I= DELOCALIZED HEAT FLUX IN LASER-INDUCED PLASMAS
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Title of Thesis
DELOCALIZED HEAT FLUX IN LASER-INDUCED PLASMAS

Author(s)
Muhammad Suleman Qaisar
Institute/University/Department Details
Department of Physics/ Quaid-i-Azam University, Islamabad
Session
1994
Subject
Physics
Number of Pages
98
Keywords (Extracted from title, table of contents and abstract of thesis)
delocalized heat flux, laser-induced plasmas, fokker planck equation, ambipolar field, inverse-bremsstrahlung absorption effect, high-z plasma, low-z plasma

Abstract
Delocalized (Non local) heat flux in laser-induced plasma is analytically studied using reduced Fokker Planck equation. Different physical effects have been studied with the varying degrees of sophistications. Weak ambipolar field on heat flux is investigated in high-Z plasma using diffusive or P21- approximation for solving reduced Fokker-Planck equation. This work is generalized for finite-Z plasma using nondiffusive or P32-approximation and including inverse-bremsstrahlung absorption effect. The expressions for heat flux obtained involve complicated form of the nonlocal propagators. Limiting cases for very smooth and very steep gradient situations are discussed in detail. Our calculations show how various physical effects influence the heat flux. In particular we find that the inverse bremsstrahlung absorption process slightly enhances the heat flux in both the limiting cases. The ambipolar field term introduces a nontrivial exponentialy damping factor in the steep gradient case, which inhibit the free streaming heat flux significantly. The flux inhibition factor deduced compares favourably with the results of some planer geometry experiments. The presence of strong ambipolar field in corona of laser induced plasmas is well known. We investigate its effect on delocalized heat flux. In this treatment the propagators involving integrations are too difficult to calculate analytically. The numerically calculated propagators are found to be significantly modified. The flux inhibition for steep gradient significantly decreases with the increase of the ambipolar field.

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1290.87 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 contents 0
108.97 KB
2 1 Introduction 1
130.34 KB
  1.1 Motivation 1
  1.2 Layou t of Thesis 8
3 2 Heat Flux for Steep Temperature Gradients 9
332.42 KB
  2.1 Introduction 9
  2.2 Fokker-Planck Equation 15
  2.3 Thermal Transport- Review of the Classical Theory 20
  2.4 Nonlocal Character of Heat Transport 23
4 3 Effect of Weak Ambipolar Field and Inverse- bremsstrahlung absorption on Nonlocal Heat Flux 30
417.42 KB
  3.1 Ambipolar Field Effect on Heat Flux using Diffusive Approximation for High-Z Plasma 32
  3.2 Ambipolar Field Effect on Heat Flux using Diffusive Approximation for Low-Z plasma 38
  3.3 Generalized Ambipolar Model with Field and Inverse- bremsstrahlung Absorption using Non-diffusive Approximation for Low-Z Plasma 45
5 4 Effect of Weak Ambipolar Field on Heat Flux using Fourier Transform Method 57
92.41 KB
  4.1 Introduction 58
  4.2 Weak Ambipolar field Effect using Fourier Transform Method 58
  4.3 Discussion of Results 62
6 5 Strong Ambipolar Field Effect on Heat Flux using Diffusive Approximation for High-Z Plasma 63
121.01 KB
  5.1 Introduction 64
  5.2 Strong Ambipolar Field Effect on Heat Flux 65
  5.3 Discussion of Results 68
7 6 Summary and Conclusions 72
95.42 KB
8 7 A Analytical Derivation of Nonlocal Propagators 77
58.33 KB
  7.1 A.l Diffusive Approximation with High-Z Plasma 77
  7.2 A.2 Non-Diffusive Approximation with Low-Z Plasma 80
9 8 Biblography 82
59.64 KB