Application of microwave diagnostics to copper chloride and carbon dioxide lasers
<p>Part A</p> <p>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...
| Summary: | <p>Part A</p>
<p>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).</p>
<p>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.</p>
<p>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).</p>
<p>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.</p>
<p>PART B</p>
<p>The aim of the project was to study the dissociation of CO<sub>2</sub> in
the glow discharge of flowing CO<sub>2</sub> lasers.</p>
<p>A TM<sub>011</sub> microwave (3 gHz) cavity was used to measure the radially
averaged electron density n<sub>e</sub> 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.</p>
<p>Several typical laser mixtures were .used: CO<sub>2</sub>-N<sub>2</sub>-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)+ H<sub>2</sub>O and pure CO<sub>2</sub>. 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 CO<sub>2</sub>, regardless
of the amount of N<sub>2</sub> and/or He present. The presence of water vapor in
the discharge decreased the degree of dissociation.</p>
<p>A simple theoretical model was developed using thermodynamic
equilibrium. The electrons were replaced in the calculations by a distributed
heat source.</p>
<p>The results are analyzed with a simple kinetic model.</p>
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