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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.

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At least 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Upgrade of DIII-D radial interferometer–polarimeter for large bandwidth, low noise, and toroidal mode number measurements

Near ion-cyclotron frequency (f ci ) fluctuations, such as those originating from Global and Compressional Alfvén Eigenmodes (GAEs/CAEs), are expected to be present in future fusion reactors but are not well understood due to the limited availability of core measurements in present-day tokamaks. The measurement bandwidth of the Radial Interferometer–Polarimeter (RIP) diagnostic has been upgraded from 1 to 5 MHz to detect these fluctuations in DIII-D. RIP adopts the three-wave technique for simultaneous polarimetric and interferometric measurements. Solid-state microwave sources operating at 650 GHz are used as probe beams and provide 5 MHz bandwidth for both polarimetric and interferometric measurements. Bandwidths of related hardware, including mixer amplifier, signal cable, and digital phase demodulator, are increased correspondingly. Measurement noise is minimized by reducing the time delay between reference and probe signals to nanosecond level and employing correlation-based techniques. Using the upgraded diagnostic, CAE/GAE-like bursting fluctuations are observed in neutral-beam heated plasmas with toroidal magnetic field B φ ≈ 1 T. Current upgrades being undertaken would enable the evaluation of toroidal mode number for these modes. Furthermore, this work opens the possibility of better understanding near ion-cyclotron frequency fluctuations in fusion relevant plasmas.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Measurement of the work statistics of an open quantum system using a quantum computer

Abstract We report on the experimental measurement of the work statistics of a genuinely open quantum system using a quantum computer. Such measurement has remained elusive thus far due to the inherent difficulty in measuring the total energy change of a system-bath compound (which is the work) in the open quantum system scenario. We overcome this difficulty by applying the interferometric scheme, originally conceived for closed systems, to the open system case and implement it on a superconducting quantum computer, taking advantage of the relatively high levels of noise on current quantum hardware to realize an open quantum system. We demonstrate that the method can be used as a diagnostic tool to probe physical properties of the system-bath compound, such as its temperature and specific transition frequencies in its spectrum. Our experiments corroborate that the interferometric scheme is a promising tool to achieve the long-sought experimental validation of the Jarzynski equality for arbitrary open quantum systems.

Oftelie, Lindsay Bassman (ORCID:0000000335421553)↗
DOE OSTI2024

Experimental evidence for the two-path description of neutron spin echo

Here, we describe an experiment that strongly supports a two-path interferometric model in which the spin-up and spin-down components of each neutron propagate coherently along spatially separated parallel paths in a typical neutron spin-echo small-angle scattering (SESANS) experiment. Specifically, we show that the usual semi-classical, single-path treatment of Larmor precession of a polarized neutron in an external magnetic field predicts a damping as a function of the spin-echo length of the SESANS signal obtained with a periodic phase grating when the transverse width of the neutron wave packet is finite. However, no such damping is observed experimentally, implying either that the Larmor model is incorrect or that the transverse extent of the wave packet is very large. In contrast, we demonstrate theoretically that a quantum-mechanical interferometric model in which the two mode-entangled (i.e., intraparticle entangled) spin states of a single neutron are separated in space when they interact with the grating accurately predicts the measured SESANS signal, which is independent of the wave packet width.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measuring Black Hole Light Echoes with Very Long Baseline Interferometry

Light passing near a black hole can follow multiple paths from an emission source to an observer due to strong gravitational lensing. Photons following different paths take different amounts of time to reach the observer, which produces an echo signature in the image. The characteristic echo delay is determined primarily by the mass of the black hole, but it is also influenced by the black hole spin and inclination to the observer. In the Kerr geometry, echo images are demagnified, rotated, and sheared copies of the direct image and lie within a restricted region of the image. Echo images have exponentially suppressed flux, and temporal correlations within the flow make it challenging to directly detect light echoes from the total light curve. In this Letter, we propose a novel method to search for light echoes by correlating the total light curve with the interferometric signal at high spatial frequencies, which is a proxy for indirect emission. We explore the viability of our method using numerical general relativistic magnetohydrodynamic simulations of a near-face-on accretion system scaled to M87-like parameters. We demonstrate that our method can be used to directly infer the echo delay period in simulated data. An echo detection would be clear evidence that we have captured photons that have circled the black hole, and a high-fidelity echo measurement would provide an independent measure of fundamental black hole parameters. Our results suggest that detecting echoes may be achievable through interferometric observations with a modest space-based very long baseline interferometry mission.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1973

A holographic interferometer system for measuring density profiles in high-velocity flows

This paper describes a holographic interferometric technique for obtaining density measurements across a test gas that is traveling at a velocity of over 5500 m/sec in an expansion tube facility. Interferometric data describing the flow in the test section are obtained using a long coherence length CW argon laser in a holographic system and a rotating drum camera recorder. The object beam, which passes through the test section, intersects the reference beam at a small angle to form an interference pattern of about 170 lines/mm, and is recorded as a hologram. Before a test, this hologram is placed in its original position and rotated slightly so that an interference pattern is generated by the intersection of the reconstructed and real-time object beams.

Burner, A. W.↗
NASA NTRS1977

Zernike test. I - Analytical aspects. II - Experimental aspects

The Zernike phenomenon is interpreted in general interferometric terms to gain insight into the optimum design of disks suitable for a particular experimental situation. The design of Zernike disks for measuring small low-order aberrations is considered and evaluated; optimum parameters for disks 2, 3, 4, and 5 microns in radius are determined for an f/12 large-space-telescope system with an obscuration ratio of 0.4 at 0.6 micron. It is shown that optimization in this case provides sensitivities of better than one hundredth of a wavelength for the measurement of low-order aberrations. The procedure for manufacturing a Zernike disk is then described in detail, and results are reported for tests of a laboratory Zernike figure sensor containing a disk manufactured according to this procedure. In the tests, a laboratory wavefront-error simulator was used to introduce small aberration ranges, measurements of the changes in reimaged pupil intensity introduced by the disk were made for several aberration settings, and the measured changes were compared with the values predicted by the interferometric theory of Zernike tests. The results are found to agree within an error of one two-hundredth of a wavelength.

Golden, L. J.↗
NASA NTRS1980

Experimental techniques for determination of the role of diffusion and convection in crystal growth from solution

Various studies of the concentration of the solution around a growing crystal using interferometric techniques are reviewed. A holographic interferometric technique used in laboratory experiments shows that a simple description of the solution based on the assumption of a purely diffusive mechanism appears inadequate since the convection, effective even in reduced columns, always affects the growth.

Zefiro, L.↗
NASA NTRS1980

Geodetic positioning using a global positioning system of satellites

Geodetic positioning using range, integrated Doppler, and interferometric observations from a constellation of twenty-four Global Positioning System satellites is analyzed. A summary of the proposals for geodetic positioning and baseline determination is given which includes a description of measurement techniques and comments on rank deficiency and error sources. An analysis of variance comparison of range, Doppler, and interferometric time delay to determine their relative geometric strength for baseline determination is included. An analytic examination to the effect of a priori constraints on positioning using simultaneous observations from two stations is presented. Dynamic point positioning and baseline determination using range and Doppler is examined in detail. Models for the error sources influencing dynamic positioning are developed. Included is a discussion of atomic clock stability, and range and Doppler observation error statistics based on random correlated atomic clock error are derived.

Fell, P. J.↗
NASA NTRS1982

Orbit determination of geosynchronous satellites by VLBI and differential VLBI

Four approaches to radio interferometric tracking of geosynchronous satellites are analyzed and compared. Quasar-based differential very-long-baseline interferometry, which requires a very sensitive receiver, can achieve meter-level position accuracy with a two-baseline system. Satellite-based differential VLBI gives somewhat lower accuracy with a compact, inexpensive receiver. Nondifferential VLBI, using less precise media and clock calibrations obtained by observing the GPS satellites, still gives 5-10 m position accuracy with two baselines. For a sufficiently inclined orbit, all interferometric approaches can yield six-component satellite state from a single baseline.

Yunck, T. P.↗
NASA NTRS1983

Stress studies in EFG

Stress distributions were calculated for a creep law to predict a rate of plastic deformation. The expected reduction in stresses is obtained. Improved schemes for calculating growth system temperature distributions were evaluated. Temperature field modeling examined the possibility of using horizontal temperature gradients to influence stress distribution in ribbon. The defect structure of 10 cm wide ribbon grown in the cartridge system was examined. A new feature is identified from an examination of cross sectional micrographs. It consists of high density dislocation bands extending through the ribbon thickness. A four point bending apparatus was constructed for high temperature study of the creep response of silicon, to be used to generate defects for comparison with as grown defects in ribbon. The feasibility of laser interferometric techniques for sheet residual stress distribution measurement is examined. The mathematical formalism for calculating residual stress from changes in surface topology caused by an applied stress in a rectangular specimen was developed, and the system for laser interferometric measurement to obtain surface topology data was tested on CZ silicon.

Source record↗
NASA NTRS1983

Simultaneous dual baseline differential VLBI

Attention is drawn to the benefits of simultaneous dual baseline radio interferometric measurements for low altitude planetary orbiter navigation. The radio interferometric data types constitute a valuable addition to conventional tracking data in the establishment of orbit-plane orientation, thanks to their measurement of inertial reference cross-track velocity. The present results show that only a few Delta-VLBI measurements, taken at either end of a conventional tracking arc, suffice for the realization of a positional accuracy of better than 1 km for the case of a Venus Orbiting Imaging Radar-type planetary orbiter. This is comparable to Deep Space Net accuracies, despite the use of a shorter baseline.

Mohan, S. N.↗
NASA NTRS1982

Benchmark notch test for life prediction

Aircraft gas turbine engine components are subjected to severe stress, temperature, and environmental conditions. Economic and reliabilty demands have prompted inordinate effort in development of analytic methods to predict stresses and strains in aircraft engines. There remains, however, the need to check or verify these analytical methodologies against actual experimental data measurements. The laser interferometric strain displacement gage was recognized as having the potential to accomplish this task and was employed in this program. The actual strains incurred at the root of a discontinuity in cyclically loaded test samples subjected to inelastic deformation at high temperature where creep deformation readily occur were measured. The steady-state, cyclic stress-strain response at the root of the discontinuity in the tested samples was analyzed for comparison with the measured results. A comprehensive set of local notch root strain measurements for a variety of load patterns in an Inconel 718 notch specimen at 649 C (1200 F) was obtained and documented using the laser interferometric strain displacement gage.

Domas, P. A.↗
NASA NTRS1985

A comparison of electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry for flow measurements

Electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry are compared as methods for the accurate measurement of refractive index and density change distributions of phase objects. Experimental results are presented to show that the two methods have comparable accuracy for measuring the first derivative of the interferometric fringe shift. The phase object for the measurements is a large crystal of KD*P, whose refractive index distribution can be changed accurately and repeatably for the comparison. Although the refractive index change causes only about one interferometric fringe shift over the entire crystal, the derivative shows considerable detail for the comparison. As electronic phase measurement methods, both methods are very accurate and are intrinsically compatible with computer controlled readout and data processing. Heterodyne moire is relatively inexpensive and has high variable sensitivity. Heterodyne holographic interferometry is better developed, and can be used with poor quality optical access to the experiment.

Decker, A. J.↗
NASA NTRS1983

Closed-loop strain controlled testing at elevated temperatures with a non-contacting gage

Normal strains were measured over a 100 micron gage length at a distance of 50 microns from the edge of a notch using a non-contacting, laser-based interferometric technique. Tests were performed at 600 C under direct strain control from this interferometric 'micro-gage'. A minicomputer system, that produced a voltage analog of strain as a final output, controlled the strain measuring apparatus. This analog output was used directly as the feedback signal to a closed-loop, electrohydraulic mechanical test system. This allowed both strain rate and strain amplitude to be controlled at the notch root of the specimen.

Martin, J. F.↗
NASA NTRS1985

A comparison of electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry for flow measurements

Electronic heterodyne moire deflectometry and electronic heterodyne holographic interferometry are compared as methods for the accurate measurement of refractive index and density change distributions of phase objects. Experimental results are presented to show that the two methods have comparable accuracy for measuring the first derivative of the interferometric fringe shift. The phase object for the measurements is a large crystal of KD P, whose refractive index distribution can be changed accurately and repeatably for the comparison. Although the refractive index change causes only about one interferometric fringe shift over the entire crystal, the derivative shows considerable detail for the comparison. As electronic phase measurement methods, both methods are very accurate and are intrinsically compatible with computer controlled readout and data processing. Heterodyne moire is relatively inexpensive and has high variable sensitivity. Heterodyne holographic interferometry is better developed, and can be used with poor quality optical access to the experiment.

Decker, A. J.↗
NASA NTRS1986

Feasibility of mapping solution properties during the growth of protein crystals

This paper summarizes the feasibility of using optical techniques for mapping the convection, temperature, and solute concentration in the solution around a growing protein crystal. Convection can be mapped by a variety of techniques which measure either refractive index differences, displacements, velocity, or solute optical absorption. For protein crystal growth, however, ordinary schlieren and interferometric techniques are marginally sensitive and most displacement marking techniques unsuitable; therefore, phase-concentration by the absorption-interferometric technique appears to be quite feasible for protein solutions because of their low dn/dC. Finally, the monitoring of protein crystal growth rates appears to be feasible by double-exposure holography or birefringence.

Shlichta, P. J.↗
NASA NTRS1987

Interferogram analysis using Fourier transform techniques

A method of interferogram analysis is described in which Fourier transform techniques are used to map the complex fringe visibility in several types of interferograms. Algorithms are developed for estimation of both the amplitude and the phase of the fringes (yielding the modulus and the phase of the holographically recorded object Fourier transform). The algorithms were applied to the reduction of interferometric seeing measurements (i.e., the estimation of the fringe amplitude only), and the reduction of interferometric tests (i.e., estimation of the fringe phase only). The method was used to analyze scatter-plate interferograms obtained at NOAO.

Roddier, Claude↗
NASA NTRS1988

Radar Detects Ocean Surface Currents

Interferometric system uses reflections from ripples. Experimental airborne interferometric synthetic-aperture radar system measures line-of-sight component of velocity of ripples on surface of ocean. With help of suitable assumptions about relationships among ripples, larger waves or swells on which they occur, and overall movement of water, component of velocity of underlying surface current perpendicular to path of airplane deduced.

Goldstein, R. M.↗