Simulation of thermal ionization in a dense helium plasma by the Feynman path integral method
- PDF / 666,586 Bytes
- 26 Pages / 612 x 792 pts (letter) Page_size
- 5 Downloads / 165 Views
TICAL, NONLINEAR, AND SOFT MATTER PHYSICS
Simulation of Thermal Ionization in a Dense Helium Plasma by the Feynman Path Integral Method S. V. Shevkunov* St. Petersburg State Polytechnic University, St. Petersburg, 195251 Russia *email: [email protected] Received February 5, 2010
Abstract—The region of equilibrium states is studied where the quantum nature of the electron component and a strong nonideality of a plasma play a key role. The problem of negative signs in the calculation of equi librium averages a system of indistinguishable quantum particles with a spin is solved in the macroscopic limit. It is demonstrated that the calculation can be conducted up to a numerical result. The complete set of symmetrized basis wave functions is constructed based on the Young symmetry operators. The combinatorial weight coefficients of the states corresponding to different graphs of connected Feynman paths in multipar ticle systems are calculated by the method of random walk over permutation classes. The kinetic energy is cal culated using a viral estimator at a finite pressure in a statistical ensemble with flexible boundaries. Based on the methods developed in the paper, the computer simulation is performed for a dense helium plasma in the temperature range from 30000 to 40000 K. The equation of state, internal energy, ionization degree, and structural characteristic of the plasma are calculated in terms of spatial correlation functions. The parameters of a pseudopotential plasma model are estimated. DOI: 10.1134/S106377611104011X
1. STATE OF THE ART OF THE PROBLEM The degree of ionization of a plasma at tempera tures from several to several tens of electronvolts and densities comparable to the density of gases under nor mal conditions strongly depends on temperature and can change by an order of magnitude with temperature varied in a relatively narrow range. This leads to a strong dependence of the thermal, electric, and spec tral properties of the plasma on external conditions. Plasma of this type can be used as a tool in a number of technological applications. In particular, such con ditions are produced in a double electric layer during explosive electron emission. Explosive emission allows one to obtain highcurrent lowenergy electron beams and can be initiated both in vacuum and in a diode filled with helium [1–4]. High electric field strengths near a cathode surface and giant emission current den sities are achieved under these conditions due to for mation of a double plasma layer. The double electric layer in an expanding plasma bunch is formed because of a strong difference in the kinetics of the electron and ion components. The plasma bunch is produced due to Joule heating by the emission current from microscopic roughnesses on the cathode surface. The microstructure and interactions between the electron and ion components at the atomic level play a key role under these conditions [5]. In the region of states considered above, pressure in the plasma achieves a few thousands atmospheres. Because of this
Data Loading...
