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Samples of 1% Pt/SnO2 catalyst were exposed to a stoichiometric gas mixture of 1% CO and 1.2% O2 in helium over a range of flowrates from 5 to 15 sccm and temperatures from 338 to 394 Kelvin. Reaction rate constants for the catalytic oxidation of carbon monoxide and their temperature dependence were determined and compared with previous literature values.
The laser materials processing facility and its capabilities are described. A CO2 laser with continuous wave, repetitive pulse, and shaped power-time cycles is employed. The laser heated crystal growth station was used to produce metal and metal oxide single crystals and for cutting and shaping experiments using Si3N4 to displace diamond shaping processes.
Laser microprobe facility is effective in the elemental analysis of small areas of heterogeneous samples. The instrument uses the focused beam of a pulsed laser to evaporate a small volume of material from a relatively massive sample.
Experience from lunar and satellite laser ranging experiments carried out at McDonald Observatory has been used to design the McDonald Laser Ranging Station (MLRS). The MLRS is a dual-purpose installation designed to obtain observations from the LAGEOS satellite and lunar targets. The instruments used at the station include a telescope assembly 0.76 meters in diameter; a Q-switched doubled neodymium YAG laser with a pulse rate of three nanoseconds; and a GaAs photodetector with Fabry-Perot interferometric filter. A functional diagram of the system is provided. The operating parameters of the instruments are summarized in a table.
Technical specifications, performance, and applications of the NASA transportable laser ranging systems (TLRS-1 and -2) for use in the Crustal Dynamics Program are described. TLRS-1 is truck-mounted, with the laser deployed through the roof. Interacting with the LAGEOS satellite, TLRS has a photoelectric receiver for gathering data on the roundtrip time of the laser beam for calculations of the range gate. The laser has a 0.1 nsec pulse at 3.5 mJ/pulse. Range is measured to within an error of 9 cm. The TLRS-2 version is configured for ease of air transport and modular breakdown and assembly. It has been activated on Easter Island. TLRS-3 and -4 are in development to serve as mobile units in South America and the Mediterranean area.
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A laser Doppler velocimeter (LDV) was used to determine the flow conditions downstream of an annular cascade of stator blades operating at an exit critical velocity ratio of 0.87. Two modes of LDV operation (continuous scan and discrete point) were investigated. Conventional pressure probe measurements were also made for comparison with the LDV results. Biasing errors that occur in the LDV measurement of velocity components were also studied. In addition, the effect of pressure probe blockage on the flow conditions was determined with the LDV. Photographs and descriptions of the test equipment used are given.
Characteristic modulation detected, enabling rejection of multimode signals. Monitoring circuit senses multiple longitudinal mode oscillation of transversely excited, atmospheric-pressure (TEA) CO2 laser. Facility developed for inclusion into coherent detection laser radar (LIDAR) system. However, circuit described of use in any experiment where desireable to record data only when laser operates in single longitudinal mode.
A computer controlled laser based characterization facility used for detailed studies of silicon photodetectors and spectral response measurement on silicon solar cell is described. The power in the laser beam is measured with respect to electrical standards using an electrically calibrated pyroelectric radiometer.
The presence and importance of polycyclic aromatic hydrocarbons (PAHs, a large family of organic compounds containing carbon and hydrogen) in the interstellar medium has already been well established. The Astrochemistry Laboratory at NASA Ames Research Center (under the direction of Louis Allamandola and Scott Sandford) has been the center of pioneering work in performing spectroscopy on these molecules under simulated interstellar conditions, and consequently in the identification of these species in the interstellar medium by comparison to astronomically obtained spectra. My project this summer was twofold: (1) We planned on obtaining absorption spectra of a number of PAHs and their cations in cold (4K) Ne matrices. The purpose of these experiments was to increase the number of different PAHs for which laboratory spectra have been obtained under these simulated interstellar conditions; and (2) I was to continue the planning and design of a new laser facility that is being established in the Astrochemistry laboratory. The laser-based experimental set-up will greatly enhance our capability in examining this astrophysically important class of compounds.
Solar cells have been used to convert sunlight to electrical energy for many years and also offer great potential for non-solar energy conversion applications. Their greatly improved performance under monochromatic light compared to sunlight, makes them suitable as photovoltaic (PV) receivers in laser power beaming applications. Laser beamed power to a PV array receiver could provide power to satellites, an orbital transfer vehicle, or a lunar base. Gallium arsenide (GaAs) and indium phosphide (InP) solar cells have calculated efficiencies of more than 50 percent under continuous illumination at the optimum wavelength. Currently high power free-electron lasers are being developed which operate in pulsed conditions. Understanding cell behavior under a laser pulse is important in the selection of the solar cell material and the laser. An experiment by NAsA lewis and JPL at the AVLIS laser facility in Livermore, CA presented experimental data on cell performance under pulsed laser illumination. Reference 5 contains an overview of technical issues concerning the use of solar cells for laser power conversion, written before the experiments were performed. As the experimental results showed, the actual effects of pulsed operation are more complicated. Reference 6 discusses simulations of the output of GaAs concentrator solar cells under pulsed laser illumination. The present paper continues this work, and compares the output of Si and GaAs solar cells.
Methods of modeling some of the dynamic effects involved in laser beam propagation through the atmosphere are addressed with emphasis on the development of simple but accurate models which are readily implemented in a physical optics code. A space relay system with a ground based laser facility is considered as an example. The modeling of such characteristic phenomena as laser output distribution, flat and curved mirrors, diffraction propagation, atmospheric effects (aberration and wind shear), adaptive mirrors, jitter, and time integration of power on target, is discussed.
A closed-cycle, continuous wave, carbon dioxide high power laser has been designed and fabricated to support research for the identification and evaluation of possible high power laser applications. The device is designed to generate up to 70 kW of laser power in annular shape beams from 1 to 9 cm in diameter. Electric discharge, either self sustained or electron beam sustained, is used for excitation. This laser facility provides a versatile tool on which research can be performed to advance the state-of-the-art technology of high power CO2 lasers in such areas as electric excitation, laser chemistry, and quality of output beams. The facility provides a well defined, continuous wave beam for various application experiments, such as propulsion, power conversion, and materials processing.
A laser particulate spectrometer (LPS) system was developed to measure the size and speed distributions of particulate contaminants. Detection of the particulates is achieved by means of light scattering and extinction effects using a single laser beam to cover a size range of 0.8 to 275 microns diameter and a speed range of 0.2 to 20 meters/second. The LPS system was designed to operate in the high-vacuum environment of a space simulation chamber with cold shroud temperatures ranging from 77 to 300 K.
We present an update on our research on collision avoidance using photon-pressure induced by ground-based lasers. In the past, we have shown the general feasibility of employing small orbit perturbations, induced by photon pressure from ground-based laser illumination, for collision avoidance in space. Possible applications would be protecting space assets from impacts with debris and stabilizing the orbital debris environment. Focusing on collision avoidance rather than de-orbit, the scheme avoids some of the security and liability implications of active debris removal, and requires less sophisticated hardware than laser ablation. In earlier research we concluded that one ground based system consisting of a 10 kW class laser, directed by a 1.5 m telescope with adaptive optics, could avoid a significant fraction of debris-debris collisions in low Earth orbit. This paper describes our recent efforts, which include refining our original analysis, employing higher fidelity simulations and performing experimental tracking tests. We investigate the efficacy of one or more laser ground stations for debris-debris collision avoidance and satellite protection using simulations to investigate multiple case studies. The approach includes modeling of laser beam propagation through the atmosphere, the debris environment (including actual trajectories and physical parameters), laser facility operations, and simulations of the resulting photon pressure. We also present the results of experimental laser debris tracking tests. These tests track potential targets of a first technical demonstration and quantify the achievable tracking performance.
The NASA Lewis Research Center has designed and fabricated a closed-cycle, continuous wave (CW), carbon dioxide (CO2) high-power laser to support research for the identification and evaluation of possible high-power laser applications. The device is designed to generate up to 70 kW of laser power in annular-shape beams from 1 to 9 cm in diameter. Electric discharge, either self-sustained or electron-beam-sustained, is used for excitation. This laser facility can be used in two ways. First, it provides a versatile tool on which research can be performed to advance the state-of-the-art technology of high-power CO2 lasers in such areas as electric excitation, laser chemistry, and quality of output beams, all of which are important whether the laser application is government or industry oriented. Second, the facility provides a well-defined, continuous wave beam for various application experiments, such as propulsion, power conversion, and materials processing.
Transitions of the type 2s-2p in the oxygenlike ions Y XXXII, Zr XXXIII, and Nb XXXIV were identified in spectra recorded at the University of Rochester's Omega laser facility. Solid targets were spherically irradiated by 24 beams of frequency-tripled (351-nm) Nd-glass laser radiation. The spectra were photographed with a 3-m grazing-incidence spectrograph. The identified transitions of the oxygenlike ions are in the range 30 to 73 A. The wavelengths for the magnetic-dipole transitions within the 2s2p4 ground configurations of these ions are predicted from the experimental energy levels.