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Results for “Fabry–Perot interferometer”

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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At least 73 records · Page 4
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NASA NTRS1977

A shock tube study of line broadening in a temperature range of 6100 to 8300 K

Line widths of the Ca(II) 3968 A and Na(I) 5890 A resonance lines broadened by electric microfields in a plasma were measured. A pressure-driven shock tube was used as the light source. Radiation from the equilibrium region behind the reflected shock wave was studied using a rapid scanning Fabry-Perot interferometer. Electron and argon atom densities of about 8 x 10 to the 16th and 1 x 10 to the 19th/cu cm, respectively, were achieved at the relatively low temperature of around 7500 K by vaporizing a cesium powder that had been added to the shock tube as a solid aerosol in argon gas. The measured line widths were predominantly Stark broadened by the electrons and ions in the plasma, although Doppler, van der Waals, instrument function and optical depth effects had to be taken into account.

Baur, J. F.↗
NASA NTRS1977

Microwave absorption of oxygen measured with a Fabry-Perot spectrometer

A semiconfocal configuration of a Fabry-Perot interferometer is described, which can be used for measuring moderately weak absorption at a fixed microwave frequency as a function of pressure by measuring the change in the Q of the system when the gas is introduced. An accuracy of 0.3 dB/km at 58.82 GHz is achieved with just conventional laboratory equipment. The absorption need not be resonant, and can be determined as a function of such physical factors as pressure, temperature, and mixture composition. Oxygen absorption measurements support calculations based on theories of line overlap inside the oxygen absorption band at subatmospheric pressure.

Poon, R. K. L.↗
NASA NTRS1977

Galatry profile convolved with the Fabry-Perot instrument function

The physical conditions in laboratory gases and in the upper atmosphere of the planets, including earth, can be deduced from a measurement of the intensity and line profile of different radiating molecules. Because of the low pressures in the upper atmospheres, many molecular lines with small pressure-broadening coefficients are collisionally narrowed. These lines are resolvable with a Fabry-Perot interferometer. Analytical expressions are given relating the measured line intensity and profile to the true line intensity and profile. A deconvolution of the measured profile gives the parameters A, beta, and K characterizing the collisionally narrowed Galatry profile. General expressions for the nonideal interferometer are discussed, and, specifically, mirror defects and a limited detector aperture are treated.

Goorvitch, D.↗
NASA NTRS1977

An optically pumped submillimeter wavelength regenerative amplifier

An optically pumped regenerative submillimeter laser amplifier is described. The amplifier uses a waveguide cavity resonator, and a Fabry-Perot interferometer composed of two dielectric-coated mirrors serves as input and output port for the submillimeter signal. Use of two mirrors enabled obtaining variations of up to 6:1 in transmission by varying the mirror spacing. When the 373-micron transition in CH3CN is excited in the oscillator by the CO2 laser pump beam, the received signal with amplification is about nine times the unamplified signal.

Galantowicz, T. A.↗
NASA NTRS1977

Upper limit for CH/plus/ toward Tau Scorpii

A Fabry-Perot interferometer was used to measure a 2-sigma upper limit of 0.39 mA for CH(plus) toward Tau Sco, a line of sight with a large amount of atomic hydrogen yet only a small amount of molecular hydrogen. The upper limit for the abundance of CH(plus) in a region where hydrogen is primarily atomic shows that no unexpectedly rapid CH(plus) formation processes are occurring and, conversely, that the CH(plus) destruction rate is not smaller than expected. It is argued that either CH(plus) is primarily formed in regions with large amounts of H2 or CH(plus) is formed at least as rapidly as the density-cubes in regions where hydrogen is mostly atomic.

Jura, M.↗
NASA NTRS1977

A search for interstellar NaH in diffuse clouds

The paper reports on a search for the (8, 0) R(0) line of the A-X transition of NaH at 3990.88 A toward Zeta Oph and Sigma Sco, which was performed using a spectroscopic photoelectric imaging Fabry-Perot interferometer at the coude focus of a 2.2-m telescope. One-sigma upper limits on the NaH equivalent width are derived (0.26 mA for Zeta Oph and 0.69 mA for Sigma Sco), and two-sigma upper limits on the NaH column densities are obtained which imply that the formation rate for NaH cannot be large. It is noted that the latter upper limits are only about one order of magnitude higher than the most optimistic expectation of the NaH column density for formation of this molecule on grains.

Snow, T. P., Jr.↗
NASA NTRS1978

Analysis and design of optically pumped far infrared oscillators and amplifiers

A waveguide laser oscillator was designed and experimental measurements made of relationships among output power, pressure, pump power, pump frequency, cavity tuning, output beam pattern, and cavity mirror properties for various active gases. A waveguide regenerative amplifier was designed and gain measurements were made for various active gases. An external Fabry-Perot interferometer was fabricated and used for accurate wavelength determination and for measurements of the refractive indices of solids transparent in the far infrared. An electronic system was designed and constructed to provide an appropriate error signal for use in feedback control of pump frequency. Pump feedback from the FIR laser was decoupled using a vibrating mirror to phase modulate the pump signal.

Galantowicz, T. A.↗
NASA NTRS1977

Infrared instrumentation on NASA airborne observatories

Two airborne observatories operated above much of the earth's atmosphere are providing effective platforms for infrared astronomical observations. A summary is given of the wide variety of instrumentation currently in use and continuing to be developed for these facilities. The classes of instruments include various far infrared photometers, filter wheel and grating spectrometers, Fourier transform spectrometers, Michelson and Fabry-Perot interferometers, a polarimeter, and a microwave line receiver.

Boggess, N. W.↗
NASA NTRS1978

Compatibility of seasonal variations in mid-latitude thermospheric models at solar maximum and low geomagnetic activity

Satellite drag data, in situ mass spectrometer data, Fabry Perot interferometer data, and incoherent scatter data were used to produce models of the concentration of atomic oxygen and molecular nitrogen in the thermosphere and of the exospheric temperature. Incoherent scatter data from two stations near 45 deg N were used. The three techniques provide similar patterns for the annual variations of the atomic oxygen concentration at 400 km, and the mean annual temperatures are within 20 K of each other for five of the six models involved. Four of the models are in good agreement concerning the annual temperature variation. There is fair agreement between incoherent scatter models and mass spectrometer models for the N2 concentrations at 400 km but disagreement between these models and the satellite drag model. It is shown that most disagreements can be resolved by changing both the vertical temperature profile and the lower-thermosphere oxygen concentration in the direction indicated by previous incoherent scatter measurements.

Alcayde, D.↗
NASA NTRS1978

Studies in optical parallel processing

Threshold and A/D devices for converting a gray scale image into a binary one were investigated for all-optical and opto-electronic approaches to parallel processing. Integrated optical logic circuits (IOC) and optical parallel logic devices (OPA) were studied as an approach to processing optical binary signals. In the IOC logic scheme, a single row of an optical image is coupled into the IOC substrate at a time through an array of optical fibers. Parallel processing is carried out out, on each image element of these rows, in the IOC substrate and the resulting output exits via a second array of optical fibers. The OPAL system for parallel processing which uses a Fabry-Perot interferometer for image thresholding and analog-to-digital conversion, achieves a higher degree of parallel processing than is possible with IOC.

Lee, S. H.↗
NASA NTRS1971

A pressure scanning Fabry-Perot magnetometer.

Description of an oscillating magnetic analyzer (KDP crystal plus Glan-Thompson prism) coupled to an echelle-interferometer spectrograph, and of single-slit magnetometer which by pressure variations can be made to scan the entire profiles of the circularly and linearly polarized Zeeman components. Freon gas is used as the scanner gas with wavelength displacements of 0.02 A per 0.1 in. Hg pressure change at the NaD lines. The available scan range is 15 A in the visual spectral region.

Fay, T. D.↗