELM‐like repetitive loads the melt motion driven by plasma pressure gradient did not contribute significantly to the erosion profile.