Electrical and Computer Engineering ETDs

Publication Date

5-1-1960

Abstract

The advent of high power lasers to the technological scene has introduced the possibility of creating new effects utilizing the interaction of this high intensity light with matter. C. M. Fowler and D. B. Thomson of the Los Alamos Scientific Laboratory suggested in 1963 the possibility of using a high power laser to pre-ionize and heat a target material to be contained in an explosively driven theta pinch machine. There had been calculations performed by John Dawson, Princeton University, and A. Engel­hardt, Westinghouse Research Laboratories, which indicated that such an approach was theoretically feasible. The laser powers required, however, were beyond the state-of­the-art at that time, and no experimental verification of the theory had been obtained. Con equently an effort (reported in this thesis) was undertaken to design and build a suitable laser for some feasibility studies. A 50-MW laboratory laser was built; however, it became possible to use a higher power commercial laser which had the advantage of being more nearly a "tool" rather than a "breadboard" device, and was therefore more amenable to experimental investigation of laser-produced plasmas. This laser was used to produce plasmas in a thin polyethylene target. A two-coil magnetic field system was built to allow the investigation of magnetic containment problems. The following measurements were made: ( 1) high speed framing camera photo­graphs of the plasma, (2) still 35 mm camera photographs using Kodak X-R type film, (3) spectrographic measurements u ing a Hilger medium quartz non-time re­solved spectrograph, ( 4) gas laser light absorption measurements, (5) individual spec­tral line intensity vs time measurements using a Jarrell-Ash monochromator, and (6) ion energies using an optical time-of-flight measuring technique. The results indicate that a _plasma having ·a "temperature" ·of a· few electron volts and a directed energy of several kiloelectron volts is produced by the laser beam. The discrepancy between the thermal energy and the directed energy is attributed to the lack of thermal equilibri­um in the plasma. The application of a 20 kilogauss magnetic field increases the ap­parent "temperature" of the plasma and reduces the directed energy. The feasibility of producing a highly ionized plasma in a moderately low-Z target has thus been demonstrated. Further studies of simpler atomic systems are recom­mended, particularly in conjunction with more highly refined measurements of plasma temperature, density, and containment effects.

Document Type

Thesis

Language

English

Degree Name

Electrical Engineering

Level of Degree

Masters

Department Name

Electrical and Computer Engineering

First Committee Member (Chair)

William Jackson Byatt

Second Committee Member

Illegible

Third Committee Member

George A. Sawyer

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