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Title of Thesis

Zahoor Ahmad
Institute/University/Department Details
Department of Physics/ Quaid-i-Azam University Islamabad
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
pinch dynamics, thermonuclear fusion, z-pinch plasma, magnetic flux, r-t instability

Fusion parameters in a Staged pinch are studied numerically. The imploding Z-pinch plasma traps an axial magnetic field Bz, compressing it to large values (of the order of several megagauss) in an extremely short time (in nanosecond). Fastly changing magnetic flux then induces an azimuthal (θ) current on the surface of the co axially placed fiber, with a rise time an order of magnitude shorter than the applied current. We have investigated the dynamics of staged pinch with different stability criterion defined to mitigate the R-T instability. First of all, spinning effect in the thick and thin shells is introduced to reduce the initial perturbations. To study the dynamics of the D-T fiber MHD model was used. To study the dynamics of gas puff, snowplow model along with thin shell model were used. We have also introduced Kr impurity in the fiber to incorporate radiation losses so as to enhance the compression. Thick puffs are considered stable as compared with the thin shells but from the numerical results we conclude that fusion parameters cannot be achieved in the presence of large values of spin velocity. It was also observed that bremsstrahlung reduction caused by opacity has very minor effects on the temperature profiles. In order to minimize the effect of the R-T instability on the implosion dynamics and to achieve the plasma parameters of interest, it was proposed to have finite thickness and multicascade liner system for the imploding shells. From numerical results of multicascade system we found that the multicascade system is good for achieving thermonuclear fusion conditions. For the optimum choice of puff-thickness and mass ratios, one may achieve a pinch plasma close to thermonuclear fusion conditions. To have better understanding of Z-pinch dynamics, we have made use of MHD model. In this model we have included bremsstrahlung radiation losses and end losses, along with magnetic field diffusion. It was found that MHD model gives relatively better results and fusion parameters are achievable.

Download Full Thesis
2253.24 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
144.51 KB
2 1 Introduction 3
558.78 KB
  1.1 A Piece From History 3
  1.2 Types Of Z Pinches 6
  1.3 Dynamic Z-Pinch 6
  1.4 Pulsed-Power 9
  1.5 Applications Of Z Pinches 11
  1.6 Layout Of The Thesis 198
3 2 Implosion Models And Methods To Mitigate R-T Instability 21
244.36 KB
  2.1 Implosion Of Thin Shell 21
  2.2 Snow-Plow Model 23
  2.3 MHD Fluid Model 25
  2.4 Rayleigh-Taylor Instability And Possible Ways To Mitigate It In Dynamical Z-Pinches 28
4 3 Staged Pinch Dynamics With Spin 31
789.73 KB
  3.1 Introduction 31
  3.2 Radiative Collapse In A An Impurity Seeded Spinning Gas-Puff Staged Pinch 33
  3.3 Plasma Dynamics In A Spinning Thick-Gas-Puff Plasma With Entrained Axial Magnetic Field 53
5 4 Staged Pinch Dynamics With Multicascade And Fluid Models 64
405.19 KB
  4.1 Staged Pinch Dynamics With Multicascade Liner System 64
  4.2 Magnetohydrodynamic Model For The Staged Pinch Plasma 79
6 5 Summary Of The Results And Recommendations For Future 87
235.63 KB