Cold cathodes for sealed-off CO2 lasers
National Aeronautics and Space Administration, 1973 - Technology & Engineering - 60 pages
Experimental results of a group of theoretically selected cold cathode materials are presented. These tests indicate Ag-CuO, Cu, and Pt-Cu as three new cold cathode materials for sealed-off CO2 lasers. The power output of a test laser with an Ag-CuO cathode and a gas volume of only 50 cu cm varied from 0.72 W to 1.1 W at 3000 hours and still yields 0.88 W after 8000 hours. Gas discharge tubes with Cu cathodes and a volume of 25 cu cm yield lifetimes in excess of 10,000 hours. Gas analysis results, obtained from a similar tube over a period of 3000 hours, look most promising. A Pt-Cu alloy cathode shows an extremely promising V-I characteristic over a period of 2800 hours.
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103 t HOURS 150 mm bore 150-mm length laser 150mm BORE GAS 20 TORR TOTAL absorption coefficient Ag-CuO cathodes BORE GAS MIX bore He CO2 bulb Cd/O CHARACTERISTICS 5.6 x cm and 75 cm-1 equivalent slit CO2 laser cold cathode Cu/O Current 5.6 x current densities Discharge Current 5.6 Discharge current IDC discharge current Po(W dissociation electrical conductivity equivalent slit width filament function of discharge gas analysis gas composition HeXe Partial Pressure hydrogen IDC mA Figure internal oxidation length laser tube ln(Io/I lower curves operating time lower operating time upper Output vs Discharge oxide layers oxygen partial pressures versus Plot of absorption Power output presence of N2 pressures versus operating Results are shown SEALED-OFF C02 LASERS shown in Figure Silver-cadmium oxide cathode sputtering deposits temperature Torr CO2 torr Figure torr total pressure upper curve V-l CHARACTERISTICS 5.6 versus I Power versus IDC voltage versus operating water vapor x 150mm BORE