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Wasilewski, P.

Publications and source records attributed to Wasilewski, P..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Magnetic Characterization of Micro Shutters for James Web Space Telescope (JWST)

Summary of Research that was part of the grant: NASA NAG5 - 13405: Magnetic Characterization of Micro Shutters for James Web Space Telescope (JWST) Period: May 1 2003-October 31 2005 The above funding resulted in following major achievements related to microshutter system for JWST. 1. The original rectangular pattern of magnetic material was changed into magnetic striped pattern to prevent unnecessary twisting during the actuation. The Original geometry favored magnetic remanence vector being oriented along the longer side of the shutter and thus resulting torque caused out of plane twist. Stripe pattern minimizes the out of plane motion and thus prolongs the life-time of microshutter device. 2. We built a new magnetic system (magnetic rotisserie) allowing an accelerated life test of microshutters at various temperatures. This system identified that shutter are capable to withstand as many as several millions of actuating cycles. Our system also identified fabrication related features, like bowing with temperature, collisions with the frame due to misalignment, delaminating of the light shields due to uncontrolled voltage release and poorly fabricated light shields.

Wasilewski, P.↗
NASA NTRS2000

Pentlandite and Magnetic Anisotropy in Allende CV3 Chondrite

The representative Natural Remanent Magnetization (NRM) carrier of Allende is nonstoichiometric pentlandite forming in a magnetic field.The magnetic anisotropy results suggest that the constituent particles were compressed before solidification and then compressed or extended in a different direction.

Funaki, M.↗
NASA NTRS1992

Mars Observer magnetic fields investigation

The magnetic fields experiment designed for the Mars Observer mission will provide definitive measurements of the Martian magnetic field from the transition and mapping orbits planned for the Mars Observer. The paper describes the instruments (which include a classical magnetometer and an electron reflection magnetometer) and techniques designed to investigate the nature of the Martian magnetic field and the Mars-solar wind interaction, the mapping of crustal magnetic fields, and studies of the Martian ionosphere, which are activities included in the Mars Observer mission objectives. Attention is also given to the flight software incorporated in the on-board data processor, and the procedures of data processing and analysis.

Acuna, M. H.↗
NASA NTRS1985

Magnetic structure of the crust

The bibuniqueness aspect of geophysical interpretation must be constrained by geological insight to limit the range of theoretically possible models. An additional step in depth understanding of the relationship between rock magnetization and geological circumstances on a grand scale is required. Views about crustal structure and the distribution of lithologies suggests a complex situation with lateral and vertical variability at all levels in the crust. Volcanic, plutonic, and metamorphic processes together with each of the observed anomalies. Important questions are addressed: (1) the location of the magnetic bottom; (2) whether the source is a discrete one or are certain parts of the crust cumulatively contributing to the overall magnetization; (3) if the anomaly to some recognizable surface expression is localized, how to arrive at a geologically realistic model incorporating magnetization contrasts which are realistic; (3) in the way the primary mineralogies are altered by metamorphism and the resulting magnetic contracts; (4) the effects of temperature and pressure on magnetization.

Wasilewski, P.↗
NASA NTRS1982

The Ivrea zone as a model for the distribution of magnetization in the continental crust

Units are identified within the Ivrea zone of northern Italy exhibiting magnetic susceptibilities greater than 0.0005 cgs, saturation magnetization values above 0.009 emu/cu cm, and Curie points as high as 570-580 C. Amphibolites from the granulite-amphibolite facies transition, and the mafic-ultramafic granulite facies lithologies exhibit high values of initial susceptibility and saturation remanence, are laterally continuous, and may be considered as a deep crustal source for long-wavelength anomalies in low-geothermal gradient areas. Evidence is presented which suggests that such mafic-ultramafic bodies as those exposed in the Toce valley were synmetamorphic additions to the base of the crust.

Wasilewski, P.↗
NASA NTRS1981

New magnetic results from Allende C3/V/

Thermomagnetic analyses of Allende C3(V) suggest that magnetic phases contributing about 15% to saturation magnetization with transition temperatures not greater than 320 C, also contribute about 90% to natural remanence (NRM) and about 80% to the saturation isothermal remanence (SIRM). Phases carrying the dominating part of of the NRM are found to be intergrown, magnetically interacting, and thermally unstable, beginning at temperatures as low as 50 C. The ratio of the NRM/SIRM ranges from 0.004 to 0.006 for the bulk meteorite and from 0.0004 to 0.005 for chondrules of all sizes. The remanent coercive force behavior suggests coexisting magnetic phases with differing Curie points or with the low temperature transitions being due to transformation of a thermally metastable phase.

Wasilewski, P.↗
NASA NTRS1981

Magnetization of small iron-nickel spheres

Magnetic properties of small iron-nickel alloy spheres, having compositions which cover the entire Fe-Ni binary, are presented. The spheres were formed during solidification in free fall following the melting of electropolished wires of appropriate composition. The spheres with Ni not greater than 25% acquired a martensitic thermal remanence while those with Ni not less than 30% acquired a thermoremanent magnetization. A magnetic remanence-composition diagram and a coercive force-composition diagram are constructed. Magnetic hysteresis loops and derived parameters demonstrate the difference between metal-bearing and oxide-bearing natural samples. The magnetic remanence varies as the sphere size in conjunction with the microstructure. These results help to explain why coercive force is generally low, remanent coercive force is generally high, and their ratio (R/C) is always large in fine metal dispersions, such as lunar samples and chondrite meteorites.

Wasilewski, P.↗
NASA NTRS1978

Reflection spectra and magnetochemistry of iron oxides and natural surfaces

The magnetic properties and spectral characteristics of iron oxides are distinctive. Diagnostic features in reflectance spectra (0.5 to 2.4 micron) for alpha Fe2O3, gamma Fe2O3, and FeOOH include location of Fe3(+) absorption features, intensity ratios at various wavelengths, and the curve shape between 1.2 micron and 2.4 micron. The reflection spectrum of natural rock surfaces are seldom those of the bulk rock because of weathering effects. Coatings are found to be dominated by iron oxides and clay. A simple macroscopic model of rock spectra (based on concepts of stains and coatings) is considered adequate for interpretation of LANDSAT data. The magnetic properties of materials associated with specific spectral types and systematic changes in both spectra and magnetic properties are considered.

Wasilewski, P.↗
NASA NTRS1977

Characteristics of first order shock induced magnetic transitions in iron and discrimination from TRM

Reflected light microscopy provides information on first-order shock transitions in iron and iron-nickel and permits discrimination of microstructures due to shock transitions from those imparted by thermal transitions. In addition, thin-foil electron microscopy is used to characterize magnetic transitions in fine-particle iron. First-order magnetic phase changes, such as that from the antiferromagnetic face centered cubic state to the ferromagnetic body centered cubic state, are studied with the aim of calibrating the shock and thermal mechanisms of magnetization in iron with a particle size range between 250 and 1200 A. The efficiency of remanence due to shock transition is also estimated.

Wasilewski, P.↗
NASA NTRS1976

Lodestone: Nature's own permanent magnet

Magnetic hysteresis and microstructural details are presented which explain why the class of magnetic iron ores defined as proto-lodestones, can behave as permanent magnets, i.e. lodestones. Certain of these proto-lodestones which are not permanent magnets can be made into permanent magnets by charging in a field greater than 1000 oersted. This fact, other experimental observations, and field evidence from antiquity and the middle ages, which seems to indicate that lodestones are found as localized patches within massive ore bodies, suggests that lightning might be responsible for the charging of lodestones. The large remanent magnetization, high values of coercive force, and good time stability for the remanent magnetization are all characteristics of proto-lodestone iron ores which behave magnetically as fine scale ( 10 micrometer) intergrowths when subjected to magnetic hysteresis analysis. The magnetic results are easily understood by analysis of the complex proto lodestone microstructural patterns observable at the micrometer scale and less.

Wasilewski, P.↗
NASA NTRS1976

Shock-loading meteoritic b.c.c. metal above the pressure transition - Remanent-magnetization stability and microstructure

The paper describes the remanent-magnetization stability and microstructure associated with samples of b.c.c. Fe-Ni from the Odessa meteorite which were shock loaded at 200, 400, 600, 800, and 1000 kbar. The samples include those which were transformation hardened as well as those which were altered by varying thermal levels associated only with the shock levels themselves. Demagnetization curves for an unshocked Odessa sample and for samples shocked at each level are presented along with saturation isothermal remanence demagnetization curves for samples shocked at 600 and 1000 kbar. It is found that: (1) the 200-kbar sample was shock-hardened with no significant thermal effects; (2) stability to demagnetization decreased in the 400- and 600-kbar specimens, indicating that recovery took place; and (3) the specimens shocked at 800 and 100 kbar had the greatest demagnetization stability. These three levels of shock effects are shown to be delimited by discrete levels of microhardness, microstructure, and stability of remanence to demagnetization. It is concluded that the first level is simply a consequence of antiferromagnetic-ferromagnetic reversal and that the other two levels contain a thermal component.

Wasilewski, P.↗
NASA NTRS1974

Possible magnetic effects due to fine particle metal and intergrown phases in lunar samples

The characteristics and forms of existence for alpha iron and gamma iron are considered along with experimental observations concerning the alpha to gamma iron transformation. Attention is given to iron-copper precipitation alloys, the origin of rotational hysteresis in lunar samples, questions of paleointensity, and results obtained in the study of lunar samples. It is pointed out that the presence of gamma iron as a significant component in lunar fines and breccia samples would make it necessary to include the gamma iron component in an interpretation of the magnetic susceptibility-temperature curves.

Wasilewski, P.↗
NASA NTRS1974

The role of nickel content and the magnetic remanence in iron-nickel alloys of lunar composition

Lunar samples are magnetic primarily due to the body centered cubic (BCC) iron and iron-nickel alloys they contain. Presented for the first time are results which demonstrate that the magnitude of the martensitic thermal remanence (MTRM) induced on quenching iron-nickel alloy in the geomagnetic field depends on the nickel content of the alloy. High magnetic stability is due to the increasing dislocation density and increasingly complex microstructures associated with increasing nickel content in the alloys. The results agree with the mechanical and structural properties of the alloys. The characteristic quench martensite microstructure observed on metallographic examination provides a recognition criterion for the MTRM mechanism. These results are important for lunar and meteoritic research intending to ascertain the paleofield responsible for the observed remanent magnetization.-

Wasilewski, P.↗
NASA NTRS1974

The significance of observed rotational magnetic hysteresis in lunar samples

Rotational magnetic hysteresis curves for lunar soils 10084, 12070, and 14259, and rock 14053 have been published. There is no adequate explanation to date for the observed large hysteresis at high fields. Lunar rock magnetism researchers consider fine particle iron to be the primary source of stable magnetic remanence in lunar samples. Iron has cubic anisotropy with added shape anisotropy for extreme particle shapes. The observed high-field hysteresis must have its source in uniaxial or unidirectional anisotropy. This implies the existence of minerals with uniaxial anisotropy or exchange-coupled spin states. Therefore, the source of this observed high-field hysteresis must be identified and understood before serious paleointensity studies are made. It is probable that the exchange-coupled spin states and/or the source of uniaxial anisotropy responsible for the high-field hysteresis might be influenced by the lunar surface diurnal temperature cycling. The possible sources of high-field hysteresis in lunar samples are presented and considered.

Wasilewski, P.↗
NASA NTRS1972

Magnetic coercivity and ferromagnetic species in lunar materials

Lunar samples have reduced coercive force, high values of R sub H (ratio of remanent coercive force to coercive force), and constriction in their magnetic hysteresis loops due to the presence of superparamagnetic and multidomain iron grains. The high R sub H values are also attributable to the magnetic shape effects of the iron grains. Spheres, cubes, and needles, as well as more irregular metal grains were observed. The coercive force values are quite meaningless unless the size and shape distributions are determined. The R sub H and the ratio of saturation remanence to saturation magnetization values can be considered characteristic of the size and shape modes of the ferromagnetic grains in a natural sample, and a classification of natural materials based on their hysteresis characteristics is presented with special reference to lunar samples.

Wasilewski, P.↗