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At least 1,783 records · Page 99

All sources NASA NTRS DOE OSTI

NASA NTRS2004

A Boresight Adjusment Mechanism For Use in Laser Altimeters

This paper describes the development of the Boresight Adjustment Mechanism (BAM) for the Geoscience Laser Altimeter System (GLAS) Instrument. The BAM was developed late in the integration and test phase of the GLAS instrument flight program. Thermal vacuum tests of the GLAS instrument indicated that the instrument-boresight alignment stability over temperature may be marginal. To reduce the risk that GLAS may not be able to meet the boresight alignment requirements an intensive effort was started to develop a BAM. Observatory-level testing and further evaluation of the boresight alignment data indicated that sufficient margin could be obtained utilizing existing instrument resources and therefore the BAM was never integrated onto the GLAS Instrument. However, the BAM was designed fabricated and fully qualified over a 4 month timeframe to be capable of precisely steering (less than 2 arcsec over plus or minus 300 arcsec) the output of three independent lasers to ensure the alignment between the transmit and receive paths of the GLAS instrument. The short timeline for the development of the mechanism resulted in several interesting design solutions. This paper discusses the requirement definition design, and testing processes of the BAM development effort how the design was affected by the extremely tight development schedule and the lessons learned throughout the process.

Hakun, Claef↗

NASA NTRS2004

Poco Graphite Inc. SuperSiC 0.25m Mirror Cryogenic Test Result

SuperSiC, a low areal density material, developed by POCO Graphite, have been used as mirror substrate for high energy lasers, laser radar systems, surveillance, telescopes, scan mirrors and satellites. SuperSiC has excellent thermal properties and cryogenic stability. It exhibits exceptional polishability for reflective optics with high strength, stiffness, and excellent thermal conductivity. A lightweighted 0.2-diameter polished SuperSic mirror was tested at cryogenic temperature at NASMSFC. Optical test results showed 6nm cry0 deformation from ambient to 30 degrees Kelvin and little to no change in its surface figure due to cry0 cycling.

Eng, Ron↗

DOE OSTI2014

System and method for laser assisted sample transfer to solution for chemical analysis

A system and method for laser desorption of an analyte from a specimen and capturing of the analyte in a suspended solvent to form a testing solution are described. The method can include providing a specimen supported by a desorption region of a specimen stage and desorbing an analyte from a target site of the specimen with a laser beam centered at a radiation wavelength (.lamda.). The desorption region is transparent to the radiation wavelength (.lamda.) and the sampling probe and a laser source emitting the laser beam are on opposite sides of a primary surface of the specimen stage. The system can also be arranged where the laser source and the sampling probe are on the same side of a primary surface of the specimen stage. The testing solution can then be analyzed using an analytical instrument or undergo further processing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1984

Airborne laser topographic mapping results

The results of terrain mapping experiments utilizing the National Aeronautics and Space Administration (NASA) Airborne Oceanographic Lidar (AOL) over forested areas are presented. The flight tests were conducted as part of a joint NASA/U.S. Army Corps of Engineers (CE) investigation aimed at evaluating the potential of an airborne laser ranging system to provide cross-sectional topographic data on flood plains that are difficult and expensive to survey using conventional techniques. The data described in this paper were obtained in the Wolf River Basin located near Memphis, TN. Results from surveys conducted under winter 'leaves off' and summer 'leaves on' conditions, aspects of day and night operation, and data obtained from decidous and coniferous tree types are compared. Data processing techniques are reviewed. Conclusions relative to accuracy and present limitations of the AOL, and airborne lidar systems in general, to terrain mapping over forested areas are discussed.

Krabill, W. B.↗

DOE OSTI2025

Additive Manufacturing of Fe-based Alloys for Nuclear Reactor Environments

This report is a Milestone 2 deliverable in FY2025, under work package MT-25AN090211 to support research and qualification activities supported by the Advanced Materials and Manufacturing Technologies (AMMT) program. It provides an update on the work done on the laser based additive manufacturing of steels for nuclear applications, conducted collaboratively by Argonne National Laboratory and Pacific Northwestern National Laboratory. Building upon FY23 and FY24 efforts, the focus of FY25 includes continued optimization of process parameters for the alloys: A709 & G92. The work package also includes fabricating test samples to conduct a thorough microstructural analysis and perform preliminary mechanical testing. The major accomplishments of this work package are summarized below, applicable to both Laser Powder Bed Fusion (LPBF) processes conducted at Argonne National Laboratory and Laser Powder Directed Energy Deposition (LP-DED) processes conducted at Pacific Northwest National Laboratory.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

NASA NTRS1984

Fundamental Equations of the LIF Hydroxyl Measurements, Appendix a

The equation relating OH concentration to the observed detector count rate for a given laser flux is defined. That equation, which will be referred to henceforth as the central equation for absolute sensitivity, will be cast in terms of standard spectroscopic quantities such as oscillator strengths, Hoenl-London factors, rotational and vibrational quantum numbers, etc., such that it may be tested directly under laboratory conditions. The working expressions used by each of the OH laser induced fluorescence (LIF) groups will be related to this central equation, thereby establishing a common language for the comparison of experimental results and the definition of LIF system performance. The relevant structural details of the OH radical via a spectroscopic description of the energy levels and transitions employed in the LIF method are detailed. The central equation relating observed count rate to absolute concentration will be derived, and that equation will be related to the observed quantities cited by each of the experimental groups engaged in the measurement of OH in the Earth's atmosphere.

Source record↗

NASA NTRSDate not supplied

High-Speed Visualization of Spray Breakup and Velocity Estimation in a Rotating Detonation Combustor Using Laser Induced Fluorescence

The underlying physical processes that liquid fuel sprays undergo in rotating detonation engines, particularly breakup and combustion, are not well understood nor are the coupling effects between the detonation and the spray. In this work, a single liquid jet of liquid fuel is inserted into a hydrogen-air RDC in order to study repetitive-one way coupled detonation interactions. High speed laser induced fluorescence of Jet-A at 300 kHz is used to visualize the dynamic processes inside the RDC for up to 10 ms per test. The employed imaging schemes allowed for unique insight into the spreading of liquid fuel in the azimuthal-axial directions via volumetric laser illumination. The Jet-A velocity field was estimated using OpenOpticalFlow and the impulse events observed colloquially agree with prior work on this test platform.

Instrumentation↗

NASA NTRSDate not supplied

High-Speed Visualization of Spray Breakup and Velocity Estimation in a Rotating Detonation Combustor Using Laser Induced Fluorescence

Instrumentation↗

NASA NTRS2007

Mobile CARS - IRS Instrument for Simultaneous Spectroscopic Measurement of Multiple Properties in Gaseous Flows

This paper describes a measurement system based on the dual-pump coherent anti-Stokes Raman spectroscopy (CARS) and interferometric Rayleigh scattering (IRS) methods. The IRS measurement is performed simultaneously with the CARS measurement using a common green laser beam as a narrow-band light source. The mobile CARS-IRS instrument is designed for the use both in laboratories as well as in ground-based combustion test facilities. Furthermore, it is designed to be easily transported between laboratory and test facility. It performs single-point spatially and temporally resolved simultaneous measurements of temperature, species mole fraction of N2, O2, and H2, and two-components of velocity. A mobile laser system can be placed inside or outside the test facility, while a beam receiving and monitoring system is placed near the measurement location. Measurements in a laboratory small-scale Mach 1.6 H2-air combustion-heated supersonic jet were performed to test the capability of the system. Final setup and pretests of a larger scale reacting jet are ongoing at NASA Langley Research Center s Direct Connect Supersonic Combustor Test Facility (DCSCTF).

Bivolaru, Daniel↗

DOE OSTI2019

Laser-driven collisionless shock accelerated ion beams (Final Report)

The major goal of the project was to study laser-driven collisionless shock ion acceleration.This acceleration mechanism has been demonstrated using CO 2 lasers, but the current state of the art CO 2 lasers cannot access peak normalized vector potentials of much greater than $a_0$ ~ 2. Therefore the favorable scalings of ion energies with $a_0$ observed using numerical modeling cannot be tested experimentally with these systems. Therefore this project is to develop an experimental platform to investigate laser-driven shock ion acceleration using 1.053 µm lasers, which can access extremely relativistic conditions, $a_0$ > 20. A near-critical cluster jet target was developed for studying this regime and the target was characterized under a number of conditions. This included a cooled cluster regime where a knife edge was used to achieve front-side scale lengths of < 60 µm. The experimental Tcubed facility was used to perform experiments and successfully measured accelerated protons in a narrow divergence beam. Particle-in-cell simulations have been performed to show shocks capable of ion acceleration can be produced. In contrast to the "ideal'' target scalelength profile described by Fiuza et al., where the electrons are strongly heated in a localized region near peak density, we show electron heating within the underdense region is rapid enough to enable collisionless shock formation. This is potentially good news for future experiments since it relaxes the strict, and difficult to assemble target requirements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2019

Design of a single-mode Rayleigh–Taylor instability experiment in the highly nonlinear regime

An experimental design, intended to investigate the evolution of the single mode Rayleigh–Taylor (RT) instability in the late time regime is proposed and theoretically analyzed. The goal of the experiment is to directly measure the evolution of the shape of the interface in time, for both low and high-Atwood numbers (A~0.0.15 and A~0.6). An objective of this study is to assess the degree to which, using 10-kJ-class lasers, one can expect to observe the predicted re-acceleration of the height of structures produced by RT, which occurs in low-A simulations. The specific design presented here shows no effects of x-ray preheat, and tolerable effects of 2D rarefactions. Observation of the reacceleration effect, at the 10-kJ scale, appears marginal for the design presented here. Finally, experiments could serve to test and validate the numerical results, and determine whether a larger-scale laser would be needed to actually observe the reacceleration effect.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Helium as a Surrogate for Deuterium in LPI Studies

Helium or neopentane can be used as surrogate gas fill for deuterium (D2) or deuterium-tritium (DT) in laser-plasma interaction studies. Surrogates are convenient to avoid flammability hazards or the integration of cryogenics in an experiment. To test the degree of equivalency between deuterium and helium, experiments were conducted in the Pecos target chamber at Sandia National Laboratories. Observables such as laser propagation and signatures of laser-plasma instabilities (LPI) were recorded for multiple laser and target configurations. It was found that some observables can differ significantly despite the apparent similarity of the gases with respect to molecular charge and weight. While a qualitative behaviour of the interaction may very well be studied by finding a suitable compromise of laser absorption, electron density, and LPI cross sections, a quantitative investigation of expected values for deuterium fills at high laser intensities is not likely to succeed with surrogate gases.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2013

Systems and methods for laser assisted sample transfer to solution for chemical analysis

Systems and methods are described for laser ablation of an analyte from a specimen and capturing of the analyte in a dispensed solvent to form a testing solution. A solvent dispensing and extraction system can form a liquid microjunction with the specimen. The solvent dispensing and extraction system can include a surface sampling probe. The laser beam can be directed through the surface sampling probe. The surface sampling probe can also serve as an atomic force microscopy probe. The surface sampling probe can form a seal with the specimen. The testing solution including the analyte can then be analyzed using an analytical instrument or undergo further processing.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2014

Systems and methods for laser assisted sample transfer to solution for chemical analysis

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Systems and methods for laser assisted sample transfer to solution for chemical analysis

47 OTHER INSTRUMENTATION↗

NASA NTRSDate not supplied

On the Use of Liquid Nitrogen Droplets as Flow Tracers in Cryogenic Flow Facilities at NASA Langley Research Center

The injection of liquid nitrogen droplets to cool the gas temperature in cryogenic wind tunnels is discussed as a method of natural seeding for velocimetry-focused, particle-based, laser diagnostics. Historical observations and issues with seeding are presented for both ground-test facilities of interest in this work at NASA Langley: the 0.3-m Transonic Cryogenic Wind Tunnel (TCT) and the National Transonic Facility (NTF). Recent observations of natural seeding with a Rayleigh scattering instrument are presented in the two facilities, which motivated the purposeful use of a pulse-burst laser system to observe the particles directly with a sequentially operated laser sheet for the first time. Time-resolved image sequences of unevaporated liquid nitrogen droplets were readily acquired for tunnel total temperatures of 200 K and below. The preliminary results promote a discussion on the fitness of these natural particles as flow tracers for either a particle image velocimetry or a particle tracking velocimetry instrument in these high-Reynolds-number facilities.

cryogenic wind tunnels↗

NASA NTRS1998

Mixing of Supersonic Streams

The Strutjet approach to Rocket Based Combined Cycle (RBCC) propulsion depends upon fuel-rich flows from the rocket nozzles and turbine exhaust products mixing with the ingested air for successful operation in the ramjet and scramjet modes. It is desirable to delay this mixing process in the air-augmented mode of operation present during low speed flight. A model of the Strutjet device has been built and is undergoing test to investigate the mixing of the streams as a function of distance from the Strutjet exit plane during simulated low speed flight conditions. Cold flow testing of a 1/6 scale Strutjet model is underway and nearing completion. Planar Laser Induced Fluorescence (PLIF) diagnostic methods are being employed to observe the mixing of the turbine exhaust gas with the gases from both the primary rockets and the ingested air simulating low speed, air augmented operation of the RBCC. The ratio of the pressure in the turbine exhaust duct to that in the rocket nozzle wall at the point of their intersection is the independent variable in these experiments. Tests were accomplished at values of 1.0, 1.5 and 2.0 for this parameter. Qualitative results illustrate the development of the mixing zone from the exit plane of the model to a distance of about 10 rocket nozzle exit diameters downstream. These data show the mixing to be confined in the vertical plane for all cases, The lateral expansion is more pronounced at a pressure ratio of 1.0 and suggests that mixing with the ingested flow would be likely beginning at a distance of 7 nozzle exit diameters downstream of the nozzle exit plane.

Hawk, C. W.↗

NASA NTRS1998

Mixing of Supersonic Streams

The Strutjet approach to Rocket Based Combined Cycle (RBCC) propulsion depends upon fuel-rich flows from the rocket nozzles and turbine exhaust products mixing with the ingested air for successful operation in the ramjet and scramjet modes. It is desirable to delay this mixing process in the air-augmented mode of operation present during low speed flight. A model of the Strutjet device has been built and is undergoing test to investigate the mixing of the streams as a function of distance from the Strutjet exit plane during simulated low speed flight conditions. Cold flow testing of a 1/6 scale Strutjet model is underway and nearing completion. Planar Laser Induced Fluorescence (PLIF) diagnostic methods are being employed to observe the mixing of the turbine exhaust gas with the gases from both the primary rockets and the ingested air simulating low speed, air augmented operation of the RBCC. The ratio of the pressure in the turbine exhaust duct to that in the rocket nozzle wall at the point of their intersection is the independent variable in these experiments. Tests were accomplished at values of 1.0, 1.5 and 2.0 for this parameter. Qualitative results illustrate the development of the mixing zone from the exit plane of the model to a distance of about 19 equivalent rocket nozzle exit diameters downstream. These data show the mixing to be confined in the vertical plane for all cases, The lateral expansion is more pronounced at a pressure ratio of 1.0 and suggests that mixing with the ingested flow would be likely beginning at a distance of 7 nozzle exit diameters downstream of the nozzle exit plane.

Hawk, C. W.↗