Search NASA⌕ Search

SEARCH · Search NASA

Results for “Germanium”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Preliminary results from the first satellite of a high-resolution germanium gamma-ray spectrometer: Description of instrument, some activation lines encountered, and studies of the diffuse spectra

Gamma radiation from terrestrial and extraterrestrial sources were investigated with a high resolution Ge(Li) spectrometer-cryogen system flown onboard a low altitude, spin stabilized, polar orbiting satellite. A brief description is given of the instrument and preliminary results obtained from earth orbit are discussed. Attempts were made to use angular distributions and geomagnetic latitude spectral variations to determine diffuse background spectrum, detect gamma ray line emissions from solar flares, and search for positron annihilation radiation coming from the direction of the galactic center.

Nakano, G. H.↗
NASA NTRS1973

Preliminary results from the first satellite of a high-resolution germanium gamma-ray spectrometer: Backgrounds from electron bremsstrahlung and from electron-positron annihilation

Detailed data are presented on the bremsstrahlung backgrounds measured by a satellite-borne high resolution Ge(Li) gamma ray spectrometer. Two bremsstrahlung classes were discussed: (1) those arising from radiation belt electrons stopping in the vicinity of the spectrometer, and (2) bremsstrahlung produced by electrons precipitating into the earth's atmosphere.

Imhof, W. L.↗
NASA NTRS1974

Geochemical affinities of cobalt and germanium toward metal, silicate, and sulfide phases at high temperature

Hydrothermal studies indicate that Co and Ge are strongly siderophile when metallic iron is in equilibrium with olivine at 900 C and 500 bars. If the metal is replaced by troilite (FeS), Ge is strongly lithophile whereas Co tends to concentrate in the sulfide phase. If iron meteorites were formed in a core derived from the sulfide phase, they would be depleted in Ge but retain Co.

Wai, C. M.↗
NASA NTRS1976

The long-term performance degradation of a radioisotope thermoelectric generator using silicon germanium

The successful utilization of a radioisotope thermoelectric generator (RTG) as the power source for spaceflight missions requires that the performance of such an RTG be predictable throughout the mission. Several mechanisms occur within the generator which tend to degrade the performance as a function of operating time. The impact which these mechanisms have on the available output power of an RTG depends primarily on such factors as time, temperature and self-limiting effects. The relative magnitudes, rates and temperature dependency of these various degradation mechanisms have been investigated separately by coupon experiments as well as 4-couple and 18-couple module experiments. This paper discusses the different individual mechanisms and summarizes their combined influence on the performance of an RTG. Also presented as part of the RTG long-term performance characteristics is the sensitivity of the available RTG output power to variations of the individual degradation mechanisms thus identifying the areas of greatest concern for a successful long-term mission.

Stapfer, G.↗
NASA NTRS1977

Germanium coated microbridge and method

A superconducting microbridge is provided for use in superconducting quantum interference devices wherein a pair of spaced layers of superconductive material are connected by a weak link bridge to establish an electrical junction. The superconductive layers and bridge are coated with a semiconductor material shunting the bridge at room temperatures to prevent the destruction of the device by minute electrical currents while the coating acts as a dielectric permitting normal electrical behavior of the microbridge at cryogenic temperatures.

Holderman, L. B.↗
NASA NTRS1977

Niobium-germanium superconducting tapes for high-field magnet applications

A process of fabricating superconducting Nb3Ge tapes by chemical vapor deposition (CVD) has been developed and tapes up to 10 meters long fabricated. The typical properties achieved were: critical temperature T sub c = 20 K, upper critical field H sub c2 = 29 tesla at 4.2 K, and J sub c = 3 to 4 x 10 to the 8th power A m(-2) at 4.2 K, 18 tesla. The relative depression of T sub c and H sub c2 compared with the best thin film samples sputtered on sapphire was due to the presence of Nb5Ge3 second-phase particles used as flux pinning centers and to strains induced by thermal mixmatch with Hastelloy B tape substrates. A peculiar field dependence of flux pinning force that was observed in both CVD and sputtered Nb3Ge indicated a premature pin-breaking mechanism or a phase inhomogeneity. Directions of further optimization work were defined.

Braginski, A. I.↗
NASA NTRS1980

Germanium-on-InP heterojunction-structure LED

Ge-on-InP heterojunction structure LED has been developed where in Ge film is evaporated onto commercially available InP substrate. Forward bias of device is approximately 1 volt, and it emits light in 9.800 angstrom region. Technique permits easy and inexpensive fabrication of LED for application at this wavelength.

Hawrylo, F. Z.↗
NASA NTRS1981

Long term behavior of silicon germanium thermoelectric generators

Results of tests of the long term performance of SiGe radioisotope thermoelectric generators (RTG) are presented. Three modules were monitored for 17,000-32,300 hr at hot junction temperatures of 1,085, 1,055, and 1,000 C; coating the unicouples with a 12,000 A thick layer of Si3N4 protected the modules from Si sublimation. Output degraded less than 0.3-0.4%/1,000 hr over the testing period. Life tests on a multihundredwatt (MHW) SiGe generator with 312 couples at a hot shoe temperature of 1,040 C dealt with power of 150 W at 30 V, with 0.5%/1,000 hr performance degradation. Si deposition on the insulation was found to enhance electrical conductance until a saturation point was reached. Disassembly of a test module after 16,750 hr revealed a Mo build-up, SiN4 coating deterioration, and Ti diffustion from the hot shoe to cooler regions of the junction. The presence of an Al2O3 insulator was recognized as preventing coating loss. Performance records from the Voyager and Les-8 satellites' RTG's are compared and show similar, 0.25%/1,000 hr degradation rates; RTG storage is judged to be feasible and the tests lead to projections of a 600,000 hr lifetime for a SiGe RTG.

Shields, V.↗
NASA NTRS1983

Computer simulation study of multiple germanium gamma-ray sensor arrays

Design studies of large high resolution gamma-ray spectrometer systems employing multiple sensors are greatly facilitated by the use of computer simulation techniques. A study has been made by interfacing a detector geometry code with the EGS-3 version of the Stanford Linear Accelerator Center Monte-Carlo Code which has been modified to run on our VAX computer. The detector responses have been simulated for input photons with energies between 0.1 and 10 MeV. Examples are given to illustrate the performance of complex sensor arrays with different configurations of the anticoincidence system. Of particular interest is a design composed of an array of 7 detector elements each consisting of a thin planar Ge (1 cm thick) detector mounted in front of and in tandem with a large coaxial Ge detector.

Nakano, G. H.↗
NASA NTRS1985

Germanium and lead: Significant differences between meteoritic and photospheric abundances?

The order of the Galactic cosmic ray source (GCRS) composition in terms of first ionization potential (FIP) was examined. For most elements, the degree of volatility is (positively) correlated with the value of the FIP, so that it is not easy to distinguish a correlation of GCRS abundances anomalies with FIP from a correlation with volatility. Only a few permit to distinguish between the two kinds of ordering: if they are depleted relative to refractory metals, volatility must be relevant, if not, FIP is relevant. Among them Cu and Zn would seem to favor FIP. Among the best indicators are Ge and Pb. The abundance anomalies in GCRS are defined relative to a standard which, for the heavy elements concerned, is commonly taken as C1 Carbonaceous Chondrites. Photospheric abundances are more directly representative of the protosolar nebula, and hence of ordinary local galactic (LG) matter. The Ge and Pb reference abundance determinations in the Photosphere and in C1 meteorites are examined and their relevance to the problem with FIP vs. volatility in GCRs is discussed.

Grevesse, N.↗
NASA NTRS1985

Far-infrared transmittance of boron-implanted germanium at liquid-helium temperatures

The transmission of far-infrared radiation of 100-microns-wavelength through Ge wafers ion implanted with B was measured at a temperature of approximately 4 K. Transmittance ranged from approximately 0.5 to 0.08 for doses from 3 x 10 to the 12th to 3 x 10 to the 15th/sq cm. The resistivity at temperatures between 4 and 1 K, and the impurity profiles of the implanted layers were also measured and correlated with the infrared transmittance.

Hadek, V.↗
NASA NTRS1987

Microstructures of undercooled germanium droplets

Undercoolings at crystal nucleation onset of liquid Ge droplets are measured and the microstructures of the droplets are examined. Undercooling values ranging from 150-415 + or 20 C were obtained. It is observed that for the samples undercooled less than 300 C prior to solidification the grain size was greater than 100 microns; for samples undercooled between 300-400 C the grain size was between 50-100 microns; and for samples undercooled greater than 400 C the grain size was 10-20 microns. Consideration is given to dendritic growth and interfacial undercooling. It is noted that there is a correlation between undercooling and as-crystallized grain structure.

Devaud, G.↗
NASA NTRS1985

Undercooling of niobium-germanium alloys in a 100 meter drop tube

The undercoolings of pure Nb and Nb-Ge alloys are examined using the 100-m drop tube of the Marshall Space Flight Center. The temperatures of the samples prior to release were measured, and IR detectors were utilized to monitor recalescence from solidification. It is observed that the Nb and Nb-Ge samples undercooled to the homogeneous nucleation limit. The data reveal that all the samples displayed a dendritic primary phase, except for alloys nucleating in the beta-phase field, which had a cellular phase. The composition of these phases are studied using EDXA; it is detected that the composition of the phases corresponds to the Jorda (1978) phase diagram.

Hofmeister, W. H.↗