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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Spectroscopic measurements of magnetic fields on solar-like stars - Techniques and results

This paper reviews the basic requirements for, and difficulties in, measuring magnetic fields on cool stars. The main types of the analysis methods are described, including methods that employ Fourier transforms; line profile models; the Mathys and Solanki (1989) method based on the difference between Fm and Fq (where Fm is the profile in nonmagnetic regions and Fq is the profile in magnetic regions); and the Basri and Marcy (1991) method based on the fact that, for optically thick lines, Zeeman splitting will increase a line's equivalent width of the Fq. The assumptions made in each case are examined and the results obtained are summarized.

Saar, Steven H.↗
NASA NTRS1982

Magsat data availability

It is pointed out that a new era in near-earth magnetic field measurements began with NASA's launch of Magsat in October 1979 into a twilight, sun-synchronous orbit with 96.76 deg inclination, 561-km apogee, and 352-km perigee. A cesium vapor and a fluxgate magnetometer were employed to measure the magnetic field. A measurement of the spacecraft attitude to 20 arcseconds was required to achieve 6 nT (nanotesla) accuracy in the component measurements. This was accomplished with the aid of two star cameras on board the spacecraft and a sun sensor attached to the vector magnetometer. Magsat remained in orbit until June 11, 1980. Magsat has conducted the first truly global geomagnetic survey since the studies performed by the Polar Orbiting Geophysical Observatory (POGO) satellites. A global vector survey was provided of the main geopotential field and lower altitude measurements of crustal anomalies were conducted. Details concerning the availability of these data are discussed.

Langel, R. A.↗
NASA NTRS1986

Measurements of magnetic fields in solar prominences

Magnetic fields can be measured, in solar prominences, by means of two different basic mechanisms that are responsible for the introduction (or the reduction) of a given amount of polarization in spectral lines: these are the Zeeman effect and the Hanle effect. Through the splitting of the magnetic components of a spectral line, the Zeeman effect is capable of introducing a certain amount of circular polarization across the line profile. The Hanle effect consist of a modification of the linear polarization that is induced in spectral lines by the anisotropic illumination of the prominence plasma by the photospheric radiation field. These two effects are briefly discussed.

Deglinnocenti, Egidio Landi↗
DOE OSTI2024

Absolute magneto-optical measurement of magnetic field on a long pulse high electrical current driven solenoid

We describe a direct absolute magneto-optical approach to measuring the magnetic field driven by long pulse width (>5 ms) and high electrical current (∼kA) in a solenoidal coil. The magnetic field and electrical current are among the most important operating parameters in lightning research and electrical power distribution and are essential to understanding the properties of the radiation output in pulsed energy accelerators as well as other research platforms. However, accurately measuring these magnetic fields and electrical currents using conventional electrical diagnostics is difficult due to the strength of ionizing radiation and electromagnetic interference. Our approach uses a fiber coupled laser beam with a rare earth element material sensing crystal that is highly resistant to electromagnetic interference, allows for absolute measurement, and does not require an external calibration. Here, we focus on device theory, operating parameters, magneto-optical results from an experiment on a high current solenoid, and comparison with a calculation of the magnetic field and reference electrical current flowing downstream of the solenoid.

Owens, Israel [Sandia National Laboratories (SNL-N↗
NASA NTRS2003

Near-Field Magnetic Dipole Moment Analysis

This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.

Harris, Patrick K.↗
NASA NTRS1994

A New Approach to Isolating External Magnetic Field Components in Spacecraft Measurements of the Earth's Magnetic Field Using Global Positioning System observables

We review the problem of separating components of the magnetic field arising from sources in the Earth's core and lithosphere, from those contributions arising external to the Earth, namely ionospheric and magnetospheric fields, in spacecraft measurements of the Earth's magnetic field.

magnetic field components ionospheric and magnetos↗
NASA NTRS2000

Computer-implemented method and apparatus for autonomous position determination using magnetic field data

A computer-implemented method and apparatus for determining position of a vehicle within 100 km autonomously from magnetic field measurements and attitude data without a priori knowledge of position. An inverted dipole solution of two possible position solutions for each measurement of magnetic field data are deterministically calculated by a program controlled processor solving the inverted first order spherical harmonic representation of the geomagnetic field for two unit position vectors 180 degrees apart and a vehicle distance from the center of the earth. Correction schemes such as a successive substitutions and a Newton-Raphson method are applied to each dipole. The two position solutions for each measurement are saved separately. Velocity vectors for the position solutions are calculated so that a total energy difference for each of the two resultant position paths is computed. The position path with the smaller absolute total energy difference is chosen as the true position path of the vehicle.

Ketchum, Eleanor A.↗
DOE OSTI2025

Advancing Reel-to-Reel Inspection Techniques for Long HTS Conductors: Comparison and Innovations

The continuous advancement of high-temperature superconductor (HTS) technologies has greatly accelerated the development and deployment of HTS applications. Among the critical tools supporting these advancements are reel-to-reel (R2R) critical current (I c ) measurement techniques, which are extensively used by both manufacturers and end users to characterize long-length REBCO conductors. These techniques play a vital role in quality assurance and quality control (QA/QC), ensuring the reliability and performance of HTS conductors and applications throughout the production cycle. We have developed a range of in-house devices for R2R measurements at the University of Houston and Princeton Plasma Physics Laboratory. These include one-dimensional (1D) scan using a magnetic circuit (MC) and two-dimensional (2D) magnetic field mapping systems based on scanning probe array microscope (SPAM) or scanning probe microscopy (SPM). Each technique offers distinct advantages: the MC system provides ultra-fast scanning speeds, ideal for rapid inspection in large-scale industrial production; the high-resolution SPM delivers detailed insights for conductor research and development; and the SPAM, with its simpler mechanical setup, can be upgraded for higher field and lower temperature conditions with a balanced 2D resolution. Here we compared the magnetization and detection capabilities of these techniques through experiments on rare-earth barium copper oxide (REBCO) coated conductor samples, with data analysis supported by numerical simulations. Based on our comprehensive comparative studies, we propose enhancements for each measurement system and provide guidelines for selecting the optimal technique combinations to meet specific application requirements.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1978

The ISEE-1 and ISEE-2 plasma wave investigation

The ISEE-1 and ISEE-2 plasma wave experiments are designed to provide basic information on wave-particle interactions in the earth's magnetosphere and in the solar wind. The ISEE-1 plasma wave instrument uses three electric dipole antennas with lengths of 215, 73.5 and 0.61 m for electric field measurements, and a triaxial search coil antenna for magnetic field measurements. The ISEE-2 instrument uses two electric dipole antennas with lengths of 30 and 0.61 m for electric field measurements and a single-axis search coil antenna for magnetic field measurements. The primary scientific objectives of the experiments are described, including the resolution of space-time relationships of plasma wave phenomena and VLBI studies. The instrumentation is described, with emphasis on the antennas and the electronics.

Gurnett, D. A.↗
NASA NTRS1991

Voltages induced on a power distribution line by overhead cloud lightning

Voltages induced by overhead cloud lightning on a 448 m open circuited power distribution line and the corresponding north-south component of the lightning magnetic field were simultaneously measured at the NASA Kennedy Space Center during the summer of 1986. The incident electric field was calculated from the measured magnetic field. The electric field was then used as an input to the computer program, EMPLIN, that calculated the voltages at the two ends of the power line. EMPLIN models the frequency domain field/power coupling theory found, for example, in Ianoz et al. The direction of the source, which is also one of the inputs to EMPLIN, was crudely determined from a three station time delay technique. The authors found reasonably good agreement between calculated and measured waveforms.

Yacoub, Ziad↗
DOE OSTI2023

Measurement of Magnetic Field using Doppler-Free Saturation Spectroscopy (DFSS) in C-2W FRC Plasma

The Cooperative Research and Development Agreement (CRADA) between Oak Ridge National Laboratory (ORNL) and TAE Technologies (TAE) focused on implementing an existing mobile Doppler-free saturation spectroscopy (DFSS) diagnostic to determine the direction of the equilibrium magnetic field within TAE’s C-2W field-reversed configuration (FRC) fusion device. Non-perturbative measurements of magnetic fields in the core of FRCs can provide critical information needed to constrain equilibrium models and for the continued advancement of the fusion research program at TAE. DFSS is a well-established, laser-based absorption spectroscopy technique used to suppress inhomogeneous (Doppler) broadening and reveal the Zeeman fine structure of the target emission lines. The collaboration involved the use of ORNL’s recently constructed mobile DFSS diagnostic. The DFSS diagnostic was shipped and installed on C- 2W in February 2023. TAE’s expertise was used to design and construct the mechanic support structures required to mount the optical hardware on C-2W. Additionally TAE provide critical input to minimize the noise imposed on the DFSS signal by vibrations of the mechanic support structure during operations. DFSS data was obtained for over 500 C-2W shots and will continue until the expiration of this CRADA on September 30 th 2023. Over the course of this work, significant progress was made to maximize the signal to noise (SNR) ratio. Analysis of recently acquired data is on-going, however, initial indications are highly suggestive that a DFSS signal above background has been successfully acquired in C-2W.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1972

Lunar portable magnetometer experiment

The purpose of the Apollo 16 lunar portable magnetometer (LPM) experiment is to measure the permanent magnetic field at different geological sites on the lunar surface. The LPM field measurements are a vector sum of the steady remanent field from the lunar crust and of the time-varying ambient fields. The remanent magnetic fields measured in the Descartes region are the largest extraterrestrial fields yet measured in situ. These measurements show for the first time that the Descartes highlands have a stronger remanent magnetization than do the mare regions of the previous Apollo landing sites. The experimental technique used in the LPM experiment is described and the preliminary results obtained are discussed.

Dyal, P.↗
DOE OSTI2023

Magneto-optical measurement of magnetic field and electrical current on a short pulse high energy pulsed power accelerator

We describe a direct magneto-optical approach to measuring the magnetic field driven by a narrow pulse width (<10 ns), 20 kA electrical current flow in the transmission line of a high energy pulsed power accelerator. The magnetic field and electrical current are among the most important operating parameters in a pulsed power accelerator and are critical to understanding the properties of the radiation output. However, accurately measuring these fields and electrical currents using conventional pulsed power diagnostics is difficult due to the strength of ionizing radiation and electromagnetic interference. Our approach uses a fiber coupled laser beam with a rare earth element sensing crystal sensor that is highly resistant to electromagnetic interference and does not require external calibration. Here, we focus on device theory, operating parameters, results from an experiment on a high energy pulsed power accelerator, and comparison to a conventional electrical current shunt sensor.

42 ENGINEERING↗
NASA NTRS1990

The discovery of magnetically controlled circumstellar matter in the helium-weak stars HD 5737 and HD 79158

The paper reports the discovery, using combined IUE spectroscopy and Zeeman polarimetric magnetic field measurements, of magnetically controlled circumstellar material in two helium-weak stars. HD 5737 = Alpha Sculptoris is, except for its extreme helium deficiency, similar to the He weak sn star HD 21699. A unique period for the magnetic and C IV and Si IV variations of 21.65 days is reported. The effective (longitudinal) field nulls coincide extremely well with C IV line strength maxima. The magnetic field and equatorial trapped plasma are highly oblique to the rotation axis (about 70 deg), and the line variations appear to be stable. Similar magnetospheric variations in HD 79158 = 36 Lyncis have been discovered, for which no period had been previously available. The period is 3.84 days, yet it too displays magnetic-equatorial plasma. The magnetospheric axis is highly oblique to the rotation axis, around 80 deg.

Shore, Steven N.↗