INFLUENCE OF WALL SCATTERING EFFECT ON ELECTRONS GAS DYNAMICS PARAMETERS IN ELECTRIC PROPULSION THRUSTERS WITH CLOSED ELECTRON DRIFT

The analysis is represented of some works devoted to the mathematical modeling of processes in plasma-ion thrusters and Hall effect thrusters. It is shown that the common in these works is the use of approximate forms of the equations of gas dynamics, which are applicable to the description of relatively dense gases, but not to analyze the processes in the rarefied plasma of electric propulsion thrusters. As a result, the above mathematical models do not represent the processes that are significantly responsible for the values of the thruster operating parameters.Authors try to partially correct this drawback by insertion into the initial approximate forms of the equations written for a point in the plasma volume, the parameters that actually represent the boundary effects and should be written not in the equations of gas dynamics themselves, but in the boundary conditions for these equations.The most complete forms of the necessary equations are given in this paper. It is shown that it is necessary to take into account electrons thermal conductivity as well as at least one (radial-azimuth) component of viscosity tensor to describe the "wall scattering" effect.It is concluded that the most productive approach in mathematical modeling is to write the most complete forms of equations with their subsequent simplification – removing the terms responsible for the processes recognized on the basis of primary numerical estimates as such, which can be neglected.

Phase-induced topological superconductivity in a planar heterostructure

Topological superconductivity in quasi-one-dimensional systems is a novel phase of matter with possible implications for quantum computation. Despite years of effort, a definitive signature of this phase in experiments is still debated. A major cause of this ambiguity is the side effects of applying a magnetic field: induced in-gap states, vortices, and alignment issues. Here we propose a planar semiconductor–superconductor heterostructure as a platform for realizing topological superconductivity without applying a magnetic field to the two-dimensional electron gas hosting the topological state. Time-reversal symmetry is broken only by phase biasing the proximitizing superconductors, which can be achieved using extremely small fluxes or bias currents far from the quasi-one-dimensional channel. Our platform is based on interference between this phase biasing and the phase arising from strong spin–orbit coupling in closed electron trajectories. The principle is demonstrated analytically using a simple model, and then shown numerically for realistic devices. We show a robust topological phase diagram, as well as explicit wavefunctions of Majorana zero modes. We discuss experimental issues regarding the practical implementation of our proposal, establishing it as an accessible scheme with contemporary experimental techniques.

Influence of an external circuit on the plasma parameters in the channel of the radio-frequency accelerator with a closed electron drift

The axial distribution of the plasma potential, concentration and temperature of electrons in an RF capacitive plasma source with the geometry of an accelerator with a closed electron drift is experimentally investigated in this work. Two cases of the external electrical discharge circuit are considered. In the first case, the electrodes were closed by direct current, in the second, they were opened. It is shown that direct current closure of the electrodes leads to a significant increase in the plasma potential and electron concentration. In a number of cases, local maxima of temperature and plasma density are observed near the electrodes, which can be associated with the occurrence of azimuthal electron drift in crossed electric and magnetic fields.

Influence of an external circuit on the plasma parameters in the channel of the radio-frequency accelerator with a closed electron drift

The axial distribution of the plasma potential, concentration and temperature of electrons in an RF capacitive plasma source with the geometry of an accelerator with a closed electron drift is experimentally investigated in this work. Two cases of the external electrical discharge circuit are considered. In the first case, the electrodes were closed by direct current, in the second, they were opened. It is shown that direct current closure of the electrodes leads to a significant increase in the plasma potential and electron concentration. In a number of cases, local maxima of temperature and plasma density are observed near the electrodes, which can be associated with the occurrence of azimuthal electron drift in crossed electric and magnetic fields.

Experimental studies of iodine stationary plasma thruster

The paper demonstrates the feasibility of using iodine as propellant for thrusters with closed electron drift and its economic viability. It describes a test setup for running experiments. It provides the results of experimental studies of the stationary plasma thruster using iodine as its propellant with xenon gas-passage hollow cathode, as well as of the operational mode of the thruster where a mixture of xenon and iodine is used. During tests gas dynamic and electrical properties of the thruster were analyzed. Thermal conditions in the iodine storage and supply system were studied. Conclusions were drawn on how the test object could be improved and upgraded. The paper describes the option to use a thermionic non-flow cathode as the compensator cathode for the operation of the iodine thruster. The paper provides the results of an experimental study of the prototype non-flow compensator cathode in diode mode. Based on the results of the studies an experimental facility was built for testing a thruster with non-flow compensator cathode. Key words: cathode, compensator cathode, thruster with closed electron drift, stationary plasma thruster, iodine.

(g−2)µ at four loops in QED

We review the four-loop QED corrections to the anomalous magnetic moment of the muon. The fermionic contributions with closed electron and tau contributions are discussed. Furthermore, we report on a new independent calculation of the universal four-loop contribution and compare with existing results.

A New Type of Plasma Accelerator with Closed Electron Drift

A new type of plasma accelerator with closed electron drift and open walls has been studied further. In particular, the current-voltage characteristics in various operation modes are obtained. Two operation modes, low- and high-current ones, with specific parameters are revealed. To make the earlier proposed physical mathematical model more adequate to the experiment, a hybrid model, in which the dynamics of neutrals and ions is described by kinetic equations, is applied. The distribution of the electric potential in the accelerating gap is numerically obtained. An insignificant difference between the potential distributions in the hydrodynamic and hybrid models consisting in higher potential gradients in the hybrid model is found.