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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Processing procedure using low-temperature platinum silicide, results in successful high-yield fabrication of large-area mesa-geometry Schottky diodes, with reverse breakdown voltages as high as 150 volts and leak currents less than 5 milliamps at 212 F.
A method for the regulation of a capacitor diode voltage multiplier dc-dc converter has been developed which has only minor penalties in weight and efficiency. An auxiliary inductor is used, which only handles a fraction of the total power, to control the output voltage through a pulse width modulation method in a buck boost circuit.
Coating for GaAs laser diodes should not alter optical and electrical properties. Borosilicate glass coating is easy to apply, breaks evenly when cleaved, and is abrasion and moisture resistant. Its low index of refraction makes thickness less critical when depositing half-wavelength coating.
Two circuit arrangements using ac and dc power source provide low-cost method for matching forward voltage drops of diodes and other semiconductors. Both circuits are simpler and less expensive than conventional, characteristic-curve tracers.
A statistical summary of electrical characterization was performed on JAN diodes and transistors. Parameters are presented with test conditions, mean, standard deviation, lowest reading, 10% point, 90% point and highest reading.
Laboratory spectra of CCL2F2 in the 10.8 micron region was recorded, using a tuneable diode laser spectrometer. Effects of air-broadening at pressures up to 48 Torr show that spectral structure should be exhibited under high resolution at altitudes as low as 19 Km. The single line, pressure-broadening coefficient for CCL2F2 was estimated to be 8 MHz/Torr FWHM.
A 1-kW capacitor-diode voltage multiplier (CDVM) was designed, fabricated and tested to demonstrate the power of feasibility of high power CDVM's and to verify the analytical techniques that had been used to predict the performance characteristics of a 6-kw CDVM. High efficiency (96.2%), a low ratio of component weight to power (0.55 kg/kW), and low output ripple voltage (less than 1%, peak to peak) were obtained during the operation of a 1-kW CDVM various input line, load current, and load fault conditions.
Heterodyne systems would be much more versatile if a broadly tunable laser, such as a semiconductor diode laser (TDL), could be used as the local oscillator (LO). Previous studies have shown that while a TDL can be used as an LO, the TDL lack sufficient power to cause the signal-to-noise ratio to be shot noise limited. The heterodyne system with a HgCdTe photodiode as the LO was characterized and the beat frequency response of the heterodyne systems was mapped out.
A 1 kW solar array and capacitor-diode voltage multiplier converter (S/A-CDVM) was successfully integrated with a 30 cm diameter mercury ion thruster system to provide ion beam power. Measurements were made to compare steady state and transient response performance of a conventional bridge converter with the S/A-CDVM converter used for the ion beam supply. The ability to recover from screen to accelerator arcs and promptly re-establish stable thruster performance was demonstrated. Solar array transient response to thruster arcing was measured.
Saturation of molecular transitions using a tuneable diode laser was demonstrated for the first time using a standing-wave cavity configuration with an f/8 beam focussed at the sample. Observed saturation effects in NH3 transitions near 888/cm include sub-Doppler (Lamb-dip) resonances at line center.
Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.
Cycling of a closed-cycle refrigerator produces temperature oscillations at the cold-tip which may be 0.5 K peak-to-peak. An active diode heater is described which compensates for the varying temperature and reduces the oscillations at the sample to about 0.003 K peak-to-peak at 9.5 K.
Various methods for determining the series resistance of p-n junction diodes and solar cells are described and compared. New methods involving the measurement of the ac admittance are shown to have certain advantages over methods proposed earlier.
A 1 kW Solar Array and Capacitor-Diode Voltage Multiplier Converter (S/A-CDVM) has been successfully integrated with a 30 cm-diameter mercury ion thruster system to provide ion beam power. Measurements were made to compare steady state and transient response performance of a conventional bridge converter with the S/A-CDVM converter used for the ion beam supply. The ability to recover from screen to accelerator arcs and promptly re-establish stable thruster performance was demonstrated. Solar array transient response to thruster arcing was also measured.
A tunable diode laser absorption spectrometer with resolution of about 0.0001/cm was used to record air-broadened spectra of CC12F2 in two regions near 922.8/cm and 921.7/cm. In the 922.8/cm region the structure shows good intensity contrast at pressures corresponding to upper atmospheric pressures. The absorption features have a spacing of 0.014/cm, which is sufficiently wide to retain spectral structure at pressures as high as 48 torr or altitudes as low as 19 km. The apparent broadening is 2 MHz/torr. The single-line broadening coefficient for CC12F2 can be estimated to be 8 + or - 2 MHz/torr FWHM. In the 921.7/cm region the high-resolution structure is discernible up to 24 torr, but the intensity contrast is not sufficiently strong to be of use in analysis of stratospheric spectra.
Saturation of molecular transitions using a tunable diode laser has been demonstrated for the first time using a standing-wave-cavity configuration with the laser beam focused at the sample. Observed saturation effects in NH3 transitions near 888 kaysers include sub-Doppler (Lamb-dip) resonances at the line center.
Proposed opticle coupling, using lenses and mirrors that replace complex mechanical systems, can combine separate tunable diode laser outputs and expand wavelength range. Method uses single cooler housing and requires no moving parts within cooler assembly.
Diodes manyfactured by Texas Instruments and Siemens performed well in group I testing. Failure analysis shows that group II testing is most detrimental to both sample lots. Same failure mode of excessive I(sub) R leakage can be clearly seen in group III testing.