Formation of volume discharges in dense gases at pulse repetition rates up to 10 kHz

Abstact It is shown that for the formation of stable volume discharges at pulse repetition frequencies up to 10 kHz and more, it is recommended to use sectioning of the discharge gap with subsequent excitation of discharges in each section from an autonomous pulse generator. The role of an autonomous pulse generator can also be performed by an auxiliary circuit that directs the necessary part of the energy stored in the main energy storage of a pulse generator with only a single switch to an individual discharge gaps. The description and results of the study of one of these variants of a partitioned discharge gap and a pulse generator are given. Pumping energy densities of 100–150 mJ-cm−3 at pulse repetition frequencies up to 8 kHz in CO2 laser mixtures and 80–100 mJ-cm−3 in N2-Ne and Xe–Ne mixtures at pulse repetition frequencies up to 10 kHz were achieved.

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.

Quantum Statistics

This chapter begins by extending the Boltzmann distribution to the case of a system that exchanges particles with its environment. This idea finds direct applications ranging from hemoglobin adsorption to ionization of atoms in stars. But the main applications are to dense “gases” in which the quantum behavior of identical particles comes into play. Examples include conduction electrons in metals and semiconductors; white dwarf and neutron stars; photon gases and thermal radiation from incandescent objects; neutrino and electron-positron production in the early universe; quasiparticles associated with vibrations and magnetic excitations in solids; and Bose-Einstein condensation of ultracold clouds of atoms.