Laser interferometry and photon scattering in plasma diagnostics.
Laser interferometry and photon scattering in high temperature plasma diagnostics
ION TEMPERATURE↗
SEARCH · Search NASA
Results for “laser diagnostics”
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.
Demonstration of the feasibility of laser induced fluorescence for arc jet flow diagnostics
Laser Induced Fluorescence (LIF) studies are carried out on nitric oxide and oxygen molecules in the arc jet flows at the NASA Johnson Space Center Reentry Testing Facility. Measurements are taken in the free stream and from a blunt body shock layer. Tests are performed under different flow conditions to determine the feasibility and sensitivity of the LIF technique for various species. This is developed as a part of high enthalpy flow diagnostics and will be useful to elucidate the rotational and vibrational temperatures. Adequate sensitivity for the detection of O(2) and NO is demonstrated. Proposed improvements of the existing system are presented.
Arepalli, Sivaram↗
Tunable diode laser spectral diagnostic studies of a pressure modulator radiometer
The successful application of high-resolution tunable diode laser spectroscopy to the diagnostic measurement of a pressure modulator radiometer (PMR) is reported, and recorded line transmission profiles for a single N2O line at 1272/cm are presented. PMR measurements obtained for mean cell pressures of about 10, 20, and 30 Torr were found to be consistent with theoretical predictions. The validity of single-pressure and two-pressure approximation representations of the mean and modulated PMR transmission spectra has been verified.
May, Randy D.↗
Diagnostics of Laser Produced Plume Under Carbon Nanotube Growth Conditions
This paper presents diagnostic data obtained from the plume of a graphite composite target during carbon nanotube production by the double-pulse laser oven method. The insitu emission spectrum (300 to 650 nm) is recorded at different locations upstream of the target and at different delay times from the lasers (IR and green). Spectral features are identified as emissions from C2 (Swan System: a (sup 3)pi(sub g) - delta (sup 3)pi(sub u) and C3 (Comet Head System: A (sup 1)pi(sub u) - chi (sup 1)sigma(sub u) (sup +). Experimental spectra are compared with computed spectra to estimate vibrational temperatures of excited state C2 in the range of 2500 to 4000 kappa The temporal evolution of the 510 nm band of C2 is monitored for two target positions in various locations which shows confinement of the plume in the inner tube and increase in plume velocity with temperature. The excitation spectra of C2 are obtained by using a dye laser to pump the (0,1) transition of the Swan System and collecting the Laser Induced Fluorescence signal from C2 These are used to obtain "ground-state" rotational and vibrational temperatures which are close to the oven temperature. Images of the plume are also collected and are compared with the spectral measurements.
Arepalli, Sivaram↗
Study of plasma diagnostics using laser interferometry with emphasis on its application to cesium plasmas
Laser interferometer and heterodyne system for cesium plasma diagnostics
Lancashire, R. B.↗
Laser-Based Diagnostic Measurements of Low Emissions Combustor Concepts
This presentation provides a summary of primarily laser-based measurement techniques we use at NASA Glenn Research Center to characterize fuel injection, fuel/air mixing, and combustion. The report highlights using Planar Laser-Induced Fluorescence, Particle Image Velocimetry, and Phase Doppler Interferometry to obtain fuel injector patternation, fuel and air velocities, and fuel drop sizes and turbulence intensities during combustion. We also present a brief comparison between combustors burning standard JP-8 Jet fuel and an alternative fuels. For this comparison, we used flame chemiluminescence and high speed imaging.
Hicks, Yolanda R.↗
Laser applications in meteorology and earth and atmospheric remote sensing; Proceedings of the Meeting, Los Angeles, CA, Jan. 16-18, 1989
Various papers on laser applications in meteorology and earth and atmospheric remote sensing are presented. The individual topics addressed include: solid state lasers for the mid-IR region, tunable chromium lasers, GaInAsSb/AlGaAsSb injection lasers for remote sensing applications, development and design of an airborne autonomous wavemeter for laser tuning, fabrication of lightweight Si/SiC lidar mirrors, low-cost double heterostructure and quantum-well laser array development, nonlinear optical processes for the mid-IR region, simulated space-based Doppler lidar performance in regions of backscatter inhomogeneities, design of CO2 recombination catalysts for closed-cycle CO2 lasers, density measurements with combined Raman-Rayleigh lidar, geodynamics applications of spaceborne laser ranging, use of aircraft laser ranging data for forest mensuration, remote active spectrometer, multiwavelngth and triple CO2 lidars for trace gas detection, analysis of laser diagnostics in plumes, laser atmospheric wind sounder, compact Doppler lidar system using commercial off-the-shelf components, and preliminary design for a laser atmospheric wind sounder.
Sokoloski, Martin M.↗
Laser Raman diagnostics in subsonic and supersonic turbulent jet diffusion flames
Ultraviolet (UV) spontaneous vibrational Raman scattering combined with laser-induced predissociative fluorescence (LIPF) is developed for temperature and multi-species concentration measurements. Simultaneous measurements of temperature, major species (H2, O2, N2, H2O), and minor species (OH) concentrations are made with a 'single' narrow band KrF excimer laser in subsonic and supersonic lifted turbulent hydrogen-air diffusion flames. The UV Raman system is calibrated with a flat-flame diffusion burner operated at several known equivalence ratios from fuel-lean to fuel-rich. Temperature measurements made by the ratio of Stokes/anti-Stokes signal and by the ideal gas law are compared. The single shot measurement precision for concentration and temperature measurement is 5 to 10 pct. Calibration constants and bandwidth factors are determined from the flat burner measurements and used in a data reduction program to arrive at temperature and species concentration measurements. These simultaneous measurements of temperature and multi-species concentrations allow a better understanding of the complex turbulence-chemistry interactions and provide information for the input and validation of CFD models.
Cheng, T. S.↗
Remote sensing; Proceedings of the Meeting, Orlando, FL, Apr. 3, 4, 1986
Advances in optical technology for remote sensing are discussed in reviews and reports of recent experimental investigations. Topics examined include industrial applications, laser diagnostics for combustion research, laser remote sensing for ranging and altimetry, and imaging systems for terrestrial remote sensing from space. Consideration is given to LIF in forensic diagnostics, time-resolved laser-induced-breakdown spectrometry for rapid analysis of alloys, CARS in practical combustion environments, airborne inertial surveying using laser tracking and profiling techniques, earth-resources instrumentation for the EOS polar platform of the Space Station, and the SAR for EOS.
Menzies, Robert T.↗
Hypersonic Wake Diagnostics Using Laser Induced Fluorescence Techniques
A review of recent research performed in iodine that involves a two photon absorption of light at 193 nm will be discussed, and it's potential application to velocimetry measurements in a hypersonic flow field will be described. An alternative seed atom, Krypton, will be presented as a good candidate for performing nonintrusive hypersonic flow diagnostics. Krypton has a metastable state with a lifetime of approximately 43 s which would prove useful for time of flight measurement (TOF) and a sensitivity to collisions that can be utilized for density measurements. Calculations using modest laser energies and experimental values show an efficiency of excited state production to be on the order of 10(exp -6) for a two photon absorption at 193 nm.
Mills, Jack L.↗
HSCT Sector Combustor Evaluations for Demonstration Engine
In LET Task 10, critical development issues of the HSCT lean-burn low emissions combustor were addressed with a range of engineering tools. Laser diagnostics and CFD analysis were applied to develop a clearer understanding of the fuel-air premixing process and premixed combustion. Subcomponent tests evaluated the emissions and operability performance of the fuel-air premixers. Sector combustor tests evaluated the performance of the integrated combustor system. A 3-cup sector was designed and procured for laser diagnostics studies at NASA Glenn. The results of these efforts supported the earlier selection of the Cyclone Swirler as the pilot stage premixer and the IMFH (Integrated Mixer Flame Holder) tube as the main stage premixer of the LPP combustor. In the combustor system preliminary design subtask, initial efforts to transform the sector combustor design into a practical subscale engine combustor met with significant challenges. Concerns about the durability of a stepped combustor dome and the need for a removable fuel injection system resulted in the invention and refinement of the MRA (Multistage Radial Axial) combustor system in 1994. The MRA combustor was selected for the HSR Phase II LPP subscale combustor testing in the CPC Program.
Greenfield, Stuart↗
A piston-actuated shock-tube, with laser-Schlieren diagnostics
The essential construction features of a piston actuated shock tube are described, and its advantages relative to the conventional use of diaphragm ruptures for shock initiation are listed. Typical operational parameters are presented to illustrate the levels of reproducibility achieved. Tests with He and N2 drivers into about 99 percent Ar covered shock speeds from 1.539 +/- 0.002-0.8143 +/- 0.002 mm/microsec, corresponding to 2390-847 K incident shock temperatures. Application of this tube for recording postshock front density gradients of the endoergic dissociation of ethane and the exoergic condensation of iron atoms via the laser-Schlieren technique is described.
Hurst, S. M.↗
Dynamics and structure of turbulent premixed flames
In earlier work (Mantel & Bilger, 1994) the structure of the turbulent premixed flame was investigated using statistics based on conditional averaging with the reaction progress variable as the conditioning variable. The DNS data base of Trouve and Poinsot (1994) was used in this investigation. Attention was focused on the conditional dissipation and conditional axial velocity in the flame with a view to modeling these quantities for use in the conditional moment closure (CMC) approach to analysis of kinetics in premixed flames (Bilger, 1993). Two remarkable findings were made: there was almost no acceleration of the axial velocity in the flame front itself; and the conditional scalar dissipation remained as high, or higher, than that found in laminar premixed flames. The first finding was surprising since in laminar flames all the fluid acceleration occurs through the flame front, and this could be expected also for turbulent premixed flames at the flamelet limit. The finding gave hope of inventing a new approach to the dynamics of turbulent premixed flames through use of rapid distortion theory or an unsteady Bernoulli equation. This could lead to a new second order closure for turbulent premixed flames. The second finding was contrary to our measurements with laser diagnostics in lean hydrocarbon flames where it is found that conditional scalar dissipation drops dramatically below that for laminar flamelets when the turbulence intensity becomes high. Such behavior was not explainable with a one-step kinetic model, even at non-unity Lewis number. It could be due to depletion of H2 from the reaction zone by preferential diffusion. The capacity of the flame to generate radicals is critically dependent on the levels of H2 present (Bilger, et al., 1991). It seemed that a DNS computation with a multistep reduced mechanism would be worthwhile if a way could be found to make this feasible. Truly innovative approaches to complex problems often come only when there is the opportunity to work close at hand with the (in this case numerical) experimental data. Not only can one spot patterns and relationships in the data which could be important, but one can also get to know the limitations of the technique being used, so that when the next experiment is being designed it will address resolvable questions. A three-year grant from the Australian Research Council has enabled us to develop a small capability at the University of Sydney to work on DNS of turbulent reacting flow, and to analyze data bases generated at CTR. Collaboration between the University of Sydney and CTR is essential to this project and finding a workable modus operandum for this collaboration, given the constraints involved, has been a major objective of the past year's effort. The overall objectives of the project are: (1) to obtain a quantitative understanding of the dynamics of turbulent premixed flames at high turbulence levels with a view to developing improved second order closure models; and (2) to carry out new DNS experiments on turbulent premixed flames using a carefully chosen multistep reduced mechanism for the chemical kinetics, with a view to elucidating the laser diagnostic findings that are contrary to the findings for DNS using one-step kinetics. In this first year the objectives have been to make the existing CTR data base more accessible to coworkers at the University of Sydney, to make progress on understanding the dynamics of the flame in this existing CTR data base, and to carefully construct a suitable multistep reduced mechanism for use in a new set of DNS experiments on turbulent premixed flames.
Bilger, R. W.↗
Collisional quenching of atoms and molecules on spacecraft thermal protection surfaces
Preliminary results of a research program to determine energy partitioning in spacecraft thermal protection materials due to atom recombination at the gas-surface interface are presented. The primary focus of the research is to understand the catalytic processes which determine heat loading on Shuttle, Aeroassisted OTV, and NASP thermal protection surfaces in nonequilibrium flight regimes. Highly sensitive laser diagnostics based on laser-induced fluorescence and resonantly-enhanced multiphoton ionization spectroscopy are used to detect atoms and metastable molecules. At low temperatures, a discharge flow reactor is employed to measure deactivation/recombination coefficients for O-atoms, N-atoms, and O2. Detection methods are presented for measuring O-atoms, O2 and N2, and results for deactivation of O2 and O-atoms on reaction-cured glass and Ni surfaces. Both atom recombination and metastable product formation are examined. Radio-frequency discharges are used to produce highly dissociated beams of atomic species at energies characteristic of the surface temperature. Auger electron spectroscopy is employed as a diagnostic of surface composition in order to accurately define and control measurement conditions.
Marinelli, W. J.↗
Designing transonic wind-tunnel test sections for flow diagnostics and laser velocimeter applications
The design, fabrication, and validation of the Basic Aerodynamic Facility (BARF), developed for the direct comparison of three-dimensional laser velocimetry (LV) and hot-wire techniques at transonic speeds, are discussed. To accommodate the installation of the three-dimensional orthogonal LV system in the BARF, the transonic slots were redesigned to house windows, and the test section mounting was redesigned to facilitate LV transversing. Two-dimensional and three-dimensional code validation tests of the LV test section showed uniform mean flow through the test section to sonic speeds, and fluctuating pressure measurements at subsonic speeds which are consistent with facilities with good flow quality.
Jones, G. S.↗
Rayleigh Scattering Measurements in NASA Langley's Hypersonic Facilities
The charts used in a presentation on Rayleigh scattering measurements in a hypersonic wind tunnel are presented. These charts depict advanced two dimensional laser diagnostics and the ArF excimer laser setup used in the measurements.
Antcliff, Richard R.↗
A laser interferometer for highly transient plasma diagnostics
Modified laser Michelson interferometer for probing highly transient plasmas occurring behind incident shock waves in shock tubes
Rowley, P. D.↗
Multiphoton ionization of N2 by the third harmonic of a Nd:YAG laser - A new avenue for air diagnostics
Laser-induced N2 ionization is accomplished using a commercially available Nd:YAG laser, and confirmed by means of ion-collection and spectral measurements. Neutral N2 is excited by six photons of the third harmonic frequency, or 355 nm, and is transformed to an ionized state. The radiation at 355 nm is separated from the fundamental and frequency-doubled Nd:YAG radiation to guarantee monochromatic incident radiation. Intense lines near 391.4 nm are found in the initial laser polarization and for a 90-degree rotation of polarization. The radiation at 391.4 nm is associated with an incoherent laser-induced flourescence process related to an ionized-state transition, and increases quadratically with laser power. A 45-mJ laser pulse focused to a diameter of 17 microns can produce an ion concentration of 3.25 x 10 to the 13th ions/cu cm. The large ion concentration and robust fluorescence signal make this technique an efficient method for time-of-flight velocimetry and in-flight testing.
Laufer, Gabriel↗