Part A
A problem restricting the development of the CuCl laser hasbeen the decrease in output power with increases of tube temperatureabove 400°C. At that temperature the CuCl vapor pressure is about.1 torr. This is a small fraction of the buffer gas pressure (He at10 torr).
The aim of the project was to measure the peak radiation temperature(assumed related to the mean energy of electrons) in thelaser discharge as a function of the tube temperature. A 24 gHz gatedmicrowave radiometer was used.
It was found that at the tube temperatures at which the outputpower began to deteriorate, the electron radiation temperature showeda sharp increase (compared with radiation temperature in pure buffer).
Using the above result, we have postulated that this sudden increaseis a result of Penning ionization of the Cu atoms. As a consequenceof this process the number of Cu atoms available for lasingdecrease.
PART B
The aim of the project was to study the dissociation of CO2 inthe glow discharge of flowing CO2 lasers.
A TM011 microwave (3 gHz) cavity was used to measure the radiallyaveraged electron density ne and the electron-neutral collision frequencyin the laser discharge. An estimate of the electric field is madefrom these two measurements. A gas chromatograph was used to measurethe chemical composition of the gases after going through the discharge. This instrument was checked against a mass spectrometer foraccuracy 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 conditionsstudied the dissociation as a function of the electron densityis uniquely determined by the STP partial flow rate of CO2, regardlessof the amount of N2 and/or He present. The presence of water vapor inthe discharge decreased the degree of dissociation.
A simple theoretical model was developed using thermodynamicequilibrium. The electrons were replaced in the calculations by a distributedheat source.
The results are analyzed with a simple kinetic model.
