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Investigation with an interferometer of the turbulent mixing of a free supersonic jet

Description: The free turbulent mixing of a supersonic jet of Mach number 1.6 has been experimentally investigated. An interferometer, of which a description is given, was used for the investigation. Density and velocity distributions through the mixing zone have been obtained. It was found that there was similarity in distribution at the cross sections investigated and that, in the subsonic portion of the mixing zone, the velocity distribution fitted the theoretical distribution for incompressible flow. It was found that the rates of spread of the mixing zone both into the jet and into the ambient air were less than those of subsonic jets.
Date: January 21, 1949
Creator: Gooderum, Paul B.; Wood, George P. & Brevoort, Maurice J.
Partner: UNT Libraries Government Documents Department

A theory and method for applying interferometry to the measurement of certain two-dimensional gaseous density fields

Description: Report presenting a theory and method for the application of interferometry to the measurement of certain two-dimensional gaseous density fields. The theory includes the effects of optical refraction on the observed interference pattern.
Date: April 1952
Creator: Howes, Walton L. & Buchele, Donald R.
Partner: UNT Libraries Government Documents Department

Investigation of a diffraction-grating interferometer for use in aerodynamic research

Description: Report presenting a description of a low-cost interferometer that is easy to adjust and has a large field of view. The instrument uses small diffraction gratings to produce and recombine separate beams of light. The usual two-parabolic-mirror schileren system can be converted inexpensivley to a diffraction-grating interferometer.
Date: November 1952
Creator: Sterrett, James R., Jr. & Erwin, John R.
Partner: UNT Libraries Government Documents Department

An investigation of supersonic turbulent boundary layers on slender bodies of revolution in free flight by use of a Mach-Zehnder interferometer and shadowgraphs

Description: Report presenting a study of slender bodies of revolution in free flight at Mach numbers 3.2 and 3.6, which were photographed and analyzed to obtain the turbulent-boundary-layer density distributions for the case of a body surface that is cold compared to recovery temperature. Results regarding density profiles, density distributions, comparison with the Crocco equation, calculation of the heat-transfer rate, and observations of the turbulent-boundary-layer image structure from shadowgraphs, and relation the interferometer results are provided.
Date: September 1958
Creator: Seiff, Alvin & Short, Barbara J.
Partner: UNT Libraries Government Documents Department

Influence of refraction on the applicability of the Zehnder-Mach interferometer to studies of cooled boundary layers

Description: Report presenting an analytical investigation to determine the applicability of the Zehnder-Mach interferometer to two-dimensional cooled-boundary-layer studies. The main factor governing a test section design other than flow characteristics is the estimate of how close to the wall the boundary layer need be studied.
Date: September 1951
Creator: Kinsler, Martin R.
Partner: UNT Libraries Government Documents Department

A New Simple Interferometer for Obtaining Quantitatively Evaluable Flow Patterns

Description: "The method described in the present report makes it possible to obtain interferometer records with the aid of any one of the available Schlieren optics by the addition of very simple expedients, which fundamentally need not to be inferior to those obtained by other methods, such as the Mach-Zehnder interferometer, for example. The method is based on the fundamental concept of the phase-contrast process developed by Zernike, but which in principle has been enlarged to such an extent that it practically represents an independent interference method for general applications. Moreover, the method offers the possibility, in case of necessity, of superposing any apparent wedge field on the density field to be gauged" (p. 1).
Date: November 1953
Creator: Erdmann, S. F.
Partner: UNT Libraries Government Documents Department

Development and Construction of an Interferometer for Optical Measurements of Density Fields

Description: "A method of interference is described in the present report which promises profitable application in aeronautical research. The physical foundation of the method and a simple method of adjustment are briefly discussed. The special technical construction of the instrument is described which guarantees its use also in the case of vibrations of the surrounding space and permits the investigation of unsteady phenomena" (p. 1).
Date: September 1947
Creator: Zobel
Partner: UNT Libraries Government Documents Department

Interferometer With Large Working Field Utilizing Schlieren Optics

Description: Report describing the optical system of a new-type interferometer utilizing schileren optics. Using this instrument, former limits to the working-field size imposed by the practical size of conventional topics are removed. Testing using the interferometer occurred in the 18- by 18-inch supersonic tunnel.
Date: January 3, 1951
Creator: Buchele, Donald R. & Day, Pierce B.
Partner: UNT Libraries Government Documents Department

Tilt sensitivity of the two-grating interferometer

Description: Fringe formation in the two-grating interferometer is analyzed in the presence of a small parallelism error between the diffraction gratings assumed in the direction of grating shear. Our analysis shows that with partially coherent illumination, fringe contrast in the interference plane is reduced in the presence of nonzero grating tilt with the effect proportional to the grating tilt angle and the grating spatial frequencies. Our analysis also shows that for a given angle between the gratings there is an angle between the final grating and the interference plane that optimizes fringe contrast across the field.
Date: January 30, 2008
Creator: Anderson, Christopher N. & Naulleau, Patrick P.
Partner: UNT Libraries Government Documents Department

Effect of Wavefront Error on 10^-7 Contrast Measurements

Description: We have measured a contrast of 6.5 {center_dot} 10{sup -8} from 10-25{lambda}/D in visible light on the Extreme Adaptive Optics testbed using a shaped pupil for diffraction suppression. The testbed was designed with a minimal number of high-quality optics to ensure low wavefront error and uses a phase shifting diffraction interferometer for metrology. This level of contrast is within the regime needed for imaging young Jupiter-like planets, a primary application of high-contrast imaging. We have concluded that wavefront error, not pupil quality, is the limiting error source for improved contrast in our system.
Date: October 6, 2005
Creator: Evans, J W; Sommargren, G; Macintosh, B; Severson, S & Dillon, D
Partner: UNT Libraries Government Documents Department

Simultaneous interferometric optical-figure characterizations for two optical elements in series: Proposition of an unconventional numerical integration scheme

Description: The article proposes a scheme to break a catch-22 loop in an optical-figure/wavefont measurement. For instance, to measure the tilt-independent optical-figure of a nominal optical flat at cryogenic temperatures, it requires a cryogenic dewar-window system for a Fizeau interferometer outside the dewar to see through. The issue is: how to calibrate in situ the window system using the yet-to-be-calibrated nominal optical flat, and vice versa, in only one cryogenic cooldown? The proposition includes: (a) interferometric phase-map measurements with the test piece slightly offset in different transverse directions, and (b) for synthesizing the 2-dimensional WDF, an unconventional numerical scheme starting with 1-dimensional bi-direction integration. The numerical scheme helps minimize the non-uniformity in integrated noise-power distribution that results from integrating data, and thus the associated uncorrelated random noise, from raw phase-maps. The numerical scheme represents a new concept specifically for integrating noise-carrying experimental data.
Date: March 20, 2006
Creator: Gwo, D
Partner: UNT Libraries Government Documents Department

Spatial filter issues

Description: Experiments and calculations indicate that the threshold pressure in spatial filters for distortion of a transmitted pulse scales approximately as I{sup O.2} and (F{number_sign}){sup 2} over the intensity range from 10{sup 14} to 2xlO{sup 15} W/CM{sup 2} . We also demonstrated an interferometric diagnostic that will be used to measure the scaling relationships governing pinhole closure in spatial filters.
Date: December 9, 1996
Creator: Murray, J.E.; Estabrook, K.G.; Milam, D.; Sell, W.D.; Van Wonterghem, R.M.; Feil, M.D. et al.
Partner: UNT Libraries Government Documents Department

Alignment of the VISA Undulator

Description: The Visible-Infrared SASE Amplifier (VISA) undulator consists of four 99cm long segments. Each undulator segment is set up on a pulsed-wire bench, to characterize the magnetic properties and to locate the magnetic axis of the FODO array. Subsequently, the location of the magnetic axis, as defined by the wire, is referenced to tooling balls on each magnet segment by means of a straightness interferometer. After installation in the vacuum chamber, the four magnet segments are aligned with respect to themselves and globally to the beam line reference laser. A specially designed alignment fixture is used to mount one straightness interferometer each in the horizontal and vertical plane of the beam. The goal of these procedures is to keep the combined rms trajectory error, due to magnetic and alignment errors, to 50{micro}m.
Date: April 15, 1999
Creator: Ruland, Robert
Partner: UNT Libraries Government Documents Department