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Title: Theoritical Study of Intense Laser Beam Interaction with Relativistic Quantum Plasma
Authors: , Ikram Ullah
Keywords: Physics
Issue Date: 2017
Publisher: Kohat University of Science and Technology, Kohat
Abstract: The interaction of intense Circularly Polarized Electro-Magnetic (CPEM) wavewith3-componentrelativistic-quantumplasmaconsistingofrelativistic degenerate electrons and positrons, and dynamic degenerate ions is theoreti cally studied. A mathematical model is structured by coupling Klein-Gordon equationsfortheelectronsandpositrons;andSchro¨dingerequationfortheions with Maxwell equations through Poisson equation. Solutions of the dispersion relationareplottedfortherelativisticquantumplasmausingelectrondensity ranging from 1030m−3 to 1036m−3 and several positron concentrations. Three modesareobserved: electronplasmawave,lowfrequency,andhighfrequency waves. One of the mode could be associated with the electron plasma wave; a higher frequency mode, that we shall refer to as the pair branch in this the sis; and a low frequency mode that could be associated with the ions. The pair branch mode having a possible association with the positron states stays unaltered by variation in the positron concentration, but varies significantly ii withachangeinthequantumparameterdefinedintermsoftheparticlenum ber density. The addition of positrons to plasma and increasing the positron concentrationsuggestenhancedopacityoftherelativisticquantumplasma. A nonlinear interaction of large amplitude CPEM waves with the plasma leads toself-inducedtransparency. Theplasmatransparencyincreaseswithincreas ing the amplitude of CPEM wave. The model so developed is then applied tostudystimulatedRamanscattering,modulationalinstabilityandstimulated BrillouinscatteringofintenseCPEMwavesinsuchplasmas. Ourresultsshow that the growth rates are affected by the positron concentration, the quantum parameter of the plasma as well as by the amplitude of the incident electro magnetic wave. Themodelisthenextendedtoa4-componentand3-componentrelativistic quantum plasmas. In the first case constituents of plasma are relativistic degenerate electrons and positrons, dynamic degenerate ions, and Thomas Fermi distributed electrons. The second type consists of relativistic degener ate electrons, dynamic degenerate ions and non-relativistic quantum beam of electrons. We have used Klein-Gordon equations for the electrons and positrons,Schro¨dingerequationfortheionsandnon-relativisticquantumbeam ofelectrons,andThomas-Fermidistributedelectronsareconsideredintheback ground. MaxwellandPoissonequationsareusedfortheelectromagneticwave. Numericalstudyofthedispersionpropertiesiscarriedoutinadensity-range of ∼ 1030 → 1036m−3 for several positron concentrations. Specifically, four modes are observed; associated with electrons, positrons, ions and beam of electrons. Onceagain,thepairbranchmodestaysunalteredbyvariationinthe iii positron concentration, but varies significantly with a change in the quantum parameter. An increase in the positron and electron beam concentrations en hancetheplasmaopacity. ThenonlinearinteractionoflargeamplitudeCPEM waveswiththeplasmasleadstoself-inducedtransparency. Thetransparency decreaseswithincreasingthepositronandelectronbeamconcentrations. The model is then applied to study stimulated Raman scattering, modulational in stability and stimulated Brillouin scattering of intense CPEM waves in such plasmas. It is observed that the growth rates of these instabilities are affected by the concentration of positrons, the quantum parameter of plasma, and intensity of the incident laser beam.
Gov't Doc #: 19048
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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