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  • INSTRUMENTATION AND PHOTOGRAPHY
  • 1995-1999  (17)
  • 1975-1979  (269)
  • 1
    Publication Date: 2011-08-17
    Description: Described in detail is a laser induced fluorescence system which has been successfully interfaced with two aircraft sampling platforms (i.e., Sabreliner jet and an L-188C Electra). This system, which has been under development for four years, presently consists of the following major components: (1) a Nd-Yag laser driven oscillator-amplifier dye laser; (2) a sampling manifold with associated fluorescence detection optics; (3) an OH calibration chamber; (4) a laser beam steering assembly; and (5) sampling electronics and data processing hardware. During the last three years, this system has been flown some 50,000 air miles making tropospheric OH radical measurements over the latitude range of 70 N to 57 S. OH concentrations measured during these flights have ranged from 30 parts-per-quadrillion (3.7 x 10 to the 5th molecules/sq cm) at altitudes of 6 km to 0.8 parts-per-trillion (2.0 x 10 to the 7th molecules/sq cm) at 0.5 km. Computations have been completed which indicate that the existing aircraft system with modest modifications should also be capable of detecting natural tropospheric levels of NO, SO2, CH2O, NO2, HNO2, NO3, H2O2 and CS2 by using both conventional laser-induced fluorescence methodology and multiphoton techniques.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 50; Dec. 197
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  • 2
    Publication Date: 2019-06-27
    Description: Measurements obtained with laser velocimetry in a Mach 2.9 separated turbulent boundary layer and in the transonic flow past a two-dimensional airfoil section are presented and compared to data realized by conventional techniques. Agreement in mean velocities was realized where the pressure measurements could be considered reliable; however, in regions of instantaneous reverse velocities, the laser results were found to be consistent with the physics of the flow whereas the pressure data were not. Streamwise turbulence intensities are also presented. In the transonic airfoil study, velocity measurements obtained immediately outside the upper surface boundary layer of a 6-inch chord NACA 64A010 airfoil are compared to edge velocities inferred from surface pressure measurements. For free-stream Mach numbers of 0.6 and 0.8, the agreement in results was very good. "Dual scatter" optical arrangements in conjunction with a single particle, counter-type signal processor were employed in these investigations.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-X-73117 , A-6510
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-27
    Description: The response of a tungsten-scintillator ionization spectrometer to accelerated particle beams has been investigated. Results obtained from exposure of the approx. 1000 g/sq cm apparatus to 5, 10, and 15 GeV/c electrons and pions as well as to 2.1 GeV/nucleon C-12 and O-16 ions are presented. These results include cascade-development curves, fractions of the primary energy measured by the spectrometer, and resolutions of the apparatus for measuring the primary energies. For 15 GeV/c electrons, an average of about 82% of the incident energy is measured by the apparatus with resolution (normal standard deviation) of about 6%. For 15 GeV/c pions, an average of about 65% of the incident energy is measured with resolution of about 18%. The energy resolution improves with increasing energy and with increasing depth of the spectrometer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Nuclear Instruments and Methods; 126; 1975
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  • 4
    Publication Date: 2019-06-27
    Description: A simple technique for single-scan T1 measurements in solids is proposed and analyzed for single exponential spin-lattice relaxation. In this technique, the direct spin heating caused by the sampling process is significantly reduced in comparison with conventional techniques by utilizing the 'solid echo' to refocus the magnetization. The applicability of this technique to both the solid and liquid phases is demonstrated.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 49; Aug. 197
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  • 5
    Publication Date: 2019-06-27
    Description: The problems of developing large-area, gas-scintillation proportional counters with high resolution are considered. It is found that simple large-area, parallel-grid proportional counters suffer from a variation in gain over the counter window. Some success has been achieved in overcoming this problem by focusing the charge cloud as it drifts into the multiplication region. Measurements are reported for various mixtures of argon and xenon as well as pure xenon.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 6
    Publication Date: 2019-07-13
    Description: Wind tunnel investigations of a shock-induced separated flow and the flow about a two-dimensional airfoil section at transonic speeds using laser velocimetry techniques are described. Laser velocimeter data are presented and compared with conventional pressure type measurements (pitot and static pressure probe measurements for the shock-induced separation, and surface pressure measurements for the two-dimensional airfoil section). In addition to these data comparisons, a simple optical arrangement for the incorporation of a Bragg cell in a laser velocimeter system is described. The effects of particle concentration gradients within a turbulent boundary layer on laser velocimeter measurements are also demonstrated.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Minnesota Symposium on Laser Anemometry; Oct 22, 1975 - Oct 24, 1975; Bloomington, MN
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  • 7
    Publication Date: 2019-07-13
    Description: The laser-induced fluorescence technique for obtaining direct measurements of atmospheric OH and other gases is described. A narrow-band UV laser is tuned to one or more of the electronic absorption bands of a specified molecule so as to cause fluorescence from a bonding excited electronic state. The monitored wavelength is longer than the laser wavelength. Equipment, specifics for OH detection, data processing, and interference are discussed, and application of the technique to the detection of NO, SO2, and CH2O is considered.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Symposium on Meteorological Observations and Instrumentation; Apr 10, 1978 - Apr 14, 1978; Denver, CO
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  • 8
    Publication Date: 2006-02-22
    Description: The measurement capabilities of laser velocimetry and holographic interferometry in transonic airfoil testing were demonstrated. Presented are representative results obtained with these two nonintrusive techniques on a 15.24 cm chord airfoil section. These results include the density field about the airfoil, flow angles in the inviscid flow and viscous flow properties including the turbulent Reynolds stresses. The accuracies of the density fields obtained by interferometry were verified from comparisons with surface pressure and laser velocimeter measurements.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Langley Res. Center Advanced Technol. Airfoil Res., Vol. 1, Pt. 2; p 589-599
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  • 9
    Publication Date: 2006-01-12
    Description: A water vapor radiometer (WVR) was developed that measures the atmospheric noise temperature at two different frequencies near 22 GHz. These noise temperature are used in empirical-theoretical equations that yield tropospheric range delay, in centimeters, through the atmosphere along the beam of the WVR. This range correction is then applied, as needed, to measurements concerning spacecraft range and to VLBI baseline determinations. The WVR design and calibration techniques are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: The Deep Space Network; p 129-135
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  • 10
    Publication Date: 2011-08-16
    Description: Two designs of plastic scintillation counters with an area of 2 sq m scanned in each case by a single photomultiplier of the FEU-49 type are described. The radial dependence of their light collection at the place of the path of the detected particle does not exceed 10% while the half width of the differential distribution of the pulse amplitudes from nonfiltered cosmic radiation at sea level is 90 to 95%, and 65%, the plastic thickness being 5 cm and 10 cm, respectively. The temperature coefficient of the counter is 0.32% per 1 C.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Cosmic Rays (NASA-TT-F-807); p 389-393
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