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COMPATIBILITY OF MATERIALS WITH HIGH TEMPERATURE POTASSIUM.
Compatibility of materials with high temperature potassium
Preliminary Results of a Study of 12 Oxidation-resistant Coatings for Cb-10ti-5zr Columbium-alloy Sheet
Oxidation resistant coatings for Cb-10Ti-52r columbium-alloy sheet
Experimental investigation of advanced super- conducting magnets. superconducting strip and its use in magnets final report
Superconducting strip for superconducting magnet coil construction
Study of properties of high field superconductors, ac field induced flux jumps Technical summary report, 21 Jun. 1965 - 26 Apr. 1966
Magnetization experiments in superimposed dc and audiofrequency ac magnetic fields on cold worked NbTi alloy samples - ac field induced flux jumps
Investigation of solubility and diffusion of oxygen in refractory metals Second quarterly report, 1 Oct. - 31 Dec. 1965
Electric resistivity measurements to determine solubility and diffusion of oxygen in tantalum, columbium, and alloys
Ultrahigh-vacuum creep behavior of columbium and tantalum alloys at 2000 deg and 2200 deg F for times greater than 1000 hours.
Ultrahigh-vacuum creep behavior of columbium and tantalum alloys at high temperature and over long period
Fabrication of an ultra-fine Cb-Cu composite by drawing.
Mechanical deformation used in fabrication of composite made of continuous columbium wires in copper matrix by drawing, noting optical inspection
Stabilized Nb-Zr strip and its use in large magnets.
Nb-Zr strip superconductor for stabilization of critical current anisotropy and coil degradation in magnets
Effect of 1000 hour thermal exposures on tensile properties of refractory metal alloys
Effect of 1000 hour thermal exposures on tensile properties of refractory metal alloys
Contamination exposures of columbium and tantalum alloy specimens Final report, 25 Feb. 1965 - 15 Jun. 1966
Contamination exposures of columbium, zirconium, and tantalum alloys under conditions of low pressures and high temperatures
Summary of the potassium - Refractory metal corrosion capsule program at NASA Lewis Research Center
Corrosion resistance of Nb and Ta tubing alloys to boiling K
Fabrication of a columbium alloy liquid metal loop.
Fabrication of columbium alloy liquid metal loop to study boiling and condensing characteristics of Na and K up to 1000 degrees F with gas tungsten arc welding in helium atmosphere
Measurements of noise in Josephson-effect mixers
We present new heterodyne receiver results obtained at 100 GHz using resistively-shunted Nb and NbN tunnel junctions. In addition, we have carried out accurate measurements of the available noise power of these devices at the L-band (1.5 GHz) IF (infrasonic) frequency. Both the heterodyne and the output noise measurements show that the noise of these devices can be a factor of five or more higher than that predicted by the simple current-biased RSJ model. The noise approaches the appropriate thermal or thermal and shot noise limits for bias voltages where the nonlinearity is not strong (i.e., V greater than I(sub C)R(sub N)), but as expected from the RSJ model, can be significantly higher at the low voltages where the mixers are typically biased. The bias voltage dependence of the noise shows structure which is associated with resonances in the RF embedding circuit. Surprisingly, we find that changes in the high-frequency (100 GHz) impedance presented to the junction can dramatically affect the magnitude and voltage dependence of the low-frequency (1.5 GHz) noise. This emphasizes the necessity of very closely matching the junction to free space over a wide frequency range.
Performance characteristics of narrow linewidth fiber laser pumped mid-IR difference frequency mixing light source for methane detection
A high-power, narrow-linewidth Yb fiber laser with a fiber Bragg grating (FBG) pumped difference frequency generation (DFG) in a periodically poled lithium niobate (PPLN) crystal was investigated in detail. A mid-IR power of approximately 2.3 microW at 3.3 micrometers with a slope efficiency of 0.85 mW/W2 was achieved. A Doppler-broadened absorption spectrum of CH4 at 3038.497 cm-1 (3.2911 micrometers) was obtained with a 0.1-m long-gas cell at a pressure of 133 Pa. The linewidth of the DFG source was evaluated to be less than 96 MHz from the observed spectral linewidth. Real-time monitoring of CH4 (approximately 1.78 ppm) in ambient air in a multipass cell which has an optical path length of 10 m was also demonstrated.
Ambient formaldehyde detection with a laser spectrometer based on difference-frequency generation in PPLN
A laser spectrometer based on difference-frequency generation in periodically poled LiNbO3 (PPLN) has been used to quantify atmospheric formaldehyde with a detection limit of 0.32 parts per billion in a given volume (ppbV) using specifically developed data-processing techniques. With state-of-the-art fiber-coupled diode-laser pump sources at 1083 nm and 1561 nm, difference-frequency radiation has been generated in the 3.53-micrometers (2832-cm-1) spectral region. Formaldehyde in ambient air in the 1- to 10-ppb V range has been detected continuously for nine and five days at two separate field sites in the Greater Houston area operated by the Texas Natural Resource Conservation Commission (TNRCC) and the Houston Regional Monitoring Corporation (HRM). The acquired spectroscopic data are compared with results obtained by a well-established wet-chemical o-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine (PFBHA) technique.
Novel diode laser-based sensors for gas sensing applications
The development of compact spectroscopic gas sensors and their applications to environmental sensing will be described. These sensors employ mid-infrared difference-frequency generation (DFG) in periodically poled lithium niobate (PPLN) crystals pumped by two single-frequency solid state lasers such as diode lasers, diode-pumped solid state, and fiber lasers. Ultrasensitive, highly selective, and real-time measurements of several important atmospheric trace gases, including carbon monoxide, nitrous oxide, carbon dioxide, formaldehyde [correction of formaldehye], and methane, have been demonstrated.
Mid-infrared difference-frequency generation source pumped by 1.1-1.5 micrometer dual-wavelength fiber amplifier for trace-gas detection
Continuous-wave mid-infrared radiation near 3.5 micrometers is generated by difference-frequency mixing of the output of a compact 1.1-1.5 micrometer dual-wavelength fiber amplifier in periodically poled LiNbO3. The diode side-pumped amplifier is constructed with double-cladding Yb-doped fiber followed by single-mode Er/Yb codoped fiber. Output powers of as much as 11 microW at 3.4 micrometers are obtained, and spectroscopic detection of CH4 and H2CO is demonstrated. c 1998 Optical Society of America.