Thesis: Ph.D.--University of Western Sydney, Macarthur. Faculty of Business and Technology. 1998. / Bibliography: p. 126-130.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (doctoral)--Lund Institute of Technology, Lund University, 1998. / Added t.p. with thesis statement inserted. Includes bibliographical references.

Thesis (doctoral)--Lund Institute of Technology, Lund University, 1998. / Added t.p. with thesis statement inserted. Includes bibliographical references.

A CO₂ laser system delivering a 12 J pulse with a FWHM of 2 ns on target was developed to serve as a driver for studies of laser plasma interactions within a cylindrical cavity. The system consisted of a hybrid oscillator, followed by an amplifier chain, and it achieved its design goals of delivering an intense CO₂ pulse, Gaussian in time and space, with a high contrast ratio on a reliable basis. The targets in which the plasma was produced consisted of small rectangular plates of lucite, with holes drilled through one of the long axes. The holes were 350 μm to 600 μm in diameter, and 10 mm in length. These dimensions allowed the laser beam, focused at the entrance of the hole, to produce sufficient intensity on the inner walls of the cylindrical cavity for plasma formation, while allowing the beam, with a waist diameter of 100 μm at the focus to deliver most of its energy within the cavity. The beam propagated via multiple reflections from the plasma through the cavity. Diagnostics were performed on the beam transmitted through the target. Streak camera images were collected of the intensity of visible emission from the plasma along the axis of the target. Anomalous results were obtained with respect to the reproducible observation of maximum visible light emission from regions at the far end cavity from where the laser beam is injected. Another unforseen but interesting result was the small divergence of the beam transmitted through the cavity. Preliminary models were developed to attempt to explain the observations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

No description available.

Thesis. 1978. Sc.D.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / Sc.D.

This thesis was motivated by the promise that some physical aspects of astrophysical jets and collimation processes can be scaled to laboratory parameters through hydrodynamic scaling laws. The simulation of astrophysical jet phenomena with laser-produced plasmas was attractive because the laser-target interaction can inject energetic, repeatable plasma into an external environment. Novel laboratory simulations of astrophysical jets involved constructing and using the YOGA laser, giving a 1064 nm, 8 ns pulse laser with energies up to 3:7 - 0:2 J. Laser-produced plasmas were characterized using Schlieren, interferometry and ICCD photography for their use in simulating jet and magnetosphere physics. The evolution of the laser-produced plasma in various conditions was compared with self-similar solutions and HYADES computer simulations. Millimeter-scale magnetized collimated out-flows were produced by a centimeter scale cylindrically symmetric electrode conguration triggered by a laser-produced plasma. A cavity with a flared nozzle surrounded the center electrode and the electrode ablation created supersonic uncollimated flows. This flow became collimated when the center electrode changed from an anode to a cathode. The plasma jets were in axially directed permanent magnetic fields with strengths up to 5000 Gauss. The collimated magnetized jets were 0.1-0.3 cm wide, up to 2.0 cm long, and had velocities of ~ 4:0 x 10⁶ cm/s. The dynamics of the evolution of the jet were compared qualitatively and quantitatively with fluxtube simulations from Bellan's formulation [6] giving a calculated estimate of ~ 2:6 x 10⁶ cm=s for jet evolution velocity and evidence for jet rotation. The density measured with interferometry was 1.9 ± .2 x 10¹⁷ cm⁻³ compared with 2.1 x10¹⁶ cm⁻³ calculated with Bellan's pressure balance formulation [6]. Kinks in the jet column were produced consistent with the Kruskal-Shafranov condition which allowed stable and symmetric jets to form with the background magnetic fields. The Euler number for the laboratory jet was 9 compared with an estimate of 40 for young stellar object jets [135] which demonstrated adequate scaling between the two frames. A second experiment was performed concerning laboratory simulations of magnetospheres with plasma winds impinging on permanent magnetic dipoles. The ratio of the magnetopause measured with ICCD photography to the calculated magnetopause standoff distance was ~2. / text

With the availability of high reflectivity multilayer mirrors and zone plate lenses, the EUV region (5nm - 40nm) of the electromagnetic spectrum is currently being explored for applications of nanoscale printing and imaging. Advances made in this area have consequences for many areas of science. Research for producing a compact, bright EUV source for laboratory use has gained momentum in recent years. For this study, EUV radiation is produced by irradiating target materials using a focused laser beam. Focused laser beam ionizes the target to create a hot, dense, pulsed plasma source, where emission is a result of the relaxation of excited levels. Spectroscopy is used as the main diagnostic to obtain the spectral signature of the plasma. Spectral characteristics are used to deduce the physical state of plasma, thus enabling the tuning of laser irradiance conditions to maximize the needed emission bandwidth. Various target materials are studied, as well as different target geometries, with spectroscopy below 200 nm on pulsed micro-plasmas being a particularly daunting task. Total range spectroscopy from 1 nm to greater than 1 micron is completed for tin-doped spherical droplet plasma source. Reliable plasma diagnostics require both accurate measurements and solid theoretical support in order to interpret the experimental results. Using existing 1D-hydrocode, temperature and density characteristics of the expanding plasma is simulated for any set of experimental conditions. Existing atomic codes written for calculating one-electron radial wavefunctions with LS-coupling scheme via Hartree-Fock method is used in order to gain details of the ion stages, populations, transitions, etc, contributing to the spectral data.

Atomic emission spectrometry (AES) with a plasma has proven to be an important method for the analysis of metallic and nonmetallic species in a variety of matrices. Not only is atomic spectrometry useful for accurate and sensitive quantitative analysis, but it can be used as a means of unambiguous qualitative determinations. The most common matrix for AES samples is liquid. Whether aqueous or organic in nature, the majority of samples are dissolved in some sort of solvent. Unfortunately, for most modes of sample introduction, a large portion of the solvent is simultaneously introduced to the plasma discharge along with the analyte species. The plasma is thus required not only to sufficiently excite the analyte, but also to desolvate and vaporize the solvent species. These processes tend to diminish the available energy of the plasma that is to be directed toward the analyte. The nature of the energy loss due to solvent loading is not well understood and is the topic of debate for different systems. It is the focus of this dissertation to determine the effect of solvent loading on the Highly Efficient Microwave Induced Plasma (HEMIP). The magnitude of solvent loading for Ar and He discharges using different sample introduction systems is determined. The solvent load is shown to have two separate constituents: aerosol and vapor. Each of these are shown to affect the plasma in different ways. Two different sample introduction systems are evaluated for their respective solvent loadings: a cooled pneumatic nebulizer / double pass spray chamber and an ultrasonic nebulization system. These systems are compared under their normal operating conditions and for the two plasma support gases. High solvent loads are shown to destabilize both the Ar and He microwave plasmas, decrease analytical sensitivity, and attenuate the energy of the plasma discharge. The conditions under which solvent loading is minimized do not have a significant effect on the operational characteristics of the sample introduction systems, but provide the optimal analytical sensitivity and limits of detection for the HEMIP. / Ph. D.