Ng, Siu Fai = 溫暖稠密物質及高能量密度物理的研究 / 吳肇輝. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 126-133). / Abstracts also in Chinese. / Ng, Siu Fai = Wen nuan chou mi wu zhi ji gao neng liang mi du wu li de yan jiu / Wu Zhaohui. / Chapter 1 --- Introduction --- p.16 / Chapter 1.1 --- General review of high energy density physics --- p.16 / Chapter 1.2 --- General review of warm dense matter --- p.20 / Chapter 1.2.1 --- Physics of warm dense matter --- p.20 / Chapter 1.2.2 --- Uncertainties of warm dense matter --- p.23 / Chapter 1.2.3 --- Challenges of warm dense matter studies --- p.25 / Chapter 1.3 --- Use of intense heavy ion beam --- p.27 / Chapter 1.4 --- Motivation and structure of this thesis --- p.32 / Chapter 2 --- Hydrodynamic simulations --- p.34 / Chapter 2.1 --- Lagrangian hydrodynamic code --- p.34 / Chapter 2.2 --- Hydrodynamic equations --- p.35 / Chapter 2.3 --- Artificial viscosity --- p.36 / Chapter 3 --- Equations of state --- p.38 / Chapter 3.1 --- Van der Waals' equation of state --- p.39 / Chapter 3.2 --- Quotidian equation of state --- p.41 / Chapter 3.3 --- Saha-based equation of state --- p.41 / Chapter 3.4 --- Inverse power potentials equation of state --- p.48 / Chapter 3.5 --- Gruneisen-type equation of state --- p.53 / Chapter 3.6 --- Discussion --- p.59 / Chapter 4 --- Single bubble sonoluminescence --- p.63 / Chapter 4.1 --- Introduction --- p.63 / Chapter 4.2 --- Theory of sonoluminescence --- p.65 / Chapter 4.2.1 --- Bubble wall dynamics --- p.66 / Chapter 4.2.2 --- Radiation transport --- p.67 / Chapter 4.2.3 --- Diffusive stability --- p.68 / Chapter 4.3 --- Numerical simulation --- p.68 / Chapter 4.3.1 --- Determination of the ambient radius --- p.69 / Chapter 4.3.2 --- Simulations using SEOS --- p.70 / Chapter 4.3.3 --- Simulations using QEOS --- p.77 / Chapter 4.4 --- Conclusion --- p.82 / Chapter 5 --- Collapsing bubble in ion-beam-heated metal --- p.83 / Chapter 5.1 --- Introduction --- p.83 / Chapter 5.2 --- Bubble collapse --- p.86 / Chapter 5.2.1 --- First step of collapse --- p.88 / Chapter 5.2.2 --- Stagnation point and bubble size --- p.89 / Chapter 5.2.3 --- Outer boundary and metal thickness --- p.91 / Chapter 5.2.4 --- Metal layer just outside bubble --- p.93 / Chapter 5.3 --- Effect of equation of state used --- p.95 / Chapter 5.3.1 --- Inverse power potentials equation of state --- p.95 / Chapter 5.3.2 --- Effect of ionization --- p.97 / Chapter 5.3.3 --- Effect of hard core --- p.97 / Chapter 5.3.4 --- Effect of EOS for metal --- p.97 / Chapter 5.4 --- Effect of proposed experimental parameters --- p.102 / Chapter 5.4.1 --- Initial gas density --- p.102 / Chapter 5.4.2 --- Energy deposition rate --- p.102 / Chapter 5.5 --- Conclusion and discussion --- p.105 / Chapter 6 --- High coupling efficiency compression by intense ion beams --- p.108 / Chapter 6.1 --- Introduction --- p.108 / Chapter 6.2 --- Ion stopping formulation --- p.111 / Chapter 6.3 --- Numerical simulation --- p.112 / Chapter 6.3.1 --- Lithium hydride target --- p.112 / Chapter 6.3.2 --- Underdense aluminum foam --- p.118 / Chapter 6.4 --- Conclusion --- p.119 / Chapter 7 --- Conclusion --- p.121 / Chapter 7.1 --- Summary --- p.121 / Chapter 7.2 --- Suggestions for future work --- p.123 / Bibliography --- p.126

Fluctuation phenomena are important to many physical systems, such as the fusion plasma. Noise theory is used to study the time and space correlations of stationary Markovian fluctuations that are statistically homogeneous and isotropic. The relaxation of the fluctuations is modeled by the diffusion equation. The spatial correlations are modeled by the exponential decay. Based on these models, the correlation function and the power spectral density of random fluctuations. We also find that the fluctuation-induced transport coefficients may be estimated by the correlation length and the correlation time. The theoretical results are compared with the observed plasma density fluctuations from tokamak and helimak experiments.

Thesis (Ph. D.)--University of Texas at Austin, 2007. Thesis (Ph. D.)--Université Paul Sabatier, 2007. / Thesis completed in partial fulfillment of the requirements for a joint Ph. D. from the University of Texas at Austin and the Université Paul Sabatier. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1980. / Microfiche copy available in Archives and Science. / Includes bibliographical references. / by Thomas Marshall Eubanks. / M.S.

Laser-plasma accelerators are of great interest because of their ability to sustain extremely large acceleration gradients, enabling compact accelerating structures. Laser-plasma acceleration is realized by using a high-intensity short pulse laser to drive a large plasma wave or wakefield in an underdense plasma. This thesis considers the effect of axial plasma density upramps on laser wakefield acceleration. Theoretical groundwork shows that tapered plasma channels can be used to mitigate one of the main limitations of laser plasma acceleration, that is, dephasing of an electron beam with respect to the plasma wave. It is shown that it is possible to maintain an electron bunch at constant phase in the longitudinal electric fields of the laser wake field. This leads to an increased energy gain of an electron trapped in the wakefield. The required shape of the density slope is difficult to implement in experiments. Therefore, a linear density ramp is also considered which is predicted to also increase the energy gain beyond that possible in a uniform density plasma. Towards an experimental implementation it was studied how a suitable gas density profile can be established in a capillary. This was done employing simulations using the computational fluid dynamics tool kit OpenFoam and comparing these to measurements of the axial density profile based on Raman scattering. It was demonstrated that a linear density ramp could be established by applying different pressures on the capillary gas inlets. The dependence of the density profile on the capillary parameters, such as, capillary diameter and length and inlet diameter were also studied. The results of the simulations and the measurement showed excellent agreement and demonstrate that approximately linear density ramps can be generated by flowing gas along a capillary of constant cross-section Laser wakefield acceleration in plasmas with longitudinally varying density was investigated in an experiment at the Astra Laser at Rutherford Laboratories. The experiment utilised ionisation injection in order to operate in the mildly non-linear regime of laser-wakefield acceleration. The measured electron energies agree well with the theoretical predictions. It was demonstrated that an increase in the energy gain can be obtained by driving the accelerator in a ramped plasma, the electron spectrum is more narrow and the injected charge increases significantly. Measurements of the X-ray spectrum emitted by the betatron motion of the accelerated electron bunch allowed the transverse radius of the bunch to be deduced. These measurements showed that retrieved electron bunch radius is inversely proportional to the longitudinal density gradient, that is a plasma density upramp (downramp) has a decreased (increased) electron bunch radius.

A spectroscopic diagnostic tool has been developed to determine the electron temperature and the neutral density in helium, hydrogen and argon plasmas from absolutely calibrated spectroscopic measurements. For each gas, a method of analysis which uses models specific to each species present in the plasma (neutral atom or singly ionized atom) has been defined. The experimental electron density is used as an input parameter to the models, and the absolutely calibrated spectroscopic data are processed beforehand to obtain the populations of the upper excited levels corresponding to the observed spectral lines. For helium plasmas, the electron temperature is inferred from the experimental helium ion excited level p = 4 population using a corona model, and then the neutral density is determined from the experimental helium neutral excited level populations using a collisional-radiative model for helium neutrals. For hydrogen plasmas, combinations of the electron temperature and the neutral density are determined from the experimental hydrogen neutral excited level populations using a collisional-radiative model specific to hydrogen atoms. For argon plasmas, the electron temperature is inferred from the experimental argon ion excited level populations using a collisional-radiative model for argon ions, and then the neutral density is determined from the experimental argon neutral excited level populations using a collisional-radiative model for argon neutrals. This diagnostic tool was applied to three experiments with different geometries and plasma conditions to test the validity of each data analysis method. The helium and hydrogen data analysis methods were tested and validated on helium and hydrogen plasmas produced in the VASIMR experiment, a plasma propulsion system concept. They gave electron temperatures and neutral densities that were consistent with other diagnostics and theory. The argon diagnostic tool was tested on argon plasmas produced in the VASIMR experiment, the Helimak experiment and the Helicon experiment. The electron temperature and neutral density obtained on both the Helimak and the Helicon experiments were consistent with other diagnostics and with theory, and validated the method of analysis. An impurity problem on the VASIMR experiment made it difficult for the data analysis to be validated.