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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Property and microstructural nonuniformity in the yttrium-barium-copper-oxide superconductor determined from electrical, magnetic, and ultrasonic measurements

The purpose of this dissertation was the following: (1) to characterize the effect of pore fraction on a comprehensive set of electrical and magnetic properties for the yttrium-barium-copper-oxide (YBCO) high temperature ceramic superconductor; and (2) to determine the viability of using a room-temperature, nondestructive characterization method to aid in the prediction of superconducting (cryogenic) properties. The latter involved correlating ultrasonic velocity measurements at room temperature with property-affecting pore fraction and oxygen content variations. The use of ultrasonic velocity for estimating pore fraction in YBCO is presented, and other polycrystalline materials are reviewed, modeled, and statistically analyzed. This provides the basis for using ultrasonic velocity to interrogate microstructure. The effect of pore fraction (0.10-0.25) on superconductor properties of YBCO samples was characterized. Spatial (within-sample) variations in microstructure and superconductor properties were investigated, and the effect of oxygen content on elastic behavior was examined. Experimental methods used included a.c. susceptibility, electrical, and ultrasonic velocity measurements. Superconductor properties measured included transition temperature, magnetic transition width, transport and magnetic critical current density, magnetic shielding, a.c. loss, and sharpness of the voltage-current characteristics. An ultrasonic velocity image constructed from measurements at 1mm increments across a YBCO sample revealed microstructural variations that correlated with variations in magnetic shielding and a.c. loss behavior. Destructive examination using quantitative image analysis revealed pore fraction to be the varying microstructural feature.

Roth, Don J.↗
NASA NTRS1986

New measurements of photospheric magnetic fields in late-type stars and emerging trends

The magnetic fields of late-type stars are measured using the method of Saar et al. (1986). The method includes radiative transfer effects and compensation for line blending; the photospheric magnetic field parameters are derived by comparing observed and theoretical line profiles using an LTE code that includes line saturation and full Zeeman pattern. The preliminary mean active region magnetic field strengths (B) and surface area coverages for 20 stars are discussed. It is observed that there is a trend of increasing B towards the cooler dwarfs stars, and the linear correlation between B and the equipartition value of the magnetic field strength suggests that the photospheric gas pressure determines the photospheric magnetic field strengths. A tendency toward larger filling factors at larger stellar angular velocities is also detected.

Saar, S. H.↗
NASA NTRS2008

Advanced Active-Magnetic-Bearing Thrust-Measurement System

An advanced thrust-measurement system utilizes active magnetic bearings to both (1) levitate a floating frame in all six degrees of freedom and (2) measure the levitation forces between the floating frame and a grounded frame. This system was developed for original use in measuring the thrust exerted by a rocket engine mounted on the floating frame, but can just as well be used in other force-measurement applications. This system offers several advantages over prior thrust-measurement systems based on mechanical support by flexures and/or load cells: The system includes multiple active magnetic bearings for each degree of freedom, so that by selective use of one, some, or all of these bearings, it is possible to test a given article over a wide force range in the same fixture, eliminating the need to transfer the article to different test fixtures to obtain the benefit of full-scale accuracy of different force-measurement devices for different force ranges. Like other active magnetic bearings, the active magnetic bearings of this system include closed-loop control subsystems, through which the stiffness and damping characteristics of the magnetic bearings can be modified electronically. The design of the system minimizes or eliminates cross-axis force-measurement errors. The active magnetic bearings are configured to provide support against movement along all three orthogonal Cartesian axes, and such that the support along a given axis does not produce force along any other axis. Moreover, by eliminating the need for such mechanical connections as flexures used in prior thrust-measurement systems, magnetic levitation of the floating frame eliminates what would otherwise be major sources of cross-axis forces and the associated measurement errors. Overall, relative to prior mechanical-support thrust-measurement systems, this system offers greater versatility for adaptation to a variety of test conditions and requirements. The basic idea of most prior active-magnetic-bearing force-measurement systems is to calculate levitation forces on the basis of simple proportionalities between changes in those forces and changes in feedback-controlled currents applied to levitating electromagnetic coils. In the prior systems, the effects of gap lengths on fringing magnetic fields and the concomitant effects on magnetic forces were neglected. In the present system, the control subsystems of the active magnetic bearings are coupled with a computer-based automatic calibration system running special-purpose software wherein gap-length-dependent fringing factors are applied to current and magnetic-flux-based force equations and combined with a multipoint calibration method to obtain greater accuracy.

Imlach, Joseph↗
NASA NTRS1973

Further study of the theta component of the interplanetary magnetic field.

Measurements of the interplanetary magnetic field taken with Imp 3, Pioneer 6, and Explorer 34 constitute a large portion of the data available at low and moderate solar activity and provide nearly continuous coverage from mid-1965 through 1966 without radial effects. Study of these observations provides further evidence for the following B sub theta effect initially discovered with Mariners 2, 4, and 5. At low or moderate solar activity, the mean value of B sub theta is negative (approximately northward in the observations) above the solar equatorial plane and positive below it for an interplanetary field directed outward from the sun, and vice versa for an inward field. Thus, for an outward field, the r-theta component of a line of magnetic force above or below the equatorial plane was skewed relative to the average value of r in the direction away from the equatorial plane. Comparisons between different spacecraft are discussed.

Rosenberg, R. L.↗
NASA NTRS1979

High spatial resolution measurements of surface magnetic fields of the lunar frontside

Using 0.5 keV electron reflection measurements from real time tracking of the Apollo 15 and 16 Subsatellites the surface fields were mapped on the lunar frontside. Although the surface coverage is poor except near the Apollo 16 Subsatellite track, over 100 distinct regions of greater than 0.2 square degrees area with maximum surface field strength equal to or greater than 12 nT were identified. Preliminary contour maps of two of the largest regions and the Reiner Gamma region observed by the orbiting magnetometer are presented.

Lin, R. P.↗
DOE OSTI2024

First measurement in a magnetic confinement fusion experiment of the H 3 + H 3 → He 5 + n intermediate two-body resonant reaction

We report on the first experimental measurements made at a magnetic confinement fusion device of the tritium(T)-tritium(T) reaction T + T → He 4 + 2 n indicating the presence of the intermediate two-body resonant reaction T + T → He 5 + n . During the second deuterium-tritium campaign (DTE2) at the Joint European Torus, measurements of fusion plasmas with high tritium concentrations, n T / ( n T + n D ) ≈ 0.99 , heated with tritium neutral beam injection, were performed using the neutron time-of-flight (TOF) spectrometer TOFOR. We detect a peak in the neutron emission TOF spectrum consistent with the two-body resonant reaction. The TT neutron emission energy spectrum is modeled using an R -matrix framework where the distributions of the most likely model parameters given our experimental TOF data are determined utilizing a Markov chain Monte Carlo approach. We compare our best estimate of the T + T neutron emission energy spectrum with results obtained at inertial confinement fusion experiments at the OMEGA facility and find a spectral shape that is consistent with the energy dependency in the neutron spectrum observed at OMEGA. Published by the American Physical Society 2024

Physics↗
NASA NTRS1976

Measurements of solar magnetic fields by Fourier transform techniques. II - Saturated and blended lines

Fourier techniques have been exhaustively calibrated using Unno's (1956) results for the absorption profile of a simple Zeeman triplet. If a simple transformation is applied to the normalized line depths, then magnetic-field strengths and inclination angles can be measured very accurately from noisy saturated line profiles. Systematic errors caused by saturation effects can be estimated and reduced by varying one parameter. When a significant fraction of the line profile is unsplit and unpolarized, large errors may be made in measurements of low fields, unless the line is sufficiently weak. For a weak line, a vertical field of 1600 gauss can be measured to 10% accuracy even when 70% of the line profile is stray light. These stray-light errors are troublesome in measuring fields of gaps and pores but not sunspots. Numerical results of the error analysis are presented graphically.

Tarbell, T. D.↗
NASA NTRS1978

Measurements of the magnetic field orientation in the Jovian ionosphere deduced from Pioneer 10 and 11 scintillation observations

In this paper the S band scintillations observed during the Pioneer 10 and 11 occultation measurements of Jupiter are analyzed. It is found that while the electron density irregularities are isotropic in the collision-dominated lower ionosphere, they are anisotropic in the upper ionosphere because of alignment along the magnetic field. By using Rytov's approximation the frequency spectrum of the log-amplitude scintillations is derived for a wave propagating in an anisotropic turbulent medium. It is shown that the spectrum depends to a large extent on the direction of anisotropy and is therefore useful for measuring the orientation of the magnetic field in regions that have not yet been probed by direct measurements. This new technique is applied to the Pioneer 10 and 11 observations, and is used to deduce the first measurements of magnetic field orientation in the ionosphere of Jupiter.

Woo, R.↗
DOE OSTI2021

Local measurement of internal magnetic field fluctuations in high-performance tokamaks

This is the final report for DOE Grant DE-FG02-08ER54984. The overall goal of this project was to develop the cross-polarization scattering (CPS) diagnostic to measure core localized magnetic turbulence in fusion research devices. Section 1 provides a brief overview of project objectives and accomplishments. Section 2 gives a more detailed description of the Project accomplishments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2006

Magnetic-Field-Response Measurement-Acquisition System

A measurement-acquisition system uses magnetic fields to power sensors and to acquire measurements from sensors. The system alleviates many shortcomings of traditional measurement-acquisition systems, which include a finite number of measurement channels, weight penalty associated with wires, use limited to a single type of measurement, wire degradation due to wear or chemical decay, and the logistics needed to add new sensors. Eliminating wiring for acquiring measurements can alleviate potential hazards associated with wires, such as damaged wires becoming ignition sources due to arcing. The sensors are designed as electrically passive inductive-capacitive or passive inductive-capacitive-resistive circuits that produce magnetic-field-responses. One or more electrical parameters (inductance, capacitance, and resistance) of each sensor can be variable and corresponds to a measured physical state of interest. The magnetic-field- response attributes (frequency, amplitude, and bandwidth) of the inductor correspond to the states of physical properties for which each sensor measures. For each sensor, the measurement-acquisition system produces a series of increasing magnetic-field harmonics within a frequency range dedicated to that sensor. For each harmonic, an antenna electrically coupled to an oscillating current (the frequency of which is that of the harmonic) produces an oscillating magnetic field. Faraday induction via the harmonic magnetic fields produces an electromotive force and therefore a current in the sensor. Once electrically active, the sensor produces its own harmonic magnetic field as the inductor stores and releases magnetic energy. The antenna of the measurement- acquisition system is switched from a transmitting to a receiving mode to acquire the magnetic-field response of the sensor. The rectified amplitude of the received response is compared to previous responses to prior transmitted harmonics, to ascertain if the measurement system has detected a response inflection. The "transmit-receive-compare" of sequential harmonics is repeated until the inflection is identified. The harmonic producing the amplitude inflection is the sensor resonant frequency. Resonant frequency and response amplitude are stored and then correlated to calibration data.

Woodward, Stanley E.↗
DOE OSTI2020

Cryogenic goniometer for measurements in pulsed magnetic fields fabricated via additive manufacturing technique

Complex high-precision mechanical devices can be fabricated using 3-dimensional printing technology with the help of computer-aided design. Using 3D stereolithography, we have constructed a cryogenic goniometer for measurements in pulsed magnetic fields of up to 100 T, at temperatures as low as 0.5 K. We review the properties of several materials tested in developing the goniometer and report on its design and performance. The goniometer allows samples to be rotated in situ to a precision of 0.2 deg, so that the field can be applied at many different angles to the samples’ symmetry directions. Following its success, we establish that 3D printing is now a viable technology for pulsed-field and other cryogenic probes.

3D printing↗
NASA NTRS1965

Magnetometer measures orthogonal components of magnetic fields

Driven magnetometer accurately measures the components of a low strength magnetic field in each of three mutually perpendicular directions. To accomplish this, it employs the principle of magnetic resonance in optically pumped rubidium vapor.

Source record↗
NASA NTRS1985

Measurements of Solar Vector Magnetic Fields

Various aspects of the measurement of solar magnetic fields are presented. The four major subdivisions of the study are: (1) theoretical understanding of solar vector magnetic fields; (3) techniques for interpretation of observational data; and (4) techniques for data display.

Hagyard, M. J.↗
NASA NTRS1975

Measurements of solar magnetic fields by Fourier transform techniques. I - Unsaturated lines

If the basic profile shapes of the normal Zeeman triplet do not have zeros in their Fourier transform, the magnetic field splitting can be determined independent of the profile shape. When the ratio of the splitting of the components is greater than the intrinsic FWHM of the component profiles, the magnetic splitting can be determined with significantly greater accuracy than the measurement accuracy of the original profile. For Gaussian shaped components and a ratio of magnetic splitting to FWHM of 1.5, the noise reduction factor is 25.

Title, A. M.↗
DOE OSTI2022

Phasing Magnet for CSX-2 Beamline at NSLS-II

A phasing magnet has been developed at National Synchrotron Light Source II (NSLS-II) for the Coherent Soft X-ray Scattering (CSX) beamline. The phasing magnet will be located at the center of the straight section in between two identical and independent variably polarized APPLE-II devices. Based on Permanent Magnet technology, the phasing magnet has been designed to achieve the required electron beam delay to properly adjust the phase matching of these two consecutive EPUs (Elliptically Polarizing Undulators) and ensure a positive interference between the photon beam emitted in each device. Also this paper will describe the mechanical and magnetic design together with the final field measurements and magnetic tuning results. Also, the spectral performance of the two EPUs and the method used to properly set the field strength of the phasing magnet for any given radiation wavelength and polarization mode will be presented as well.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Electrical, optical, and magnetic properties of amorphous yttrium iron oxide thin films and consequences for non-local resistance measurements

We present magnetic characterization, charge resistivity, and optical photoluminescence measurements on amorphous yttrium iron oxide thin films ( ⁠a-Y–Fe–O), with supporting comparisons to amorphous germanium (⁠ a-Ge) films. We measured magnetic properties with both SQUID magnetometry and polarized neutron reflectometry. These results not only confirm that a-Y–Fe–O is a disordered magnetic material with strong predominantly antiferromagnetic exchange interactions and a high degree of frustration, but also that it is best understood electrically as a disordered semiconductor. As with amorphous germanium, a-Y–Fe–O obeys expectations for variable-range hopping through localized electron states over a wide range of temperature. We also clarify the consequences of charge transport through such a semiconducting medium for non-local voltage measurements intended to probe spin transport in nominally insulating magnetic materials. We further compare non-local resistance measurements made with “quasi-dc” automated current reversal to ac measurements made with a lock-in amplifier. These show that the “quasi-dc” measurement has an effective ac current excitation with frequency up to approximately 22 Hz, and that this effective ac excitation can cause artifacts in these measurements including incorrect sign of the non-local resistance. Here, this comprehensive investigation of non-local resistance measurements in a-Y–Fe–O shows no evidence of spin transport on micrometer length scales, which is contrary to our original work, and in line with more recent investigations by other groups.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗