Date of Award

12-1996

Document Type

Thesis

Degree Name

Master of Science in Applied Physics

Department

Department of Engineering Physics

First Advisor

Paul J. Wolf, PhD

Abstract

Ba, BaO, Sr and SrO were ablated by 248 nm laser pulses at fluences ranging from 270 mJ-/cm2 to 575 mJ-/cm2 in vacuum and in 25 mtorr atmospheres of N2, O2 and microwave-discharged O2. The spectral emissions of these plumes were compared for indications of ionization due to Ba or Sr collisions with each gas. The addition of a background gas increased the ion and neutral signature across the spectrum. SrO band emission was observed at 16,600-16,900/cm and possible BaO band emissions were observed in the 18,250-18,400/cm, 19,000-19700/cm and 19,800-20,000/cm regions. A screened plate ion probe was use to establish the ion content of the Ba plume. A time of flight study established low-pressure (1 to 35 mtorr) and low-fluence (40 to 160 mJ-/cm2 relationships on Ba+ velocity and population. Observed ion velocities ranged from 3.1 km/sec. To 4.5 km/sec. Results indicate the addition of a background gas at pressures less than 25 mtorr quenches Ba+ in the plume and retards the plume expansion.

AFIT Designator

AFIT-GAP-ENP-96D-4

DTIC Accession Number

ADA325126

Comments

Plain text title form: Investigation of Ba, BaO, Sr and SrO Pulsed Laser-Induced Vapor Plumes in N2, O2, Microwave Discharged O2, and Vacuum at Low Laser Fluence

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