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.

The possibility of controlling the electrostatic field distribution in plasma has yielded wide prospects for modern technologies. As a magnetic field primarily allows for creating electric fields in plasma, it serves as an additional obstacle for the current flow through a medium. In the present paper, an axially symmetric system is considered in which the magnetic field is directed along the axis and concentric electrodes are located at the ends. The electrodes are negatively biased. A model which solves the problem of the radial distribution of the plasma potential inside the cylindrical plasma column supported by the end electrodes is proposed. The most commonly encountered configurations of the electrical connection for the end electrodes are considered, and the particular solutions to the problem of the radial distribution are presented. The contribution of ions and electrons to the transverse conductivity is evaluated in detail. The influence of a thermionic element on the radial profile of the plasma potential is considered. To verify the proposed model, an experimental study of the reflex discharge is carried out with both cold electrodes and a thermionic element on the axis. A comparison of the computational model results with experimental data is given. The presented model makes it possible to solve the problem concerning the plasma potential distribution in the case of an arbitrary number of end electrodes, and also to take into account the inhomogeneity of the distribution of plasma density, neutral gas pressure and electron temperature along the radius.

Distribution of electrostatic potential in direct current reflex discharge plasma has been studied experimentally. Measurements have been conducted by the single floating probe method. The influence of 0–0.2 T magnetic field, 1–200 mTorr pressure, 0–2 kV discharge voltage, and electrodes geometry on plasma column electrostatic potential was investigated. The possibility for the formation of a preset potential profile required for the realization of plasma separation of spent nuclear fuel was demonstrated.

Experimental study of the diffuse vacuum arc discharge on the nonthermionic lead cathode is presented. At the working cathode temperatures of 1.2-1.6-kK current-voltage characteristic of the discharge, cathode heat operation regime and its erosion rate were measured. Using probe methods, electron temperature (0.3-1.2 eV) and heavy particles (atoms and ions) mean charge (0.17-0.28 e) were determined in after-anode plasma. Evaluated current densities on the cathode are in agreement with a hypothesis on the ion mechanism of charge transfer on its surface. Parameters of the obtained discharge have been compared with the characteristics of the earlier investigated diffuse vacuum arcs on nonthermionic chromium and on thermionic gadolinium cathodes. The obtained data might be useful when creating plasma sources for verifying the plasma separation method of the spent nuclear fuel using the nonradioactive 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.

A diffuse (spotless) vacuum arc was investigated on a hot cathode made from cerium dioxide. The discharge is obtained in the following range of current, voltage, and cathode temperature of I = 15–150 A, V_a = 9–14 V, and T_c = 2.1–2.4 kK. The main characteristics of the plasma flow in space behind the anode with a hole were determined: it was found that the electron temperature at the working parameters lies in the range of 0.4–1 eV, the ions are predominantly singly charged, the average charge of the outgoing heavy particles reaches 0.9 e (elementary charge), and the most probable kinetic energy of the ions does not exceed 9 eV. Potentially found regimes of vacuum arc operation are promising for use in the work on implementation of the plasma method for spent nuclear fuel and/or radioactive waste reprocessing.