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Hochuli, U. E.

Publications and source records attributed to Hochuli, U. E..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Efficient 30-W, 140-MHz rf amplifier for CW CO2 waveguide laser excitation

Details of a 30-W, 140-MHz rf amplifier for CW CO2 waveguide laser excitation are presented. The amplifier delivers 30 W into a 50-Ohm load while requiring only 40 W of dc power from a 28-V supply and 100 mW of rf drive power for an overall efficiency of 75 percent. A coupling-starting network design theory is given that provides the initiation over voltage for the discharge plasma from an rf power source of limited output voltage capability. The network then matches the drive circuit to the new input impedance of the operating discharge without any adjustments. This design theory applies to the whole class of networks whose losses can be approximated by a loss conductance in parallel with the gas discharge.

Hochuli, U. E.↗
NASA NTRS1986

Life problems of dc and RF-excited low-power CW CO2 waveguide lasers

A number of different, RF-excited 3-W CW CO2 waveguide lasers have been built. Four of these lasers, after continuously working for 15,000-30,000 h, still yield about 70 percent of their original power output. The design variations cover N2and CO-bearing gas mixtures, as well as internal- and external-capacitively coupled excitation electrodes. A similar laser survived 50,000 5-min-ON/5-min-OFF cycles without significant mirror damage. It was not possible to find suitable cold cathodes that allow the building of longitudinally dc-excited CW CO2 waveguide lasers that work for such extended periods of time.

Hochuli, U. E.↗
NASA NTRS1981

Continued life test results for an ensemble of CO2 lasers

The life test results of five 16 low pressure CW CO2 lasers with a nominal output of 1 watt are presented. One laser quickly died while the remaining four lasers reached half power output at 38,000, 40,000, 40,000 and 40,000 hours respectively. These results show the potential for a 50,000 hour laser while the average life of the 16 tested lasers was 22,500 hours. It is further indicated that the cathode sputtering products, which settle on the glass walls of the cathode sleeve, form an increasingly heavy film as the laser ages.

Hochuli, U. E.↗
NASA NTRS1978

Life test results for an ensemble of CO2 lasers

The effects of cathode material, cathode operating temperature, anode configuration, window materials, and hydrogen additives on laser lifetime are determined. Internally oxidized copper and silber-copper alloy cathodes were tested. The cathode operating temperature was raised in some tubes through the use of thermal insulation. Lasers incorporating thermally insulated silver copper oxide cathodes clearly yielded the longest lifetimes-typically in excess of 22,000 hours. The use of platinum sheet versus platinum pin anodes had no observable effect on laser lifetime. Similarly, the choice of germanium, cadmium telluride, or zinc selenide as the optical window material appears to have no impact on lifetime.

Peruso, C. J.↗
NASA NTRS1976

Life problems of small CO2 waveguide lasers

Gas discharge tube results, using the cathode technology developed for the ordinary one watt CW CO2 laser, promise life of at least a few thousand hours for the longitudinally excited waveguide laser. Actual lasers still suffer from excessive cathode sputtering, mirror deposits, and cathode flickering. The present state of this technology offers no easy solutions to extend the life of the transversely excited, pulsed CO2 waveguide laser.

Hochuli, U. E.↗
NASA NTRS1974

Cold cathodes for sealed-off CO2 lasers

Cold cathodes for CO2 lasers should possess a very low sputtering rate, have a minimum of negative ions in the sputtering products, and consume no oxygen. These conditions can be satisfied by selecting cathode materials from those elements of group I in the periodic table which form semiconducting oxide layers and then exposing these elements to a reducing gas mixture. Experimental results show that silver, internally oxidized silver-copper alloys, and pure copper satisfy most of these requirements in He-CO2-CO-Xe gas mixtures. Infrared CO and CO2 gas analysis performed on simple gas discharge tubes using such cathodes indicate that laser lives of 10,000 hr can be expected.

Hochuli, U. E.↗
NASA NTRS1973

Cold cathodes for sealed off CO2 lasers

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.

Hochuli, U. E.↗