The present paper considers the “spoke” instability experimentally studied in the reflex discharge with the thermionic cathode by means of the system of floating probes. It appears that the instability is of the Simon-Hoh type. We investigate the dependences of its phase velocity on the radial coordinate, gas pressure, electric and magnetic fields. The phase velocity value is close to the E/B drift speed. It was revealed, that the observed instability arises due to the small difference in azimuthal velocities of the ion and electron rotation.

The results of flyer acceleration up to the velocity of 10 km/s at the Angara-5-1 facility at the current of 5 MA by the magnetic field pressure are presented. 1D and 2D simulation of aluminum flyer acceleration is performed. The simulation results agree with each other and with the experimental data.

The effect of the spatial distribution of electric potential on the separating properties of the plasma mass separator that operates in a configuration with crossed radial electric and longitudinal magnetic fields is studied. The single-particle approximation is used to obtain analytical expressions that connect the electric potential distribution and the angular mass spectrum. A mathematical algorithm is described that allows one to recover the distribution of electric potential from the given shape of the mass spectrum. It is shown that the local inhomogeneity of the electric potential profile allows one to achieve the deposition of mass groups in the diametrically opposite regions of the separator. Data is presented that confirms the possibility of creating experimentally both the positive and the negative local inhomogeneity of the potential. The results of this work can be used to increase the efficiency of the process of plasma mass separation of ions of different elements.

The study is devoted to enhanced CeO2 evaporation in the temperature range between 2130 and 2650 K from refractory crucibles made of different materials: molybdenum, tantalum, and tungsten. The composition datum of vapor and films deposited on collectors receiving evaporation products were obtained by quadrupole mass spectroscopy and by energy-dispersive X-ray spectroscopy. One of approximation coefficients of the temperature dependence of CeO2 vapor in the range between 2150 and 2220 K was measured. The study is of interest for a variety of technologies utilizing refractory oxide evaporation with high productivity, including the plasma mass separation methods.

The current state of research on generating and controlling a radial electric field in a magnetized plasma in cylindrical geometry is reviewed. Such systems are widely used in many plasma-physics applications ranging from thermonuclear fusion and plasma mass separation to the development of plasma thrusters. Primarily experimental studies are analyzed with an emphasis on the installation parameters and experiments conditions that enable generating controlled distributions of electrical potential. Data reported by various research teams are summarized in tables, allowing predictions of the potential reproducible under specific experimental conditions.

This work is devoted to determining the azimuthal ion rotation velocity in a reflex discharge with a thermionic cathode. For the experimental determination of the ion velocity, a Mach probe with directional particle collection was used. The Mach probe rotation velocity measurements are compared with the drift speed in crossed Ex B fields, where the radial electric field is measured with an emissive probe. The rotation of the plasma was found to be predominantly due to this drift, corrected for centrifugal effects. One of the important results of the work is the determination of the ion temperature. The obtained value Ti=0.12 eV, agrees with the ion temperature estimates in works with similar experimental conditions. A general parameter has been obtained that makes it possible to estimate the necessity to take into account centrifugal effects under given conditions. Keywords: plasma, thermionic cathode, reflex discharge, ion rotation, crossed fields.

Одной из актуальных задач атомной энергетики является переработка отработавшего ядерного топлива. Такая переработка подразумевает отделение актиноидов от продуктов деления урана. Одним из методов переработки может стать плазменная масс сепарация. В ОИВТ РАН в последние 10 лет активно велись исследования, направленные на развитие различных аспектов, связанных с плазменной масс-сепарацией. В статье приведен обзор основных результатов этих исследований по четырем направлениям: численные расчеты и анализ схем сепарации; генерация плазмы буферного газа и создание потенциала в ней; источник плазмы для инжекции смеси разделяемых веществ; сепарация модельных веществ.

This work is devoted to the modeling of a Penning discharge with a hot cathode, which is used to create a background plasma with a radial electric field in a plasma mass separator. We used a 2D3V electrostatic particle-in-cell plus Monte Carlo Collision (PIC/MCC) simulation model with a gyrokinetic approximation for magnetized electrons and a geometrical scaling scheme. The proposed model predicts the development of a rotating spoke structure, leading to fluctuations in the electric potential. The fluctuation amplitude and the averaged radial profile of the potential are in qualitative agreement with experiment. On the example of a model flow of silver and lead ions, we have shown that potential fluctuations can impair separation, leading to a partial overlap of ion deposition spots on a substrate. Each of the separated fractions contain about 11% impurities.

This paper presents the results of an investigation of the temporal evolution of vacuum arc discharge with a hot ceramic cathode (CeO 2 ) and the ionic composition of the generated plasma. A vacuum arc discharge with a hot cathode is a high-performance plasma source that can generate plasma of almost any material or their mixture. The temporal evolution of the discharge voltage and the ionic composition of the plasma were studied, and the time for stable source operation was established. The dependence of the plasma ionic composition on the discharge current (40–90 A) and the crucible temperature (2200–2300 K) was also investigated. A significant influence of the crucible material in which the consumable cathode was placed on the discharge parameters was revealed. The effect of switching between the cathodic spot and the diffuse modes with varying of the parameters of the vacuum arc was discovered, and the predominance of the diffuse mode was determined. The results obtained can be useful both in the development of plasma sources for ceramic materials and in the enhancement of theoretical models of processes near the cathode in vacuum arcs.

This work is devoted to determining the azimuthal ion rotation velocity in a reflex discharge with a thermionic cathode. For the experimental determination of the ion velocity, a Mach probe with directional particle collection was used. The Mach probe rotation velocity measurements are compared with the drift speed in crossed ExB fields, where the radial electric field is measured with an emissive probe. The rotation of the plasma was found to be predominantly due to this drift, corrected for centrifugal effects. One of the important results of the work is the determination of the ion temperature. The obtained value Ti=0.12 eV, agrees with the ion temperature estimates in works with similar experimental conditions. A general parameter has been obtained that makes it possible to estimate the necessity to take into account centrifugal effects under given conditions.

Plasma mass separation requires a lot of diagnostic techniques that not only demonstrate the separation effect but also show the efficiency of the process. During the test experiments, plasma flux to be separated may contain neutral particles that avoid the separation process due to their insensitivity to electromagnetic field. We present the diagnostics of the lost substance in experiments on plasma mass separation. The obtained data of the diagnostics helps determine the law of particle evaporation from the plasma source. We show that neutral flux is unable to distort the result of separation diagnostics. The presented approach can be used in experiments aimed at enhancing the separation effect and achieving target productivity for industry applications.

One of the relevant tasks of nuclear power industry is the reprocessing of spent nuclear fuel. Such processing implies the separation of actinides from uranium fission products. One of the processing methods can be plasma mass separation. In the last 10 years, research aimed at the development of various aspects related to plasma mass separation has been actively conducted at the Joint Institute for High Temperatures of the Russian Academy of Sciences. The article provides an overview of the main results of these studies in four areas: numerical calculations and analysis of separation schemes; generation of background plasma and formation of plasma potential distribution; plasma source for injection of a mixture of separated substances; and demonstration of the model substances separation.

The details of the charged particle separation by mass in the configuration with axial magnetic and radial electric fields are studied. The radial electric field, oriented to the discharge axis, is induced in a background reflex discharge with a hot cathode (−550 V, 8–14 A). The plasma source is based on a hot cathode arc discharge with independent metal vapor injection (18–21 V, 30 A) was situated at 18 cm from the axis. It was shown that the separated Ag + Pb mixture is transported across the magnetic field under the background discharge electric field. Effective separation is possible in such a system, while the separation coefficient increases from 4.9 to 6.2–8.4 when the mixture injection point is moved away from the background discharge axis from 18 to 23 cm. The effect of mixture injection on the plasma potential distribution is examined. It was shown that the presence of a plasma source of separated substances can cause a local (1–2 cm) distortion of the background plasma potential profile. Such distortion, as well as fluctuations of the background plasma potential, can significantly affect the width of the deposited spots of separated substances.

One of the alternative 'dry' methods for spent nuclear fuel (SNF) reprocessing is the plasma mass separation technique. This letter describes the first experiments that demonstrate the fundamental feasibility of a plasma mass separation approach in crossed electric and magnetic fields in collisionless mode. The Ag + Pb mixture was used to simulate the heavy (>235 u) and light (<150 u) components of the SNF. The Ag + Pb mixture was transformed into a plasma jet and ejected along the magnetic field. The action of the electric field caused the deposition of mixture components on the substrate in the form of localized spots. The estimated separation factor was of 35.

This work is devoted to the development of a plasma mass separation method with a potential well for spent nuclear fuel reprocessing. The configuration of the separation chamber with an axial magnetic field up to 0.25 T and a radial electric field up to 3 kV/m is considered. Using numerical simulation, we study the ion flux motion with the same mass composition as the spent nuclear fuel injected along magnetic field lines. The effect of fields and initial injection parameters on the spatial separation of actinides from uranium fission products is investigated. The simulation of the ion flux motion is also performed taking into account elastic collisions of ions with background gas atoms. Elastic collision cross sections for U+, Pu+, Cs+, and Sr+ ions in helium and argon are obtained theoretically. We show that in argon, the separation is possible up to a pressure of the order of 1 mTorr, while in helium, it is possible to separate elements by mass groups in the collisional regime at pressures up to about 10 mTorr.

The review covers the results of predominantly experimental studies of stationary vacuum arcs with diffuse cathode attachment that burns in vapor of the cathode material with a current density of less than 100 A/cm 2 . Such discharges are of great interest for a number of technologies that require the formation of high-intensity plasma flows without a droplet fraction. The discharges on cathodes made of graphite, pure metals, and oxides, as well as mixed cathodes, are considered. The specificity of the processes on vacuum arc cathodes is characterized by the ratio of the fluxes of thermally vaporized atoms and thermionic electrons. The review presents the results of studies of cathode materials with an atom-electron ratio of ~10 –2 to ~10 8 . Data on the working cathode temperature, the current–voltage characteristic of the discharge, the heat flux from the plasma to the cathode, the plasma parameters, its radiation spectrum, and the ion energy in the cathode jet are presented. Depending on the cathode material, the working temperature ranged from 1.2 to 2.5 kK. An analysis of the features of the charge-transfer processes on various cathodes is also presented.

One of the urgent tasks of the nuclear power industry today is reprocessing of spent nuclear fuel (SNF) and radioactive waste (RW), which is necessary to switch to a closed fuel cycle in order to use the reactor fuel resources to more extent by separating minor actinides for reuse of refabricated fuel. Another equally important driver for the creation and implementation of such technology is the environmental requirements aimed at reducing the disposal of radioactive waste and the scope of high-level waste transportation. It should be noted that any civil technology for SNF reprocessing must meet the requirement of non- proliferation of nuclear weapons, i.e. is obliged to prevent the release of plutonium, including by changing the operating modes of the equipment. There are promising hydrometallurgical and pyrochemical technologies developed at present day, as well as plasma processing methods. This report presents the engineering and physical fundamentals of plasma separation of SNF and RW. The potential advantages of plasma technologies for SNF or RW processing include a small amount of additional waste, the ability to adapt to different types of SNF and RW, and a possibility of implementing the technology into existing and designed material processing cycles and varying the processing scale from on-site to plant-size ones within large facilities. An important feature of plasma methods, i.e. insufficient selectivity for the separation of minor actinides from each other, shall also be mentioned. It is precisely such “crude” approach that ensures acceptable civilian processing technology, which satisfies the conditions for non-proliferation of nuclear weapons. The paper proposes an approach aimed to use the accelerating potential to overcome the energy and angular distribution of plasma ions at the entrance to the separation area and a potential well for the spatial separation of ions of different masses. It considers the physical principles of the plasma separation method and its main stages. There are provided experimental results achieved so far at a pilot facility for testing the plasma separation method. The results of calculations of ion trajectories and energy cost estimates are shown, demonstrating the prospects of the plasma method for process application. The process flow diagram of plasma processing and the steps to be taken to develop the technology are also discussed.

The formation of plasma on the surface of a current-carrying electrode of a high-current facility when a current flows through it with a linear density of up to 4 MA/cm and is coated with lead foil or ceramic is studied. The propagation velocity of a dense plasma from a stainless steel electrode is 2–10 km/s, and when the electrode is coated with lead, it is 1–6 km/s. In these experiments, there is no load typical for such facilities—a source of intense X-ray radiation. The plasma propagation from ceramic-coated electrodes starts 200 ns later than that for metal electrodes.