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

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We have performed a series of experiments developing the techniques of volumetric, isochoric heating of matter to high energy density states, and the subsequent probing of the release isentrope. Using ultrafast, ultra intense laser systems with pulse lengths from 100fs - 1ps and pulse energies between 2 J and 100 J, we generated strong secondary radiation, in the form of K[subscript alpha] x-rays and directed proton beams, which we used to rapidly heat a foil sample to temperatures from ~ 1 eV to ~ 25 eV at solid density, thus entering the strongly coupled, partially ionized regime of warm dense matter, in which the equation of state is poorly understood. The first set of experiments examines the possibility of using laser generated K[subscript alpha] x-rays in isochoric heating experiments and concludes that this technique will require the use of higher energies and higher Z materials than were used in this thesis to achieve warm dense matter conditions. In the second set of experiments, we used an ultrafast, lasergenerated proton beam with a temperature of ~ 2 MeV and cutoff energy of ~ 40 MeV to volumetrically and isochorically heat a sample foil to > 20 eV. With singleshot diagnostics, we measured the evolution of the temperature with 3:3 ps resolution over the _rst 35 ps of expansion by streaked optical pyrometry, and measured the evolution of the target expansion over the same timescale with sub-ps resolution by chirped pulse interferometry. In this way we were able to verify the equation of state and ion-balance in the SESAME equation of state tables with a Saha ionization model and distinguish this as more accurate than other, simpler models. This thesis establishes an experimental framework for acquiring equation of state data in the regime of warm dense matter that is distinct and complimentary to that acquired by the techniques of shock heating. / text

We study particle production and its density evolution and equilibration in hot dense medium, such as hadronic gas after quark gluon plasma hadronization and relativistic electron positron photon plasma. For this study we use kinetic momentum integrated equations for particles density evolution with Lorentz invariant reaction rates. We extend these equations, used before for two-to-two particles reactions (1 + 2 ↔ 3 + 4), to the case of two-to-one and backward reactions (1 + 2 ↔ 3). One type of hot dense medium, which we study, is hadronic gas produced at quark gluon plasma hadronization in heavy ions collisions in SPS, RHIC and LHC experiments. We study hadron production at quark gluon plasma hadronization and their evolution in thermal hadronic gas phase. We consider non-equilibrium hadronization model, for which the yields of the light quark hadrons are defined by entropy conservation. Yields of hadrons containing heavier (strange, charm, bottom) quarks are mainly controlled by flavor conservation. We predict yields of charm and bottom hadrons within this non-equilibrium statistical hadronization model. Then we use this non-equilibrium hadronization as the initial condition in the study of hadronic kinetic phase. During this time period some hadronic resonances can be produced in lighter hadrons fusion. This reaction is opposite to resonance decay. Production of resonances is dominant over decay if there is non-equilibrium excess of decay products. Within this model we explain apparently contradictory experimental results reported in RHIC experiments: ∑(1385) yield is enhanced while ∧(1520) yield is suppressed compared to the statistical hadronization model expectation obtained without kinetic phase. We also predict Δ(1232) enhancement. The second type of plasma medium we consider is the relativistic electron position photon plasma (EP³) drop. This plasma is expected to be produced in decay of supercritical field created in ultrashort laser pulse. We study at what conditions this plasma drop is opaque for photons and therefore may reach thermal and chemical equilibrium. Further we consider muon and pion production in this plasma also as a diagnostic tool. Such heavy particles can be diagnostic tool to study the properties of EP³ plasma, similar to the role taken by heavy hadrons production in heavy ions collisions. Finally all these theoretical developments can be applied to begin a study of particles evolution in early universe in temperatures domain from QGP hadronization (160 MeV) to nucleosynthesis (0.1 MeV). The first results on pion equilibration are presented here.

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

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

No description available.

This thesis presents results from two strands of work towards realizing a free-electron laser (FEL) driven by electron bunches generated by a laser-wakefield accelerator (LWFA). The first strand focuses on selecting operating parameters for such a light source, on the basis of currently achievable bunch parameters as well as near-term projections. The viability of LWFA-driven incoherent undulator sources producing nanojoule-level pulses of femtosecond duration at wavelengths of 5 nm and 0.5 nm is demonstrated. A study on the prospective operation of an FEL at 32 nm is carried out, on the basis of scaling laws and full 3-D time-dependent simulations. A working point is selected, based on realistic bunch parameters. At that working point saturation is expected to occur within a length of 1.6 m with peak power at the 0.1 GW-level. This level, as well as the stability of the amplification process, can be improved significantly by seeding the FEL with an external radiation source. In the context of FEL seeding, we study the ability of conventional simulation codes to correctly handle seeds from high-harmonic generation (HHG) sources, which have a broad bandwidth and temporal structure on the attosecond scale. Namely, they violate the slowly-varying envelope approximation (SVEA) that underpins the governing equations in conventional codes. For this purpose we develop a 1-D simulation code that works outside the SVEA. We carry out a set of benchmarks that lead us to conclude that conventional codes are adequately capable of simulating seeding with broadband radiation, which is in line with an analytical treatment of the interaction. The second strand of work is experimental, and focuses on on the use of coherent transition radiation (CTR) as an electron bunch diagnostic. The thesis presents results from two experimental campaigns at the MPI für Quantenoptik in Garching, Germany. We present the first set of single-shot measurements of CTR over a continuous wavelength range from 420 nm to 7 μm. Data over such a broad spectral range allows for the first reconstruction of the longitudinal profiles of electron bunches from a laser-wakefield accelerator, indicating full-width at half-maximum bunch lengths around 1.4 μm (4.7 fs), corresponding to peak currents of several kiloampères. The bunch profiles are reconstructed through the application of phase reconstruction algorithms that were initially developed for studying x-ray diffraction data, and are adapted here for the first time to the analysis of CTR data. The measurements allow for an analysis of acceleration dynamics, and suggest that upon depletion of the driving laser the accelerated bunch can itself drive a wake in which electrons are injected. High levels of coherence at optical wavelengths indicate the presence of an interaction between the bunch and the driving laser pulse.

The effect of the refraction of a laser beam propagating through three different phase objects, i.e. a laser produced plasma and two different gas media, is investigated in this thesis. It is shown that these effects have useful applications. As an introduction to the work performed, a basic discussion of the theory of light is given. In the first experimental study, the accuracy of using the Refractive Fringe Diagnostic, as a tool to determine the electron density profiles of laser produced plasmas, is investigated [Buccellato et al. (1992)]. A comparative study is performed between an established method of determining the electron density profiles of laser produced plasmas, i.e. Nomarski interferometry, and the Refractive Fringe Diagnostic, by comparing experimental data obtained from the same laser shot. For the electron density profiles investigated, it is shown that the Refractive Fringe Diagnostic over-estimates the electron density by an order of magnitude. It is suggested that the electron density errors are due to the inherent assumptions of the Refractive Fringe Diagnostic. To verify this, a numerical simulation into the accuracy of the RFD is performed on a mathematically modelled plasma. The discrepancy in the numerical results are consistent with those of the experimental results and these can be attributed to the assumptions made by the Refractive Fringe Diagnostic. Laser light refracted by a gas medium, with a specific density profile, may produce a near diffraction limited focal spot. The remaining two experimental investigations deal with two novel gas lenses: the Pulsed Gas Lens and the Colliding Shock Lens. A radially expanding cylinder of gas produces a suitable density structure to focus laser light. A design of a gas lens, the Pulsed Gas Lens, using this principle is proposed as a final focusing lens for a laser fusion power station [Buccellato et al. (1993a)]. To establish the feasibility of such a lens a proof-of- principle design for the lens is given. A numerical simulation of this lens is performed by modelling the gas flow from the lens and raytracing through the determined density profiles inside the lens. It is found that this lens can be used as a focusing element. To establish certain practical aspects of the proof-of- principle design, a beam deflection device was constructed and tested. This beam deflection device models the lensing principle of the proposed lens. The laser beam deflection observed did not match the computed deflection. The opening mechanism for the proof-of-principle design did not produce an instantaneous opening of the chamber as was assumed in the simulation. The opening mechanism must be modified to decrease the opening time. Diverging spherical shock waves, produced by pairs of opposing electrodes evenly spaced on a circumference, produce a converging cylindrically symmetric shock wave. After convergence a suitable density structure exists for near diffraction li.mited focusing to occur. It is found that the Colliding Shock Lens is a varifocal lens: the focal length and lens diameter increase with time [Buccellato et al. (1993b)]. A numerical simulation is performed to model the operation of the Colliding Shock Lens. The numerical results compare favourably with the experimental results. From the simulation it is established that the lens diameter can be scaled up by increasing the physical size of the lens and the input energy to the lens. Potential applications of the colliding shock lens are discussed. To conclude this thesis, the results of the separate investigations are summarised. / Thesis (Ph.D.)-University of Natal, 1994.

No description available.