Date of Award

9-3-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Engineering Physics

First Advisor

Glen P. Perram, PhD

Abstract

The application of spectral and imagery diagnostics to YBa2Cu3O7 (YBCO) laser-ablated plumes was systematically studied to determine their effectiveness for process control. Emission signatures were collected for plumes created by ablating bulk YBCO with a pulsed laser source. A KrF (λ=248 nm) laser source operating at 4-10 J/cm2 at a 4-10 Hz pulse repetition frequency was used to ablate a bulk YBCO target at O2 background pressures ranging from 50 to 400 mTorr. Emission spectra were collected over the 500 to 860 nm bandpass at distances from the target ranging from 31.4 to 55.0 mm. Of 87 observed emission lines, 76 were assigned to specific transitions with the aid of calibration lamps and reference to tables of energy levels. Line fluences were corrected for self-absorption, and electronic state distributions were calculated using the most recent NIST transition probabilities. Electronic temperatures ranged from 0.28 ± 0.01 eV to 0.37 ± 0.03 eV for yttrium, 0.28 ± 0.01 eV to 0.35 ± 0.03 eV for barium, and 0.40 ± 0.02 eV to 0.48 ± 0.05 eV for copper, and are consistent with prior reported results. These results were relatively insensitive to position and oxygen background pressure. Imagery data obtained with a spectrally-filtered intensified CCD camera was used to determine plume velocities, shock strengths, and time-of-flight curves. A model using the time-of-flight data was developed to investigate the possible effect of time-varying temperatures and number densities on time-integrated electronic state distributions. This model predicted a slight elevation of Cu temperatures compared to Ba, however, the difference was not sufficient to explain experimental results. Surprisal analysis of Y, Ba, and Cu neutral emission spectra resulted in linear constraints, consistent with an exponential gap law for electronic excitation, with a different constraint for each type of emitter.

AFIT Designator

AFIT-DSP-ENP-08-S05

DTIC Accession Number

ADA489661

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