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Title:Studies of oxygen-helium discharges for use in electric oxygen-iodine lasers
Author(s):Zimmerman, Joseph W.
Director of Research:Solomon, Wayne C.
Doctoral Committee Chair(s):Solomon, Wayne C.
Doctoral Committee Member(s):Elliott, Gregory S.; Carroll, David L.; Coleman, James J.; Burton, Rodney L.
Department / Program:Aerospace Engineering
Discipline:Aerospace Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Electric OIL (EOIL)
electric oxygen-iodine laser
transverse RF discharge
singlet delta oxygen
Abstract:In recent work, the performance of the Electric Oxygen-Iodine Laser (ElectricOIL), developed in partnership by researchers at the University of Illinois and CU Aerospace, has been greatly improved through systematic study of various components of this new laser technology. One major contribution to the advancement of ElectricOIL technology has been the development of electric discharges capable of producing significant flow rates of the precursor electronically-excited molecular oxygen, O2(a). O2(a) serves as an energy reservoir in the laser system, pumping atomic iodine by near-resonant energy transfer producing gain and laser on the I(2P1/2) --> I(2P3/2) transition at 1315 nm. Initial experimental work with radio-frequency discharges showed the importance of controlling O-atom flow rates to reduce quenching losses of energy stored in O2(a), and determined proper selection of the helium diluent ratio and specific power deposition (power per O2 flow rate). Further experimental investigations with transverse capacitive radio-frequency discharges in O2/He/NO mixtures in the pressure range of 1-100 Torr and power range of 0.1-1.2 kW have indicated that O2(a) production is a strong function of geometry (transverse gap), excitation frequency, and pressure. These parameters along with gas flow mixture dictate the current density at which the discharge operates, and its modal characteristics (normal vs. abnormal, homogeneous vs. inhomogeneous). A key result is that to encourage efficient O2(a) production these parameters should be selected in order to promote a homogeneous (low current density) discharge. The discharge behavior is characterized using terminal current-voltage-characteristics, microwave interferometer measurements, and plasma emission intensity measurements. Numerous spectroscopic measurements of O2(a), oxygen atoms, and discharge excited states are made in order to describe the discharge performance dependent on various parameters. The influence of NO on O-atom flow rates and O2(a) production is investigated. Progress of laser power extraction since initial reports in 2005 is overviewed.
Issue Date:2011-01-14
Rights Information:Copyright 2010 Joseph W. Zimmerman
Date Available in IDEALS:2011-01-14
Date Deposited:December 2

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