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Application of microwave diagnostics to copper chloride and carbon dioxide lasers

Citation

Sovero, Emilio (1977) Application of microwave diagnostics to copper chloride and carbon dioxide lasers. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:02182014-152349321

Abstract

Part A

A problem restricting the development of the CuCl laser has been the decrease in output power with increases of tube temperature above 400°C. At that temperature the CuCl vapor pressure is about .1 torr. This is a small fraction of the buffer gas pressure (He at 10 torr).

The aim of the project was to measure the peak radiation temperature (assumed related to the mean energy of electrons) in the laser discharge as a function of the tube temperature. A 24 gHz gated microwave radiometer was used.

It was found that at the tube temperatures at which the output power began to deteriorate, the electron radiation temperature showed a sharp increase (compared with radiation temperature in pure buffer).

Using the above result, we have postulated that this sudden increase is a result of Penning ionization of the Cu atoms. As a consequence of this process the number of Cu atoms available for lasing decrease.

PART B

The aim of the project was to study the dissociation of CO2 in the glow discharge of flowing CO2 lasers.

A TM011 microwave (3 gHz) cavity was used to measure the radially averaged electron density ne and the electron-neutral collision frequency in the laser discharge. An estimate of the electric field is made from these two measurements. A gas chromatograph was used to measure the chemical composition of the gases after going through the discharge. This instrument was checked against a mass spectrometer for accuracy and sensitivity.

Several typical laser mixtures were .used: CO2-N2-He (1,3,16), (1,3,0), (1,0,16), (1,2,10), (1,2,0), (1,0,10), (2,3,15), (2,3,0), (2,0,15), (1,3,16)+ H2O and pure CO2. Results show that for the conditions studied the dissociation as a function of the electron density is uniquely determined by the STP partial flow rate of CO2, regardless of the amount of N2 and/or He present. The presence of water vapor in the discharge decreased the degree of dissociation.

A simple theoretical model was developed using thermodynamic equilibrium. The electrons were replaced in the calculations by a distributed heat source.

The results are analyzed with a simple kinetic model.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Applied Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Applied Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Culick, Fred E. C.
Thesis Committee:
  • Culick, Fred E. C. (chair)
  • Yariv, Amnon
  • Gould, Roy Walter
  • Corngold, Noel Robert
Defense Date:26 May 1977
Non-Caltech Author Email:easovero (AT) ieee.org
Record Number:CaltechTHESIS:02182014-152349321
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:02182014-152349321
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8082
Collection:CaltechTHESIS
Deposited By: Benjamin Perez
Deposited On:19 Feb 2014 00:07
Last Modified:19 Feb 2014 00:07

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