Search NASA⌕ Search

SEARCH · Search NASA

Results for “Beam sensitive”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Alignment apparatus using a laser having a gravitationally sensitive cavity reflector

A description is given of a device for determining a true gravitational vertical. The apparatus is composed of a vertically disposed laser with a gravitationally sensitive lower regeneration reflector. The reflector enables an output beam to be developed only when the optical axis of the laser is disposed normal to the gravitationally sensitive reflective surface. In an alternative embodiment, the devices is combined with a servo system to provide a gravitationally stabilized horizontal platform.

Billman, K. W.↗
NASA NTRS1974

Study of multiple hologram recording in lithium niobate

The results of detailed experimental and theoretical considerations relating to multiple hologram recording in lithium niobate are reported. The following problem areas are identified and discussed: (1) the angular selectivity of the stored holograms, (2) interference effects due to the crystal surfaces, (3) beam divergence effects, (4) material recording sensitivity, and (5) scattered light from material inhomogeneities.

Gaylord, T. K.↗
NASA NTRS1976

Some inconsistencies of the finite element method as applied to inelastic response

The inadequacy of a two noded beam-column element with a linear axial and a cubic transverse displacement field for inelastic analysis is demonstrated. For complete equilibrium satisfaction in the linear elastic range a three noded beam-column element is shown to be consistent. Next, the sensitivity of the inelastic response to numerical solutions of the inelastic response of a cantilever beam resulting from approximate integration of strain energy are brought out and finally, consequences of this on the nonlinear transient response of structures are considered.

Kamat, M. P.↗
NASA NTRS1976

Evaluation of clad scintillating light pipes

Arrays of fibers made of scintillating material were used as position-sensitive detectors or hodoscopes for beam-finding at ion accelerators. Experiments were made with alpha's from an Am241 source incident upon one end of the fiber, the other end being viewed with a photomultiplier tube. The scintillation light was not detected in any of the fibers tested beyond about 5 cm. The effective useful lengths for detection of relativistic heavy ions were given.

Source record↗
NASA NTRS1984

Far-infrared sources in the vicinity of the supernova remnant W28

The W28 supernova remnant molecular cloud complex has been surveyed in the 40-250 micron spectral range with a three-sigma sensitivity of 100-165 Jy per beam. Only two sources have been found. One, located near the center of the SNR, has a luminosity of 54,000 solar luminosities and can be identified with the thermal radio source G6.6-0.1. The energizing source is probably an O-type ZAMS star. The second source, which is near the boundary of the SNR at a sharp gradient of OH absorption, has a luminosity of 6000 solar luminosities and has no radio counterpart. It is best explained as a B1 ZAMS star or a pre-main sequence object presumably formed from the impact of an expanding SNR with a molecular cloud. No far-IR emission is observed at the position of the CO molecular cloud, which seems to have been impacted by the SNR.

Odenwald, S. F.↗
NASA NTRS1986

Two complimentary methods for aligning linear arrays

Two approaches are presented for implementing a simple method for aligning the object and image planes of linear arrays of elemental detectors. Both variants begin by firing a laser beam into cubic beamsplitters which change the direction of the resulting parallel beams to one perpendicular to the array. A neutral density filter is located along the beam path and an optical microscope is located beyond the exit plane of the beamsplitters. In the first variant, the beam is tuned to the spectral sensitivity of the elements. In the second version, a lens and a microscope are situated outside the exit plane of the beamsplitters, and spectral tuning is unnecessary. Subsequent rotations of the array are shown to reveal the coincidence or lack of coincidence of the image plane and the linear array.

Finkel, Mitchell W.↗
NASA NTRS1989

Position-And-Direction Sensor For Light Beams

Optoelectronic sensor measures both position and direction of incidence of laser beam or other narrow beam of light. New sensor part of robotic welding system in which laser beam reflected from pool of molten metal and monitored by lateral-position sensor. To provide unambiguous measurement of both lateral position and direction of incident beam, sensor includes two position-sensitive photodetectors or linear arrays of photodetectors.

Smith, Matthew A.↗
NASA NTRS1990

Energy input and HI spin temperatures in low pressure regions

Two recent (unpublished) HI emission/absorption studies carried out with good sensitivity using the Arecibo 21 cm beam are discussed. One study (Colgan, Salpeter and Terzian) looked for high velocity clouds of our own Galaxy in absorption in the directions of 63 of the brightest continuum sources reachable with the Arecibo telescope. HI emission mapping in the neighborhood of these directions was also carried out. The other study (Corbelli and Schneider) looked for absorption along lines of sight to about 50 weaker sources which pass within a few diameters of nearby disk galaxies. Neither study detected any absorption.

Corbelli, E.↗
NASA NTRS1992

Gamma-ray bursts and radio pulsar glitches

Upper limits to gamma-ray fluxes produced in conjunction with a radio pulsar glitch are presented. The glitch occurred on the Vela pulsar on December 24, 1988 and was the first to be observed as it occurred. Sensitive gamma-ray burst detectors aboard the Phobos 2 spacecraft were operating at this time, but recorded no significant burst at the time of the glitch. It is concluded that if a gamma-ray burst was generated in the energy range to which the Phobos detectors were sensitive, and if it was not beamed away from the spacecraft, the efficiency of glitch energy conversion into gamma-rays could not have exceeded 10 exp -4.

Hartmann, D.↗
NASA NTRS1992

Self-sensing piezoelectric actuation - Analysis and application to controlled structures

Issues related to modeling and implementation of a self-sensing piezoelectric actuator are investigated. The necessary formulation for modeling the simultaneous sensing and actuation phenomenon is provided. Open and closed loop experiments performed on a cantilevered beam test specimen are described. The sensitivity of the results to representative errors introduced in the implementation of the transducer is demonstrated analytically and experimentally. The self-sensing actuator is also implemented using an active piezoelectric strut in a truss structure.

Anderson, Eric H.↗
NASA NTRS1993

The road to the Deep Space Network

The history and current status of the NASA Deep Space Network, a system of 13 antennas of various designs and sizes located around the world to stay in continuous contact with spacecraft out to the edge of the solar system, are reviewed. A major step in the evolution of the Deep Space Network is considered to be the installation of 210-ft-diameter antennas to support sophisticated spacecraft sending data at higher rate back to earth at Goldstone in 1966 and at Tidbinbilla and Robledo de Chevala in 1973. New 340-meter multifrequency beam-waveguide antenna, in which weather sensitive microwave components were to be put in an equipment room, was installed for research and development at Goldstone in 1990.

Waff, Craig B.↗
NASA NTRS1994

Design and evaluation of an electromagnetic beam waveguide for measuring electrical properties of materials

A beam waveguide was designed that is based upon the propagation characteristics of the fundamental Gaussian beam and the focusing properties of spherical dielectric lenses. The 20-GHz, two-horn, four-lens system was constructed and experimentally evaluated by probing the field in a plane perpendicular to the beam axis at the center of the beam waveguide system. The critical parameters were determined by numerical sensitivity studies, and the lens-horn critical spacing was adjusted to better focus the beam at the probe plane. The measured performance was analyzed by consideration of higher order Gaussian-Laguerre beam modes. The beam waveguide system was successfully used in the measurements of the electromagnetic transmission properties of Shuttle thermal-protection tiles while the tile surface was being heated to reentry-level temperatures with a high-power laser.

Bailey, M. C.↗
NASA NTRS1999

High-power continuous-wave mid-infrared radiation generated by difference frequency mixing of diode-laser-seeded fiber amplifiers and its application to dual-beam spectroscopy

We report the generation of up to 0.7 mW of narrow-linewidth (<60-MHz) radiation at 3.3 micrometers by difference frequency mixing of a Nd:YAG-seeded 1.6-W Yb fiber amplifier and a 1.5-micrometers diode-laser-seeded 0.6-W Er/Yb fiber amplifier in periodically poled LiNbO3. A conversion efficiency of 0.09%/W (0.47 mWW-2 cm-1) was achieved. A room-air CH4 spectrum acquired with a compact 80-m multipass cell and a dual-beam spectroscopic configuration indicates an absorption sensitivity of +/-2.8 x 10(-5) (+/-1 sigma), corresponding to a sub-parts-in-10(9) (ppb) CH4 sensitivity (0.8 ppb).

Non-NASA Center↗
NASA NTRS1989

On the accuracy of shape sensitivity derivatives

Six methods for calculating shape sensitivity derivatives are compared for a two-material beam problem with a moving interface. It is found that as the finite-element mesh is refined, displacement sensitivity derivatives converge more slowly than the displacement themselves. Five of the methods agree fairly well, but the adjoint variational surface method provides substantially different results. However, the difference is found to reflect convergence from another direction to the same answer, rather than reduced accuracy.

Haftka, Raphael T.↗
NASA NTRS2001

LISA Telescope Sensitivity Analysis

The results of a LISA telescope sensitivity analysis will be presented, The emphasis will be on the outgoing beam of the Dall-Kirkham' telescope and its far field phase patterns. The computed sensitivity analysis will include motions of the secondary with respect to the primary, changes in shape of the primary and secondary, effect of aberrations of the input laser beam and the effect the telescope thin film coatings on polarization. An end-to-end optical model will also be discussed.

Waluschka, Eugene↗
NASA NTRS2000

Limits on Arcminute Scale Cosmic Microwave Background Anisotropy with the BIMA Array

We have used the Berkeley-Illinois-Maryland-Association (BIMA) millimeter array outfitted with sensitive cm-wave receivers to search for Cosmic Microwave Background (CMB) anisotropies on arcminute scales. The interferometer was placed in a compact configuration which produces high brightness sensitivity, while providing discrimination against point sources. Operating at a frequency of 28.5 GHz, the FWHM primary beam of the instrument is 6.6 arcminutes. We have made sensitive images of seven fields, five of which where chosen specifically to have low IR dust contrast and be free of bright radio sources. Additional observations with the Owens Valley Radio Observatory (OVRO) millimeter array were used to assist in the location and removal of radio point sources. Applying a Bayesian analysis to the raw visibility data, we place limits on CMB anisotropy flat-band power Q_flat = 5.6 (+3.0, -5.6) uK and Q_flat < 14.1 uK at 68% and 95% confidence. The sensitivity of this experiment to flat band power peaks at a multipole of l = 5470, which corresponds to an angular scale of approximately 2 arcminutes The most likely value of Q_flat is similar to the level of the expected secondary anisotropies.

Holzapfel, W. L.↗
NASA NTRS1992

Single mode variable-sensitivity fiber optic sensors

We review spatially-weighted optical fiber sensors that filter specific vibration modes from one dimensional beams placed in clamped-free and clamped-clamped configurations. The sensitivity of the sensor is varied along the length of the fiber by tapering circular-core, dual-mode optical fibers. Selective vibration mode suppression on the order of 10 dB was obtained. We describe experimental results and propose future extensions to single mode sensor applications.

Murphy, K. A.↗