Kinetički i fluidni modeli neravnotežnog transporta elektrona u gasovima i tečnostima

Abstract

Ova doktorska disertacija sadrži dve celine. U prvoj celini su proučavani transportni koefi- cijenti trećeg reda za rojeve naelektrisanih čestica u gasovima. Struktura transportnog tenzora trećeg reda u svim konfiguracijama električnog i magnetskog polja određena je primenom metoda grupnih projektora. Fizička interpretacija individualnih komponenti ovog tenzora je analizirana na osnovu fluks gradijentne relacije i generalisane difuzione jednačine. Zavisnost transportnih koeficijenata trećeg reda od redukovanog električnog polja i njihova osetljivost na elementarne sudarne procese ispitane su za veliki broj modelnih i realnih gasova u Monte Carlo simulacijama i na osnovu numeričkih rešenja Boltzmann-ove jednačine. U drugoj celini je razmatran transport elektrona u tečnom argonu, tečnom kriptonu i tečnom ksenonu primenom Monte Carlo simulacija. Proučavani su uticaji efekata koherentnog rasejanja i različitih načina za aproksimaciju neelastičnih sudara u tečnoj fazi na izračunate vrednosti transportnih koeficijentata u ovim tečnostima. Poseban akcenat je stavljen na proučavanje strukturno indukovane negativne diferencijalne provodnosti u tečnom ksenonu na osnovu prostorno razloženih karakteristika roja i funkcija raspodele elektrona. Transportni koeficijenti za rojeve elektrona u atomskim tečnostima su iskorišćeni kao ulazni podaci u 1.5-dimenzionom klasičnom fluidnom modelu prvog reda i u fluidnom modelu zasnovanom na razvoju izvornog člana u jednačini kontinuiteta po gradijentima koncentracije. Ovi fluidni modeli upotrebljeni su za ispitivanje tranzicije lavina elektrona u strimere i propagacije negativnih strimera u atomskim tečnostima visoke mobilnosti. Pored toga, na osnovu ovih modela je razmatrano na koji način različit tretman neelastičnih sudara, priroda transportnih koeficijenata i rekombinacija kvazislobodnih elektrona i pozitivnih šupljina utiču na dinamiku i osobine strimerske plazme.

The present doctoral dissertation contains two parts. The first part deals with the study of the third-order transport coefficients of charged-particle swarms in gases. The structure of the third-order transport tensor has been determined by employing the group projector technique in all configurations of electric and magnetic fields. The physical interpretation of the individual components of this tensor has been analyzed by employing the flux gradient relation and the generalized diffusion equation. The variation of the third-order transport coefficients with the reduced electric field and their sensitivity to elementary scattering processes have been determined for a wide range of model and real gases by using Monte Carlo simulations and the numerical solutions of the Boltzmann equation. The second part of this thesis deals with the transport of electrons in liquid argon, liquid krypton and liquid xenon by employing Monte Carlo simulations. The sensitivity of the calculated values of the transport properties in these liquids to coherent scattering effects and different approximations of inelastic scattering in the liquid phase has been investigated. A special emphasis has been placed on the study of the kinetic phenomenon of negative differential conductivity in liquid xenon by using spatially resolved swarm data and electron energy distribution functions. Transport coefficients of electron swarms in atomic liquids are used as input data in 1.5 dimensional classical first order fluid model, as well as in the fluid model which is based on the density gradient expansion of the source term in the equation of continuity. Both fluid models are employed in investigating the transition of electron avalanches into streamers and the propagation of negative streamers in high-mobility atomic liquids. In addition, the presented models are used for investigating how the dynamics and properties of the streamer plasma are influenced by the different treatment of inelastic collisions, nature of transport coefficients and the recombination of quasi-free electrons and positive holes.