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Sample records for magnetically shielded room

  1. Demagnetization of magnetically shielded rooms

    SciTech Connect

    Thiel, F.; Schnabel, A.; Knappe-Grueneberg, S.; Stollfuss, D.; Burghoff, M.

    2007-03-15

    Magnetically shielded rooms for specific high resolution physiological measurements exploiting the magnetic field, e.g., of the brain (dc-magnetoencephalograpy), low-field NMR, or magnetic marker monitoring, need to be reproducibly demagnetized to achieve reliable measurement conditions. We propose a theoretical, experimental, and instrumental base whereupon the parameters which affect the quality of the demagnetization process are described and how they have to be handled. It is demonstrated how conventional demagnetization equipment could be improved to achieve reproducible conditions. The interrelations between the residual field and the variability at the end of the demagnetization process are explained on the basis of the physics of ferromagnetism and our theoretical predictions are evaluated experimentally.

  2. A magnetically shielded room with ultra low residual field and gradient.

    PubMed

    Altarev, I; Babcock, E; Beck, D; Burghoff, M; Chesnevskaya, S; Chupp, T; Degenkolb, S; Fan, I; Fierlinger, P; Frei, A; Gutsmiedl, E; Knappe-Grüneberg, S; Kuchler, F; Lauer, T; Link, P; Lins, T; Marino, M; McAndrew, J; Niessen, B; Paul, S; Petzoldt, G; Schläpfer, U; Schnabel, A; Sharma, S; Singh, J; Stoepler, R; Stuiber, S; Sturm, M; Taubenheim, B; Trahms, L; Voigt, J; Zechlau, T

    2014-07-01

    A versatile and portable magnetically shielded room with a field of (700 ± 200) pT within a central volume of 1 m × 1 m × 1 m and a field gradient less than 300 pT/m, achieved without any external field stabilization or compensation, is described. This performance represents more than a hundredfold improvement of the state of the art for a two-layer magnetic shield and provides an environment suitable for a next generation of precision experiments in fundamental physics at low energies; in particular, searches for electric dipole moments of fundamental systems and tests of Lorentz-invariance based on spin-precession experiments. Studies of the residual fields and their sources enable improved design of future ultra-low gradient environments and experimental apparatus. This has implications for developments of magnetometry beyond the femto-Tesla scale in, for example, biomagnetism, geosciences, and security applications and in general low-field nuclear magnetic resonance (NMR) measurements.

  3. A magnetically shielded room with ultra low residual field and gradient

    NASA Astrophysics Data System (ADS)

    Altarev, I.; Babcock, E.; Beck, D.; Burghoff, M.; Chesnevskaya, S.; Chupp, T.; Degenkolb, S.; Fan, I.; Fierlinger, P.; Frei, A.; Gutsmiedl, E.; Knappe-Grüneberg, S.; Kuchler, F.; Lauer, T.; Link, P.; Lins, T.; Marino, M.; McAndrew, J.; Niessen, B.; Paul, S.; Petzoldt, G.; Schläpfer, U.; Schnabel, A.; Sharma, S.; Singh, J.; Stoepler, R.; Stuiber, S.; Sturm, M.; Taubenheim, B.; Trahms, L.; Voigt, J.; Zechlau, T.

    2014-07-01

    A versatile and portable magnetically shielded room with a field of (700 ± 200) pT within a central volume of 1 m × 1 m × 1 m and a field gradient less than 300 pT/m, achieved without any external field stabilization or compensation, is described. This performance represents more than a hundredfold improvement of the state of the art for a two-layer magnetic shield and provides an environment suitable for a next generation of precision experiments in fundamental physics at low energies; in particular, searches for electric dipole moments of fundamental systems and tests of Lorentz-invariance based on spin-precession experiments. Studies of the residual fields and their sources enable improved design of future ultra-low gradient environments and experimental apparatus. This has implications for developments of magnetometry beyond the femto-Tesla scale in, for example, biomagnetism, geosciences, and security applications and in general low-field nuclear magnetic resonance (NMR) measurements.

  4. A magnetically shielded room with ultra low residual field and gradient

    SciTech Connect

    Altarev, I.; Chesnevskaya, S.; Gutsmiedl, E.; Kuchler, F.; Lins, T.; Marino, M.; McAndrew, J.; Niessen, B.; Paul, S.; Petzoldt, G.; Singh, J.; Stoepler, R.; Stuiber, S.; Sturm, M.; Taubenheim, B.; Babcock, E.; Beck, D.; Sharma, S.; Burghoff, M.; Fan, I.; and others

    2014-07-15

    A versatile and portable magnetically shielded room with a field of (700 ± 200) pT within a central volume of 1 m × 1 m × 1 m and a field gradient less than 300 pT/m, achieved without any external field stabilization or compensation, is described. This performance represents more than a hundredfold improvement of the state of the art for a two-layer magnetic shield and provides an environment suitable for a next generation of precision experiments in fundamental physics at low energies; in particular, searches for electric dipole moments of fundamental systems and tests of Lorentz-invariance based on spin-precession experiments. Studies of the residual fields and their sources enable improved design of future ultra-low gradient environments and experimental apparatus. This has implications for developments of magnetometry beyond the femto-Tesla scale in, for example, biomagnetism, geosciences, and security applications and in general low-field nuclear magnetic resonance (NMR) measurements.

  5. Magnetic shielding

    DOEpatents

    Kerns, J.A.; Stone, R.R.; Fabyan, J.

    1987-10-06

    A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient magnetic field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines. 3 figs.

  6. Magnetic shielding

    DOEpatents

    Kerns, John A.; Stone, Roger R.; Fabyan, Joseph

    1987-01-01

    A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient magnetic field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines.

  7. Magnetic shielding

    DOEpatents

    Kerns, J.A.; Stone, R.R.; Fabyan, J.

    1985-02-12

    A magnetically-conductive filler material bridges the gap between a multi-part magnetic shield structure which substantially encloses a predetermined volume so as to minimize the ingress or egress of magnetic fields with respect to that volume. The filler material includes a heavy concentration of single-magnetic-domain-sized particles of a magnetically conductive material (e.g. soft iron, carbon steel or the like) dispersed throughout a carrier material which is generally a non-magnetic material that is at least sometimes in a plastic or liquid state. The maximum cross-sectional particle dimension is substantially less than the nominal dimension of the gap to be filled. An epoxy base material (i.e. without any hardening additive) low volatility vacuum greases or the like may be used for the carrier material. The structure is preferably exposed to the expected ambient field while the carrier is in a plastic or liquid state so as to facilitate alignment of the single-magnetic-domain-sized particles with the expected magnetic field lines.

  8. Dynamical cancellation of pulse-induced transients in a metallic shielded room for ultra-low-field magnetic resonance imaging

    SciTech Connect

    Zevenhoven, Koos C. J. Ilmoniemi, Risto J.; Dong, Hui; Clarke, John

    2015-01-19

    Pulse-induced transients such as eddy currents can cause problems in measurement techniques where a signal is acquired after an applied preparatory pulse. In ultra-low-field magnetic resonance imaging, performed in magnetic fields typically of the order of 100 μT, the signal-to-noise ratio is enhanced in part by prepolarizing the proton spins with a pulse of much larger magnetic field and in part by detecting the signal with a Superconducting QUantum Interference Device (SQUID). The pulse turn-off, however, can induce large eddy currents in the shielded room, producing an inhomogeneous magnetic-field transient that both seriously distorts the spin dynamics and exceeds the range of the SQUID readout. It is essential to reduce this transient substantially before image acquisition. We introduce dynamical cancellation (DynaCan), a technique in which a precisely designed current waveform is applied to a separate coil during the later part and turn off of the polarizing pulse. This waveform, which bears no resemblance to the polarizing pulse, is designed to drive the eddy currents to zero at the precise moment that the polarizing field becomes zero. We present the theory used to optimize the waveform using a detailed computational model with corrections from measured magnetic-field transients. SQUID-based measurements with DynaCan demonstrate a cancellation of 99%. Dynamical cancellation has the great advantage that, for a given system, the cancellation accuracy can be optimized in software. This technique can be applied to both metal and high-permeability alloy shielded rooms, and even to transients other than eddy currents.

  9. Influence of demagnetization coil configuration on residual field in an extremely magnetically shielded room: Model and measurements

    NASA Astrophysics Data System (ADS)

    Knappe-Grueneberg, Silvia; Schnabel, Allard; Wuebbeler, Gerd; Burghoff, Martin

    2008-04-01

    The Berlin magnetically shielded room 2 (BMSR-2) features a magnetic residual field below 500pT and a field gradient level less than 0.5pT/mm, which are needed for very sensitive human biomagnetic recordings or low field NMR. Nevertheless, below 15Hz, signals are compromised by an additional noise contribution due to vibration forced sensor movements in the field gradient. Due to extreme shielding, the residual field and its homogeneity are determined mainly by the demagnetization results of the mumetal shells. Eight different demagnetization coil configurations can be realized, each results in a characteristic field pattern. The spatial dc flux density inside BMSR-2 is measured with a movable superconducting quantum interference device system with an accuracy better than 50pT. Residual field and field distribution of the current-driven coils fit well to an air-core coil model, if the high permeable core and the return lines outside of the shells are neglected. Finally, we homogenize the residual field by selecting a proper coil configuration.

  10. Magnetic shielding for superconducting RF cavities

    NASA Astrophysics Data System (ADS)

    Masuzawa, M.; Terashima, A.; Tsuchiya, K.; Ueki, R.

    2017-03-01

    Magnetic shielding is a key technology for superconducting radio frequency (RF) cavities. There are basically two approaches for shielding: (1) surround the cavity of interest with high permeability material and divert magnetic flux around it (passive shielding); and (2) create a magnetic field using coils that cancels the ambient magnetic field in the area of interest (active shielding). The choice of approach depends on the magnitude of the ambient magnetic field, residual magnetic field tolerance, shape of the magnetic shield, usage, cost, etc. However, passive shielding is more commonly used for superconducting RF cavities. The issue with passive shielding is that as the volume to be shielded increases, the size of the shielding material increases, thereby leading to cost increase. A recent trend is to place a magnetic shield in a cryogenic environment inside a cryostat, very close to the cavities, reducing the size and volume of the magnetic shield. In this case, the shielding effectiveness at cryogenic temperatures becomes important. We measured the permeabilities of various shielding materials at both room temperature and cryogenic temperature (4 K) and studied shielding degradation at that cryogenic temperature.

  11. Hybrid Shielding for Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Mullins, David; Royal, Kevin

    2017-01-01

    Precision symmetry measurements such as the search for the electric dipole moment of the neutron require magnetic shielding rooms to reduce the ambient field to the pT scale. The massive mu-metal sheets and large separation between layers make these shield rooms bulky and expensive. Active field cancellation systems used to reduce the surrounding field are limited in uniformity of cancellation. A novel approach to reducing the space between shield layers and increasing the effectiveness of active cancellation is to combine the two systems into a hybrid system, with active and passive layers interspersed. We demonstrate this idea in a prototype with an active layer sandwiched between two passive layers of shielding.

  12. Magnetic shielding for the Fermilab Vertical Cavity Test Facility

    SciTech Connect

    Ginsburg, Camille M.; Reid, Clark; Sergatskov, Dmitri A.; /Fermilab

    2008-09-01

    A superconducting RF cavity has to be shielded from magnetic fields present during cool down below the critical temperature to avoid freezing in the magnetic flux at localized impurities, thereby degrading the cavity intrinsic quality factor Q{sub 0}. The magnetic shielding designed for the Fermilab vertical cavity test facility (VCTF), a facility for CW RF vertical testing of bare ILC 1.3 GHz 9-cell SRF cavities, was recently completed. For the magnetic shielding design, we used two cylindrical layers: a room temperature 'outer' shield of Amumetal (80% Ni alloy), and a 2K 'inner' shield of Cryoperm 10. The magnetic and mechanical design of the magnetic shielding and measurement of the remanent magnetic field inside the shielding are described.

  13. Development of a vector-tensor system to measure the absolute magnetic flux density and its gradient in magnetically shielded rooms

    SciTech Connect

    Voigt, J.; Knappe-Grüneberg, S.; Gutkelch, D.; Neuber, S.; Schnabel, A.; Burghoff, M.; Haueisen, J.

    2015-05-15

    Several experiments in fundamental physics demand an environment of very low, homogeneous, and stable magnetic fields. For the magnetic characterization of such environments, we present a portable SQUID system that measures the absolute magnetic flux density vector and the gradient tensor. This vector-tensor system contains 13 integrated low-critical temperature (LTc) superconducting quantum interference devices (SQUIDs) inside a small cylindrical liquid helium Dewar with a height of 31 cm and 37 cm in diameter. The achievable resolution depends on the flux density of the field under investigation and its temporal drift. Inside a seven-layer mu-metal shield, an accuracy better than ±23 pT for the components of the static magnetic field vector and ±2 pT/cm for each of the nine components of the gradient tensor is reached by using the shifting method.

  14. Charge shielding in magnetized plasmas

    SciTech Connect

    Wang Shaojie; Stroth, Ulrich; Van Oost, Guido

    2010-11-15

    The shielding of a charge sheet in a magnetized plasma is investigated by taking account of the diamagnetic drift start-up current in addition to the polarization current. For a charge sheet with an infinitesimal width, the shielding is the same as the conventional Debye shielding if the charge sheet is perpendicular to the magnetic field; the shielding length is {radical}(2) times larger than the conventional one if the charge sheet is parallel to the magnetic field. When the scale length of the charge sheet is comparable or smaller than the ion Larmor radius, the electric field is significantly enhanced within the charge sheet, while far away from the charge sheet, the electric field is shielded to the usual 1/{epsilon}{sub r} level (where {epsilon}{sub r} is the diamagnetic coefficient of the magnetized plasma).

  15. Saturated High Permeability Magnetic Shields

    NASA Astrophysics Data System (ADS)

    Trenkel, Christian

    2016-05-01

    High permeability magnetic shields can be used in space to mitigate the effect of magnetic sources by several orders of magnitude. Nevertheless, the presence of significant amounts of ferromagnetic material on-board a spacecraft carries, by itself, a certain risk in terms of meeting magnetic cleanliness requirements. One possibility is that the shield is accidentally magnetised irreversibly, either by a strong external field, or mechanical shock. A second possibility is that the shield will acquire an induced moment in the presence of external fields (DC or AC), and could potentially amplify them.Here, we propose the use of high permeability shields which are driven into their fully saturated state - by the source that is being shielded. This approach limits the shielding effect to perhaps one or two orders of magnitude, but is expected to mitigate the above risks substantially. We present extensive numerical simulations describing the design principle behind optimised, fully saturated shields, as well as some results to substantiate the above claims.

  16. Analysis and improvement of cyclotron thallium target room shield.

    PubMed

    Hajiloo, N; Raisali, G; Aslani, G

    2008-01-01

    Because of high neutron and gamma-ray intensities generated during bombardment of a thallium-203 target, a thallium target-room shield and different ways of improving it have been investigated. Leakage of neutron and gamma ray dose rates at various points behind the shield are calculated by simulating the transport of neutrons and photons using the Monte Carlo N Particle transport computer code. By considering target-room geometry, its associated shield and neutron and gamma ray source strengths and spectra, three designs for enhancing shield performance have been analysed: a shielding door at the maze entrance, covering maze walls with layers of some effective materials and adding a shadow-shield in the target room in front of the radiation source. Dose calculations were carried out separately for different materials and dimensions for all the shielding scenarios considered. The shadow-shield has been demonstrated to be one suitable for neutron and gamma dose equivalent reduction. A 7.5-cm thick polyethylene shadow-shield reduces both dose equivalent rate at maze entrance door and leakage from the shield by a factor of 3.

  17. MCG measurement in the environment of active magnetic shield.

    PubMed

    Yamazaki, K; Kato, K; Kobayashi, K; Igarashi, A; Sato, T; Haga, A; Kasai, N

    2004-11-30

    MCG (Magnetocardiography) measurement by a SQUID gradiometer was attempted with only active magnetic shielding (active shielding). A three-axis-canceling-coil active shielding system, where three 16-10-16 turns-coil sets were put in the orthogonal directions, produces a homogeneous magnetic field in a considerable volume surrounding the center. Fluxgate sensors were used as the reference sensors of the system. The system can reduce environmental magnetic noise at low frequencies of less than a few Hz, at 50 Hz and at 150 Hz. Reducing such disturbances stabilizes biomagnetic measurement conditions for SQUIDs in the absence of magnetically shielded rooms (MSR). After filtering and averaging the measured MCG data by a first-order SQUID gradiometer with only the active shielding during the daytime, the QRS complex and T wave was clearly presented.

  18. SQUID holder with high magnetic shielding

    NASA Technical Reports Server (NTRS)

    Rigby, K. W.; Marek, D.; Chui, T. C. P.

    1990-01-01

    A SQUID holder designed for high magnetic shielding is discussed. It is shown how to estimate the attenuation of the magnetic field from the normal magnetic modes for an approximate geometry. The estimate agrees satisfactorily with the attenuation measured with a commercial RF SQUID installed in the holder. The holder attenuates external magnetic fields by more than 10 to the 9th at the SQUID input. With the SQUID input shorted, the response to external fields is 0.00001 Phi(0)/G.

  19. Hysteresis prediction inside magnetic shields and application

    SciTech Connect

    Morić, Igor; De Graeve, Charles-Marie; Grosjean, Olivier; Laurent, Philippe

    2014-07-15

    We have developed a simple model that is able to describe and predict hysteresis behavior inside Mumetal magnetic shields, when the shields are submitted to ultra-low frequency (<0.01 Hz) magnetic perturbations with amplitudes lower than 60 μT. This predictive model has been implemented in a software to perform an active compensation system. With this compensation the attenuation of longitudinal magnetic fields is increased by two orders of magnitude. The system is now integrated in the cold atom space clock called PHARAO. The clock will fly onboard the International Space Station in the frame of the ACES space mission.

  20. Hysteresis prediction inside magnetic shields and application.

    PubMed

    Morić, Igor; De Graeve, Charles-Marie; Grosjean, Olivier; Laurent, Philippe

    2014-07-01

    We have developed a simple model that is able to describe and predict hysteresis behavior inside Mumetal magnetic shields, when the shields are submitted to ultra-low frequency (<0.01 Hz) magnetic perturbations with amplitudes lower than 60 μT. This predictive model has been implemented in a software to perform an active compensation system. With this compensation the attenuation of longitudinal magnetic fields is increased by two orders of magnitude. The system is now integrated in the cold atom space clock called PHARAO. The clock will fly onboard the International Space Station in the frame of the ACES space mission.

  1. Undulator Beam Pipe Magnetic Shielding Effect Tests

    SciTech Connect

    Fisher, Andrew; Wolf, Zachary; /SLAC

    2010-11-23

    The proposed stainless steel beampipe for the LCLS undulator has a measurable shielding effect on the magnetic field of the LCLS undulators. This note describes the tests used to determine the magnitude of the shielding effect, as well as deviations in the shielding effect caused by placing different phase shims in the undulator gap. The effect of the proposed Steel strongback which will be used to support the beam pipe, was also studied. A hall probe on a 3 axis movement system was set up to measure the main component of the magnetic field in the Prototype Undulator. To account for temperature variations of the magnetic field of the undulator for successive tests, a correction is applied which is described in this technical note. Using this method, we found the shielding effect, the amount which the field inside the gap was reduced due to the placement of the beampipe, to be {approx}10 Gauss. A series of tests was also performed to determine the effect of phase shims and X and Y correction shims on the shielding. The largest effect on shielding was found for the .3 mm phase shims. The effect of the .3 mm phase shims was to increase the shielding effect {approx}4 Gauss. The tolerance for the shielding effect of the phase shims is less than 1 gauss. The effect of the strongback was seen in its permanent magnetic field. It introduced a dipole field across the measured section of the undulator of {approx}3 gauss. This note documents the tests performed to determine these effects, as well as the results of those tests.

  2. Experimental characterization of magnetic materials for the magnetic shielding of cryomodules in particle accelerators

    DOE PAGES

    Sah, Sanjay; Myneni, Ganapati; Atulasimha, Jayasimha

    2015-10-26

    The magnetic properties of two important passive magnetic shielding materials (A4K and Amumetal) for accelerator applications, subjected to various processing and heat treatment conditions are studied comprehensively over a wide range of temperatures: from cryogenic to room temperature. Furthermore, we analyze the effect of processing on the extent of degradation of the magnetic properties of both materials and investigate the possibility of restoring these properties by re-annealing.

  3. Passive magnetic shielding in static gradient fields

    NASA Astrophysics Data System (ADS)

    Bidinosti, C. P.; Martin, J. W.

    2014-04-01

    The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied for two idealized shield models: concentric spherical and infinitely-long cylindrical shells of linear material. It is found that higher-order multipoles of an externally applied magnetic field are always shielded progressively better for either geometry by a factor related to the order of the multipole. In regard to the design of internal coil systems, we determine reaction factors for the general multipole field and provide examples of how one can take advantage of the coupling of the coils to the innermost shell to optimize the uniformity of the field. Furthermore, we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields close to the outermost shell. Overall this work provides a comprehensive framework that is useful for the analysis and optimization of dc magnetic shields, serving as a theoretical and conceptual design guide as well as a starting point and benchmark for finite-element analysis.

  4. Eddy current-shielded x-space relaxometer for sensitive magnetic nanoparticle characterization.

    PubMed

    Bauer, L M; Hensley, D W; Zheng, B; Tay, Z W; Goodwill, P W; Griswold, M A; Conolly, S M

    2016-05-01

    The development of magnetic particle imaging (MPI) has created a need for optimized magnetic nanoparticles. Magnetic particle relaxometry is an excellent tool for characterizing potential tracers for MPI. In this paper, we describe the design and construction of a high-throughput tabletop relaxometer that is able to make sensitive measurements of MPI tracers without the need for a dedicated shield room.

  5. Micromagnetics of side shielded perpendicular magnetic recording heads

    NASA Astrophysics Data System (ADS)

    Takano, Kenichi; Liu, Yue; Liu, Kowang; Bai, Daniel Z.; Min, Tai; Wu, Yan; Dovek, Moris

    Micromagnetic models of side shielded perpendicular magnetic recording heads show detailed magnetization configuration of the trailing and side shield during the dynamic writing process. The calculation result indicates possible origins of three kinds. The leakage field at the side shield edge, the side shield saturation, and trailing and side shield domain switching. The side shield edge and the saturation induced fields are based on the geometric boundary and they are limited to just around the side shield edge. However the shield switching field can spread to far track position from the side shield to the trailing shield, and it originates from magnetic boundary of the domains and wall formed during the dynamic writing process. As a result, it produces bump field at far track positions in some trailing and side shields.

  6. A magnetic shield/dual purpose mission

    NASA Technical Reports Server (NTRS)

    Watkins, Seth; Albertelli, Jamil; Copeland, R. Braden; Correll, Eric; Dales, Chris; Davis, Dana; Davis, Nechole; Duck, Rob; Feaster, Sandi; Grant, Patrick

    1994-01-01

    The objective of this work is to design, build, and fly a dual-purpose payload whose function is to produce a large volume, low intensity magnetic field and to test the concept of using such a magnetic field to protect manned spacecraft against particle radiation. An additional mission objective is to study the effect of this moving field on upper atmosphere plasmas. Both mission objectives appear to be capable of being tested using the same superconducting coil. The potential benefits of this magnetic shield concept apply directly to both earth-orbital and interplanetary missions. This payload would be a first step in assessing the true potential of large volume magnetic fields in the U.S. space program. Either converted launch systems or piggyback payload opportunities may be appropriate for this mission. The use of superconducting coils for magnetic shielding against solar flare radiation during manned interplanetary missions has long been contemplated and was considered in detail in the years preceding the Apollo mission. With the advent of new superconductors, it has now become realistic to reconsider this concept for a Mars mission. Even in near-earth orbits, large volume magnetic fields produced using conventional metallic superconductors allow novel plasma physics experiments to be contemplated. Both deployed field-coil and non-deployed field-coil shielding arrangements have been investigated, with the latter being most suitable for an initial test payload in a polar orbit.

  7. Superconducting magnetic shielding apparatus and method

    DOEpatents

    Clem, J.R.; Clem, J.R.

    1983-10-11

    Disclosed are a method and apparatus for providing magnetic shielding around a working volume. The apparatus includes a hollow elongated superconducting shell or cylinder having an elongated low magnetic pinning central portion, and two high magnetic pinning end regions. Transition portions of varying magnetic pinning properties are interposed between the central and end portions. The apparatus further includes a solenoid substantially coextensive with and overlying the superconducting cylinder, so as to be magnetically coupled therewith. The method includes the steps passing a longitudinally directed current through the superconducting cylinder so as to depin magnetic reservoirs trapped in the cylinder. Next, a circumferentially directed current is passed through the cylinder, while a longitudinally directed current is maintained. Depinned magnetic reservoirs are moved to the end portions of the cylinder, where they are trapped. 5 figs.

  8. Superconducting magnetic shielding apparatus and method

    DOEpatents

    Clem, J.R.

    1982-07-09

    Disclosed is a method and apparatus for providing magnetic shielding around a working volume. The apparatus includes a hollow elongated superconducting shell or cylinder having an elongated low magnetic pinning central portion, and two high magnetic pinning end regions. Transition portions of varying magnetic pinning properties are interposed between the central and end portions. The apparatus further includes a solenoid substantially coextensive with and overlying the superconducting cylinder, so as to be magnetically coupled therewith. The method includes the steps passing a longitudinally directed current through the superconducting cylinder so as to depin magnetic reservoirs trapped in the cylinder. Next, a circumferentially directed current is passed through the cylinder, while a longitudinally directed current is maintained. Depinned magnetic reservoirs are moved to the end portions of the cylinder, where they are trapped.

  9. Superconducting magnetic shielding apparatus and method

    DOEpatents

    Clem, John R.; Clem, John R.

    1983-01-01

    Disclosed is a method and apparatus for providing magnetic shielding around a working volume. The apparatus includes a hollow elongated superconducting shell or cylinder having an elongated low magnetic pinning central portion, and two high magnetic pinning end regions. Transition portions of varying magnetic pinning properties are interposed between the central and end portions. The apparatus further includes a solenoid substantially coextensive with and overlying the superconducting cylinder, so as to be magnetically coupled therewith. The method includes the steps passing a longitudinally directed current through the superconducting cylinder so as to depin magnetic reservoirs trapped in the cylinder. Next, a circumferentially directed current is passed through the cylinder, while a longitudinally directed current is maintained. Depinned magnetic reservoirs are moved to the end portions of the cylinder, where they are trapped.

  10. Magnetocardiography of animals in magnetically shielded environment with active compensation.

    PubMed

    Horng, H E; Liao, S H; Hsu, S J; Yang, H C; Wu, J Y; Chen, C C; Wu, C H; Wu, C C

    2004-11-30

    A high-Tc 1st-order electronic superconducting quantum interference device (SQUID) gradiometer system is constructed to study the magnetocardiogram (MCG) of rabbits in a moderately magnetically shielded environment with active compensation. In the noisy hospital environment, the noise cannot be completely reduced with the 1st-order gradiometer, therefore, a reference SQUID with active compensation was used to further reduce the noise level leaking into the room. The MCG system was equipped with a x-y translation bed. We used a low-pass filter with the cut off frequency at 44 Hz, a high-pass filter with the cut off frequency at 0.1 Hz and the 60 Hz notch filter to reduce the power line interference. The noise level of the 1st order gradiometer MCG system in this moderately magnetically shielded room was about 1 pT/square root of Hz1/2 at 1 Hz. The MCG of a normal rabbits was measured with this system and a MCG contour map and a current density distribution was constructed.

  11. Semicrystalline Polymer Composites for Magnetic Shielding Applications

    NASA Astrophysics Data System (ADS)

    Bhadrakumari, S.; Predeep, P.

    2008-11-01

    To investigate a possible modification of mechanical strength of conventional ceramic superconductors for magnetic shielding and levitation applications, a series of flexible composites are fabricated by mixing high Tc YBCO superconductor with Linear Low Density Polyethylene (LLDPE). The structural investigation and magnetic studies of the composites are carried out by Raman Spectroscopy and A.C. Magnetic Susceptibility measurements. Raman spectra of pure YBCO sample and composite samples showed sharp bands, indicating the presence of characteristic structural units in the composites. The intensity of these bands is found to increase with increasing percentage of superconductor. The composites showed a large diamagnetic susceptibility that increases with increasing volume fraction of superconductor filler. Susceptibility measurements showed that the intrinsic diamagnetic properties of the superconducting materials are preserved in the composites and there is no change in the transition temperature of the superconductor.

  12. LPT. Shield test facility (TAN645) interior. Mechanical equipment room with ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LPT. Shield test facility (TAN-645) interior. Mechanical equipment room with switchgear and control boards. Photographer: Jack L. Anderson. Date: February 20, 1959. INEEL negative no. 59-858 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  13. LPT. Shield test facility (TAN645) interior. Mechanical equipment room with ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LPT. Shield test facility (TAN-645) interior. Mechanical equipment room with airwasher and refrigeration compressor. Photographer: Jack L. Anderson. Date: February 20, 1959. INEEL negative no. 59-855 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  14. Shielding hospital rooms for brachytherapy patients: design, regulatory and cost/benefit factors.

    PubMed

    Gitterman, M; Webster, E W

    1984-03-01

    The current regulations of the U.S. Nuclear Regulatory Commission (NRC) normally require limitation of radiation exposure in any part of unrestricted occupied areas to 2 mrem in any one hour and to 100 mrem in 7 days. To meet these limits when patients are treated therapeutically with radioactive materials, it is advisable to designate specific rooms in a hospital and often necessary to incorporate substantial costly shielding into one or more walls and the room door. Plans have been formulated for shielding existing hospital rooms housing brachytherapy patients receiving 192Ir and 137Cs therapy in order to meet the above NRC requirements for adjacent corridors and rooms. Typical shielding thicknesses required are 4-6 in. of concrete for certain walls and 1/4 in. of lead in the doors. Shielding costs are approx. $6000 per room for one shielded wall and a shielded door. Applying recent estimates of the cancer risk from low-level gamma radiation, the cost of shielding per cancer fatality averted has been estimated to range from $1.8 million to $10.9 million. Cost/benefit comparisons with many other life-saving activities suggest that these costs and the application of the 2 mrem/hr limit which necessitated them are not justified.

  15. Magnetic Shield for Adiabatic Demagnetization Refrigerators (ADR)

    NASA Technical Reports Server (NTRS)

    Chui, Talso C.; Haddad, Nicolas E.

    2013-01-01

    A new method was developed for creating a less expensive shield for ADRs using 1018 carbon steel. This shield has been designed to have similar performance to the expensive vanadium permendur shields, but the cost is 30 to 50% less. Also, these shields can be stocked in a variety of sizes, eliminating the need for special forgings, which also greatly reduces cost.

  16. Shielding considerations for an operating room based intraoperative electron radiotherapy unit.

    PubMed

    Mills, M D; Almond, P R; Boyer, A L; Ochran, T G; Madigan, W; Rich, T A; Dally, E B

    1990-05-01

    The leakage radiation characteristics of a dedicated intraoperative radiotherapy linear accelerator have been measured on a machine designed to minimize the shielding required to allow it to be placed in an operating room suite. The scattering foil design was optimized to produce a flat beam for the field sizes employed while generating minimal bremsstrahlung contamination over the available energy range. More lead shielding was used in the treatment head than is used in conventional accelerators. A small amount of borated polyethylene shielding was also employed since neutron production was present at measurable levels. The room shielding installed in the operating room was demonstrated to be adequate to treat at least 20 patients each month to an average dose of 20 Gy. The worst case exposure was found to be 73% maximum permissible exposure. Administrative control was required for adjoining areas when calibrations and maintenance were performed.

  17. MTR WING, TRA604. SECTIONS SHOW COUNTING ROOM SHIELDING AND MAZE. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MTR WING, TRA-604. SECTIONS SHOW COUNTING ROOM SHIELDING AND MAZE. RECORD ROOM BELOW. STAIRWAYS TO BASEMENT AND FAN LOFT. BLAW-KNOX 3150-804-7, 11/1950. INL INDEX NO. 531-0604-00-098-100632, REV. 2. - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  18. Criteria for establishing shielding of multi-detector computed tomography (MDCT) rooms.

    PubMed

    Verdun, F R; Aroua, A; Baechler, S; Schmidt, S; Trueb, P R; Bochud, F O

    2010-01-01

    The aim of this work is to compare two methods used for determining the proper shielding of computed tomography (CT) rooms while considering recent technological advances in CT scanners. The approaches of the German Institute for Standardisation and the US National Council on Radiation Protection and Measurements were compared and a series of radiation measurements were performed in several CT rooms at the Lausanne University Hospital. The following three-step procedure is proposed for assuring sufficient shielding of rooms hosting new CT units with spiral mode acquisition and various X-ray beam collimation widths: (1) calculate the ambient equivalent dose for a representative average weekly dose length product at the position where shielding is required; (2) from the maximum permissible weekly dose at the location of interest, calculate the transmission factor F that must be taken to ensure proper shielding and (3) convert the transmission factor into a thickness of lead shielding. A similar approach could be adopted to use when designing shielding for fluoroscopy rooms, where the basic quantity would be the dose area product instead of the load of current (milliampere-minute).

  19. Exploring Chemical Bonds through Variations in Magnetic Shielding.

    PubMed

    Karadakov, Peter B; Horner, Kate E

    2016-02-09

    Differences in nuclear isotropic magnetic shieldings give rise to the chemical shifts measured in NMR experiments. In contrast to existing NMR experimental techniques, quantum chemical methods are capable of calculating isotropic magnetic shieldings not just at nuclei, but also at any point in the space surrounding a molecule. Using s-trans-1,3-butadiene, ethane, ethene, and ethyne as examples, we show that the variations in isotropic magnetic shielding around a molecule, represented as isosurfaces and contour plots, provide an unexpectedly clear picture of chemical bonding, which is much more detailed than the traditional description in terms of the total electron density.

  20. Calculation of Dental Exam Room X-Ray Shielding in Walls and Entrances

    DTIC Science & Technology

    2012-08-24

    currently uses 5/16 in drywall on all walls. No specialty shielding products (e.g., lead) are currently being used on any walls. f. The window and...needed for Q (Eq. 2). This calculation assumes the use of a 100-kVp beam. (3) With the use of 5/16 in drywall , no radiation shielding properties are...the doonl’ilay entry t o the room. Both sides of the room contain offices1 single sheet of 5/15n drywall on each side of each \\!Vall to combine

  1. Electric control of magnetism at room temperature.

    PubMed

    Wang, Liaoyu; Wang, Dunhui; Cao, Qingqi; Zheng, Yuanxia; Xuan, Haicheng; Gao, Jinlong; Du, Youwei

    2012-01-01

    In the single-phase multiferroics, the coupling between electric polarization (P) and magnetization (M) would enable the magnetoelectric (ME) effect, namely M induced and modulated by E, and conversely P by H. Especially, the manipulation of magnetization by an electric field at room-temperature is of great importance in technological applications, such as new information storage technology, four-state logic device, magnetoelectric sensors, low-power magnetoelectric device and so on. Furthermore, it can reduce power consumption and realize device miniaturization, which is very useful for the practical applications. In an M-type hexaferrite SrCo(2)Ti(2)Fe(8)O(19), large magnetization and electric polarization were observed simultaneously at room-temperature. Moreover, large effect of electric field-controlled magnetization was observed even without magnetic bias field. These results illuminate a promising potential to apply in magnetoelectric devices at room temperature and imply plentiful physics behind them.

  2. Electric control of magnetism at room temperature

    PubMed Central

    Wang, Liaoyu; Wang, Dunhui; Cao, Qingqi; Zheng, Yuanxia; Xuan, Haicheng; Gao, Jinlong; Du, Youwei

    2012-01-01

    In the single-phase multiferroics, the coupling between electric polarization (P) and magnetization (M) would enable the magnetoelectric (ME) effect, namely M induced and modulated by E, and conversely P by H. Especially, the manipulation of magnetization by an electric field at room-temperature is of great importance in technological applications, such as new information storage technology, four-state logic device, magnetoelectric sensors, low-power magnetoelectric device and so on. Furthermore, it can reduce power consumption and realize device miniaturization, which is very useful for the practical applications. In an M-type hexaferrite SrCo2Ti2Fe8O19, large magnetization and electric polarization were observed simultaneously at room-temperature. Moreover, large effect of electric field-controlled magnetization was observed even without magnetic bias field. These results illuminate a promising potential to apply in magnetoelectric devices at room temperature and imply plentiful physics behind them. PMID:22355737

  3. Magnetic shielding tests for MFTF-B neutral beamlines

    SciTech Connect

    Kerns, J.; Fabyan, J.; Wood, R.; Koger, P.

    1983-11-16

    A test program to determine the effectiveness of various magnetic shielding designs for MFTF-B beamlines was established at Lawrence Livermore National Laboratory (LLNL). The proposed one-tenth-scale shielding-design models were tested in a uniform field produced by a Helmholtz coil pair. A similar technique was used for the MFTF source-injector assemblies, and the model test results were confirmed during the Technology Demonstration in 1982. The results of these tests on shielding designs for MFTF-B had an impact on the beamline design for MFTF-B. The iron-core magnet and finger assembly originally proposed were replaced by a simple, air-core, race-track-coil, bending magnet. Only the source injector needs to be magnetically shielded from the fields of approximately 400 gauss.

  4. Upgrade of the LHC magnet interconnections thermal shielding

    SciTech Connect

    Musso, Andrea; Barlow, Graeme; Bastard, Alain; Charrondiere, Maryline; Deferne, Guy; Dib, Gaëlle; Duret, Max; Guinchard, Michael; Prin, Hervé; Craen, Arnaud Vande; Villiger, Gilles; Chrul, Anna; Damianoglou, Dimitrios; Strychalski, Michał; Wright, Loren

    2014-01-29

    The about 1700 interconnections (ICs) between the Large Hadron Collider (LHC) superconducting magnets include thermal shielding at 50-75 K, providing continuity to the thermal shielding of the magnet cryostats to reduce the overall radiation heat loads to the 1.9 K helium bath of the magnets. The IC shield, made of aluminum, is conduction-cooled via a welded bridge to the thermal shield of the adjacent magnets which is actively cooled. TIG welding of these bridges made in the LHC tunnel at installation of the magnets induced a considerable risk of fire hazard due to the proximity of the multi-layer insulation of the magnet shields. A fire incident occurred in one of the machine sectors during machine installation, but fortunately with limited consequences thanks to prompt intervention of the operators. LHC is now undergoing a 2 years technical stop during which all magnet's ICs will have to be opened to consolidate the magnet electrical connections. The IC thermal shields will therefore have to be removed and re-installed after the work is completed. In order to eliminate the risk of fire hazard when re-welding, it has been decided to review the design of the IC shields, by replacing the welded bridges with a mechanical clamping which also preserves its thermal function. An additional advantage of this new solution is the ease in dismantling for maintenance, and eliminating weld-grinding operations at removal needing radioprotection measures because of material activation after long-term operation of the LHC. This paper describes the new design of the IC shields and in particular the theoretical and experimental validation of its thermal performance. Furthermore a status report of the on-going upgrade work in the LHC is given.

  5. Upgrade of the LHC magnet interconnections thermal shielding

    NASA Astrophysics Data System (ADS)

    Musso, Andrea; Barlow, Graeme; Bastard, Alain; Charrondiere, Maryline; Chrul, Anna; Damianoglou, Dimitrios; Deferne, Guy; Dib, Gaëlle; Duret, Max; Guinchard, Michael; Prin, Hervé; Strychalski, Michał; Craen, Arnaud Vande; Villiger, Gilles; Wright, Loren

    2014-01-01

    The about 1700 interconnections (ICs) between the Large Hadron Collider (LHC) superconducting magnets include thermal shielding at 50-75 K, providing continuity to the thermal shielding of the magnet cryostats to reduce the overall radiation heat loads to the 1.9 K helium bath of the magnets. The IC shield, made of aluminum, is conduction-cooled via a welded bridge to the thermal shield of the adjacent magnets which is actively cooled. TIG welding of these bridges made in the LHC tunnel at installation of the magnets induced a considerable risk of fire hazard due to the proximity of the multi-layer insulation of the magnet shields. A fire incident occurred in one of the machine sectors during machine installation, but fortunately with limited consequences thanks to prompt intervention of the operators. LHC is now undergoing a 2 years technical stop during which all magnet's ICs will have to be opened to consolidate the magnet electrical connections. The IC thermal shields will therefore have to be removed and re-installed after the work is completed. In order to eliminate the risk of fire hazard when re-welding, it has been decided to review the design of the IC shields, by replacing the welded bridges with a mechanical clamping which also preserves its thermal function. An additional advantage of this new solution is the ease in dismantling for maintenance, and eliminating weld-grinding operations at removal needing radioprotection measures because of material activation after long-term operation of the LHC. This paper describes the new design of the IC shields and in particular the theoretical and experimental validation of its thermal performance. Furthermore a status report of the on-going upgrade work in the LHC is given.

  6. Conductive shield for ultra-low-field magnetic resonance imaging: Theory and measurements of eddy currents

    PubMed Central

    Zevenhoven, Koos C. J.; Busch, Sarah; Hatridge, Michael; Öisjöen, Fredrik; Ilmoniemi, Risto J.; Clarke, John

    2014-01-01

    Eddy currents induced by applied magnetic-field pulses have been a common issue in ultra-low-field magnetic resonance imaging. In particular, a relatively large prepolarizing field—applied before each signal acquisition sequence to increase the signal—induces currents in the walls of the surrounding conductive shielded room. The magnetic-field transient generated by the eddy currents may cause severe image distortions and signal loss, especially with the large prepolarizing coils designed for in vivo imaging. We derive a theory of eddy currents in thin conducting structures and enclosures to provide intuitive understanding and efficient computations. We present detailed measurements of the eddy-current patterns and their time evolution in a previous-generation shielded room. The analysis led to the design and construction of a new shielded room with symmetrically placed 1.6-mm-thick aluminum sheets that were weakly coupled electrically. The currents flowing around the entire room were heavily damped, resulting in a decay time constant of about 6 ms for both the measured and computed field transients. The measured eddy-current vector maps were in excellent agreement with predictions based on the theory, suggesting that both the experimental methods and the theory were successful and could be applied to a wide variety of thin conducting structures. PMID:24753629

  7. Shielding design of a treatment room for an accelerator-based neutron source for BNCT

    SciTech Connect

    Evans, J.F.; Blue, T.E.

    1995-12-31

    For several years, research has been ongoing in the Ohio State University (OSU) Nuclear Engineering Program toward the development of an accelerator-based irradiation facility (ANIF) neutron source for boron neutron capture therapy (BNCT). The ANIF, which is planned to be built in a hospital, has been conceptually designed and analyzed. After Qu, an OSU researcher, determined that the shielding design of a 6-MV X-ray treatment room was inadequate to protect personnel from an accelerator neutron source operating at 30 mA, we decided to analyze and determine the shielding requirements of a treatment room for an ANIF. We determined the amount of shielding that would be sufficient to protect facility personnel from excessive radiation exposure caused by operation of the accelerator at 30 mA.

  8. LPT. Shield test facility (TAN646) interior. Water treatment room contains ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LPT. Shield test facility (TAN-646) interior. Water treatment room contains water softeners, deionizers, and display panel. Note metal ceiling and walls. Photographer: Jack L. Anderson. Date: February 20, 1959. INEEL negative no. 59-856 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  9. LPT. Shield test facility (TAN645) interior. Boiler room shows one ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LPT. Shield test facility (TAN-645) interior. Boiler room shows one boiler, diesel electric stand unit, and related equipment. Pumice block walls. Photographer: Jack L. Anderson. Date: January 19, 1959. INEEL negative no. 59-286 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  10. A novel self-shielding permanent-magnet rotor assembly

    NASA Astrophysics Data System (ADS)

    Potenziani, E., II; Leupold, H. A.; Basarab, D. J.

    1988-11-01

    The use of permanent magnets in brushless motors and generators is highly desirable in that they have great potential for reducing weight and increasing efficiency. A self-shielding cylindrical permanent-magnet assembly has been designed and was found to produce high fields at the outer magnet surface and very little flux leakage into the interior rotor space. Construction of this assembly is simplified because it is composed of magnets of simple triangular cross sections, which have only four distinct orientations. The self-shielding nature of the design obviates any need for ferromagnetic material for flux shaping or shielding, thus simplifying greatly the mathematical analysis of the design and reducing its weight and bulk. Finite element methods are used to analyze a hypothetical permanent-magnet rotor assembly with regard to various design parameters.

  11. Radiation shielding design of BNCT treatment room for D-T neutron source.

    PubMed

    Pouryavi, Mehdi; Farhad Masoudi, S; Rahmani, Faezeh

    2015-05-01

    Recent studies have shown that D-T neutron generator can be used as a proper neutron source for Boron Neutron Capture Therapy (BNCT) of deep-seated brain tumors. In this paper, radiation shielding calculations have been conducted based on the computational method for designing a BNCT treatment room for a recent proposed D-T neutron source. By using the MCNP-4C code, the geometry of the treatment room has been designed and optimized in such a way that the equivalent dose rate out of the treatment room to be less than 0.5μSv/h for uncontrolled areas. The treatment room contains walls, monitoring window, maze and entrance door. According to the radiation protection viewpoint, dose rate results of out of the proposed room showed that using D-T neutron source for BNCT is safe.

  12. Nuclear Magnetic Shieldings of Stacked Aromatic and Antiaromatic Molecules.

    PubMed

    Sundholm, Dage; Rauhalahti, Markus; Özcan, Nergiz; Mera-Adasme, Raúl; Kussmann, Jörg; Luenser, Arne; Ochsenfeld, Christian

    2017-04-04

    Nuclear magnetic shieldings have been calculated at the density functional theory (DFT) level for stacks of benzene, hexadehydro[12]annulene, dodecadehydro[18]annulene, and hexabenzocoronene. The magnetic shieldings due to the ring currents in the adjacent molecules have been estimated by calculating nucleus independent molecular shieldings for the monomer in the atomic positions of neighbor molecules. The calculations show that the independent shielding model works reasonably well for the (1)H NMR shieldings of benzene and hexadehydro[12]annulene, whereas for the larger molecules and for the (13)C NMR shieldings the interaction between the molecules leads to shielding effects that are at least of the same size as the ring current contributions from the adjacent molecules. A better agreement is obtained when the nearest neighbors are also considered at full quantum mechanical (QM) level. The calculations suggest that the nearest solvent molecules must be included in the quantum mechanical system, at least when estimating solvent shifts at the molecular mechanics (MM) level. Current density calculations show that the stacking does not significantly affect the ring current strengths of the individual molecules, whereas the shape of the ring current for a single molecule differs from that of the stacked molecules.

  13. Magnetic shielding for a spaceborne adiabatic demagnetization refrigerator (ADR)

    NASA Technical Reports Server (NTRS)

    Warner, Brent A.; Shirron, Peter J.; Castles, Stephen H.; Serlemitsos, Aristides T.

    1991-01-01

    The Goddard Space Flight Center has studied magnetic shielding for an adiabatic demagnetization refrigerator. Four types of shielding were studied: active coils, passive ferromagnetic shells, passive superconducting coils, and passive superconducting shells. The passive superconducting shells failed by allowing flux penetration. The other three methods were successful, singly or together. Experimental studies of passive ferromagnetic shielding are compared with calculations made using the Poisson Group of programs, distributed by the Los Alamos Accelerator Code Group of the Los Alamos National Laboratory. Agreement between calculation and experiment is good. The ferromagnetic material is a silicon iron alloy.

  14. Superconducting and hybrid systems for magnetic field shielding

    NASA Astrophysics Data System (ADS)

    Gozzelino, L.; Gerbaldo, R.; Ghigo, G.; Laviano, F.; Truccato, M.; Agostino, A.

    2016-03-01

    In this paper we investigate and compare the shielding properties of superconducting and hybrid superconducting/ferromagnetic systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. First, we reproduced, by finite-element calculations, the induction magnetic field values measured along the symmetry axis in a superconducting (MgB2) and in a hybrid configuration (MgB2/Fe) as a function of the applied magnetic field and of the position. The calculations are carried out using the vector potential formalism, taking into account simultaneously the non-linear properties of both the superconducting and the ferromagnetic material. On the basis of the good agreement between the experimental and the computed data we apply the same model to study the influence of the geometric parameters of the ferromagnetic cup as well as of the thickness of the lateral gap between the two cups on the shielding properties of the superconducting cup. The results show that in the considered non-ideal geometry, where the edge effect in the flux penetration cannot be disregarded, the superconducting shield is always the most efficient solution at low magnetic fields. However, a partial recovery of the shielding capability of the hybrid configuration occurs if a mismatch in the open edges of the two cups is considered. In contrast, at high magnetic fields the hybrid configurations are always the most effective. In particular, the highest shielding factor was found for solutions with the ferromagnetic cup protruding over the superconducting one.

  15. Some folded issues related to over-shielded and unplanned rooms for medical linear accelerators - A case study

    NASA Astrophysics Data System (ADS)

    Muhammad, Wazir; Ullah, Asad; Hussain, Amjad; Ali, Nawab; Alam, Khan; Khan, Gulzar; Matiullah; Maeng, Seongjin; Lee, Sang Hoon

    2015-08-01

    A medical linear accelerator (LINAC) room must be properly shielded to limit the outside radiation exposure to an acceptable safe level defined by individual state and international regulations. However, along with this prime objective, some additional issues are also important. The current case-study was designed to unfold the issues related to over-shielded and unplanned treatment rooms for LINACs. In this connection, an apparently unplanned and over-shielded treatment room of 610 × 610 cm2 in size was compared with a properly designed treatment room of 762 × 762 cm2 in size ( i.e., by following the procedures and recommendations of the IAEA Safety Reports Series No. 47 and NCRP 151). Evaluation of the unplanned room indicated that it was over-shielded and that its size was not suitable for total body irradiation (TBI), although the license for such a treatment facility had been acquired for the installed machine. An overall 14.96% reduction in the total shielding volume ( i.e., concrete) for an optimally planned room as compared to a non-planned room was estimated. Furthermore, the inner room's dimensions were increased by 25%, in order to accommodate TBI patients. These results show that planning and design of the treatment rooms are imperative to avoid extra financial burden to the hospitals and to provide enough space for easy and safe handling of the patients. A spacious room is ideal for storing treatment accessories and facilitates TBI treatment.

  16. Magnetic shielding and vacuum test for passive hydrogen masers

    NASA Technical Reports Server (NTRS)

    Gubser, D. U.; Wolf, S. A.; Jacoby, A. B.; Jones, L. D.

    1982-01-01

    Vibration tests on high permeability magnetic shields used in the SAO-NRL Advanced Development Model (ADM) hydrogen maser were made. Magnetic shielding factors were measured before and after vibration. Preliminary results indicate considerable (25%) degradation. Test results on the NRL designed vacuum pumping station for the ADM hydrogen maser are also discussed. This system employs sintered zirconium carbon getter pumps to pump hydrogen plus small ion pumps to pump the inert gases. In situ activation tests and pumping characteristics indicate that the system can meet design specifications.

  17. Active Magnetic Shielding for Long Duration Manned Space Missions

    NASA Astrophysics Data System (ADS)

    Battiston, R.; Burger, W. J.; Cavelli, V.; Musenich, R.; Datskov, V. I.; Della Torre, A.; Venditti, F.; Hovland, S.; Meinke, R. B.; Van Sciver, S.; Westover, S. C.; Spillantini, P.

    2013-09-01

    The radiation risk due to ionizing particles is a critical issue for long duration manned space missions. The ionization losses in the materials of the spacecraft provide passive shielding effectively stopping low energy particles. However, the estimates of the material required to obtain an acceptable level of radiation result in a prohibitive mass. Active electromagnetic shields, which deflect the charged particles, have been considered as an alternative solution. A study of active magnetic shielding based on high-temperature superconductors (HTS) was initiated in an ESA study, and continued in the context of the NASA Innovative Advanced Concepts (NIAC) program. The aim of the effort was to provide a realistic evaluation of the possibilities based on the current technological level. The different configurations considered were assessed in terms of their technical feasibility and shielding efficiency.

  18. Magnetic Shielding Studies for Electric Dipole Moment Experiments

    NASA Astrophysics Data System (ADS)

    Gould, Harvey; Feinberg, B.

    2014-09-01

    Electric dipole moment experiments are necessarily sensitive to magnetic fields and hence require effective magnetic shielding. In testing the shielding factor of single-layer Permalloy (Carpenter HyMu ``80'' ®) cylinders, we find time-dependent effects lasting tens of minutes to thousands of minutes when a static magnetic field is applied to a Permalloy cylinder that has been demagnetized in a region of near-zero field. A decrease in the magnetic field, measured at the center of the cylinder, of about 20 percent is observed for applied fields ranging from 0.5 A/m to 16 A/m. The latter applied field is comparable to the Earth's magnetic field. Effects that resemble these have been seen in other ferromagnetic materials.

  19. High frequency electromagnetic interference shielding magnetic polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    He, Qingliang

    Electromagnetic interference is one of the most concerned pollution and problem right now since more and more electronic devices have been extensively utilized in our daily lives. Besides the interference, long time exposure to electromagnetic radiation may also result in severe damage to human body. In order to mitigate the undesirable part of the electromagnetic wave energy and maintain the long term sustainable development of our modern civilized society, new technology development based researches have been made to solve this problem. However, one of the major challenges facing to the electromagnetic interference shielding is the relatively low shielding efficiency and the high cost as well as the complicated shielding material manufacture. From the materials science point of view, the key solutions to these challenges are strongly depended on the breakthrough of the current limit of shielding material design and manufacture (such as hierarchical material design with controllable and predictable arrangement in nanoscale particle configuration via an easy in-situ manner). From the chemical engineering point of view, the upgrading of advanced material shielding performance and the enlarged production scale for shielding materials (for example, configure the effective components in the shielding material in order to lower their usage, eliminate the "rate-limiting" step to enlarge the production scale) are of great importance. In this dissertation, the design and preparation of morphology controlled magnetic nanoparticles and their reinforced polypropylene polymer nanocomposites will be covered first. Then, the functionalities of these polymer nanocomposites will be demonstrated. Based on the innovative materials design and synergistic effect on the performance advancement, the magnetic polypropylene polymer nanocomposites with desired multifunctionalities are designed and produced targeting to the electromagnetic interference shielding application. In addition

  20. Calculation of an optimized design of magnetic shields with integrated demagnetization coils

    NASA Astrophysics Data System (ADS)

    Sun, Z.; Schnabel, A.; Burghoff, M.; Li, L.

    2016-07-01

    Magnetic shielding made from permalloy is frequently used to provide a time-stable magnetic field environment. A low magnetic field and low field gradients inside the shield can be obtained by using demagnetization coils through the walls, encircling edges of the shield. We first introduce and test the computational models to calculate magnetic properties of large size shields with thin shielding walls. We then vary the size, location and shape of the openings for the demagnetization coils at the corners of a cubic shield. It turns out that the effect on the shielding factor and the expected influence on the residual magnetic field homogeneity in the vicinity of the center of the shield is negligible. Thus, a low-cost version for the openings can be chosen and their size could be enlarged to allow for additional cables and easier handling. A construction of a shield with beveled edges and open corners turned out to substantially improve the shielding factor.

  1. Segmented contracted basis sets optimized for nuclear magnetic shielding.

    PubMed

    Jensen, Frank

    2015-01-13

    A family of segmented contracted basis sets is proposed, denoted pcSseg-n, which are optimized for calculating nuclear magnetic shielding constants. For the elements H-Ar, these are computationally more efficient than the previously proposed general contracted pcS-n basis sets, and the new basis sets are extended to also include the elements K-Kr. The pcSseg-n basis sets are optimized at the density functional level of theory, but it has been shown previously that these property-optimized basis sets are also suitable for calculating shielding constants with correlated wave function methods. The pcSseg-n basis sets are available in qualities ranging from (unpolarized) double-ζ to pentuple-ζ quality and should be suitable for both routine and benchmark calculations of nuclear magnetic shielding constants. The ability to rigorously separate basis set and method errors should aid in developing more accurate methods.

  2. Active magnetic radiation shielding system analysis and key technologies.

    PubMed

    Washburn, S A; Blattnig, S R; Singleterry, R C; Westover, S C

    2015-01-01

    Many active magnetic shielding designs have been proposed in order to reduce the radiation exposure received by astronauts on long duration, deep space missions. While these designs are promising, they pose significant engineering challenges. This work presents a survey of the major systems required for such unconfined magnetic field design, allowing the identification of key technologies for future development. Basic mass calculations are developed for each system and are used to determine the resulting galactic cosmic radiation exposure for a generic solenoid design, using a range of magnetic field strength and thickness values, allowing some of the basic characteristics of such a design to be observed. This study focuses on a solenoid shaped, active magnetic shield design; however, many of the principles discussed are applicable regardless of the exact design configuration, particularly the key technologies cited.

  3. Induced Magnetic Field Due to Reaction Wheel Shielding

    NASA Astrophysics Data System (ADS)

    Pudney, M. A.; Kapfunde, G.; Trougnou, L.

    2016-05-01

    In situ magnetic field measurements are of critical importance to unanswered questions on the inner heliosphere, such as: how the corona and solar wind are accelerated and heated; how the solar magnetic field evolves over a solar cycle; and how this field links into space. However, accurate spacecraft magnetometer measurements require reliable in-flight calibration. The magnetic interference caused by reaction wheels on magnetometer measurements in space is well known, and a common mitigation method is to use magnetic shielding. However, the presence of high-permeability material in-flight has the side-effect of distorting the true ambient field. We present a theoretical analysis of this distortion, and suggest a transfer function that can be used to recover the ambient field from the distorted dataset. Experimental measurements on a shield prototype for the Solar Orbiter mission agree with predictions to within an order of magnitude, demonstrating a distortion of approximately 1 part in 104.

  4. QED theory of the nuclear magnetic shielding in hydrogenlike ions.

    PubMed

    Yerokhin, V A; Pachucki, K; Harman, Z; Keitel, C H

    2011-07-22

    The shielding of the nuclear magnetic moment by the bound electron in hydrogenlike ions is calculated ab initio with inclusion of relativistic, nuclear, and quantum electrodynamics (QED) effects. The QED correction is evaluated to all orders in the nuclear binding strength parameter and, independently, to the first order in the expansion in this parameter. The results obtained lay the basis for the high-precision determination of nuclear magnetic dipole moments from measurements of the g factor of hydrogenlike ions.

  5. Method for expanding the uniformly shielded area in a short-length open-ended cylindrical magnetic shield

    NASA Astrophysics Data System (ADS)

    Oshita, K.; Sasada, I.; Naka, H.; Paperno, E.

    1999-04-01

    A compensation method is proposed by which the uniformly shielded area of the axial magnetic field in a relatively short, open-structure axial magnetic shield can be extended. An open-ended cylindrical magnetic shield of 120 cm in length, 52 cm inner diameter, and a ˜0.5 mm total thickness of the shielding material is used to demonstrate the idea. The shield axis is oriented along the horizontal component (˜320 mG) of the Earth's magnetic field. A simple way to increase the axial shielding factor is to use a pair of compensating coaxial ring coils set at both open ends of the shield. This increases, however, the radial gradient of the shielded field since the axial compensation field is stronger towards the shield axis. In order to decrease the radial gradient, an additional ring coil is wound around the middle part of the outer surface of the shield. The compensating field generated by this central ring coil is stronger towards the inner surface of the shield, and it helps, therefore, to unify the axial resultant field over a wider area inside the shield. The axial shielding factor obtained with this compensation according to the proposed method is 128, in contrast to only 16.4 obtained with compensation by a set of two ring coils. The field gradients observed are 1.2 μG/cm along the length direction and 2.7 μG/cm along the radial direction, in contrast to the 14 μG/cm axial and 78 μG/cm radial gradients obtained with compensation by a set of two ring coils.

  6. Neutral shielding and cloaking of magnetic fields using isotropic media

    NASA Astrophysics Data System (ADS)

    Kroon, Lars; Järrendahl, Kenneth

    2017-01-01

    A method for designing magnetic shields that do not perturb applied multipole fields in the static regime is developed. Cylindrical core-shell structures with two layers characterized by homogeneous isotropic permeabilities are found to support neutral shielding of multipole fields and unique cloaking solutions of arbitrary multipole order. An extra degree of freedom is provided by every layer added to the structure which may be exploited with an effective design formula for cloaking of additional field terms. The theory is illustrated with numerical simulations.

  7. Concerning superconducting inertial guidance gyroscopes inside superconducting magnetic shields

    SciTech Connect

    Satterthwaite, J.C.; Gawlinski, E.T.

    1997-12-01

    Superconductors can in theory be used to detect rotation by Josephson interference or by detection of the London field, a magnetic induction that fills the interior of any rotating bulk superconductor. One might hope to use these properties of superconductors to build a practical inertial guidance gyroscope. A problem arises from the necessity of surrounding the device with superconducting magnetic shielding: the London field generated by a co-rotating shield eliminates the response of the superconducting device within the shield. The present article demonstrates this point more rigorously than has been done before, discussing solutions of Ampere`s law for rotating and nonrotating superconductors and paying careful attention to boundary conditions. Beginning with a supercurrent density derivable from either the Ginzburg-Landau or the London theory of superconductivity, the article shows: (1) that a superconducting device cannot distinguish between rotation and an applied magnetic field; (2) that a superconducting device surrounded by a co-rotating superconducting shield cannot detect rotation. The term `superconducting gyroscope` in this article refers only to a device whose working principle is the response of the superconductor itself to rotation, not to any device in which superconducting electronic components are used to detect some other effect. {copyright} {ital 1997 American Institute of Physics.}

  8. Magnetic heat pumping near room temperature

    NASA Technical Reports Server (NTRS)

    Brown, G. V.

    1976-01-01

    It is shown that magnetic heat pumping can be made practical at room temperature by using a ferromagnetic material with a Curie point at or near operating temperature and an appropriate regenerative thermodynamic cycle. Measurements are performed which show that gadolinium is a resonable working material and it is found that the application of a 7-T magnetic field to gadolinium at the Curie point (293 K) causes a heat release of 4 kJ/kg under isothermal conditions or a temperature rise of 14 K under adiabatic conditions. A regeneration technique can be used to lift the load of the lattice and electronic heat capacities off the magnetic system in order to span a reasonable temperature difference and to pump as much entropy per cycle as possible

  9. Dynamic modeling of the behavior of permalloy for magnetic shielding

    NASA Astrophysics Data System (ADS)

    Sun, Z.; Reisner, M.; Fierlinger, P.; Schnabel, A.; Stuiber, S.; Li, L.

    2016-05-01

    The minimization of the remanent magnetization of ferromagnetic materials is a prerequisite for a reproducible low magnetic field inside shields. To realistically describe this so-called magnetic equilibration procedure, this paper proposes two approaches for the calculation of time- and space-dependent fields in the presence of ferromagnetic materials like permalloy. The first method is based on the Jiles-Atherton model and also takes into account frequency dependent effects. The second method is the newly developed empirical phase shift model, tailored specially for the simulation of the equilibration procedure. Both approaches are compared to experimental tests and show good quantitative agreement.

  10. Mode Transitions in Magnetically Shielded Hall Effect Thrusters

    NASA Technical Reports Server (NTRS)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Huang, Wensheng; Kamhawi, Hani; Hofer, Richard R.; Jorns, Benjamin A.; Polk, James E.

    2014-01-01

    A mode transition study is conducted in magnetically shielded thrusters where the magnetic field magnitude is varied to induce mode transitions. Three different oscillatory modes are identified with the 20-kW NASA-300MS-2 and the 6-kW H6MS: Mode 1) global mode similar to unshielded thrusters at low magnetic fields, Mode 2) cathode oscillations at nominal magnetic fields, and Mode 3) combined spoke, cathode and breathing mode oscillations at high magnetic fields. Mode 1 exhibits large amplitude, low frequency (1-10 kHz), breathing mode type oscillations where discharge current mean value and oscillation amplitude peak. The mean discharge current is minimized while thrust-to-power and anode efficiency are maximized in Mode 2, where higher frequency (50-90 kHz), low amplitude, cathode oscillations dominate. Thrust is maximized in Mode 3 and decreases by 5-6% with decreasing magnetic field strength. The presence or absence of spokes and strong cathode oscillations do not affect each other or discharge current. Similar to unshielded thrusters, mode transitions and plasma oscillations affect magnetically shielded thruster performance and should be characterized during system development.

  11. High-Permeability Magnetic Polymer Additives for Lightweight Electromagnetic Shielding

    DTIC Science & Technology

    2015-08-01

    dopants in polymeric electromagnetic (EM) shielding materials. The research hypothesis was that ferromagnetic polymers can be realized via doping... organic materials (no metal content) with no net magnetic moment. Because polymers can be synthesized with aromatic carbon (C) rings, however, similar...structures of the general form MxLyClx+y. Such dopants can be introduced to polymeric materials either by entrapment inside the polymer matrix (physical

  12. Electrically shielded enclosure with magnetically retained removable cover

    DOEpatents

    Rivers, Craig J.; Lee, Roanne A.; Jones, Glenn E.

    1996-01-01

    Disclosed is an electrically shielded enclosure having electrical components therein and a removable electrically shielded cover over an opening in the enclosure with a magnetic securement mechanism provided to removably secure the cover to the enclosure in a manner which will provide easy access, yet also provide an electrical seal between the cover and the enclosure capable of preventing the passage of electrical radiation through the joint between the cover and the enclosure. Magnets are provided on the enclosure peripherally around the opening and facing the cover, and a ferromagnetic surface is provided on the mating surface of the cover facing the magnets, with a continuous electrical seal provided between the magnets and the ferromagnetic surface on the cover to prevent the leakage of electromagnetic radiation therethrough. In one embodiment the electrical seal includes a flexible metal casing or surface, which is attached to the enclosure and positioned between the magnets and the ferromagnetic surface on the cover, and which is sufficiently flexible to be capable of conforming to the ferromagnetic surface to provide an electrical seal between the cover and the enclosure. In another embodiment, the electrical seal includes a metal mesh associated with the enclosure and positioned between the magnets on the enclosure and the ferromagnetic surface on the cover. The metal mesh is also capable of conforming to the surface of the ferromagnetic surface to thereby provide an electrical seal between the cover and the enclosure.

  13. Magnetic shielding of Hall thrusters at high discharge voltages

    SciTech Connect

    Mikellides, Ioannis G. Hofer, Richard R.; Katz, Ira; Goebel, Dan M.

    2014-08-07

    A series of numerical simulations and experiments have been performed to assess the effectiveness of magnetic shielding in a Hall thruster operating in the discharge voltage range of 300–700 V (I{sub sp} ≈ 2000–2700 s) at 6 kW, and 800 V (I{sub sp} ≈ 3000) at 9 kW. At 6 kW, the magnetic field topology with which highly effective magnetic shielding was previously demonstrated at 300 V has been retained for all other discharge voltages; only the magnitude of the field has been changed to achieve optimum thruster performance. It is found that magnetic shielding remains highly effective for all discharge voltages studied. This is because the channel is long enough to allow hot electrons near the channel exit to cool significantly upon reaching the anode. Thus, despite the rise of the maximum electron temperature in the channel with discharge voltage, the electrons along the grazing lines of force remain cold enough to eliminate or reduce significantly parallel gradients of the plasma potential near the walls. Computed maximum erosion rates in the range of 300–700 V are found not to exceed 10{sup −2} mm/kh. Such rates are ∼3 orders of magnitude less than those observed in the unshielded version of the same thruster at 300 V. At 9 kW and 800 V, saturation of the magnetic circuit did not allow for precisely the same magnetic shielding topology as that employed during the 6-kW operation since this thruster was not designed to operate at this condition. Consequently, the maximum erosion rate at the inner wall is found to be ∼1 order of magnitude higher (∼10{sup −1} mm/kh) than that at 6 kW. At the outer wall, the ion energy is found to be below the sputtering yield threshold so no measurable erosion is expected.

  14. Anisotropic Pressure, Transport, and Shielding of Magnetic Perturbations

    SciTech Connect

    H.E. Mynick and A.H. Boozer

    2008-05-23

    We compute the effect on a tokamak of applying a nonaxisymmetric magnetic perturbation δΒ. An equilibrium with scalar pressure p yields zero net radial current, and therefore zero torque. Thus, the usual approach, which assumes scalar pressure, is not self-consistent, and masks the close connection which exists between that radial current and the in-surface currents, which provide shielding or amplification of δΒ. Here, we analytically compute the pressure anisoptropy, anisoptropy, pll, p⊥ ≠ p, and from this, both the radial and in-surface currents. The surface-average of the radial current recovers earlier expressions for ripple transport, while the in-surface currents provide an expression for the amount of self-consistent shielding the plasma provides.

  15. Magnetic shielding of a laboratory Hall thruster. II. Experiments

    SciTech Connect

    Hofer, Richard R. Goebel, Dan M.; Mikellides, Ioannis G.; Katz, Ira

    2014-01-28

    The physics of magnetic shielding in Hall thrusters were validated through laboratory experiments demonstrating essentially erosionless, high-performance operation. The magnetic field near the walls of a laboratory Hall thruster was modified to effectively eliminate wall erosion while maintaining the magnetic field topology away from the walls necessary to retain efficient operation. Plasma measurements at the walls validate our understanding of magnetic shielding as derived from the theory. The plasma potential was maintained very near the anode potential, the electron temperature was reduced by a factor of two to three, and the ion current density was reduced by at least a factor of two. Measurements of the carbon backsputter rate, wall geometry, and direct measurement of plasma properties at the wall indicate that the wall erosion rate was reduced by a factor of 1000 relative to the unshielded thruster. These changes effectively eliminate wall erosion as a life limitation in Hall thrusters, enabling a new class of deep-space missions that could not previously be attempted.

  16. Magnetic shielding of interplanetary spacecraft against solar flare radiation

    NASA Technical Reports Server (NTRS)

    Cocks, Franklin H.; Watkins, Seth

    1993-01-01

    The ultimate objective of this work is to design, build, and fly a dual-purpose, piggyback payload whose function is to produce a large volume, low intensity magnetic field and to test the concept of using such a magnetic field (1) to protect spacecraft against solar flare protons, (2) to produce a thrust of sufficient magnitude to stabilize low satellite orbits against orbital decay from atmospheric drag, and (3) to test the magsail concept. These all appear to be capable of being tested using the same deployed high temperature superconducting coil. In certain orbits, high temperature superconducting wire, which has now been developed to the point where silver-sheathed high T sub c wires one mm in diameter are commercially available, can be used to produce the magnetic moments required for shielding without requiring any mechanical cooling system. The potential benefits of this concept apply directly to both earth-orbital and interplanetary missions. The usefulness of a protective shield for manned missions needs scarcely to be emphasized. Similarly, the usefulness of increasing orbit perigee without expenditure of propellant is obvious. This payload would be a first step in assessing the true potential of large volume magnetic fields in the US space program. The objective of this design research is to develop an innovative, prototype deployed high temperature superconducting coil (DHTSC) system.

  17. Magnetic shield for turbomolecular pump of the Magnetized Plasma Linear Experimental device at Saha Institute of Nuclear Physics.

    PubMed

    Biswas, Subir; Chattopadhyay, Monobir; Pal, Rabindranath

    2011-01-01

    The turbo molecular pump of the Magnetized Plasma Linear Experimental device is protected from damage by a magnetic shield. As the pump runs continuously in a magnetic field environment during a plasma physics experiment, it may get damaged owing to eddy current effect. For design and testing of the shield, first we simulate in details various aspects of magnetic shield layouts using a readily available field design code. The performance of the shield made from two half cylinders of soft iron material, is experimentally observed to agree very well with the simulation results.

  18. NMR shielding constants in PH3, absolute shielding scale, and the nuclear magnetic moment of 31P.

    PubMed

    Lantto, Perttu; Jackowski, Karol; Makulski, Włodzimierz; Olejniczak, Małgorzata; Jaszuński, Michał

    2011-09-29

    Ab initio values of the absolute shielding constants of phosphorus and hydrogen in PH(3) were determined, and their accuracy is discussed. In particular, we analyzed the relativistic corrections to nuclear magnetic resonance (NMR) shielding constants, comparing the constants computed using the four-component Dirac-Hartree-Fock approach, the four-component density functional theory (DFT), and the Breit-Pauli perturbation theory (BPPT) with nonrelativistic Hartree-Fock or DFT reference functions. For the equilibrium geometry, we obtained σ(P) = 624.309 ppm and σ(H) = 29.761 ppm. Resonance frequencies of both nuclei were measured in gas-phase NMR experiments, and the results were extrapolated to zero density to provide the frequency ratio for an isolated PH(3) molecule. This ratio, together with the computed shielding constants, was used to determine a new value of the nuclear magnetic dipole moment of (31)P: μ(P) = 1.1309246(50) μ(N).

  19. Magnetic shielding in a low temperature torsion pendulum experiment. [superconducting cylinders for attenuation earth field

    NASA Technical Reports Server (NTRS)

    Phillips, P. R.

    1979-01-01

    A new type of ether drift experiment searches for anomalous torques on a permanent magnet. A torsion pendulum is used at liquid helium temperature, so that superconducting cylinders can be used to shield magnetic fields. Lead shields attenuate the earth's field, while Nb-Sn shields fastened to the pendulum contain the fields of the magnet. The paper describes the technique by which the earth's field can be reduced below 0.0001 G while simultaneously the moment of the magnet can be reduced by a factor 7 x 10 to the 4th.

  20. Physical design of magnetic shielding for LEReC cooling section

    SciTech Connect

    Seletskiy, S.; Fedotov, A.; Gassner, D.; Kayran, D.; Mahler, G.; Meng, W.; Thieberger, P.

    2016-04-05

    The goal of this note is to set basic parameters for the magnetic shielding of LEReC CS with required design attenuation. We considered physical design of magnetic shielding of LEReC cooling section. The schematic of this design along with the list of its basic parameters is shown in Fig. 3. We are planning to use 2 layers of 1 mm thick cylindrical mu-metal shields with μ=11000. The radius of the first layer sitting on top of vacuum chamber is 63.5 mm. The second layer radius is 150 mm. Such shielding guarantees adequate transverse angles of electron beam trajectory in the CS.

  1. Multilayer film shields for the protection of PMT from constant magnetic field.

    PubMed

    Dmitrenko, V V; Besson, David; Nyunt, PhyoWai; Grabchikov, S S; Grachev, V M; Muraviev-Smirnov, C C; Ulin, S E; Uteshev, Z M; Vlasik, K F

    2015-01-01

    Photomultiplier tubes (PMTs) are widely used in physical experiments as well as in applied devices. PMTs are sensitive to magnetic field, so creation of effective magnetic shields for their protection is very important. In this paper, the results of measurements of shielding effectiveness of multilayer film magnetic shields on PMT-85 are presented. Shields were formed by alternating layers of a material with high magnetic permeability (Ni-Fe) and high electric conductivity-Cu. The maximum number of bilayers reached 45. It is shown that in weak magnetic fields up to 0.5 mT, the output signal amplitude from PMT-85 does not change for all used multilayer shields. In strong magnetic field of 2-4 mT, the output signal amplitude decrease with 10%-40% depending from the number of layers in the shield. The Pulse distribution of PMT-85 in magnetic field 0.2-4 mT slightly changed in the range 1.1%-1.3% for the case when the number of layers do not exceed 10 and practically did not change for a shield with 45 double layers.

  2. Analytical-HZETRN Model for Rapid Assessment of Active Magnetic Radiation Shielding

    NASA Technical Reports Server (NTRS)

    Washburn, S. A.; Blattnig, S. R.; Singleterry, R. C.; Westover, S. C.

    2014-01-01

    The use of active radiation shielding designs has the potential to reduce the radiation exposure received by astronauts on deep-space missions at a significantly lower mass penalty than designs utilizing only passive shielding. Unfortunately, the determination of the radiation exposure inside these shielded environments often involves lengthy and computationally intensive Monte Carlo analysis. In order to evaluate the large trade space of design parameters associated with a magnetic radiation shield design, an analytical model was developed for the determination of flux inside a solenoid magnetic field due to the Galactic Cosmic Radiation (GCR) radiation environment. This analytical model was then coupled with NASA's radiation transport code, HZETRN, to account for the effects of passive/structural shielding mass. The resulting model can rapidly obtain results for a given configuration and can therefore be used to analyze an entire trade space of potential variables in less time than is required for even a single Monte Carlo run. Analyzing this trade space for a solenoid magnetic shield design indicates that active shield bending powers greater than 15 Tm and passive/structural shielding thicknesses greater than 40 g/cm2 have a limited impact on reducing dose equivalent values. Also, it is shown that higher magnetic field strengths are more effective than thicker magnetic fields at reducing dose equivalent.

  3. Analytical-HZETRN model for rapid assessment of active magnetic radiation shielding

    NASA Astrophysics Data System (ADS)

    Washburn, S. A.; Blattnig, S. R.; Singleterry, R. C.; Westover, S. C.

    2014-01-01

    The use of active radiation shielding designs has the potential to reduce the radiation exposure received by astronauts on deep-space missions at a significantly lower mass penalty than designs utilizing only passive shielding. Unfortunately, the determination of the radiation exposure inside these shielded environments often involves lengthy and computationally intensive Monte Carlo analysis. In order to evaluate the large trade space of design parameters associated with a magnetic radiation shield design, an analytical model was developed for the determination of flux inside a solenoid magnetic field due to the Galactic Cosmic Radiation (GCR) radiation environment. This analytical model was then coupled with NASA's radiation transport code, HZETRN, to account for the effects of passive/structural shielding mass. The resulting model can rapidly obtain results for a given configuration and can therefore be used to analyze an entire trade space of potential variables in less time than is required for even a single Monte Carlo run. Analyzing this trade space for a solenoid magnetic shield design indicates that active shield bending powers greater than ∼15 Tm and passive/structural shielding thicknesses greater than 40 g/cm2 have a limited impact on reducing dose equivalent values. Also, it is shown that higher magnetic field strengths are more effective than thicker magnetic fields at reducing dose equivalent.

  4. Four-component relativistic theory for nuclear magnetic shielding: magnetically balanced gauge-including atomic orbitals.

    PubMed

    Cheng, Lan; Xiao, Yunlong; Liu, Wenjian

    2009-12-28

    It is recognized only recently that the incorporation of the magnetic balance condition is absolutely essential for four-component relativistic theories of magnetic properties. Another important issue to be handled is the so-called gauge problem in calculations of, e.g., molecular magnetic shielding tensors with finite bases. It is shown here that the magnetic balance can be adapted to distributed gauge origins, leading to, e.g., magnetically balanced gauge-including atomic orbitals (MB-GIAOs) in which each magnetically balanced atomic orbital has its own local gauge origin placed on its center. Such a MB-GIAO scheme can be combined with any level of theory for electron correlation. The first implementation is done here at the coupled-perturbed Dirac-Kohn-Sham level. The calculated molecular magnetic shielding tensors are not only independent of the choice of gauge origin but also converge rapidly to the basis set limit. Close inspections reveal that (zeroth order) negative energy states are only important for the expansion of first order electronic core orbitals. Their contributions to the paramagnetism are therefore transferable from atoms to molecule and are essentially canceled out for chemical shifts. This allows for simplifications of the coupled-perturbed equations.

  5. Room temperature organic magnets derived from sp3 functionalized graphene

    PubMed Central

    Tuček, Jiří; Holá, Kateřina; Bourlinos, Athanasios B.; Błoński, Piotr; Bakandritsos, Aristides; Ugolotti, Juri; Dubecký, Matúš; Karlický, František; Ranc, Václav; Čépe, Klára; Otyepka, Michal; Zbořil, Radek

    2017-01-01

    Materials based on metallic elements that have d orbitals and exhibit room temperature magnetism have been known for centuries and applied in a huge range of technologies. Development of room temperature carbon magnets containing exclusively sp orbitals is viewed as great challenge in chemistry, physics, spintronics and materials science. Here we describe a series of room temperature organic magnets prepared by a simple and controllable route based on the substitution of fluorine atoms in fluorographene with hydroxyl groups. Depending on the chemical composition (an F/OH ratio) and sp3 coverage, these new graphene derivatives show room temperature antiferromagnetic ordering, which has never been observed for any sp-based materials. Such 2D magnets undergo a transition to a ferromagnetic state at low temperatures, showing an extraordinarily high magnetic moment. The developed theoretical model addresses the origin of the room temperature magnetism in terms of sp2-conjugated diradical motifs embedded in an sp3 matrix and superexchange interactions via –OH functionalization. PMID:28216636

  6. Room temperature organic magnets derived from sp(3) functionalized graphene.

    PubMed

    Tuček, Jiří; Holá, Kateřina; Bourlinos, Athanasios B; Błoński, Piotr; Bakandritsos, Aristides; Ugolotti, Juri; Dubecký, Matúš; Karlický, František; Ranc, Václav; Čépe, Klára; Otyepka, Michal; Zbořil, Radek

    2017-02-20

    Materials based on metallic elements that have d orbitals and exhibit room temperature magnetism have been known for centuries and applied in a huge range of technologies. Development of room temperature carbon magnets containing exclusively sp orbitals is viewed as great challenge in chemistry, physics, spintronics and materials science. Here we describe a series of room temperature organic magnets prepared by a simple and controllable route based on the substitution of fluorine atoms in fluorographene with hydroxyl groups. Depending on the chemical composition (an F/OH ratio) and sp(3) coverage, these new graphene derivatives show room temperature antiferromagnetic ordering, which has never been observed for any sp-based materials. Such 2D magnets undergo a transition to a ferromagnetic state at low temperatures, showing an extraordinarily high magnetic moment. The developed theoretical model addresses the origin of the room temperature magnetism in terms of sp(2)-conjugated diradical motifs embedded in an sp(3) matrix and superexchange interactions via -OH functionalization.

  7. Room temperature organic magnets derived from sp3 functionalized graphene

    NASA Astrophysics Data System (ADS)

    Tuček, Jiří; Holá, Kateřina; Bourlinos, Athanasios B.; Błoński, Piotr; Bakandritsos, Aristides; Ugolotti, Juri; Dubecký, Matúš; Karlický, František; Ranc, Václav; Čépe, Klára; Otyepka, Michal; Zbořil, Radek

    2017-02-01

    Materials based on metallic elements that have d orbitals and exhibit room temperature magnetism have been known for centuries and applied in a huge range of technologies. Development of room temperature carbon magnets containing exclusively sp orbitals is viewed as great challenge in chemistry, physics, spintronics and materials science. Here we describe a series of room temperature organic magnets prepared by a simple and controllable route based on the substitution of fluorine atoms in fluorographene with hydroxyl groups. Depending on the chemical composition (an F/OH ratio) and sp3 coverage, these new graphene derivatives show room temperature antiferromagnetic ordering, which has never been observed for any sp-based materials. Such 2D magnets undergo a transition to a ferromagnetic state at low temperatures, showing an extraordinarily high magnetic moment. The developed theoretical model addresses the origin of the room temperature magnetism in terms of sp2-conjugated diradical motifs embedded in an sp3 matrix and superexchange interactions via -OH functionalization.

  8. Structural Design and Thermal Analysis for Thermal Shields of the MICE Coupling Magnets

    SciTech Connect

    Green, Michael A.; Pan, Heng; Liu, X. K.; Wang, Li; Wu, Hong; Chen, A. B.; Guo, X.L.

    2009-07-01

    A superconducting coupling magnet made from copper matrix NbTi conductors operating at 4 K will be used in the Muon Ionization Cooling Experiment (MICE) to produce up to 2.6 T on the magnet centerline to keep the muon beam within the thin RF cavity indows. The coupling magnet is to be cooled by two cryocoolers with a total cooling capacity of 3 W at 4.2 K. In order to keep a certain operating temperature margin, the most important is to reduce the heat leakage imposed on cold surfaces of coil cold mass assembly. An ntermediate temperature shield system placed between the coupling coil and warm vacuum chamber is adopted. The shield system consists of upper neck shield, main shields, flexible connections and eight supports, which is to be cooled by the first stage cold heads of two ryocoolers with cooling capacity of 55 W at 60 K each. The maximum temperature difference on the shields should be less than 20 K, so the thermal analyses for the shields with different thicknesses, materials, flexible connections for shields' cooling and structure design for heir supports were carried out. 1100 Al is finally adopted and the maximum temperature difference is around 15 K with 4 mm shield thickness. The paper is to present detailed analyses on the shield system design.

  9. Structural Design and Thermal Analysis for Thermal Shields of the Mice Coupling Magnets

    NASA Astrophysics Data System (ADS)

    Pan, H.; Liu, X. K.; Wang, L.; Guo, X. L.; Wu, H.; Chen, A. B.; Green, M. A.

    2010-04-01

    A superconducting coupling magnet made from copper matrix NbTi conductors operating at 4 K will be used in the Muon Ionization Cooling Experiment (MICE) to produce up to 2.6 T on the magnet centerline to keep the muon beam within the thin RF cavity windows. The coupling magnet is to be cooled by two cryocoolers with a total cooling capacity of 3 W at 4.2 K. In order to keep a certain operating temperature margin, the most important is to reduce the heat leakage imposed on cold surfaces of coil cold mass assembly. An intermediate temperature shield system placed between the coupling coil and warm vacuum chamber is adopted. The shield system consists of upper neck shield, main shields, flexible connections and eight supports, which is to be cooled by the first stage cold heads of two cryocoolers with cooling capacity of 55 W at 60 K each. The maximum temperature difference on the shields should be less than 20 K, so the thermal analyses for the shields with different thicknesses, materials, flexible connections for shields' cooling and structure design for their supports were carried out. 1100 Al is finally adopted and the maximum temperature difference is around 15 K with 4 mm shield thickness. The paper is to present detailed analyses on the shield system design.

  10. MAGNETIC SHIELDING OF EXOMOONS BEYOND THE CIRCUMPLANETARY HABITABLE EDGE

    SciTech Connect

    Heller, René; Zuluaga, Jorge I. E-mail: jzuluaga@fisica.udea.edu.co

    2013-10-20

    With most planets and planetary candidates detected in the stellar habitable zone (HZ) being super-Earths and gas giants rather than Earth-like planets, we naturally wonder if their moons could be habitable. The first detection of such an exomoon has now become feasible, and due to observational biases it will be at least twice as massive as Mars. However, formation models predict that moons can hardly be as massive as Earth. Hence, a giant planet's magnetosphere could be the only possibility for such a moon to be shielded from cosmic and stellar high-energy radiation. Yet, the planetary radiation belt could also have detrimental effects on exomoon habitability. Here we synthesize models for the evolution of the magnetic environment of giant planets with thresholds from the runaway greenhouse (RG) effect to assess the habitability of exomoons. For modest eccentricities, we find that satellites around Neptune-sized planets in the center of the HZ around K dwarf stars will either be in an RG state and not be habitable, or they will be in wide orbits where they will not be affected by the planetary magnetosphere. Saturn-like planets have stronger fields, and Jupiter-like planets could coat close-in habitable moons soon after formation. Moons at distances between about 5 and 20 planetary radii from a giant planet can be habitable from an illumination and tidal heating point of view, but still the planetary magnetosphere would critically influence their habitability.

  11. Assessment of Pole Erosion in a Magnetically Shielded Hall Thruster

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Ortega, Alejandro L.

    2014-01-01

    Numerical simulations of a 6-kW laboratory Hall thruster called H6 have been performed to quantify the erosion rate at the inner pole. The assessments have been made in two versions of the thruster, namely the unshielded (H6US) and magnetically shielded (H6MS) configurations. The simulations have been performed with the 2-D axisymmetric code Hall2De which employs a new multi-fluid ion algorithm to capture the presence of low-energy ions in the vicinity of the poles. It is found that the maximum computed erosion rate at the inner pole of the H6MS exceeds the measured rate of back-sputtered deposits by 4.5 times. This explains only part of the surface roughening that was observed after a 150-h wear test, which covered most of the pole area exposed to the plasma. For the majority of the pole surface the computed erosion rates are found to be below the back-sputter rate and comparable to those in the H6US which exhibited little to no sputtering in previous tests. Possible explanations for the discrepancy are discussed.

  12. HZE particle shielding using confined magnetic fields. [high-energy heavy ions

    NASA Technical Reports Server (NTRS)

    Townsend, L. W.

    1983-01-01

    The great rigidities characteristic of high energy heavy ion (HZE) particles are judged to preclude near term use of confined magnetic fields of reasonable dimensions and strengths for small spacecraft shielding on long duration manned missions. It is noted that a Mars mission-class shield, although effective against solar protons, would be useless for HZE particles unless the mass and size of the shield are increased by several orders of magnitude (to yield a shield comparable to those contemplated for permanent space stations).

  13. Evaluation of a method to shield a welding electron beam from magnetic interference

    NASA Technical Reports Server (NTRS)

    Wall, W. A.

    1976-01-01

    It is known that electron beams are easily deflected by magnetic and electrostatic fields. Therefore, to prevent weld defects, stray electromagnetic fields are avoided in electron beam welding chambers if at all possible. The successful results of tests conducted at MSFC to evaluate a simple magnetic shield made from steel tubing are reported. Tests indicate that this shield was up to 85 percent effective in reducing magnetic effects on the electron beam of a welding machine. In addition, residual magnetic fields within the shield were so nearly uniform that the net effect on the beam alignment was negligible. It is concluded that the shield, with the addition of a tungsten liner, could be used in production welding.

  14. Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields

    DOEpatents

    Epstein, Arthur J.; Morin, Brian G.

    1998-01-01

    The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors.

  15. Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields

    DOEpatents

    Epstein, A.J.; Morin, B.G.

    1998-10-13

    The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors. 21 figs.

  16. Closed bore XMR (CBXMR) systems for aortic valve replacement: Active magnetic shielding of x-ray tubes

    SciTech Connect

    Bracken, John A.; DeCrescenzo, Giovanni; Komljenovic, Philip; Lillaney, Prasheel V.; Fahrig, Rebecca; Rowlands, J. A.

    2009-05-15

    Hybrid closed bore x-ray/MRI systems are being developed to improve the safety and efficacy of percutaneous aortic valve replacement procedures by harnessing the complementary strengths of the x-ray and MRI modalities in a single interventional suite without requiring patient transfer between two rooms. These systems are composed of an x-ray C-arm in close proximity ({approx_equal}1 m) to an MRI scanner. The MRI magnetic fringe field can cause the electron beam in the x-ray tube to deflect. The deflection causes the x-ray field of view to shift position on the detector receptacle. This could result in unnecessary radiation exposure to the patient and the staff in the cardiac catheterization laboratory. Therefore, the electron beam deflection must be corrected. The authors developed an active magnetic shielding system that can correct for electron beam deflection to within an accuracy of 5% without truncating the field of view or increasing exposure to the patient. This system was able to automatically adjust to different field strengths as the external magnetic field acting on the x-ray tube was changed. Although a small torque was observed on the shielding coils of the active shielding system when they were placed in a magnetic field, this torque will not impact their performance if they are securely mounted on the x-ray tube and the C-arm. The heating of the coils of the shielding system for use in the clinic caused by electric current was found to be slow enough not to require a dedicated cooling system for one percutaneous aortic valve replacement procedure. However, a cooling system will be required if multiple procedures are performed in one session.

  17. Relativistic effects on the nuclear magnetic shielding in the MF (M=Cu, Ag, Au) series

    SciTech Connect

    David, Jorge; Restrepo, Albeiro

    2007-11-15

    Relativistic effects on the nuclear magnetic shielding {sigma}(M) of the series of diatomics MF (M=Cu, Ag, Au) are calculated and analyzed using the Dirac-Hartree-Fock (DHF) method in the random phase approximation (RPA). Significant differences due to relativistic effects on the shielding constant {sigma}(M) are found in this series of atoms. The high electronegativity of the fluorine atom works in conjunction with the spin-orbit coupling to increase the calculated value for {sigma}(Au). An unusually large diamagnetic contribution to the shielding constant is observed. Nonrelativistic nuclear magnetic shielding [{sigma}{sup NR}(M)] shows very good linear correlation with the nuclear charge (Z) of the metal, while the relativistic shielding [{sigma}{sup rel}(M)] varies as Z{sup 2.26}.

  18. Effects of fluctuating magnetic fields on a superconducting bulk rotor shielded with superconducting rings

    NASA Astrophysics Data System (ADS)

    Yamagishi, K.; Ogawa, J.; Tsukamoto, O.

    2014-05-01

    We study the effect of a fluctuating magnetic field, which is one of the technical problems for trapped magnetic fields in a bulk superconductor, to realize a practical bulk superconductor rotating machine. Previous research and other's research has shown that fluctuating magnetic fields reduce the strength of trapped magnetic fields in superconducting bulk modules [1, 2]. This deters development of applications of AC rotating machines because superconducting bulk modules are always exposed to a fluctuating magnetic field. Therefore, it is necessary to develop a method to control decrease of the trapped magnetic field. We propose a method to use the shielding ring of a superconducting wire to achieve this goal and the effects are confirmed experimentally [3]. We are now building test equipment for examining the performance of a shielding ring in a bulk rotating machine. This paper reports the test result for the shielding ring applied to the bulk superconducting rotor that is a part of the test equipment.

  19. Shielding design of a treatment room for an accelerator-based epithermal neutron irradiation facility for BNCT

    SciTech Connect

    Evans, J.F.; Blue, T.E.

    1996-11-01

    Protecting the facility personnel and the general public from radiation exposure is a primary safety concern of an accelerator-based epithermal neutron irradiation facility. This work makes an attempt at answering the questions {open_quotes}How much?{close_quotes} and {open_quotes}What kind?{close_quotes} of shielding will meet the occupational limits of such a facility. Shielding effectiveness is compared for ordinary and barytes concretes in combination with and without borated polyethylene. A calculational model was developed of a treatment room, patient {open_quotes}scatterer,{close_quotes} and the epithermal neutron beam. The Monte Carlo code, MCNP, was used to compute the total effective dose equivalent rates at specific points of interest outside of the treatment room. A conservative occupational effective dose rate limit of 0.01 mSv h{sup {minus}1} was the guideline for this study. Conservative Monte Carlo calculations show that constructing the treatment room walls with 1.5 m of ordinary concrete, 1.2 m of barytes concrete, 1.0 m of ordinary concrete preceded by 10 cm of 5% boron-polyethylene, or 0.8 m of barytes concrete preceded by 10 cm of 5% boron-polyethylene will adequately protect facility personnel. 20 refs., 8 figs., 2 tabs.

  20. Shielding design of a treatment room for an accelerator-based epithermal neutron irradiation facility for BNCT.

    PubMed

    Evans, J F; Blue, T E

    1996-11-01

    Protecting the facility personnel and the general public from radiation exposure is a primary safety concern of an accelerator-based epithermal neutron irradiation facility. This work makes an attempt at answering the questions "How much?" and "What kind?" of shielding will meet the occupational limits of such a facility. Shielding effectiveness is compared for ordinary and barytes concretes in combination with and without borated polyethylene. A calculational model was developed of a treatment room , patient "scatterer," and the epithermal neutron beam. The Monte Carlo code, MCNP, was used to compute the total effective dose equivalent rates at specific points of interest outside of the treatment room. A conservative occupational effective dose rate limit of 0.01 mSv h-1 was the guideline for this study. Conservative Monte Carlo calculations show that constructing the treatment room walls with 1.5 m of ordinary concrete, 1.2 m of barytes concrete, 1.0 m of ordinary concrete preceded by 10 cm of 5% boron-polyethylene, or 0.8 m of barytes concrete preceded by 10 cm of 5% boron-polyethylene will adequately protect facility personnel.

  1. Application of shielding current in bulk HTS to control magnetic field distribution

    NASA Astrophysics Data System (ADS)

    Kii, T.

    2016-03-01

    Superconducting shielding current is excited when external field is applied to superconductor. In case for field cooling of bulk superconductor, shielding current is an origin of strong trapped field. When external field is changed to a properly arranged bulk HTS array, various magnetic field distribution can be formed by an excited shielding current in each bulk HTS. This paper presents a simple intuitively method to design magnetic field distribution using supercurrents in bulk high-temperature superconductor (HTS) array. In this method, an ideal current path for intended field distribution is represented by shielding currents in bulk HTS array. Expected performance can be roughly estimated by using Biot-Savart law. As examples, Maxwell coil pair and helical field generator are designed. This method can be applied to design various magnet devices using bulk HTS array.

  2. Shielding of Sensitive Electronic Devices in Magnetic Nanoparticle Hyperthermia Using Arrays of Coils

    NASA Astrophysics Data System (ADS)

    Spirou, S. V.; Tsialios, P.; Loudos, G.

    2015-09-01

    In Magnetic Nanoparticle Hyperthermia (MNH) an externally applied electromagnetic field transfers energy to the magnetic nanoparticles in the body, which in turn convert this energy into heat, thus locally heating the tissue they are located in. This external electromagnetic field is sufficiently strong so as to cause interference and affect sensitive electronic equipment. Standard shielding of magnetic fields involves Faraday cages or coating with high-permeability shielding alloys; however, these techniques cannot be used with optically sensitive devices, such as those employed in Optical Coherence Tomography or radionuclide imaging. In this work we present a method to achieve magnetic shielding using an array of coils. The magnetic field generated by a single coil was calculated using the COMSOL physics simulation toolkit. Software was written in C/C++ to import the single-coil data, and then calculate the positions, number of turns and currents in the shielding coils in order to minimize the magnetic field strength at the desired location. Simulations and calculations have shown that just two shielding coils can reduce the magnetic field by 2-3 orders of magnitude.

  3. Design of a three-axis magnetic field measurement system for the magnetic shield of the ring laser gyroscope

    NASA Astrophysics Data System (ADS)

    Rong, Chuiyu; Yao, Xu

    2015-10-01

    The magnetic field is one of the main causes of zero drift in a Ring Laser Gyroscope (RLG), which should be avoided by adopting a magnetic shielding system. The Gauss Meter is usually used to measure the magnetic shielding effectiveness. Generally, the traditional Gauss Meter has advantages of high measure range and high reliability, however, its drawbacks such as complex structure, high price and the PC client software cannot be customized at will, are also obvious. In this paper, aiming at a type of experimental magnetic shielding box of RLG, we design a new portable three-axis magnetic field measurement system. This system has both high modularity degree and reliability, with measuring range at ±48Gs, max resolution at 1.5mGs and can measure the magnetic field in x, y and z direction simultaneously. Besides, its PC client software can be easily customized to achieve the automatic DAQ, analysis, plotting and storage functions. The experiment shows that, this system can meet the measuring requirements of certain type of experimental magnetic shielding box for RLG, meanwhile, for the measurement of some other magnetic shielding effectiveness, this system is also applicable.

  4. Magnetic properties of stainless steels at room and cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Oxley, Paul; Goodell, Jennifer; Molt, Robert

    2009-07-01

    The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room temperature and at 77 K. The steel samples studied were in the annealed state as received from the manufacturer. Our room temperature measurements indicate significantly harder magnetic properties than those quoted in the ASM International Handbook, which studied fully annealed stainless steel samples. Despite having harder magnetic properties than fully annealed steels some of the as-received steels still display soft magnetic properties adequate for magnetic applications. The carbon content of the steels was found to affect the permeability and coercive force, with lower-carbon steels displaying significantly higher permeability and lower coercive force. The decrease in coercive force with reduced carbon content is attributed to fewer carbide inclusions which inhibit domain wall motion. Cooling to 77 K resulted in harder magnetic properties. Averaged over the ten steels tested the maximum permeability decreased by 8%, the coercive force increased by 14%, and the residual and saturation flux densities increased by 4% and 3%, respectively. The change in coercive force when cooled is comparable to the theoretical prediction for iron, based on a model of domain wall motion inhibited by inclusions. The modest changes of the magnetic properties indicate that the stainless steels can still be used in magnetic applications at very low temperatures.

  5. Shorter Life Span of Microorganisms and Plants as a Consequence of Shielded Magnetic Environment

    NASA Astrophysics Data System (ADS)

    Dobrota, C.; Piso, I. M.; Bathory, D.

    The geomagnetic field is an essential environmental factor for life and health on this planet. In order to survey how magnetic fields affect the life span and the nitrogenase (an iron-sulphur enzyme) activity of Azotobacter chroococcum as well as the life span, the main organic synthesis and the water balance of plants (22 species), the biological tests were incubated under shielded magnetic field and also in normal geo-magnetic environment. The shielding level was about 10-6 of the terrestrial magnetic field.Life cycles of all organisms require the co-ordinated control of a complex set of interlocked physiological processes and metabolic pathways. Such processes are likely to be regulated by a large number of genes. Our researches suggest that the main point in biological structures, which seems to be affected by the low magnetic environment, is the water molecule. Magnetic field induces a molecular alignment. Under shielded conditions, unstructured water molecules with fewer hydrogen bonds, which are producing a more reactive environment, are occurring. As compared to control, the life span of both microorganisms and plants was shorter in shielded environment. A higher nitrogenase affinity for the substrate was recorded in normal geo-magnetic field compared to low magnetic field. The synthesis of carbohydrates, lipids, proteins and enzymes was modified under experimental conditions. The stomatal conductance was higher between 158 and 300% in shielded environment indicating an important water loss from the plant cells.Our results support the idea that the shielded magnetic environment induces different reactions depending on the time of exposure and on the main metabolic pathways of the cells.

  6. Options for Shielding Tokamak Cooling Water Electrical Components against High Magnetic Fields

    SciTech Connect

    Korsah, Kofi; Michael, Smith; Kim, Seokho H; Charles, Neumeyer

    2011-01-01

    The Tokamak Cooling Water System (TCWS) Instrumentation and Control (I&C) components of ITER will be located in areas of relatively high magnetic fields. Previous tests on electrical and I&C components have indicated that shielding will be required to protect these components from such magnetic fields. To accomplish this, studies were performed by AREVA Federal Services (AFS) in support of the TCWS Design project with the intent of identifying an optimal solution for shielding I&C components. This report presents a summary of these studies and presents design options for providing magnetic shielding to ITER TCWS I&C components and electrical equipment that are susceptible to the magnetic fields present.

  7. Quasi-Static Magnetic Field Shielding Using Longitudinal Mu-Near-Zero Metamaterials

    NASA Astrophysics Data System (ADS)

    Lipworth, Guy; Ensworth, Joshua; Seetharam, Kushal; Lee, Jae Seung; Schmalenberg, Paul; Nomura, Tsuyoshi; Reynolds, Matthew S.; Smith, David R.; Urzhumov, Yaroslav

    2015-08-01

    The control of quasi-static magnetic fields is of considerable interest in applications including the reduction of electromagnetic interference (EMI), wireless power transfer (WPT), and magnetic resonance imaging (MRI). The shielding of static or quasi-static magnetic fields is typically accomplished through the use of inherently magnetic materials with large magnetic permeability, such as ferrites, used sometimes in combination with metallic sheets and/or active field cancellation. Ferrite materials, however, can be expensive, heavy and brittle. Inspired by recent demonstrations of epsilon-, mu- and index-near-zero metamaterials, here we show how a longitudinal mu-near-zero (LMNZ) layer can serve as a strong frequency-selective reflector of magnetic fields when operating in the near-field region of dipole-like sources. Experimental measurements with a fabricated LMNZ sheet constructed from an artificial magnetic conductor - formed from non-magnetic, conducting, metamaterial elements - confirm that the artificial structure provides significantly improved shielding as compared with a commercially available ferrite of the same size. Furthermore, we design a structure to shield simultaneously at the fundamental and first harmonic frequencies. Such frequency-selective behavior can be potentially useful for shielding electromagnetic sources that may also generate higher order harmonics, while leaving the transmission of other frequencies unaffected.

  8. Quasi-Static Magnetic Field Shielding Using Longitudinal Mu-Near-Zero Metamaterials

    PubMed Central

    Lipworth, Guy; Ensworth, Joshua; Seetharam, Kushal; Lee, Jae Seung; Schmalenberg, Paul; Nomura, Tsuyoshi; Reynolds, Matthew S.; Smith, David R.; Urzhumov, Yaroslav

    2015-01-01

    The control of quasi-static magnetic fields is of considerable interest in applications including the reduction of electromagnetic interference (EMI), wireless power transfer (WPT), and magnetic resonance imaging (MRI). The shielding of static or quasi-static magnetic fields is typically accomplished through the use of inherently magnetic materials with large magnetic permeability, such as ferrites, used sometimes in combination with metallic sheets and/or active field cancellation. Ferrite materials, however, can be expensive, heavy and brittle. Inspired by recent demonstrations of epsilon-, mu- and index-near-zero metamaterials, here we show how a longitudinal mu-near-zero (LMNZ) layer can serve as a strong frequency-selective reflector of magnetic fields when operating in the near-field region of dipole-like sources. Experimental measurements with a fabricated LMNZ sheet constructed from an artificial magnetic conductor – formed from non-magnetic, conducting, metamaterial elements – confirm that the artificial structure provides significantly improved shielding as compared with a commercially available ferrite of the same size. Furthermore, we design a structure to shield simultaneously at the fundamental and first harmonic frequencies. Such frequency-selective behavior can be potentially useful for shielding electromagnetic sources that may also generate higher order harmonics, while leaving the transmission of other frequencies unaffected. PMID:26234929

  9. Quasi-Static Magnetic Field Shielding Using Longitudinal Mu-Near-Zero Metamaterials.

    PubMed

    Lipworth, Guy; Ensworth, Joshua; Seetharam, Kushal; Lee, Jae Seung; Schmalenberg, Paul; Nomura, Tsuyoshi; Reynolds, Matthew S; Smith, David R; Urzhumov, Yaroslav

    2015-08-03

    The control of quasi-static magnetic fields is of considerable interest in applications including the reduction of electromagnetic interference (EMI), wireless power transfer (WPT), and magnetic resonance imaging (MRI). The shielding of static or quasi-static magnetic fields is typically accomplished through the use of inherently magnetic materials with large magnetic permeability, such as ferrites, used sometimes in combination with metallic sheets and/or active field cancellation. Ferrite materials, however, can be expensive, heavy and brittle. Inspired by recent demonstrations of epsilon-, mu- and index-near-zero metamaterials, here we show how a longitudinal mu-near-zero (LMNZ) layer can serve as a strong frequency-selective reflector of magnetic fields when operating in the near-field region of dipole-like sources. Experimental measurements with a fabricated LMNZ sheet constructed from an artificial magnetic conductor - formed from non-magnetic, conducting, metamaterial elements - confirm that the artificial structure provides significantly improved shielding as compared with a commercially available ferrite of the same size. Furthermore, we design a structure to shield simultaneously at the fundamental and first harmonic frequencies. Such frequency-selective behavior can be potentially useful for shielding electromagnetic sources that may also generate higher order harmonics, while leaving the transmission of other frequencies unaffected.

  10. A large-scale magnetic shield with 10{sup 6} damping at millihertz frequencies

    SciTech Connect

    Altarev, I.; Bales, M.; Fierlinger, K.; Fierlinger, P.; Kuchler, F.; Marino, M. G.; Niessen, B.; Petzoldt, G.; Singh, J. T.; Stoepler, R.; Stuiber, S.; Sturm, M.; Taubenheim, B.; Beck, D. H.; Chupp, T.; Lins, T.; Schläpfer, U.; Schnabel, A.; Voigt, J.

    2015-05-14

    We present a magnetically shielded environment with a damping factor larger than 1 × 10{sup 6} at the mHz frequency regime and an extremely low field and gradient over an extended volume. This extraordinary shielding performance represents an improvement of the state-of-the-art in the difficult regime of damping very low-frequency distortions by more than an order of magnitude. This technology enables a new generation of high-precision measurements in fundamental physics and metrology, including searches for new physics far beyond the reach of accelerator-based experiments. We discuss the technical realization of the shield with its improvements in design.

  11. Nuclear magnetic shielding constants of liquid water: Insights from hybrid quantum mechanics/molecular mechanics models

    NASA Astrophysics Data System (ADS)

    Kongsted, Jacob; Nielsen, Christian B.; Mikkelsen, Kurt V.; Christiansen, Ove; Ruud, Kenneth

    2007-01-01

    We present a gauge-origin independent method for the calculation of nuclear magnetic shielding tensors of molecules in a structured and polarizable environment. The method is based on a combination of density functional theory (DFT) or Hartree-Fock wave functions with molecular mechanics. The method is unique in the sense that it includes three important properties that need to be fulfilled in accurate calculations of nuclear magnetic shielding constants: (i) the model includes electron correlation effects, (ii) the model uses gauge-including atomic orbitals to give gauge-origin independent results, and (iii) the effect of the environment is treated self-consistently using a discrete reaction-field methodology. The authors present sample calculations of the isotropic nuclear magnetic shielding constants of liquid water based on a large number of solute-solvent configurations derived from molecular dynamics simulations employing potentials which treat solvent polarization either explicitly or implicitly. For both the O17 and H1 isotropic shielding constants the best predicted results compare fairly well with the experimental data, i.e., they reproduce the experimental solvent shifts to within 4ppm for the O17 shielding and 1ppm for the H1 shielding.

  12. Magnetic Shielding of an Adiabatic Demagnetization Refrigerator for TES Microcalorimeter Operation

    NASA Astrophysics Data System (ADS)

    Hishi, U.; Fujimoto, R.; Kunihisa, T.; Takakura, S.; Mitsude, T.; Kamiya, K.; Kotake, M.; Hoshino, A.; Shinozaki, K.

    2014-09-01

    We are developing a compact adiabatic demagnetization refrigerator (ADR) dedicated for TES X-ray microcalorimeter operation. Ferric ammonium alum (FAA) was grown in a stainless-steel container in our laboratory. This salt pill was mounted together with a superconducting magnet and a conventional mechanical heat-switch in a dedicated helium cryostat. Using this system, we achieved mK and a hold time of h below 100 mK. Initially, we used a 3 mm thick silicon steel shield around the ADR magnet and a Nb/Cryoperm double shield around the detector. However, this silicon steel shield allowed a mT field at the detector position when a full field (3 T) was applied, and caused the Nb shield around the detector to trap a magnetic field. The observed transition curve of a TES was broad ( mK) compared to mK obtained in a dilution refrigerator. By increasing the shield thickness to 12 mm, transition width was improved to mK, which suggests that the shields work as expected. When we operated a TES microcalorimeter, energy resolution was eV (FWHM) at 5.9 keV.

  13. A model for the rapid evaluation of active magnetic shielding designs

    NASA Astrophysics Data System (ADS)

    Washburn, Scott Allen

    The use of active magnetic radiation shielding designs has the potential to reduce the radiation exposure received by astronauts on deep-space missions at a significantly lower mass penalty than designs that utilize only passive shielding. One of the common techniques for assessing the effectiveness of active or passive shielding designs is the use of Monte Carlo analysis to determine crew radiation exposure. Unfortunately, Monte Carlo analysis is a lengthy and computationally intensive process, and the associated time requirements to generate results make a broad analysis of the active magnetic shield design trade space impractical using this method. The ability to conduct a broad analysis of system design variables would allow the selection of configurations suited to specific mission goals, including mission radiation exposure limits, duration, and destination. Therefore, a rapid analysis method is required in order to effectively assess active shielding design parameters, and this body of work was developed in order to address this need. Any shielding analysis should also use complete representations of the radiation environment and detailed transport analyses to account for secondary particle production mechanisms. This body of work addresses both of these issues by utilizing the full Galactic Cosmic Radiation GCR flux spectrum and a detailed transport analysis to account for secondary particle effects due to mass interactions. Additionally, there is a complex relationship between the size and strength of an active shielding design and the amount and type of mass required to create it. This mass can significantly impact the resulting flux and radiation exposures inside the active shield, and any shielding analysis should not only include passive mass, but should attempt to provide a reasonable estimate of the actual mass associated with a given design. Therefore, a survey of active shielding systems is presented so that reasonable mass quantity and composition

  14. The Magnetic and Shielding Effects of Ring Current on Radiation Belt Dynamics

    NASA Technical Reports Server (NTRS)

    Fok, Mei-Ching

    2012-01-01

    The ring current plays many key roles in controlling magnetospheric dynamics. A well-known example is the magnetic depression produced by the ring current, which alters the drift paths of radiation belt electrons and may cause significant electron flux dropout. Little attention is paid to the ring current shielding effect on radiation belt dynamics. A recent simulation study that combines the Comprehensive Ring Current Model (CRCM) with the Radiation Belt Environment (RBE) model has revealed that the ring current-associated shielding field directly and/or indirectly weakens the relativistic electron flux increase during magnetic storms. In this talk, we will discuss how ring current magnetic field and electric shielding moderate the radiation belt enhancement.

  15. Magnet Architectures and Active Radiation Shielding Study - SR2S Workshop

    NASA Technical Reports Server (NTRS)

    Westover, Shane; Meinke, Rainer; Burger, William; Ilin, Andrew; Nerolich, Shaun; Washburn, Scott

    2014-01-01

    Analyze new coil configurations with maturing superconductor technology -Develop vehicle-level concept solutions and identify engineering challenges and risks -Shielding performance analysis Recent advances in superconducting magnet technology and manufacturing have opened the door for re-evaluating active shielding solutions as an alternative to mass prohibitive passive shielding.Publications on static magnetic field environments and its bio-effects were reviewed. Short-term exposure information is available suggesting long term exposure may be okay. Further research likely needed. center dotMagnetic field safety requirements exist for controlled work environments. The following effects have been noted with little noted adverse effects -Magnetohydrodynamic (MHD) effects on ionized fluids (e.g. blood) creating an aortic voltage change -MHD interaction elevates blood pressure (BP) center dot5 Tesla equates to 5% BP elevation -Prosthetic devises and pacemakers are an issue (access limit of 5 gauss).

  16. Magnetically suspended stepping motors for clean room and vacuum environments

    NASA Technical Reports Server (NTRS)

    Higuchi, Toshiro

    1994-01-01

    To answer the growing needs for super-clean or contact free actuators for uses in clean rooms, vacuum chambers, and space, innovative actuators which combine the functions of stepping motors and magnetic bearings in one body were developed. The rotor of the magnetically suspended stepping motor is suspended like a magnetic bearing and rotated and positioned like a stepping motor. The important trait of the motor is that it is not a simple mixture or combination of a stepping motor and conventional magnetic bearing, but an amalgam of a stepping motor and a magnetic bearing. Owing to optimal design and feed-back control, a toothed stator and rotor are all that are needed structurewise for stable suspension. More than ten types of motors such as linear type, high accuracy rotary type, two-dimensional type, and high vacuum type were built and tested. This paper describes the structure and design of these motors and their performance for such applications as precise positioning rotary table, linear conveyor system, and theta-zeta positioner for clean room and high vacuum use.

  17. Room Temperature Characterization of a Magnetic Bearing for Turbomachinery

    NASA Technical Reports Server (NTRS)

    Montague, Gerald; Jansen, Mark; Provenza, Andrew; Jansen, Ralph; Ebihara, Ben; Palazzolo, Alan

    2002-01-01

    Open loop, experimental force and power measurements of a three-axis, radial, heteropolar magnetic bearing at room temperature for rotor speeds up to 20,000 RPM are presented in this paper. The bearing, NASA Glenn Research Center's and Texas A&M's third generation high temperature magnetic bearing, was designed to operate in a 1000 F (540 C) environment and was primarily optimized for maximum load capacity. The experimentally measured force produced by one C-core of this bearing was 630 lb. (2.8 kN) at 16 A, while a load of 650 lbs (2.89 kN) was predicted at 16 A using 1D circuit analysis. The maximum predicted radial load for one of the three axes is 1,440 lbs (6.41 kN) at room temperature. The maximum measured load of an axis was 1050 lbs. (4.73 kN). Results of test under rotating conditions showed that rotor speed has a negligible effect on the bearing's load capacity. A single C-core required approximately 70 W of power to generate 300 lb (1.34 kN) of magnetic force. The room temperature data presented was measured after three thermal cycles up to 1000 F (540 C), totaling six hours at elevated temperatures.

  18. A three-layer magnetic shielding for the MAIUS-1 mission on a sounding rocket.

    PubMed

    Kubelka-Lange, André; Herrmann, Sven; Grosse, Jens; Lämmerzahl, Claus; Rasel, Ernst M; Braxmaier, Claus

    2016-06-01

    Bose-Einstein-Condensates (BECs) can be used as a very sensitive tool for experiments on fundamental questions in physics like testing the equivalence principle using matter wave interferometry. Since the sensitivity of these experiments in ground-based environments is limited by the available free fall time, the QUANTUS project started to perform BEC interferometry experiments in micro-gravity. After successful campaigns in the drop tower, the next step is a space-borne experiment. The MAIUS-mission will be an atom-optical experiment that will show the feasibility of experiments with ultra-cold quantum gases in microgravity in a sounding rocket. The experiment will create a BEC of 10(5) (87)Rb-atoms in less than 5 s and will demonstrate application of basic atom interferometer techniques over a flight time of 6 min. The hardware is specifically designed to match the requirements of a sounding rocket mission. Special attention is thereby spent on the appropriate magnetic shielding from varying magnetic fields during the rocket flight, since the experiment procedures are very sensitive to external magnetic fields. A three-layer magnetic shielding provides a high shielding effectiveness factor of at least 1000 for an undisturbed operation of the experiment. The design of this magnetic shielding, the magnetic properties, simulations, and tests of its suitability for a sounding rocket flight are presented in this article.

  19. Shielding, but not zeroing of the ambient magnetic field reduces stress-induced analgesia in mice.

    PubMed Central

    Choleris, E; Del Seppia, C; Thomas, A W; Luschi, P; Ghione, G; Moran, G R; Prato, F S

    2002-01-01

    Magnetic field exposure was consistently found to affect pain inhibition (i.e. analgesia). Recently, we showed that an extreme reduction of the ambient magnetic and electric environment, by mu-metal shielding, also affected stress-induced analgesia (SIA) in C57 mice. Using CD1 mice, we report here the same findings from replication studies performed independently in Pisa, Italy and London, ON, Canada. Also, neither selective vector nulling of the static component of the ambient magnetic field with Helmholtz coils, nor copper shielding of only the ambient electric field, affected SIA in mice. We further show that a pre-stress exposure to the mu-metal box is necessary for the anti-analgesic effects to occur. The differential effects of the two near-zero magnetic conditions may depend on the elimination (obtained only by mu-metal shielding) of the extremely weak time-varying component of the magnetic environment. This would provide the first direct and repeatable evidence for a behavioural and physiological effect of very weak time-varying magnetic fields, suggesting the existence of a very sensitive magnetic discrimination in the endogenous mechanisms that underlie SIA. This has important implications for other reported effects of exposures to very weak magnetic fields and for the theoretical work that considers the mechanisms underlying the biological detection of weak magnetic fields. PMID:11798436

  20. Tuning magnetic spirals beyond room temperature with chemical disorder

    PubMed Central

    Morin, Mickaël; Canévet, Emmanuel; Raynaud, Adrien; Bartkowiak, Marek; Sheptyakov, Denis; Ban, Voraksmy; Kenzelmann, Michel; Pomjakushina, Ekaterina; Conder, Kazimierz; Medarde, Marisa

    2016-01-01

    In the past years, magnetism-driven ferroelectricity and gigantic magnetoelectric effects have been reported for a number of frustrated magnets featuring ordered spiral magnetic phases. Such materials are of high-current interest due to their potential for spintronics and low-power magnetoelectric devices. However, their low-magnetic ordering temperatures (typically <100 K) greatly restrict their fields of application. Here we demonstrate that the onset temperature of the spiral phase in the perovskite YBaCuFeO5 can be increased by more than 150 K through a controlled manipulation of the Fe/Cu chemical disorder. Moreover, we show that this novel mechanism can stabilize the magnetic spiral state of YBaCuFeO5 above the symbolic value of 25 °C at zero magnetic field. Our findings demonstrate that the properties of magnetic spirals, including its wavelength and stability range, can be engineered through the control of chemical disorder, offering a great potential for the design of materials with magnetoelectric properties beyond room temperature. PMID:27982127

  1. Tuning magnetic spirals beyond room temperature with chemical disorder

    NASA Astrophysics Data System (ADS)

    Morin, Mickaël; Canévet, Emmanuel; Raynaud, Adrien; Bartkowiak, Marek; Sheptyakov, Denis; Ban, Voraksmy; Kenzelmann, Michel; Pomjakushina, Ekaterina; Conder, Kazimierz; Medarde, Marisa

    2016-12-01

    In the past years, magnetism-driven ferroelectricity and gigantic magnetoelectric effects have been reported for a number of frustrated magnets featuring ordered spiral magnetic phases. Such materials are of high-current interest due to their potential for spintronics and low-power magnetoelectric devices. However, their low-magnetic ordering temperatures (typically <100 K) greatly restrict their fields of application. Here we demonstrate that the onset temperature of the spiral phase in the perovskite YBaCuFeO5 can be increased by more than 150 K through a controlled manipulation of the Fe/Cu chemical disorder. Moreover, we show that this novel mechanism can stabilize the magnetic spiral state of YBaCuFeO5 above the symbolic value of 25 °C at zero magnetic field. Our findings demonstrate that the properties of magnetic spirals, including its wavelength and stability range, can be engineered through the control of chemical disorder, offering a great potential for the design of materials with magnetoelectric properties beyond room temperature.

  2. Passive shielding effect on space profile of magnetic field emissions for wireless power transfer to vehicles

    SciTech Connect

    Batra, T. Schaltz, E.

    2015-05-07

    Magnetic fields emitted by wireless power transfer systems are of high importance with respect to human safety and health. Aluminum and ferrite are used in the system to reduce the fields and are termed as passive shielding. In this paper, the influence of these materials on the space profile has been investigated with the help of simulations on Comsol for the four possible geometries—no shielding, ferrite, aluminum, and full shielding. As the reflected impedance varies for the four geometries, the primary current is varied accordingly to maintain constant power transfer to the secondary side. Surrounding magnetic field plots in the vertical direction show that maxima's of the two coils for the no shielding geometry are centered at the respective coils and for the remaining three are displaced closer to each other. This closeness would lead to more effective addition of the two coil fields and an increase in the resultant field from space point of view. This closeness varies with distance in the horizontal direction and vertical gap between the coils and is explained in the paper. This paper provides a better understanding of effect of the passive shielding materials on the space nature of magnetic fields for wireless power transfer for vehicle applications.

  3. NMR absolute shielding scale and nuclear magnetic dipole moment of (207)Pb.

    PubMed

    Adrjan, Bożena; Makulski, Włodzimierz; Jackowski, Karol; Demissie, Taye B; Ruud, Kenneth; Antušek, Andrej; Jaszuński, Michał

    2016-06-28

    An absolute shielding scale is proposed for (207)Pb nuclear magnetic resonance (NMR) spectroscopy. It is based on ab initio calculations performed on an isolated tetramethyllead Pb(CH3)4 molecule and the assignment of the experimental resonance frequency from the gas-phase NMR spectra of Pb(CH3)4, extrapolated to zero density of the buffer gas to obtain the result for an isolated molecule. The computed (207)Pb shielding constant is 10 790 ppm for the isolated molecule, leading to a shielding of 10799.7 ppm for liquid Pb(CH3)4 which is the accepted reference standard for (207)Pb NMR spectra. The new experimental and theoretical data are used to determine μ((207)Pb), the nuclear magnetic dipole moment of (207)Pb, by applying the standard relationship between NMR frequencies, shielding constants and nuclear moments of two nuclei in the same external magnetic field. Using the gas-phase (207)Pb and (reference) proton results and the theoretical value of the Pb shielding in Pb(CH3)4, we find μ((207)Pb) = 0.59064 μN. The analysis of new experimental and theoretical data obtained for the Pb(2+) ion in water solutions provides similar values of μ((207)Pb), in the range of 0.59000-0.59131 μN.

  4. The Effectiveness of Magnetic Shielding in High-Isp Hall Thrusters

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Hofer, Richard R.; Katz, Ira; Goebel, Dan M.

    2013-01-01

    A series of numerical simulations and experiments have been performed to assess the effectiveness of magnetic shielding in a Hall thruster operating in the discharge voltage range of 300-700 V (Isp 2000-2700 s) at 6 kW, and 800 V (Isp 3000) at 9 kW. In this paper we report on the simulation results and their validation with experimental measurements. At 6 kW the magnetic field topology with which we recently demonstrated highly effective magnetic shielding at 300 V was retained for all other discharge voltages; only the magnitude of the field was changed to achieve optimum thruster performance. It is found that magnetic shielding remains highly effective for all discharge voltages studied. Maximum erosion rates that remain fairly constant across the range of 300-700 V are computed, with values not exceeding 10-2 mm/kh. Such rates are 3 orders of magnitude less than those observed in the unshielded version of the same thruster at 300 V. At 9 kW and 800 V, saturation of the magnetic circuit did not permit us to attain precisely the same magnetic shielding topology as that employed during the 6-kW operation since this thruster was not designed to operate at this condition. Consequently, the maximum erosion rate at the inner wall is found to be 1 order of magnitude higher (10-1 mm/kh) than that at the 6-kW level. At the outer wall the ion energy is below the sputtering yield threshold so no measurable erosion is expected. The reasons behind the effectiveness of magnetic shielding at higher discharge voltages are discussed.

  5. Magnetic Anomalies of the Fennoscandian Shield on a 2km resolution grid

    NASA Astrophysics Data System (ADS)

    Korhonen, Juha V.; Aaro, Sven; Reidar Skilbrei, Jan; All, Tarmo

    2010-05-01

    Joint magnetic anomaly grid of the Fennoscandian Shield was released 2002, smoothed and used as data for the WDMAM2007. In comparison with MF5 this grid showed superior characteristics to other sets. The data will be released as a 2 km resolution grid for the WDMAM2011 with eventual updates of anomaly levels.

  6. Magnetic Shielding of the Acceleration Channel Walls in a Long-Life Hall Thruster

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard R.; Goebel, Dan M.; de Grys, Kristi; Mathers, Alex

    2010-01-01

    In a Qualification Life Test (QLT) of the BPT-4000 Hall thruster that recently accumulated greater than 10,000 h it was found that the erosion of the acceleration channel practically stopped after approximately 5,600 h. Numerical simulations of this thruster using a 2-D axisymmetric, magnetic field-aligned-mesh (MFAM) plasma solver reveal that the process that led to this significant reduction of the erosion was multifaceted. It is found that when the channel receded from its early-in-life geometry to its steady-state configuration several changes in the near-wall plasma and sheath were induced by the magnetic field that, collectively, constituted an effective shielding of the walls from any significant ion bombardment. Because all such changes in the behavior of the ionized gas near the eroding surfaces were caused by the topology of the magnetic field there, we term this process "magnetic shielding."

  7. Characteristics of magnetic shields for protection PMT in the LHCb hadron calorimeter

    NASA Astrophysics Data System (ADS)

    Dmitrenko, V. V.; Vlasik, K. F.; Grachev, V. M.; Muravyev-Smirnov, S. S.; Novikov, A. S.; Ulin, S. E.; Uteshev, Z. M.; Shustov, A. E.; Petrenko, D. V.; Chernysheva, I. V.; Lobova, E. I.; Nepochataya, O. E.

    2017-01-01

    CERN is preparing the new experiment aimed at the detection of weakly interacting massive long-lived particles. The experiment was called SHiP. The instrumental and technological solutions successfully used in experimental setups ATLAS, LHCb and others will be applied in experimental setup SHiP. One of these units is a hadrons calorimeter. It uses several thousands photomultiplier tubes (PMT) placed in protective magnetic shields because PMTs are located near strong permanent magnets. Taking into account that since the creation of the experimental setup LHCb has been passed more than 10 years and there are new manufacturing techniques of magnetic screens appeared, we investigate the characteristics of shielding screens used in the LHCb, and proposed the recommendations to magnetic screens’ designs for SHiP experiment.

  8. Room-temperature Magnetic Ordering in Functionalized Graphene

    PubMed Central

    Hong, Jeongmin; Bekyarova, Elena; Liang, Ping; de Heer, Walt A.; Haddon, Robert C.; Khizroev, Sakhrat

    2012-01-01

    Despite theoretical predictions, the question of room-temperature magnetic order in graphene must be conclusively resolved before graphene can fully achieve its potential as a spintronic medium. Through scanning tunneling microscopy (STM) and point I-V measurements, the current study reveals that unlike pristine samples, graphene nanostructures, when functionalized with aryl radicals, can sustain magnetic order. STM images show 1-D and 2-D periodic super-lattices originating from the functionalization of a single sub-lattice of the bipartite graphene structure. Field-dependent super-lattices in 3-nm wide “zigzag” nanoribbons indicate local moments with parallel and anti-parallel ordering along and across the edges, respectively. Anti-parallel ordering is observed in 2-D segments with sizes of over 20 nm. The field dependence of STM images and point I-V curves indicates a spin polarized local density of states (LDOS), an out-of-plane anisotropy field of less than 10 Oe, and an exchange coupling field of 100 Oe at room temperature. PMID:22953045

  9. Kinetic shielding of magnetic islands in 3-D equilibria

    NASA Astrophysics Data System (ADS)

    Hegna, C. C.

    2010-11-01

    Kinetic theory is employed to calculate corrections to analytic predictions of saturated magnetic islands due to pressure gradients in 3-D magnetic configurations. The theory calculates the dominant trapped particle response to 3-D field induced net bounce averaged radial drifts. The associated kinetic response describes plasma currents that flow within magnetic surfaces. In general, these currents have a component that resonates with the helical angle of the magnetic island and affect saturated island sizes through the parallel currents generated to satisfy quasineutrality. The resulting kinetic response generally opposes the effects of singular Pfirsch-Schlüter currents that arise at the rational surfaces of general 3-D MHD equilibria. Accounting for both the MHD and kinetic responses, self-consistent magnetic island widths are calculated using Ampere's law. The kinetic effect is largest at lowest collisionality suggesting high-β stellarators are more resilient to retaining flux surface integrity at high-temperatures than predictions from conventional MHD based theory would imply.

  10. Double-layer rotor magnetic shield performance analysis in high temperature superconducting synchronous generators under short circuit fault conditions

    NASA Astrophysics Data System (ADS)

    Hekmati, Arsalan; Aliahmadi, Mehdi

    2016-12-01

    High temperature superconducting, HTS, synchronous machines benefit from a rotor magnetic shield in order to protect superconducting coils against asynchronous magnetic fields. This magnetic shield, however, suffers from exerted Lorentz forces generated in light of induced eddy currents during transient conditions, e.g. stator windings short-circuit fault. In addition, to the exerted electromagnetic forces, eddy current losses and the associated effects on the cryogenic system are the other consequences of shielding HTS coils. This study aims at investigating the Rotor Magnetic Shield, RMS, performance in HTS synchronous generators under stator winding short-circuit fault conditions. The induced eddy currents in different circumferential positions of the rotor magnetic shield along with associated Joule heating losses would be studied using 2-D time-stepping Finite Element Analysis, FEA. The investigation of Lorentz forces exerted on the magnetic shield during transient conditions has also been performed in this paper. The obtained results show that double line-to-ground fault is of the most importance among different types of short-circuit faults. It was revealed that when it comes to the design of the rotor magnetic shields, in addition to the eddy current distribution and the associated ohmic losses, two phase-to-ground fault should be taken into account since the produced electromagnetic forces in the time of fault conditions are more severe during double line-to-ground fault.

  11. Shielding of longitudinal magnetic fields with thin, closely, spaced concentric cylindrical shells with applications to atomic clocks

    NASA Technical Reports Server (NTRS)

    Wolf, S. A.; Gubser, D. U.; Cox, J. E.

    1978-01-01

    A general formula is given for the longitudinal shielding effectiveness of N closed concentric cylinders. The use of these equations is demonstrated by application to the design of magnetic shields for hydrogen maser atomic clocks. Examples of design tradeoffs such as size, weight, and material thickness are discussed. Experimental results on three sets of shields fabricated by three manufacturers are presented. Two of the sets were designed employing the techniques described. Agreement between the experimental results and the design calculations is then demonstrated.

  12. UCSD High Energy X-ray Timing Experiment magnetic shield design and test results

    NASA Technical Reports Server (NTRS)

    Rothschild, Richard E.; Pelling, Michael R.; Hink, Paul L.

    1991-01-01

    Results are reported from an effort to define a passive magnetic field concept for the High Energy X-ray Timing Experiment (HEXTE), in the interest of reducing the detector-gain variations due to 0.5-1.0-sec timescale magnetic field variations. This will allow a sensitivity of the order of 1 percent of the HEXTE background. While aperture modulation and automatic gain control will minimize effects on timescales of tens of seconds and longer, passive magnetic shielding of the photomultiplier tubes will address 1-sec timescale variations due to aperture motions.

  13. Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid

    SciTech Connect

    Hedditch, John Bowden-Reid, Richard Khachan, Joe

    2015-10-15

    Theory for a gridded inertial electrostatic confinement (IEC) fusion system is presented, which shows a net energy gain is possible if the grid is magnetically shielded from ion impact. A simplified grid geometry is studied, consisting of two negatively biased coaxial current-carrying rings, oriented such that their opposing magnetic fields produce a spindle cusp. Our analysis indicates that better than break-even performance is possible even in a deuterium-deuterium system at bench-top scales. The proposed device has the unusual property that it can avoid both the cusp losses of traditional magnetic fusion systems and the grid losses of traditional IEC configurations.

  14. Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid

    NASA Astrophysics Data System (ADS)

    Hedditch, John; Bowden-Reid, Richard; Khachan, Joe

    2015-10-01

    Theory for a gridded inertial electrostatic confinement (IEC) fusion system is presented, which shows a net energy gain is possible if the grid is magnetically shielded from ion impact. A simplified grid geometry is studied, consisting of two negatively biased coaxial current-carrying rings, oriented such that their opposing magnetic fields produce a spindle cusp. Our analysis indicates that better than break-even performance is possible even in a deuterium-deuterium system at bench-top scales. The proposed device has the unusual property that it can avoid both the cusp losses of traditional magnetic fusion systems and the grid losses of traditional IEC configurations.

  15. A Monte Carlo-based radiation safety assessment for astronauts in an environment with confined magnetic field shielding.

    PubMed

    Geng, Changran; Tang, Xiaobin; Gong, Chunhui; Guan, Fada; Johns, Jesse; Shu, Diyun; Chen, Da

    2015-12-01

    The active shielding technique has great potential for radiation protection in space exploration because it has the advantage of a significant mass saving compared with the passive shielding technique. This paper demonstrates a Monte Carlo-based approach to evaluating the shielding effectiveness of the active shielding technique using confined magnetic fields (CMFs). The International Commission on Radiological Protection reference anthropomorphic phantom, as well as the toroidal CMF, was modeled using the Monte Carlo toolkit Geant4. The penetrating primary particle fluence, organ-specific dose equivalent, and male effective dose were calculated for particles in galactic cosmic radiation (GCR) and solar particle events (SPEs). Results show that the SPE protons can be easily shielded against, even almost completely deflected, by the toroidal magnetic field. GCR particles can also be more effectively shielded against by increasing the magnetic field strength. Our results also show that the introduction of a structural Al wall in the CMF did not provide additional shielding for GCR; in fact it can weaken the total shielding effect of the CMF. This study demonstrated the feasibility of accurately determining the radiation field inside the environment and evaluating the organ dose equivalents for astronauts under active shielding using the CMF.

  16. Thermo-electromagnetic properties of a magnetically shielded superconductor strip: theoretical foundations and numerical simulations

    NASA Astrophysics Data System (ADS)

    Ma, G. T.; Rauh, H.

    2013-10-01

    Numerical simulations of thermo-electromagnetic properties of a thin type-II superconductor strip surrounded by open cavity soft-magnetic shields and exposed to an oscillating transverse magnetic field are performed by resorting to the quasistatic approximation of a vector potential approach in conjunction with the classical description of conduction of heat. The underlying definition of the superconducting constituent makes use of an extended ‘smoothed’ Bean model of the critical state, which includes the field and temperature dependence of the induced supercurrent as well. The delineation of the magnetic shields exploits the reversible-paramagnet approximation in the Langevin form, as appropriate for magnetizations with narrow Z-type loops, and considers induced eddy currents too. The coolant is envisaged as acting like a bath that instantly takes away surplus heat. Based on the Jacobian-free Newton-Krylov approach and the backward Euler scheme, the numerical analysis at hand is tailored to the problem of a high width/thickness aspect ratio of the superconductor strip. Assigning representative materials characteristics and conditions of the applied magnetic field, the main findings for a practically relevant magnet configuration include: (i) an overall rise of the maximum temperature of the superconductor strip tending to saturation in a superconducting thermo-electromagnetic steady state above the operating temperature, magnetic shielding lending increased stability and smoothing the temperature profile along the width of the superconductor strip; (ii) a washing out of the profile of the magnetic induction and a lowering of its strength, a relaxation of the profile of the supercurrent density and an increase of its strength, a tightening of the power loss density and a reduction of its strength, all inside the superconductor strip. The hysteretic ac loss suffered by the superconductor strip is seen to be cut back or, at most, to converge on that of an

  17. Vorticity and magnetic shielding in a type-II superconductor.

    PubMed

    Cardoso, Marco; Bicudo, Pedro; Sacramento, Pedro D

    2006-09-20

    We study in detail, solving the Bogoliubov-de Gennes equations, the magnetic field, supercurrent and order parameter profiles originated by a solenoid or magnetic whisker inserted in a type-II superconductor. We consider solutions of different vorticities, n, in the various cases. The results confirm the connection between the vorticity, the internal currents and the boundstates in a self-consistent way. The number of boundstates is given by the vorticity of the phase of the gap function as in the case with no external solenoid. In the limiting case of an infinitely thin solenoid, like a Dirac string, the solution is qualitatively different. The quasiparticle spectrum and wavefunctions are a function of n-n(ext), where n(ext) is the vorticity of the solenoid. The flux is in all cases determined by the vorticity of the gap function.

  18. Atom interferometry in space: Thermal management and magnetic shielding

    SciTech Connect

    Milke, Alexander; Kubelka-Lange, André; Gürlebeck, Norman Rievers, Benny; Herrmann, Sven; Schuldt, Thilo; Braxmaier, Claus

    2014-08-15

    Atom interferometry is an exciting tool to probe fundamental physics. It is considered especially apt to test the universality of free fall by using two different sorts of atoms. The increasing sensitivity required for this kind of experiment sets severe requirements on its environments, instrument control, and systematic effects. This can partially be mitigated by going to space as was proposed, for example, in the Spacetime Explorer and Quantum Equivalence Principle Space Test (STE-QUEST) mission. However, the requirements on the instrument are still very challenging. For example, the specifications of the STE-QUEST mission imply that the Feshbach coils of the atom interferometer are allowed to change their radius only by about 260 nm or 2.6 × 10{sup −4} % due to thermal expansion although they consume an average power of 22 W. Also Earth's magnetic field has to be suppressed by a factor of 10{sup 5}. We show in this article that with the right design such thermal and magnetic requirements can indeed be met and that these are not an impediment for the exciting physics possible with atom interferometers in space.

  19. Atom interferometry in space: thermal management and magnetic shielding.

    PubMed

    Milke, Alexander; Kubelka-Lange, André; Gürlebeck, Norman; Rievers, Benny; Herrmann, Sven; Schuldt, Thilo; Braxmaier, Claus

    2014-08-01

    Atom interferometry is an exciting tool to probe fundamental physics. It is considered especially apt to test the universality of free fall by using two different sorts of atoms. The increasing sensitivity required for this kind of experiment sets severe requirements on its environments, instrument control, and systematic effects. This can partially be mitigated by going to space as was proposed, for example, in the Spacetime Explorer and Quantum Equivalence Principle Space Test (STE-QUEST) mission. However, the requirements on the instrument are still very challenging. For example, the specifications of the STE-QUEST mission imply that the Feshbach coils of the atom interferometer are allowed to change their radius only by about 260 nm or 2.6 × 10(-4) % due to thermal expansion although they consume an average power of 22 W. Also Earth's magnetic field has to be suppressed by a factor of 10(5). We show in this article that with the right design such thermal and magnetic requirements can indeed be met and that these are not an impediment for the exciting physics possible with atom interferometers in space.

  20. Engineering Nanostructures by Decorating Magnetic Nanoparticles onto Graphene Oxide Sheets to Shield Electromagnetic Radiations.

    PubMed

    Mural, Prasanna Kumar S; Pawar, Shital Patangrao; Jayanthi, Swetha; Madras, Giridhar; Sood, Ajay K; Bose, Suryasarathi

    2015-08-05

    In this study, a minimum reflection loss of -70 dB was achieved for a 6 mm thick shield (at 17.1 GHz frequency) employing a unique approach. This was accomplished by engineering nanostructures through decoration of magnetic nanoparticles (nickel, Ni) onto graphene oxide (GO) sheets. Enhanced electromagnetic (EM) shielding was derived by selectively localizing the nanoscopic particles in a specific phase of polyethylene (PE)/poly(ethylene oxide) (PEO) blends. By introduction of a conducting inclusion (like multiwall carbon nanotubes, MWNTs) together with the engineered nanostructures (nickel-decorated GO, GO-Ni), the shielding efficiency can be enhanced significantly in contrast to physically mixing the particles in the blends. For instance, the composites showed a shielding efficiency >25 dB for a combination of MWNTs (3 wt %) and Ni nanoparticles (52 wt %) in PE/PEO blends. However, similar shielding effectiveness could be achieved for a combination of MWNTs (3 wt %) and 10 vol % of GO-Ni where in the effective concentration of Ni was only 19 wt %. The GO-Ni sheets facilitated in an efficient charge transfer as manifested from high electrical conductivity in the blends besides enhancing the permeability in the blends. It is envisioned that GO is simultaneously reduced in the process of synthesizing GO-Ni, and this facilitated in efficient charge transfer between the neighboring CNTs. More interestingly, the blends with MWNTs/GO-Ni attenuated the incoming EM radiation mostly by absorption. This study opens new avenues in designing polyolefin-based lightweight shielding materials by engineering nanostructures for numerous applications.

  1. Low Frequency Plasma Oscillations in a 6-kW Magnetically Shielded Hall Thruster

    NASA Technical Reports Server (NTRS)

    Jorns, Benjamin A.; Hofery, Richard R.

    2013-01-01

    The oscillations from 0-100 kHz in a 6-kW magnetically shielded thruster are experimen- tally characterized. Changes in plasma parameters that result from the magnetic shielding of Hall thrusters have the potential to significantly alter thruster transients. A detailed investigation of the resulting oscillations is necessary both for the purpose of determin- ing the underlying physical processes governing time-dependent behavior in magnetically shielded thrusters as well as for improving thruster models. In this investigation, a high speed camera and a translating ion saturation probe are employed to examine the spatial extent and nature of oscillations from 0-100 kHz in the H6MS thruster. Two modes are identified at 8 kHz and 75-90 kHz. The low frequency mode is azimuthally uniform across the thruster face while the high frequency oscillation is concentrated close to the thruster centerline with an m = 1 azimuthal dependence. These experimental results are discussed in the context of wave theory as well as published observations from an unshielded variant of the H6MS thruster.

  2. Leading-order relativistic effects on nuclear magnetic resonance shielding tensors.

    PubMed

    Manninen, Pekka; Ruud, Kenneth; Lantto, Perttu; Vaara, Juha

    2005-03-15

    We present perturbational ab initio calculations of the nuclear-spin-dependent relativistic corrections to the nuclear magnetic resonance shielding tensors that constitute, together with the other relativistic terms reported by us earlier, the full leading-order perturbational set of results for the one-electron relativistic contributions to this observable, based on the (Breit-)Pauli Hamiltonian. These contributions are considered for the H(2)X (X = O,S,Se,Te,Po) and HX (X = F,Cl,Br,I,At) molecules, as well as the noble gas (Ne, Ar, Kr, Xe, Rn) atoms. The corrections are evaluated using the relativistic and magnetic operators as perturbations on an equal footing, calculated using analytical linear and quadratic response theory applied on top of a nonrelativistic reference state provided by self-consistent field calculations. The (1)H and heavy-atom nuclear magnetic shielding tensors are compared with four component, nearly basis-set-limit Dirac-Hartree-Fock calculations that include positronic excitations, as well as available literature data. Besides the easy interpretability of the different contributions in terms of familiar nonrelativistic concepts, the accuracy of the present perturbational scheme is striking for the isotropic part of the shielding tensor, for systems including elements up to Xe.

  3. Structural Analysis of Thermal Shields During a Quench of a Torus Magnet for the 12 GeV Upgrade

    SciTech Connect

    Pastor, Orlando; Willard, Thomas; Ghoshal, Probir K.; Kashy, David H.; Wiseman, Mark A.; Kashikhin, V.; Young, Glenn R.; Elouadrhiri, Latifa; Rode, Claus H.

    2015-06-01

    A toroidal magnet system consisting of six superconducting coils is being built for the Jefferson Lab 12- GeV accelerator upgrade project. This paper details the analysis of eddy current effects during a quench event on the aluminum thermal shield. The shield has been analyzed for mechanical stresses induced as a result of a coil quench as well as a fast discharge of the complete magnet system. The shield has been designed to reduce the eddy current effects and result in stresses within allowable limits.

  4. Experimental characterization of the hydride 1H shielding tensors for HIrX2(PR3)2 and HRhCl2(PR3)2: extremely shielded hydride protons with unusually large magnetic shielding anisotropies.

    PubMed

    Garbacz, Piotr; Terskikh, Victor V; Ferguson, Michael J; Bernard, Guy M; Kędziorek, Mariusz; Wasylishen, Roderick E

    2014-02-20

    The hydride proton magnetic shielding tensors for a series of iridium(III) and rhodium(III) complexes are determined. Although it has long been known that hydridic protons for transition-metal hydrides are often extremely shielded, this is the first experimental determination of the shielding tensors for such complexes. Isolating the (1)H NMR signal for a hydride proton requires careful experimental strategies because the spectra are generally dominated by ligand (1)H signals. We show that this can be accomplished for complexes containing as many as 66 ligand protons by substituting the latter with deuterium and by using hyperbolic secant pulses to selectively irradiate the hydride proton signal. We also demonstrate that the quality of the results is improved by performing experiments at the highest practical magnetic field (21.14 T for the work presented here). The hydride protons for iridium hydride complexes HIrX2(PR3)2 (X = Cl, Br, or I; R = isopropyl, cyclohexyl) are highly shielded with isotropic chemical shifts of approximately -50 ppm and are also highly anisotropic, with spans (=δ11 - δ33) ranging from 85.1 to 110.7 ppm. The hydridic protons for related rhodium complexes HRhCl2(PR3)2 also have unusual magnetic shielding properties with chemical shifts and spans of approximately -32 and 85 ppm, respectively. Relativistic density functional theory computations were performed to determine the orientation of the principal components of the hydride proton shielding tensors and to provide insights into the origin of these highly anisotropic shielding tensors. The results of our computations agree well with experiment, and our conclusions concerning the importance of relativistic effects support those recently reported by Kaupp and co-workers.

  5. Evaluation of Superconducting Magnet Shield Configurations for Long Duration Manned Space Missions

    PubMed Central

    Ambroglini, Filippo; Battiston, Roberto; Burger, William J.

    2016-01-01

    A manned mission to Mars would present an important long-term health risk to the crew members due to the prolonged exposure to the ionizing radiation of galactic cosmic-rays. The radiation levels would largely exceed those encountered in the Apollo missions. An increase in the passive shielding provided by the spacecraft implies a significant increase of the mass. The advent of superconducting magnets in the early 1960s was considered an attractive alternative. The technology allows to generate magnetic fields capable to deflect the cosmic-rays in a manner analogous to the reduction of the particle fluxes in the upper atmosphere due to the Earth’s dipole magnetic field. A series of the three studies have been conducted over the last 5 years, funded successively by European Space Agency (ESA), the NASA Innovative Advanced Concepts (NIAC) program, and the Union European’s Seventh Framework Programme (FP7). The shielding configurations studied are based on high-temperature superconductors, which eliminate the need to operate with liquid helium. The mass estimates of the coils and supporting structure of the engineering designs are based on the current and expected near-future performance of the superconducting materials. In each case, the shield performance, in terms of dose reduction, is provided by a 3-dimensional Monte Carlo simulation, which treats in detail the electromagnetic and hadronic interactions of the galactic-cosmic rays, and the secondary particles they produce in the materials of the shield and spacecraft. A summary of the results of the studies, representing one of the most detailed and comprehensive efforts made in the field, is presented. PMID:27376023

  6. Four-component relativistic theory for nuclear magnetic shielding constants: critical assessments of different approaches.

    PubMed

    Xiao, Yunlong; Liu, Wenjian; Cheng, Lan; Peng, Daoling

    2007-06-07

    Both formal and numerical analyses have been carried out on various exact and approximate variants of the four-component relativistic theory for nuclear magnetic shielding constants. These include the standard linear response theory (LRT), the full or external field-dependent unitary transformations of the Dirac operator, as well as the orbital decomposition approach. In contrast with LRT, the latter schemes take explicitly into account both the kinetic and magnetic balances between the large and small components of the Dirac spinors, and are therefore much less demanding on the basis sets. In addition, the diamagnetic contributions, which are otherwise "missing" in LRT, appear naturally in the latter schemes. Nevertheless, the definitions of paramagnetic and diamagnetic terms are not the same in the different schemes, but the difference is only of O(c(-2)) and thus vanishes in the nonrelativistic limit. It is shown that, as an operator theory, the full field-dependent unitary transformation approach cannot be applied to singular magnetic fields such as that due to the magnetic point dipole moment of a nucleus. However, the inherent singularities can be avoided by the corresponding matrix formulation (with a partial closed summation). All the schemes are combined with the Dirac-Kohn-Sham ansatz for ground state calculations, and by using virtually complete basis sets a new and more accurate set of absolute nuclear magnetic resonance shielding scales for the rare gases He-Rn have been established.

  7. Lithospheric sources of magnetic anomalies of the Aldan shield and Alpha Ridge

    NASA Astrophysics Data System (ADS)

    Litvinova, Tamara; Petrova, Alevtina

    2013-04-01

    Regional anomaly Aldan Shield is dated to ancient greenstone belt of the earth's crust. Belt is characterized by high depth forming sequences. Rocks of the upper and middle part of the section contain ferruginous quartzite. Geomagnetic and density sections allowed to estimate the power density and magnetic crustal heterogeneities. The methodology of constructing the cuts is the spectral-spatial representation of the fields, convertible into the underlying magnetic and density cuts. According to satellite data confirms the presence of regional anomalies within the Aldan shield, at an altitude of 100 km, it is about 100 nT. The presence of the Central Aldan crast-mantle fault depth of 50-80 km defines metallogenic situation of the region. The structure of the Aldan Shield detects rotational structure. Regional magnetic anomalies arc tangent frame Central Aldan region. May suggest that such behavior of anomalies is caused by of the ancient (Pre-Cambrian) fireplace mantle (the nucleus). Studies have shown that lithospheric sources Aldan shield on satellite magnetic anomalies and magnetic anomalies (ΔT) a Russia are located at depths of 30 to 35 and 40 to 70 km. They are confined to vertical zone deconsolidated at depths of about 30 and 40 - 70 km. By magnetic anomalies (ΔT) a Russian in the crust of the Aldan shield a depth of 15 - 17 km and 25 - 30 km depth revealed magnetite zone, the formation of which is due to the processes of regional metamorphism of ancient crust. Studies have shown the limits of the depth distribution of magnetite zones, mosaic developed within the crust of the Aldan shield after repeated activation of the processes of regional metamorphism.Alpha Ridge in the Arctic Ocean is one of the largest igneous provinces in the world. Tectonic history of the Arctic while not significantly deciphered. Deep structure of the Earth's crust are poorly understood Linearly elongated magnetic anomalies Alpha Ridge clearly seen at the height of the satellite

  8. Design of a magnetic shielding system for the time of flight enhanced diagnostics neutron spectrometer at Experimental Advanced Superconducting Tokamak.

    PubMed

    Cui, Z Q; Chen, Z J; Xie, X F; Peng, X Y; Hu, Z M; Du, T F; Ge, L J; Zhang, X; Yuan, X; Xia, Z W; Hu, L Q; Zhong, G Q; Lin, S Y; Wan, B N; Fan, T S; Chen, J X; Li, X Q; Zhang, G H

    2014-11-01

    The novel neutron spectrometer TOFED (Time of Flight Enhanced Diagnostics), comprising 90 individual photomultiplier tubes coupled with 85 plastic scintillation detectors through light guides, has been constructed and installed at Experimental Advanced Superconducting Tokamak. A dedicated magnetic shielding system has been constructed for TOFED, and is designed to guarantee the normal operation of photomultiplier tubes in the stray magnetic field leaking from the tokamak device. Experimental measurements and numerical simulations carried out employing the finite element method are combined to optimize the design of the magnetic shielding system. The system allows detectors to work properly in an external magnetic field of 200 G.

  9. On the magnetic shielding anisotropy at the lithium sites of zeolite Li4Na8A

    NASA Astrophysics Data System (ADS)

    Schimiczek, B.; Greth, R.; Boddenberg, B.

    6Li NMR spectra under static and magic angle spinning conditions of a 33% lithium exchanged zeolite NaA were investigated. The asymmetric shape of the static spectra is due to the combined action of axially symmetric lectric field gradient and magnetic shielding tensors with a common principal axis coordinate frame. The anisotropy of the shielding tensor is evaluated to be Δσ=-21 ppm. The unusually large modulus of Δσ can be reproduced approximately with a model which considers the atoms surrounding the reference 6Li cations as spherical charge distributions. It is concluded that the lithium cations are located on the threefold symmetry axes normal to the six-ring planes in the near neighbourhood of the six oxygen atoms. This conclusion is corroborated by the agreement the calculated and experimentally determined dipolar linewidths.

  10. Nuclear relaxation in an electric field enables the determination of isotropic magnetic shielding

    NASA Astrophysics Data System (ADS)

    Garbacz, Piotr

    2016-08-01

    It is shown that in contrast to the case of nuclear relaxation in a magnetic field B, simultaneous application of the magnetic field B and an additional electric field E causes transverse relaxation of a spin-1/2 nucleus with the rate proportional to the square of the isotropic part of the magnetic shielding tensor. This effect can contribute noticeably to the transverse relaxation rate of heavy nuclei in molecules that possess permanent electric dipole moments. Relativistic quantum mechanical computations indicate that for 205Tl nucleus in a Pt-Tl bonded complex, Pt(CN)5Tl, the transverse relaxation rate induced by the electric field is of the order of 1 s-1 at E = 5 kV/mm and B = 10 T.

  11. Decontamination of the Activation Product Based on a Legal Revision of the Cyclotron Vault Room on the Non-self-shield Compact Medical Cyclotron.

    PubMed

    Komiya, Isao; Umezu, Yoshiyuki; Fujibuchi, Toshioh; Nakamura, Kazumasa; Baba, Shingo; Honda, Hiroshi

    The non-self-shield compact medical cyclotron and the cyclotron vault room were in operation for 27 years. They have now been decommissioned. We efficiently implemented a technique to identify an activation product in the cyclotron vault room. Firstly, the distribution of radioactive concentrations in the concrete of the cyclotron vault room was estimated by calculation from the record of the cyclotron operation. Secondly, the comparison of calculated results with an actual measurement was performed using a NaI scintillation survey meter and a high-purity germanium detector. The calculated values were overestimated as compared to the values measured using the NaI scintillation survey meter and the high-purity germanium detector. However, it could limit the decontamination area. By simulating the activation range, we were able to minimize the concrete core sampling. Finally, the appropriate range of radioactivated area in the cyclotron vault room was decontaminated based on the results of the calculation. After decontamination, the radioactive concentration was below the detection limit value in all areas inside the cyclotron vault room. By these procedures, the decommissioning process of the cyclotron vault room was more efficiently performed.

  12. Magnetic Shielding of the Channel Walls in a Hall Plasma Accelerator

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard R.; Goebel, Dan M.; deGrys, Kristi; Mathers, Alex

    2011-01-01

    In a qualification life test of a Hall thruster it was found that the erosion of the acceleration channel practically stopped after approx 5,600 h. Numerical simulations using a two-dimensional axisymmetric plasma solver with a magnetic field-aligned mesh reveal that when the channel receded from its early-in-life to its steady-state configuration the following changes occurred near the wall: (1) reduction of the electric field parallel to the wall that prohibited ions from acquiring significant impact kinetic energy before entering the sheath, (2) reduction of the potential fall in the sheath that further diminished the total energy ions gained before striking the material, and (3) reduction of the ion number density that decreased the flux of ions to the wall. All these changes, found to have been induced by the magnetic field, constituted collectively an effective shielding of the walls from any significant ion bombardment. Thus, we term this process in Hall thrusters "magnetic shielding."

  13. Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase I: Numerical Simulations

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard R.

    2011-01-01

    In a proof-of-principle effort to demonstrate the feasibility of magnetically shielded (MS) Hall thrusters, an existing laboratory thruster has been modified with the guidance of physics-based numerical simulation. When operated at a discharge power of 6-kilowatts the modified thruster has been designed to reduce the total energy and flux of ions to the channel insulators by greater than 1 and greater than 3 orders of magnitude, respectively. The erosion rates in this MS thruster configuration are predicted to be at least 2-4 orders of magnitude lower than those in the baseline (BL) configuration. At such rates no detectable erosion is expected to occur.

  14. Relativistic, QED, and nuclear mass effects in the magnetic shielding of 3He.

    PubMed

    Rudziński, Adam; Puchalski, Mariusz; Pachucki, Krzysztof

    2009-06-28

    The magnetic shielding sigma of (3)He is studied. The complete relativistic corrections of order O(alpha(2)), leading QED corrections of order O(alpha(3) ln alpha), and finite nuclear mass effects of order O(m/m(N)) are calculated with high numerical precision. The resulting theoretical predictions for sigma = 59.967 43(10)x10(-6) are the most accurate to date among all elements and support the use of (3)He as a NMR standard.

  15. Converging Nuclear Magnetic Shielding Calculations with Respect to Basis and System Size in Protein Systems

    PubMed Central

    Hartman, Joshua D.; Neubauer, Thomas J.; Caulkins, Bethany G.; Mueller, Leonard J.; Beran, Gregory J. O.

    2015-01-01

    Ab initio chemical shielding calculations greatly facilitate the interpretation of nuclear magnetic resonance (NMR) chemical shifts in biological systems, but the large sizes of these systems requires approximations in the chemical models used to represent them. Achieving good convergence in the predicted chemical shieldings is necessary before one can unravel how other complex structural and dynamical factors affect the NMR measurements. Here, we investigate how to balance trade-offs between using a better basis set or a larger cluster model for predicting the chemical shieldings of the substrates in two representative examples of protein-substrate systems involving different domains in tryptophan synthase: the N-(4′-trifluoromethoxybenzoyl)-2-aminoethyl phosphate (F9) ligand which binds in the α active site, and the 2-aminophenol (2AP) quinonoid intermediate formed in the β active site. We first demonstrate that a chemically intuitive three-layer, locally dense basis model that uses a large basis on the substrate, a medium triple-zeta basis to describe its hydrogen-bonding partners and/or surrounding van derWaals cavity, and a crude basis set for more distant atoms provides chemical shieldings in good agreement with much more expensive large basis calculations. Second, long-range quantum mechanical interactions are important, and one can accurately estimate them as a small-basis correction to larger-basis calculations on a smaller cluster. The combination of these approaches enables one to perform density functional theory NMR chemical shift calculations in protein systems that are well-converged with respect to both basis set and cluster size. PMID:25993979

  16. Comparison of four methods used in determination of secondary shielding requirements for a teletherapy facility: a case study of 137Cs room in Tanzania.

    PubMed

    Muhogora, W E; Nyanda, A M; Ngoye, W M

    2004-12-01

    The performance of four methods often used to calculate the secondary barrier requirements is evaluated for a typical 137Cs-therapy room as a case study. The first two methods are provided by the NCRP49 and IAEA and both consider the influence of the primary, leakage and scattered radiation at a point as corrected for the workload, use and occupancy factors. A different shielding model encompasses the third method, which determines the doses as corrected for build-up effects assuming the narrow beam geometry. The fourth method is based on the calculation of the dose rates from the source activity with a relevant gamma constant. In all four methods, an appropriate transmission factor for the protective barrier in question is applied. The results show that for controlled area, the similarity in the calculated thicknesses using all four methods was nearly within 50%. For uncontrolled areas, a significant difference of magnitude up to a factor of 2.4 was found, which is mainly attributed to the non-consideration of occupancy factors in the latter two methods. Nevertheless, the non-agreement is useful to validate the specific assumptions taken for the employed shielding method. Despite being slightly high, it is concluded that the current shielding methods based on NCRP fundamentals are satisfactorily optimal in planning new therapy facilities. However for existing facilities, such as those undesigned according to the standard requirements, the combination of the four different methods with the dose rate measurements tend to offer a better cost effective shielding option. Retrospectively, additional 41-cm thick concrete is recommended for the unshielded southern barrier of the 137Cs room. Interestingly, the recommended thickness agrees to within +/-5% with that estimated by using the recently recommended method by IAEA.

  17. Third-Scale Prototype of a Shielded Magnet for Measurement of the Electric Dipole Moment of the Neutron

    NASA Astrophysics Data System (ADS)

    Biswas, Aritra

    2015-10-01

    Discovery of an electric dipole moment in neutrons (nEDM) would be a novel instance of CP violation, with implications for extending the Standard Model and potentially helping explain matter-antimatter asymmetry. Experiments using shifts in polarized neutron spin-precession frequency to measure the nEDM are prone to a geometric phase (GP) effect, caused by gradients of the magnetic field, that can create a false signal. Preventing the GP effect requires precise engineering to create a space-uniform magnetic field. We present a third-scale prototype of a shielded magnet suitable for a more precise nEDM measurement, with improvements over earlier models. The field is produced by a cosθ coil wound with superconducting (SC) wire. Two cylindrical shields made of ferromagnetic Metglas and SC lead surround the magnet; the lead shield is closed on top and bottom with SC lead endcaps. An aluminum shell surrounds these components and serves as a vacuum chamber, cooling its interior to 4 K such that the coil wire and lead shield become SC. A cavity in this shell serves as a warm bore, allowing a magnetic probe to explore the field around fiducial volumes which will be used to measure the nEDM in the full-scale experiment. The magnetic field profile of this prototype is presented.

  18. Design of the shielding wall of a cyclotron room and the activation interpretation using the Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Jang, D. G.; Kim, J. M.; Kim, J. H.

    2017-01-01

    Medical cyclotron is mainly a facility used for producing radiopharmaceutical products, which secondarily generate high energy radiation when producing a radiopharmaceutical product. In this study, the intention is that the reductions in spatial dose rate for the radiation generated when cyclotron is operated and the absorbed dose rate, according to the width of shielding wall, will be analyzed. The simulation planned targetry and protons of 16.5 MeV, 60μA through a Monte Carlo simulation, and as a result of the simulation, it has been found through an analysis that a concrete shielding wall of 200 cm is needed, according to the absorbed dose rate of the shielding wall thickness of cyclotron, and the concrete gives an external exposure level of 1 μSv/hr after 19 years of cyclotron operation as it is activated by the nuclear reaction of cyclotron. When taking into account the mechanical life span of cyclotron, it is deemed necessary to develop additional shielding and a low activation material.

  19. Design and validation of a large-format transition edge sensor array magnetic shielding system for space application

    NASA Astrophysics Data System (ADS)

    Bergen, A.; van Weers, H. J.; Bruineman, C.; Dhallé, M. M. J.; Krooshoop, H. J. G.; ter Brake, H. J. M.; Ravensberg, K.; Jackson, B. D.; Wafelbakker, C. K.

    2016-10-01

    The paper describes the development and the experimental validation of a cryogenic magnetic shielding system for transition edge sensor based space detector arrays. The system consists of an outer mu-metal shield and an inner superconducting niobium shield. First, a basic comparison is made between thin-walled mu-metal and superconducting shields, giving an off-axis expression for the field inside a cup-shaped superconductor as a function of the transverse external field. Starting from these preliminary analytical considerations, the design of an adequate and realistic shielding configuration for future space flight applications (either X-IFU [D. Barret et al., e-print arXiv:1308.6784 [astro-ph.IM] (2013)] or SAFARI [B. Jackson et al., IEEE Trans. Terahertz Sci. Technol. 2, 12 (2012)]) is described in more detail. The numerical design and verification tools (static and dynamic finite element method (FEM) models) are discussed together with their required input, i.e., the magnetic-field dependent permeability data. Next, the actual manufacturing of the shields is described, including a method to create a superconducting joint between the two superconducting shield elements that avoid flux penetration through the seam. The final part of the paper presents the experimental verification of the model predictions and the validation of the shield's performance. The shields were cooled through the superconducting transition temperature of niobium in zero applied magnetic field (<10 nT) or in a DC field with magnitude ˜100 μT, applied either along the system's symmetry axis or perpendicular to it. After cool-down, DC trapped flux profiles were measured along the shield axis with a flux-gate magnetometer and the attenuation of externally applied AC fields (100 μT, 0.1 Hz, both axial and transverse) was verified along this axis with superconducting quantum interference device magnetometers. The system's measured on-axis shielding factor is greater than 106, well exceeding

  20. Design and validation of a large-format transition edge sensor array magnetic shielding system for space application.

    PubMed

    Bergen, A; van Weers, H J; Bruineman, C; Dhallé, M M J; Krooshoop, H J G; Ter Brake, H J M; Ravensberg, K; Jackson, B D; Wafelbakker, C K

    2016-10-01

    The paper describes the development and the experimental validation of a cryogenic magnetic shielding system for transition edge sensor based space detector arrays. The system consists of an outer mu-metal shield and an inner superconducting niobium shield. First, a basic comparison is made between thin-walled mu-metal and superconducting shields, giving an off-axis expression for the field inside a cup-shaped superconductor as a function of the transverse external field. Starting from these preliminary analytical considerations, the design of an adequate and realistic shielding configuration for future space flight applications (either X-IFU [D. Barret et al., e-print arXiv:1308.6784 [astro-ph.IM] (2013)] or SAFARI [B. Jackson et al., IEEE Trans. Terahertz Sci. Technol. 2, 12 (2012)]) is described in more detail. The numerical design and verification tools (static and dynamic finite element method (FEM) models) are discussed together with their required input, i.e., the magnetic-field dependent permeability data. Next, the actual manufacturing of the shields is described, including a method to create a superconducting joint between the two superconducting shield elements that avoid flux penetration through the seam. The final part of the paper presents the experimental verification of the model predictions and the validation of the shield's performance. The shields were cooled through the superconducting transition temperature of niobium in zero applied magnetic field (<10 nT) or in a DC field with magnitude ∼100 μT, applied either along the system's symmetry axis or perpendicular to it. After cool-down, DC trapped flux profiles were measured along the shield axis with a flux-gate magnetometer and the attenuation of externally applied AC fields (100 μT, 0.1 Hz, both axial and transverse) was verified along this axis with superconducting quantum interference device magnetometers. The system's measured on-axis shielding factor is greater than 10(6), well

  1. A miniature continuous adiabatic demagnetization refrigerator with compact shielded superconducting magnets

    NASA Astrophysics Data System (ADS)

    Duval, Jean-Marc; Cain, Benjamin M.; Timbie, Peter T.

    2004-10-01

    Cryogenic detectors for astrophysics depend on cryocoolers capable of achieving temperatures below ~ 100 mK. In order to provide continuous cooling at 50 mK for space or laboratory applications, we are designing a miniature adiabatic demagnetization refrigerator (MADR) anchored at a reservoir at 5 K. Continuous cooling is obtained by the use of several paramagnetic pills placed in series with heat switches. All operations are fully electronic and this technology can be adapted fairly easily for a wide range of temperatures and cooling powers. We are focusing on reducing the size and mass of the cooler. For that purpose we have developed and tested magnetoresistive heat switches based on single crystals of tungsten. Several superconducting magnets are required for this cooler and we have designed and manufactured compact magnets. A special focus has been put on the reduction of parasitic magnetic fields in the cold stage, while minimizing the mass of the shields. A prototype continuous MADR, using magnetoresistive heat switches, small paramagnetic pills and compact magnets has been tested. A design of MADR that will provide ~ 5 uW of continuous cooling down to 50 mK is described.

  2. Design and fabrication of liquid nitrogen thermal shields for the MFTF yin-yang magnets

    SciTech Connect

    Johnson, G.L.; Chang, Y.; VanSant, J.H.

    1981-10-12

    This paper documents the design and fabrication of thin liquid nitrogen-cooled panels installed on the 340-ton MFTF yin-yang superconducting magnet system. The 344 panels are made of polished 316-L stainless steel with the pillowed fluid channels formed by inflation with a high pressure gas. Strict leak-rate limits required the manufacturer to thermal shock the panels with LN/sub 2/ and then vacuum leak check them with He. The thin-walled panel supports are made from an epoxy base, fiberglass composite which is reliable at cryogenic vacuum conditions. Quick and reliable welding of the manifold system was assured using a pair of automated tube welders on the more than 4000 feet of tubing and 1000 butt-weld fittings. To assure sufficient flow for single-phase LN/sub 2/ flow conditions, we performed a hydraulic network flow analysis. This allowed for some optimization of shield-inlet-flow conditions and manifold design. To verify operating fluid pressure and temperature, special pressure transducers and platinum resistance thermometers capable of operation at cryogenic conditions in a vacuum, high magnetic field, and long-term neutron bombardment were installed. Final assembly is complete. The final installation on the magnet was difficult due to the orientation of the magnet assembly and the restricted access to some installation surfaces.

  3. Magnetic switching of ferroelectric domains at room temperature in multiferroic PZTFT

    PubMed Central

    Evans, D.M.; Schilling, A.; Kumar, Ashok; Sanchez, D.; Ortega, N.; Arredondo, M.; Katiyar, R.S.; Gregg, J.M.; Scott, J.F.

    2013-01-01

    Single-phase magnetoelectric multiferroics are ferroelectric materials that display some form of magnetism. In addition, magnetic and ferroelectric order parameters are not independent of one another. Thus, the application of either an electric or magnetic field simultaneously alters both the electrical dipole configuration and the magnetic state of the material. The technological possibilities that could arise from magnetoelectric multiferroics are considerable and a range of functional devices has already been envisioned. Realising these devices, however, requires coupling effects to be significant and to occur at room temperature. Although such characteristics can be created in piezoelectric-magnetostrictive composites, to date they have only been weakly evident in single-phase multiferroics. Here in a newly discovered room temperature multiferroic, we demonstrate significant room temperature coupling by monitoring changes in ferroelectric domain patterns induced by magnetic fields. An order of magnitude estimate of the effective coupling coefficient suggests a value of ~1 × 10−7 sm−1. PMID:23443562

  4. Magnetic shielding of a laboratory Hall thruster. I. Theory and validation

    SciTech Connect

    Mikellides, Ioannis G. Katz, Ira; Hofer, Richard R.; Goebel, Dan M.

    2014-01-28

    We demonstrate a technique by which erosion of the acceleration channel in Hall thrusters can be reduced by at least a few orders of magnitude. The first principles of the technique, now known as “magnetic shielding,” have been derived based on the findings of 2-D numerical simulations. The simulations, in turn, guided the modification of an existing 6-kW laboratory Hall thruster to test the theory and are the main subject of this Part I article. Part II expands on the results of the experiments. Near the walls of the magnetically shielded (MS) thruster theory and experiment agree that (1) the plasma potential has been sustained at values near the discharge voltage, and (2) the electron temperature has been lowered compared to the unshielded thruster. Erosion rates deduced directly from the wall probes show reductions of at least ∼3 orders of magnitude at the MS inner wall when an ion energy threshold of 30.5 V is used in the sputtering yield model of the channel material. At the outer wall the probes reveal that the ion energy was below the assumed threshold. Using a threshold of 25 V, the simulations predict a minimum reduction of ∼600 at the MS inner wall. At the MS outer wall ion energies are found to be below 25 V. When a 50-V threshold is used the computed ion energies are below the threshold at both sides of the channel. Uncertainties, sensitivities, and differences between theory and experiment are also discussed. The elimination of wall erosion in Hall thrusters solves a problem that has remained unsettled for more than five decades.

  5. Mechanism analysis of Magnetohydrodynamic heat shield system and optimization of externally applied magnetic field

    NASA Astrophysics Data System (ADS)

    Li, Kai; Liu, Jun; Liu, Weiqiang

    2017-04-01

    As a novel thermal protection technique for hypersonic vehicles, Magnetohydrodynamic (MHD) heat shield system has been proved to be of great intrinsic value in the hypersonic field. In order to analyze the thermal protection mechanisms of such a system, a physical model is constructed for analyzing the effect of the Lorentz force components in the counter and normal directions. With a series of numerical simulations, the dominating Lorentz force components are analyzed for the MHD heat flux mitigation in different regions of a typical reentry vehicle. Then, a novel magnetic field with variable included angle between magnetic induction line and streamline is designed, which significantly improves the performance of MHD thermal protection in the stagnation and shoulder areas. After that, the relationships between MHD shock control and MHD thermal protection are investigated, based on which the magnetic field above is secondarily optimized obtaining better performances of both shock control and thermal protection. Results show that the MHD thermal protection is mainly determined by the Lorentz force's effect on the boundary layer. From the stagnation to the shoulder region, the flow deceleration effect of the counter-flow component is weakened while the flow deflection effect of the normal component is enhanced. Moreover, there is no obviously positive correlation between the MHD shock control and thermal protection. But once a good Lorentz force's effect on the boundary layer is guaranteed, the thermal protection performance can be further improved with an enlarged shock stand-off distance by strengthening the counter-flow Lorentz force right after shock.

  6. Structural setting and magnetic properties of pseudotachylyte in a deep crustal shear zone, western Canadian shield

    NASA Astrophysics Data System (ADS)

    Orlandini, O. F.; Mahan, K. H.; Brown, L. L.; Regan, S.; Williams, M. L.

    2012-12-01

    Seismic slip commonly produces pseudotachylytes, a glassy vein-filling substance that is typically interpreted as either a frictional melt or an ultra-triturated cataclasite. In either form, pseudotachylytes are commonly magnetite enriched, even in magnetite-free host rocks, and therefore are potentially useful as high fidelity recorders of natural magnetic fields at the time of slip in a wide array of lithologies. Pseudotachylytes generally have high magnetic susceptibility and thus should preserve the dominant field present as the material passes the Curie temperatures of magnetic minerals, primarily magnetite. Two potential sources have been proposed for the dominant magnetic field recorded: the earth's magnetic field at the time of slip or the temporary and orders of magnitude more intense field created by the presence of coseismic currents along the failure plane. Pseudotachylytes of the Cora Lake shear zone (CLsz) in the Athabasca Granulite Terrain, western Canadian shield, are consistently hosted in high strain ultramylonitic orthogneiss. Sinistral and extensional oblique-slip in the CLsz occurred at high-pressure granulite-grade conditions of ~1.0 GPa and >800°C and may have persisted to somewhat lower P-T conditions (~0.8 GPa, 700 °C) during ductile deformation. Pseudotachylyte-bearing slip surfaces have sinistral offset, matching the larger shear zone, and clasts of wall rock in the more brecciated veins display field evidence for ductile shear along the same plane prior to brittle failure. The presence of undeformed pseudotachylyte in kinematically compatible fracture arrays localized in ultramylonite indicates that brittle failure may have occurred in the waning stages of shear zone activity and at similar deep crustal conditions. Field-documented occurrences of pseudotachylyte include 2 cm-thick veins that run subparallel to mylonitic foliation and contain small flow-aligned clasts and large, heavily brecciated foliation-crosscutting zones up to

  7. Magnetic field dependence of shielding current density in Y-Ba-Cu-O rings at 77 K

    SciTech Connect

    Polak, M.; Majoros, M.; Hanic, F.; Pitel, J.; Kedrova, M.; Kottman, P.; Talapa, J.; Vencel, L. )

    1989-06-01

    A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current density J{sub cs} and the intergranular transport current density J{sub ct} are identical if the measurement conditions are similar. A degradation of J{sub cs} measured in the external field with AC ripple has been observed.

  8. A high-Tc SQUID micro-detector with a high performance magnetic shield for contaminant detection in industrial products

    NASA Astrophysics Data System (ADS)

    Tanaka, Saburo; Fujita, H.; Hatsukade, Y.; Otani, T.; Suzuki, S.; Nagaishi, T.

    2007-11-01

    A high-Tc superconducting quantum interference device (SQUID) system for the detection of magnetic foreign matter in industrial products was developed. There is a possibility that ultra-small metallic foreign matter has been accidentally mixed with industrial products such as lithium ion batteries. Metallic particles with outer dimensions less than 100 µm cannot be detected by conventional x-ray imaging. Therefore we developed a detection system based on a high-Tc SQUID microscope with a high performance magnetic shield. The use of SQUID microscopes with a 0.5 mm thick vacuum window was proposed. This design enables the SQUID to approach the object to be measured as close as 1 mm and enhances the sensitivity. A new magnetic shield with sleeves was carefully designed and built. As a result, we could successfully measure small particles sized 100 µm. This detection level was hard to achieve using a conventional x-ray detection method.

  9. Does apartment's distance to an in-built transformer room predict magnetic field exposure levels?

    PubMed

    Huss, Anke; Goris, Kelly; Vermeulen, Roel; Kromhout, Hans

    2013-01-01

    It has been shown that magnetic field exposure in apartments located directly on top or adjacent to transformer rooms is higher compared with exposure in apartments located further away from the transformer rooms. It is unclear whether this also translates into exposure contrast among individuals living in these apartments. We performed spot measurements of magnetic fields in 35 apartments in 14 apartment buildings with an in-built transformer and additionally performed 24-h personal measurements in a subsample of 24 individuals. Apartments placed directly on top of or adjacent to a transformer room had on average exposures of 0.42 μT, apartments on the second floor on top of a transformer room, or sharing a corner or edge with the transformer room had 0.11 μT, and apartments located further away from the transformer room had levels of 0.06 μT. Personal exposure levels were approximately a factor 2 lower compared with apartment averages, but still showed exposure contrasts, but only for those individuals who live in the apartments directly on top or adjacent to a transformer room compared with those living further away, with 0.23 versus 0.06 μT for personal exposure when indoors, respectively. A classification of individuals into 'high' and 'low' exposed based on the location of their apartment within a building with an in-built transformer is possible and could be applied in future epidemiological studies.

  10. Room-temperature magnetic gradiometry with fiber-coupled nitrogen-vacancy centers in diamond.

    PubMed

    Blakley, S M; Fedotov, I V; Kilin, S Ya; Zheltikov, A M

    2015-08-15

    Differential optical detection of a magnetic resonance induced in nitrogen-vacancy (NV) centers in diamond is shown to enable a high-spatial-resolution room-temperature magnetic-field gradiometry on a fiber platform. An ultracompact design of this fiber-based solid-state magnetic gradiometer is achieved by integrating an NV-diamond magnetic sensor with a two-fiber opto-microwave interface, which couples NV centers to microwave and optical fields, used to resonantly drive and interrogate the spin of NV centers.

  11. Low and room temperature magnetic features of the traffic related urban airborne PM

    NASA Astrophysics Data System (ADS)

    Winkler, A.; Sagnotti, L.

    2012-04-01

    We used magnetic measurements and analyses - such as hysteresis loops and FORCs both at room temperature and at 10K, isothermal remanent magnetization (IRM) vs temperature curves (from 10K to 293K) and IRM vs time decay curves - to characterize the magnetic properties of the traffic related airborne particulate matter (PM) in Rome. This study was specifically addressed to the identification of the ultrafine superparamagnetic (SP) particles, which are particularly sensitive to thermal relaxation effects, and on the eventual detection of low temperature phase transitions which may affect various magnetic minerals. We compared the magnetic properties at 10K and at room temperature of Quercus ilex leaves, disk brakes, diesel and gasoline exhaust pipes powders collected from vehicles circulating in Rome. The magnetic properties of the investigated powders significantly change upon cooling, and no clear phase transition occurs, suggesting that the thermal dependence is mainly triggered by the widespread presence of ultrafine SP particles. The contribution of the SP fraction to the total remanence of traffic related PM samples was quantified at room temperature measuring the decay of a IRM 100 s after the application of a saturation magnetic field. This same method has been also tested at 10K to investigate the temperature dependence of the observed time decay.

  12. Development of a compact magnetic resonance imaging system for a cold room

    NASA Astrophysics Data System (ADS)

    Adachi, Satoru; Ozeki, Toshihiro; Shigeki, Ryosuke; Handa, Shinya; Kose, Katsumi; Haishi, Tomoyuki; Aoki, Masaaki

    2009-05-01

    A compact magnetic resonance imaging (MRI) system for a cold (-5 °C) room has been developed to acquire MR images below the freezing point of water. The MRI system consists of a 1.0 T permanent magnet, a higher-order shim coil set, and a gradient coil probe, installed in the cold room, and a compact MRI console installed in a room at normal temperature (20-25 °C). The most difficult problem for the installation of the MRI system in the cold room was the degradation of the field homogeneity of the permanent magnet shimmed at 25 °C. To overcome this problem, higher-order shim coils were developed and the temperature variation of the magnetic field distribution was measured using a standard phantom with and without shim coil currents. As a result, it was confirmed that the homogeneity (the difference between the minimum and maximum values) of the magnetic field in the 17×17×19 mm3 rectangular parallelepiped region was improved from 117 to 59 ppm using an appropriate combination of shim coil currents. A snowpack immersed in dodecane (C12H26) was imaged using a driven-equilibrium three-dimensional (3D) spin-echo sequence at -5 °C. The visualized 3D structure of the snowpack demonstrated the effectiveness of our approach.

  13. A simple scheme for magnetic balance in four-component relativistic Kohn-Sham calculations of nuclear magnetic resonance shielding constants in a Gaussian basis.

    PubMed

    Olejniczak, Małgorzata; Bast, Radovan; Saue, Trond; Pecul, Magdalena

    2012-01-07

    We report the implementation of nuclear magnetic resonance (NMR) shielding tensors within the four-component relativistic Kohn-Sham density functional theory including non-collinear spin magnetization and employing London atomic orbitals to ensure gauge origin independent results, together with a new and efficient scheme for assuring correct balance between the large and small components of a molecular four-component spinor in the presence of an external magnetic field (simple magnetic balance). To test our formalism we have carried out calculations of NMR shielding tensors for the HX series (X = F, Cl, Br, I, At), the Xe atom, and the Xe dimer. The advantage of simple magnetic balance scheme combined with the use of London atomic orbitals is the fast convergence of results (when compared with restricted kinetic balance) and elimination of linear dependencies in the basis set (when compared to unrestricted kinetic balance). The effect of including spin magnetization in the description of NMR shielding tensor has been found important for hydrogen atoms in heavy HX molecules, causing an increase of isotropic values of 10%, but negligible for heavy atoms.

  14. Transition-metal-based magnetic refrigerants for room-temperature applications.

    PubMed

    Tegus, O; Brück, E; Buschow, K H J; de Boer, F R

    2002-01-10

    Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) have recently been demonstrated as a promising alternative to conventional vapour-cycle refrigeration. In a material displaying the MCE, the alignment of randomly oriented magnetic moments by an external magnetic field results in heating. This heat can then be removed from the MCE material to the ambient atmosphere by heat transfer. If the magnetic field is subsequently turned off, the magnetic moments randomize again, which leads to cooling of the material below the ambient temperature. Here we report the discovery of a large magnetic entropy change in MnFeP0.45As0.55, a material that has a Curie temperature of about 300 K and which allows magnetic refrigeration at room temperature. The magnetic entropy changes reach values of 14.5 J K-1 kg-1 and 18 J K-1 kg-1 for field changes of 2 T and 5 T, respectively. The so-called giant-MCE material Gd5Ge2Si2 (ref. 2) displays similar entropy changes, but can only be used below room temperature. The refrigerant capacity of our material is also significantly greater than that of Gd (ref. 3). The large entropy change is attributed to a field-induced first-order phase transition enhancing the effect of the applied magnetic field.

  15. Optical multichannel room temperature magnetic field imaging system for clinical application

    PubMed Central

    Lembke, G.; Erné, S. N.; Nowak, H.; Menhorn, B.; Pasquarelli, A.

    2014-01-01

    Optically pumped magnetometers (OPM) are a very promising alternative to the superconducting quantum interference devices (SQUIDs) used nowadays for Magnetic Field Imaging (MFI), a new method of diagnosis based on the measurement of the magnetic field of the human heart. We present a first measurement combining a multichannel OPM-sensor with an existing MFI-system resulting in a fully functional room temperature MFI-system. PMID:24688820

  16. Plasma oscillations in a 6-kW magnetically shielded Hall thruster

    SciTech Connect

    Jorns, Benjamin A. Hofer, Richard R.

    2014-05-15

    Plasma oscillations from 0–100 kHz in a 6-kW magnetically shielded Hall thruster are experimentally characterized with a high-speed, optical camera. Two modes are identified at 7–12 kHz and 70–90 kHz. The low frequency mode is found to be azimuthally uniform across the thruster face, while the high frequency oscillation is peaked close to the centerline-mounted cathode with an m = 1 azimuthal dependence. An analysis of these results in the context of wave-based theory suggests that the low frequency wave is the breathing mode oscillation, while the higher frequency mode is gradient-driven. The effect of these oscillations on thruster operation is examined through an analysis of thruster discharge current and a comparison with published observations from an unshielded variant of the thruster. Most notably, it is found that although the oscillation spectra of the two thrusters are different, they exhibit nearly identical steady-state behavior.

  17. Transient Weakening of Earth's Magnetic Shield Probed by a Cosmic Ray Burst.

    PubMed

    Mohanty, P K; Arunbabu, K P; Aziz, T; Dugad, S R; Gupta, S K; Hariharan, B; Jagadeesan, P; Jain, A; Morris, S D; Rao, B S; Hayashi, Y; Kawakami, S; Oshima, A; Shibata, S; Raha, S; Subramanian, P; Kojima, H

    2016-10-21

    The GRAPES-3 tracking muon telescope in Ooty, India measures muon intensity at high cutoff rigidities (15-24 GV) along nine independent directions covering 2.3 sr. The arrival of a coronal mass ejection on 22 June 2015 18:40 UT had triggered a severe G4-class geomagnetic storm (storm). Starting 19:00 UT, the GRAPES-3 muon telescope recorded a 2 h high-energy (∼20  GeV) burst of galactic cosmic rays (GCRs) that was strongly correlated with a 40 nT surge in the interplanetary magnetic field (IMF). Simulations have shown that a large (17×) compression of the IMF to 680 nT, followed by reconnection with the geomagnetic field (GMF) leading to lower cutoff rigidities could generate this burst. Here, 680 nT represents a short-term change in GMF around Earth, averaged over 7 times its volume. The GCRs, due to lowering of cutoff rigidities, were deflected from Earth's day side by ∼210° in longitude, offering a natural explanation of its night-time detection by the GRAPES-3. The simultaneous occurrence of the burst in all nine directions suggests its origin close to Earth. It also indicates a transient weakening of Earth's magnetic shield, and may hold clues for a better understanding of future superstorms that could cripple modern technological infrastructure on Earth, and endanger the lives of the astronauts in space.

  18. Multiferroic Nanopatterned Hybrid Material with Room-Temperature Magnetic Switching of the Electric Polarization.

    PubMed

    Cai, Ronggang; Antohe, Vlad-Andrei; Hu, Zhijun; Nysten, Bernard; Piraux, Luc; Jonas, Alain M

    2017-02-01

    A nanopatterned hybrid layer is designed, wherein the electric polarization can be flipped at room temperature by a magnetic field aided by an electrical field. This is achieved by embedding ferromagnetic nanopillars in a continuous organic ferroelectric layer, and amplifying the magnetostriction-generated stress gradients by scaling down the supracrystalline cell of the material.

  19. Critical Analysis of Cluster Models and Exchange-Correlation Functionals for Calculating Magnetic Shielding in Molecular Solids.

    PubMed

    Holmes, Sean T; Iuliucci, Robbie J; Mueller, Karl T; Dybowski, Cecil

    2015-11-10

    Calculations of the principal components of magnetic-shielding tensors in crystalline solids require the inclusion of the effects of lattice structure on the local electronic environment to obtain significant agreement with experimental NMR measurements. We assess periodic (GIPAW) and GIAO/symmetry-adapted cluster (SAC) models for computing magnetic-shielding tensors by calculations on a test set containing 72 insulating molecular solids, with a total of 393 principal components of chemical-shift tensors from 13C, 15N, 19F, and 31P sites. When clusters are carefully designed to represent the local solid-state environment and when periodic calculations include sufficient variability, both methods predict magnetic-shielding tensors that agree well with experimental chemical-shift values, demonstrating the correspondence of the two computational techniques. At the basis-set limit, we find that the small differences in the computed values have no statistical significance for three of the four nuclides considered. Subsequently, we explore the effects of additional DFT methods available only with the GIAO/cluster approach, particularly the use of hybrid-GGA functionals, meta-GGA functionals, and hybrid meta-GGA functionals that demonstrate improved agreement in calculations on symmetry-adapted clusters. We demonstrate that meta-GGA functionals improve computed NMR parameters over those obtained by GGA functionals in all cases, and that hybrid functionals improve computed results over the respective pure DFT functional for all nuclides except 15N.

  20. Calculations of atomic magnetic nuclear shielding constants based on the two-component normalized elimination of the small component method.

    PubMed

    Yoshizawa, Terutaka; Zou, Wenli; Cremer, Dieter

    2017-04-07

    A new method for calculating nuclear magnetic resonance shielding constants of relativistic atoms based on the two-component (2c), spin-orbit coupling including Dirac-exact NESC (Normalized Elimination of the Small Component) approach is developed where each term of the diamagnetic and paramagnetic contribution to the isotropic shielding constant σiso is expressed in terms of analytical energy derivatives with regard to the magnetic field B and the nuclear magnetic moment . The picture change caused by renormalization of the wave function is correctly described. 2c-NESC/HF (Hartree-Fock) results for the σiso values of 13 atoms with a closed shell ground state reveal a deviation from 4c-DHF (Dirac-HF) values by 0.01%-0.76%. Since the 2-electron part is effectively calculated using a modified screened nuclear shielding approach, the calculation is efficient and based on a series of matrix manipulations scaling with (2M)(3) (M: number of basis functions).

  1. Magnetic microscopy based on high-Tc SQUIDs for room temperature samples

    NASA Astrophysics Data System (ADS)

    Wang, H. W.; Kong, X. Y.; Ren, Y. F.; Yu, H. W.; Ding, H. S.; Zhao, S. P.; Chen, G. H.; Zhang, L. H.; Zhou, Y. L.; Yang, Q. S.

    2003-11-01

    The SQUID microscope is the most suitable instrument for imaging magnetic fields above sample surfaces if one is mainly interested in field sensitivity. In this paper, both the magnetic moment sensitivity and spatial resolution of the SQUID microscope are analysed with a simple point moment model. The result shows that the ratio of SQUID sensor size to sensor-sample distance effectively influences the sensitivity and spatial resolution. In comparison with some experimental results of magnetic images for room temperature samples from our high-Tc SQUID microscope in an unshielded environment, a brief discussion for further improvement is presented.

  2. Shielding for thermal neutrons.

    PubMed

    McCall, R C

    1997-01-01

    The problem of calculating the neutron capture gamma-ray dose rate due to thermal neutron capture in a boron or cadmium rectangular shield is considered. An example is given for shielding for a door at the exit of medical accelerator room maze in order to determine the optimum location of lead relative to the borated polyethylene.

  3. 33S hyperfine interactions in H2S and SO2 and revision of the sulfur nuclear magnetic shielding scale

    NASA Astrophysics Data System (ADS)

    Helgaker, Trygve; Gauss, Jürgen; Cazzoli, Gabriele; Puzzarini, Cristina

    2013-12-01

    Using the Lamb-dip technique, the hyperfine structure in the rotational spectra of H233S and 33SO2 has been resolved and the corresponding parameters—that is, the sulfur quadrupole-coupling and spin-rotation tensors—were determined. The experimental parameters are in good agreement with results from high-level coupled-cluster calculations, provided that up to quadruple excitations are considered in the cluster operator, sufficiently large basis sets are used, and vibrational corrections are accounted for. The 33S spin-rotation tensor for H2S has been used to establish a new sulfur nuclear magnetic shielding scale, combining the paramagnetic part of the shielding as obtained from the spin-rotation tensor with a calculated value for the diamagnetic part as well as computed vibrational and temperature corrections. The value of 716(5) ppm obtained in this way for the sulfur shielding of H2S is in good agreement with results from high-accuracy quantum-chemical calculations but leads to a shielding scale that is about 28 ppm lower than the one suggested previously in the literature, based on the 33S spin-rotation constant of OCS.

  4. Advances in methods to obtain and characterise room temperature magnetic ZnO

    SciTech Connect

    Lorite, I.; Kumar, P.; Esquinazi, P.; Straube, B.; Villafuerte, M.; Ohldag, H.; Rodríguez Torres, C. E.; Perez de Heluani, S.; Antonov, V. N.; Bekenov, L. V.; Ernst, A.; and others

    2015-02-23

    We report the existence of magnetic order at room temperature in Li-doped ZnO microwires after low energy H{sup +} implantation. The microwires with diameters between 0.3 and 10 μm were prepared by a carbothermal process. We combine spectroscopy techniques to elucidate the influence of the electronic structure and local environment of Zn, O, and Li and their vacancies on the magnetic response. Ferromagnetism at room temperature is obtained only after implanting H{sup +} in Li-doped ZnO. The overall results indicate that low-energy proton implantation is an effective method to produce the necessary amount of stable Zn vacancies near the Li ions to trigger the magnetic order.

  5. Thirty Years of Near Room Temperature Magnetic Cooling: Where we are Today and Future Prospects

    SciTech Connect

    K.A. Gschneidner, Jr; V.K. Pecharsky'

    2008-05-01

    The seminal study by Brown in 1976 showed that it was possible to use the magnetocaloric effect to produce a substantial cooling effect near room temperature. About 15 years later Green et al. built a device which actually cooled a load other than the magnetocaloric material itself and the heat exchange fluid. The major breakthrough, however, occurred in 1997 when the Ames Laboratory/Astronautics proof-of-principle refrigerator showed that magnetic refrigeration was competitive with conventional gas compression cooling. Since then, over 25 magnetic cooling units have been built and tested throughout the world. The current status of near room temperature magnetic cooling is reviewed, including a discussion of the major problems facing commercialization and potential solutions thereof. The future outlook for this revolutionary technology is discussed.

  6. A room-temperature magnetic semiconductor from a ferromagnetic metallic glass

    NASA Astrophysics Data System (ADS)

    Liu, Wenjian; Zhang, Hongxia; Shi, Jin-An; Wang, Zhongchang; Song, Cheng; Wang, Xiangrong; Lu, Siyuan; Zhou, Xiangjun; Gu, Lin; Louzguine-Luzgin, Dmitri V.; Chen, Mingwei; Yao, Kefu; Chen, Na

    2016-12-01

    Emerging for future spintronic/electronic applications, magnetic semiconductors have stimulated intense interest due to their promises for new functionalities and device concepts. So far, the so-called diluted magnetic semiconductors attract many attentions, yet it remains challenging to increase their Curie temperatures above room temperature, particularly those based on III-V semiconductors. In contrast to the concept of doping magnetic elements into conventional semiconductors to make diluted magnetic semiconductors, here we propose to oxidize originally ferromagnetic metals/alloys to form new species of magnetic semiconductors. We introduce oxygen into a ferromagnetic metallic glass to form a Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor with a Curie temperature above 600 K. The demonstration of p-n heterojunctions and electric field control of the room-temperature ferromagnetism in this material reflects its p-type semiconducting character, with a mobility of 0.1 cm2 V-1 s-1. Our findings may pave a new way to realize high Curie temperature magnetic semiconductors with unusual multifunctionalities.

  7. A room-temperature magnetic semiconductor from a ferromagnetic metallic glass

    PubMed Central

    Liu, Wenjian; Zhang, Hongxia; Shi, Jin-an; Wang, Zhongchang; Song, Cheng; Wang, Xiangrong; Lu, Siyuan; Zhou, Xiangjun; Gu, Lin; Louzguine-Luzgin, Dmitri V.; Chen, Mingwei; Yao, Kefu; Chen, Na

    2016-01-01

    Emerging for future spintronic/electronic applications, magnetic semiconductors have stimulated intense interest due to their promises for new functionalities and device concepts. So far, the so-called diluted magnetic semiconductors attract many attentions, yet it remains challenging to increase their Curie temperatures above room temperature, particularly those based on III–V semiconductors. In contrast to the concept of doping magnetic elements into conventional semiconductors to make diluted magnetic semiconductors, here we propose to oxidize originally ferromagnetic metals/alloys to form new species of magnetic semiconductors. We introduce oxygen into a ferromagnetic metallic glass to form a Co28.6Fe12.4Ta4.3B8.7O46 magnetic semiconductor with a Curie temperature above 600 K. The demonstration of p–n heterojunctions and electric field control of the room-temperature ferromagnetism in this material reflects its p-type semiconducting character, with a mobility of 0.1 cm2 V−1 s−1. Our findings may pave a new way to realize high Curie temperature magnetic semiconductors with unusual multifunctionalities. PMID:27929059

  8. Nuclear magnetic resonance shielding constants in XH4 group XIV hydrides

    NASA Astrophysics Data System (ADS)

    Jaszuński, Michał; Ruud, Kenneth

    2006-07-01

    Self-consistent field and multiconfigurational self-consistent field wave functions are used to analyse NMR shielding constants in the XH4 hydrides, X = C, Si, Ge, Sn and Pb. All relativistic corrections to order α4, where α is the fine structure constant, are included in the evaluation of the perturbation corrections to the non-relativistic shielding constants. Each of the relativistic corrections is compared to the results obtained for group XVI and XVII hydrides and noble-gas atoms. For the heavy nuclei, the computed relativistic corrections can be used to improve the absolute shielding scale.

  9. Performance predictions for a room temperature, Ericsson cycle, magnetic heat pump

    NASA Astrophysics Data System (ADS)

    Purnell, J. G.

    1982-05-01

    The performance potential of a room temperature magnetic heat pump utilizing Gadolinium and operating on an Ericsson Cycle was investigated at magnetic flux densities of 2 and 7-Tesla which represent the upper limits of conventional and superconducting electromagnetics, respectively. At a coefficient of performance of 5, a 7-Tesla system would provide a cooling capacity of at best 1200 BTU per hour per pound of Gadolinium while a 2-Tesla system would operate at approximately 130 BTU per hour per pound of Gadolinium. Magnetic circuit efficiency was not determined but must be high (95-percent or better) in order for the magnetic heat pump performance to compete with conventional cooling systems. It is unlikely the magnetic heat pump investigated could approach the performance and compactness of the conventional cooling systems unless field strengths much greater than 7-Tesla are possible.

  10. Improved field localization in transcranial magnetic stimulation of the brain with the utilization of a conductive shield plate in the stimulator.

    PubMed

    Kim, Dong-Hun; Georghiou, George E; Won, Chulho

    2006-04-01

    In this paper, a carefully designed conductive shield plate is presented, which helps to improve localization of the electric field distribution induced by transcranial magnetic stimulation for neuron stimulation. The shield plate is introduced between a figure-of-eight coil and the head. In order to accurately predict the field distribution inside the brain and to examine the effects of the shield plate, a realistic head model is constructed from magnetic resonance image data with the help of image processing tools and the finite-element method in three dimensions is employed. Finally, to show the improvements obtained, the results are compared with two conventional coil designs. It is found that an incorporation of the shield plate into the coil, effectively improves the induced field localization by more than 50%, and prevents other parts of the brain from exposure to high pulsed magnetic fields.

  11. Electric-field manipulation of magnetization rotation and tunneling magnetoresistance of magnetic tunnel junctions at room temperature

    NASA Astrophysics Data System (ADS)

    Chen, Aitian; Li, Peisen; Li, Dalai; Zhao, Yonggang; Zhang, Sen; Yang, Lifeng; Liu, Yan; Zhu, Meihong; Zhang, Huiyun; Han, Xiufeng

    2015-03-01

    Recent studies on the electric-field control of tunneling magnetoresistance (TMR) have attracted considerable attention for low power consumption. So far two methods have been demonstrated for electric-field control of TMR. One method uses ferroelectric or multiferroic barriers, which is limited by low temperature. The other is nanoscale thin film magnetic tunnel junction (MTJ), but the assistance of a magnetic field is required. Therefore, electric-field control of TMR at room temperature without a magnetic field is highly desired. One promising way is to employ strain-mediated coupling in ferromagnetic/piezoelectric structure. Though MTJs/piezoelectric has been predicted by theory, experiment work is still lacking. We deposited CoFeB/AlOx/CoFeB on Pb(Mg1/3Nb2/3)0.7Ti0.3O3 (PMN-PT) ferroelectric single crystal. Under external electric fields, PMN-PT will produce a piezostrain due to piezoelectric effect, and the piezostrain transfers to ferromagnetic film to change the magnetic anisotropy. We demonstrate a reversible, continuous magnetization rotation and manipulation of TMR at room temperature by electric fields without the assistance of a magnetic field.

  12. A new class of chiral materials hosting magnetic skyrmions beyond room temperature.

    PubMed

    Tokunaga, Y; Yu, X Z; White, J S; Rønnow, H M; Morikawa, D; Taguchi, Y; Tokura, Y

    2015-07-02

    Skyrmions, topologically protected vortex-like nanometric spin textures in magnets, have been attracting increasing attention for emergent electromagnetic responses and possible technological applications for spintronics. In particular, metallic magnets with chiral and cubic/tetragonal crystal structure may have high potential to host skyrmions that can be driven by low electrical current excitation. However, experimental observations of skyrmions have been limited to below room temperature for the metallic chiral magnets, specifically for the MnSi-type B20 compounds. Towards technological applications, transcending this limitation is crucial. Here we demonstrate the formation of skyrmions with unique spin helicity both at and above room temperature in a family of cubic chiral magnets: β-Mn-type Co-Zn-Mn alloys with a different chiral space group from that of B20 compounds. Lorentz transmission electron microscopy, magnetization and small-angle neutron scattering measurements unambiguously reveal formation of a skyrmion crystal under application of a magnetic field in both thin-plate and bulk forms.

  13. A new class of chiral materials hosting magnetic skyrmions beyond room temperature

    PubMed Central

    Tokunaga, Y.; Yu, X. Z.; White, J. S.; Rønnow, H. M.; Morikawa, D.; Taguchi, Y.; Tokura, Y.

    2015-01-01

    Skyrmions, topologically protected vortex-like nanometric spin textures in magnets, have been attracting increasing attention for emergent electromagnetic responses and possible technological applications for spintronics. In particular, metallic magnets with chiral and cubic/tetragonal crystal structure may have high potential to host skyrmions that can be driven by low electrical current excitation. However, experimental observations of skyrmions have been limited to below room temperature for the metallic chiral magnets, specifically for the MnSi-type B20 compounds. Towards technological applications, transcending this limitation is crucial. Here we demonstrate the formation of skyrmions with unique spin helicity both at and above room temperature in a family of cubic chiral magnets: β-Mn-type Co-Zn-Mn alloys with a different chiral space group from that of B20 compounds. Lorentz transmission electron microscopy, magnetization and small-angle neutron scattering measurements unambiguously reveal formation of a skyrmion crystal under application of a magnetic field in both thin-plate and bulk forms. PMID:26134284

  14. WE-G-17A-09: Novel Magnetic Shielding Design for Inline and Perpendicular Integrated 6 MV Linac and 1.0 T MRI Systems

    SciTech Connect

    Li, X; Ma, B; Kuang, Y; Diao, X

    2014-06-15

    Purpose: The influence of fringe magnetic fields delivered by magnetic resonance imaging (MRI) on the beam generation and transportation in Linac is still a major challenge for the integration of linear accelerator and MRI (Linac-MRI). In this study, we investigated an optimal magnetic shielding design for Linac-MRI and further characterized the beam trajectory in electron gun. Methods: Both inline and perpendicular configurations were analyzed in this study. The configurations, comprising a Linac-MRI with a 100cm SAD and an open 1.0 T superconductive magnet, were simulated by the 3D finite element method (FEM). The steel shielding around the Linac was included in the 3D model, the thickness of which was varied from 1mm to 20mm, and magnetic field maps were acquired with and without additional shielding. The treatment beam trajectory in electron gun was evaluated using OPERA 3d SCALA with and without shielding cases. Results: When Linac was not shielded, the uniformity of diameter sphere volume (DSV) (30cm) was about 5 parts per million (ppm) and the fringe magnetic fields in electron gun were more than 0.3 T. With shielding, the magnetic fields in electron gun were reduced to less than 0.01 T. For the inline configuration, the radial magnetic fields in the Linac were about 0.02T. A cylinder steel shield used (5mm thick) altered the uniformity of DSV to 1000 ppm. For the perpendicular configuration, the Linac transverse magnetic fields were more than 0.3T, which altered the beam trajectory significantly. A 8mm-thick cylinder steel shield surrounding the Linac was used to compensate the output losses of Linac, which shifted the magnetic fields' uniformity of DSV to 400 ppm. Conclusion: For both configurations, the Linac shielding was used to ensure normal operation of the Linac. The effect of magnetic fields on the uniformity of DSV could be modulated by the shimming technique of the MRI magnet. NIH/NIGMS grant U54 GM104944, Lincy Endowed Assistant Professorship.

  15. Dual-room 1.5-T intraoperative magnetic resonance imaging suite with a movable magnet: implementation and preliminary experience.

    PubMed

    Chen, Xiaolei; Xu, Bai-nan; Meng, Xianghui; Zhang, Jun; Yu, Xingguang; Zhou, Dingbiao

    2012-01-01

    We hereby report our initial clinical experience of a dual-room intraoperative magnetic resonance imaging (iMRI) suite with a movable 1.5-T magnet for both neurosurgical and independent diagnostic uses. The findings from the first 45 patients who underwent scheduled neurosurgical procedures with iMRI in this suite (mean age, 41.3 ± 12.0 years; intracranial tumors, 39 patients; cerebral vascular lesions, 5 patients; epilepsy surgery, 1 patient) were reported. The extent of resection depicted at intraoperative imaging, the surgical consequences of iMRI, and the clinical practicability of the suite were analyzed. Fourteen resections with a trans-sphenoidal/transoral approach and 31 craniotomies were performed. Eighty-two iMRI examinations were performed in the operating room, while during the same period of time, 430 diagnostic scans were finished in the diagnostic room. In 22 (48.9%) of 45 patients, iMRI revealed accessible residual tumors leading to further resection. No iMRI-related adverse event occurred. Complete lesion removal was achieved in 36 (80%) of all 45 cases. It is concluded that the dual-room 1.5-T iMRI suite can be successfully integrated into standard neurosurgical workflow. The layout of the dual-room suite can enable the maximum use of the system and save costs by sharing use of the 1.5-T magnet between neurosurgical and diagnostic use. Intraoperative MR imaging may provide valuable information that allows intraoperative modification of the surgical strategy.

  16. Room-temperature perpendicular magnetic anisotropy of MgO/Fe/MgO ultrathin films

    SciTech Connect

    Kozioł-Rachwał, A.; Ślęzak, T.; Przewoźnik, J.; Skowroński, W.; Stobiecki, T.; Wilgocka-Ślęzak, D.; Qin, Q. H.; Dijken, S. van; Korecki, J.

    2013-12-14

    We used the anomalous Hall effect to study the magnetic properties of MgO/Fe(t)/MgO(001) structures in which the Fe thickness t ranged from 4 Å to 14 Å. For the iron deposited at 140 K, we obtained perpendicular magnetization at room temperature below the critical thickness of t{sub c} = (9 ± 1) Å. In the vicinity of t{sub c}, the easy magnetization axis switched from an out-of-plane orientation to an in-plane orientation, and the observed spin-reorientation transition was considered in terms of the competition among different anisotropies. The perpendicular magnetization direction was attributed to magnetoelastic anisotropy. Finally, the temperature-dependent spin-reorientation transition was analyzed for Fe thicknesses close to t{sub c}.

  17. Hidden spin-order-induced room-temperature ferroelectricity in a peculiar conical magnetic structure

    NASA Astrophysics Data System (ADS)

    Shen, Shi-Peng; Liu, Xin-Zhi; Chai, Yi-Sheng; Studer, Andrew; Rule, Kirrily; Zhai, Kun; Yan, Li-Qin; Shang, Da-Shan; Klose, Frank; Liu, Yun-Tao; Chen, Dong-Feng; Sun, Young

    2017-03-01

    A novel mechanism of spin-induced ferroelectricity is unraveled in the alternating longitudinal conical (ALC) magnetic structure. Because the noncollinear ALC structure possesses a c -axis component with collinear ↑-↑-↓-↓ spin order, spin-driven ferroelectricity along the c axis due to the exchange striction mechanism is predicted. Our experiments verify this prediction in the Y-type hexaferrite B a0.3S r1.7C o2F e11Al O22 , where ferroelectricity along the c axis is observed up to room temperature. Neutron diffraction data clearly reveal the ALC phase and its evolution with magnetic fields. The c -axis electric polarization can be well modulated by applying either a b -plane or c -axis magnetic fields, even at 305 K. This kind of spin-induced ferroelectricity associated with the ALC magnetic structure provides a new resource of type II multiferroics.

  18. The Magnetocaloric Effect and Magnetic Refrigeration Near Room Temperature: Materials and Models

    NASA Astrophysics Data System (ADS)

    Franco, V.; Blázquez, J. S.; Ingale, B.; Conde, A.

    2012-08-01

    In the past 20 years, there has been a surge in research on the magnetocaloric response of materials, due mainly to the possibility of applying this effect for magnetic refrigeration close to room temperature. This review is devoted to the main families of materials suitable for this application and to the procedures proposed to predict their response. Apart from the possible technological applications, we also discuss the use of magnetocaloric characterization to gain fundamental insight into the nature of the underlying phase transition.

  19. Influence of particle size on the magnetic spectrum of NiCuZn ferrites for electromagnetic shielding applications

    NASA Astrophysics Data System (ADS)

    Wu, Xiaohan; Yan, Shuoqing; Liu, Weihu; Feng, Zekun; Chen, Yajie; Harris, Vincent G.

    2016-03-01

    The effect of ferrite particle size on the magnetic spectra (1 MHz to 1 GHz) of NiCuZn polycrystalline ferrites doped with Co2O3 and Bi2O3 were systematically investigated. The experiments indicate that the ferrite particle size tailored by grinding time and corresponding sintering temperatures is crucial to achieving high permeability, high Q-factor and low magnetic loss, at 13.56 MHz for electromagnetic shielding applications especially in the near field communication (NFC) field. It is evident that high-performance NiZnCu ferrite materials are strongly tailored by morphology and microstructure. It is conclusive that fine ferrite particles and relatively low sintering temperatures are favorable to lowering magnetic loss and enhancing permeability. This work has built a foundation for improvement of the ferrite slurry used for fabrication of large area tape-casting ferrite sheets.

  20. A deployable high temperature superconducting coil (DHTSC) - A novel concept for producing magnetic shields against both solar flare and Galactic radiation during manned interplanetary missions

    NASA Technical Reports Server (NTRS)

    Cocks, F. Hadley

    1991-01-01

    The discovery of materials which are superconducting above 100 K makes possible the use of superconducting coils deployed beyong the hull of an interplanetary spacecraft to produce a magnetic shield capable of giving protection not only against solar flare radiation, but also even against Galactic radiation. Such deployed coils can be of very large size and can thus achieve the great magnetic moments required using only relatively low currents. Deployable high-temperature-superconducting coil magnetic shields appear to offer very substantial reductions in mass and energy compared to other concepts and could readily provide the radiation protection needed for a Mars mission or space colonies.

  1. Relativistic calculation of nuclear magnetic shielding tensor using the regular approximation to the normalized elimination of the small component. II. Consideration of perturbations in the metric operator.

    PubMed

    Maeda, H; Ootani, Y; Fukui, H

    2007-05-07

    A previous relativistic shielding calculation theory based on the regular approximation to the normalized elimination of the small component approach is improved by the inclusion of the magnetic interaction term contained in the metric operator. In order to consider effects of the metric perturbation, the self-consistent perturbation theory is used for the case of perturbation-dependent overlap integrals. The calculation results show that the second-order regular approximation results obtained for the isotropic shielding constants of halogen nuclei are well improved by the inclusion of the metric perturbation to reproduce the fully relativistic four-component Dirac-Hartree-Fock results. However, it is shown that the metric perturbation hardly or does not affect the anisotropy of the halogen shielding tensors and the proton magnetic shieldings.

  2. Solvent effects on zero-point vibrational corrections to optical rotations and nuclear magnetic resonance shielding constants

    NASA Astrophysics Data System (ADS)

    Kongsted, Jacob; Ruud, Kenneth

    2008-01-01

    We present a study of solvent effects on the zero-point vibrational corrections (ZPVC) to optical rotations and nuclear magnetic resonance shielding constants of solvated molecules. The model used to calculate vibrational corrections rely on an expansion of the potential and property surfaces around an effective molecular geometry and includes both harmonic and anharmonic corrections. Numerical examples are presented for ( S)-propylene oxide in various solvents as well as for acetone and the three diazene molecules. We find that solvent effects on the ZPVCs may be significant and in some cases crucial to accurately predict solvent shifts on molecular properties.

  3. Ab initio study of NMR shielding of alkali earth metal ions in water complexes and magnetic moments of alkali earth metal nuclei

    NASA Astrophysics Data System (ADS)

    Antušek, Andrej; Rodziewicz, Pawel; Keḑziera, Dariusz; Kaczmarek-Keḑziera, Anna; Jaszuński, Michał

    2013-11-01

    Ab initio calculations of NMR shielding constants of alkali earth metal ions in the series of water clusters are presented. The shielding constants for systems modeling the structure of the solvation layer of these ions are determined by adding to the coupled cluster singles-and-doubles (CCSD) results the calculated relativistic corrections. The relative magnitude of the dynamical effects, estimated for a typical solvated ion from Car-Parrinello molecular dynamics, is very small. The computed shielding constants are used next to obtain new values of the nuclear magnetic dipole moments of alkali earth metal nuclei.

  4. Magnetic refrigeration: an eco-friendly technology for the refrigeration at room temperature

    NASA Astrophysics Data System (ADS)

    Aprea, C.; Greco, A.; Maiorino, A.; Masselli, C.

    2015-11-01

    Magnetic refrigeration is an emerging, environment-friendly technology based on a magnetic solid that acts as a refrigerant by magneto-caloric effect (MCE). In the case of ferromagnetic materials MCE is a warming as the magnetic moments of the atom are aligned by the application of a magnetic field, and the corresponding cooling upon removal of the magnetic field. There are two types of magnetic phase changes that may occur at the Curie point: first order magnetic transition (FOMT) and second order magnetic transition (SOMT). The reference cycle for magnetic refrigeration is AMR (Active Magnetic Regenerative cycle) where the magnetic material matrix works both as a refrigerating medium and as a heat regenerating medium, while the fluid flowing in the porous matrix works as a heat transfer medium. Regeneration can be accomplished by blowing a heat transfer fluid in a reciprocating fashion through the regenerator made of magnetocaloric material that is alternately magnetized and demagnetized. In this paper, attention is directed towards the near room-temperature range. We compare the energetic performance of a commercial R134a refrigeration plant to that of a magnetic refrigerator working with an AMR cycle. Attention is devoted to the evaluation of the environmental impact in terms of a greenhouse effect. The comparison is performed in term of TEWI index (Total Equivalent Warming Impact) that takes into account both direct and indirect contributions to global warming. In this paper the AMR cycle works with different magnetic refrigerants: pure gadolinium, second order phase magnetic transition (Pr0.45Sr0.35MnO3) and first order phase magnetic transition alloys (Gd5Si2Ge2, LaFe11.384Mn0.356Si1.26H1.52, LaFe1105Co0.94Si110 and MnFeP0.45As0.55). The comparison, carried out by means of a mathematical model, clearly shows that GdSi2Ge2 and LaFe11.384Mn0.356Si1.26H1.52 has a TEWI index always lower than that of a vapor compression plant. Furthermore, the TEWI of the AMR

  5. FAST TRACK COMMUNICATION: Magnetic control of large room-temperature polarization

    NASA Astrophysics Data System (ADS)

    Kumar, Ashok; Sharma, G. L.; Katiyar, R. S.; Pirc, R.; Blinc, R.; Scott, J. F.

    2009-09-01

    Numerous authors have referred to room-temperature magnetic switching of large electric polarizations as 'the Holy Grail' of magnetoelectricity. We report this long-sought effect, obtained using a new physical process of coupling between magnetic and ferroelectric nanoregions. Solid state solutions of PFW [Pb(Fe2/3W1/3)O3] and PZT [Pb(Zr0.53Ti0.47)O3] exhibit some bi-relaxor qualities, with both ferroelectric relaxor characteristics and magnetic relaxor phenomena. Near 20% PFW the ferroelectric relaxor state is nearly unstable at room temperature against long-range ferroelectricity. Here we report magnetic switching between the normal ferroelectric state and a magnetically quenched ferroelectric state that resembles relaxors. This gives both a new room-temperature, single-phase, multiferroic magnetoelectric, (PbFe0.67W0.33O3)0.2(PbZr0.53Ti0.47O3)0.8 ('0.2PFW/0.8PZT'), with polarization, loss (<1%), and resistivity (typically 108-109 Ω cm) equal to or superior to those of BiFeO3, and also a new and very large magnetoelectric effect: switching not from +Pr to -Pr with applied H, but from Pr to zero with applied H of less than a tesla. This switching of the polarization occurs not because of a conventional magnetically induced phase transition, but because of dynamic effects: increasing H lengthens the relaxation time by 500 × from<200 ns to>100 µs, and it strongly couples the polarization relaxation and spin relaxations. The diverging polarization relaxation time accurately fits a modified Vogel-Fulcher equation in which the freezing temperature Tf is replaced by a critical freezing field Hf that is 0.92 ± 0.07 T. This field dependence and the critical field Hc are derived analytically from the spherical random bond random field model with no adjustable parameters and an E2H2 coupling. This device permits three-state logic (+Pr,0,-Pr) and a condenser with >5000% magnetic field change in its capacitance; for H = 0 the coercive voltage is 1.4 V across 300 nm for

  6. Non-magnetic organic/inorganic spin injector at room temperature

    SciTech Connect

    Mathew, Shinto P.; Mondal, Prakash Chandra; Naaman, Ron; Moshe, Hagay; Mastai, Yitzhak

    2014-12-15

    Spin injection into solid-state devices is commonly performed by use of ferromagnetic metal electrodes. Here, we present a spin injector design without permanent magnet; rather, the spin selectivity is determined by a chiral tunneling barrier. The chiral tunneling barrier is composed of an ultrathin Al{sub 2}O{sub 3} layer that is deposited on top of a chiral self-assembled monolayer (SAM), which consists of cysteine or oligopeptide molecules. The experimentally observed magnetoresistance can be up to 20% at room temperature, and it displays an uncommon asymmetric curve as a function of the applied magnetic field. These findings show that the spin injector transmits only one spin orientation, independent of external magnetic field. The sign of the magnetoresistance depends on the handedness of the molecules in the SAM, which act as a spin filter, and the magnitude of the magnetoresistance depends only weakly on temperature.

  7. Metastable gamma-Iron Nickel Nanostructures for Magnetic Refrigeration Near Room Temperature

    NASA Astrophysics Data System (ADS)

    Ucar, Huseyin

    The observation of a giant magnetocaloric effect in Gd5Ge 1.9Si2Fe0.1 has stimulated the magnetocaloric research in the last two decades. However, the high price of Gd and its proclivity to corrosion of these compounds have prevented their commercial use. To reduce raw materials cost, transition metal-based alloys are investigated to replace rare earth-based materials. Environmental considerations, substitution for scarce and strategic elements, and cost considerations all speak to potential contributions of these new materials to sustainability. Efforts in improving the refrigeration capacity (RC) of refrigerants mainly rely on broadening the magnetic entropy change. One promising technique is to couple two phases of magnetic materials with desirable properties. Second is the investigation of nanoparticle synthesis routes, with ball milling being the most widely used one. The motivation for the nanoparticles synthesis is rooted in their inherent tendency to have distributed exchange coupling, which will broaden the magnetic entropy curve. As proven with the cost analysis, the focus is believed to shift from improving the RC of refrigerants toward finding the most economically advantageous magnetic refrigerant with the highest performance. Mechanically alloyed Fe70Ni30 and Fe72Ni 28 alloys were characterized in terms of their structural and magnetic properties. Previous studies showed that single phase FCC gamma-FeNi alloys with 26-30 at. % Ni have Curie temperatures, TC, near room temperature. Having TC near room temperatures along with large magnetization makes gamma-FeNi alloys attractive for room temperature magnetocaloric cooling technologies. To obtain a single gamma-phase, particles were solution annealed in the gamma-phase field and water quenched. The preferential oxidation of Fe during ball milling was used as a means to tune the TC of the alloy. Refrigeration capacities, RCFWHM, of the Fe70Ni30 and the Fe72Ni28 alloys were calculated to be 470 J/kg and

  8. Electric field control of nonvolatile four-state magnetization at room temperature

    NASA Astrophysics Data System (ADS)

    Chun, Sae Hwan; Chai, Yi Sheng; Jeon, Byung-Gu; Kim, Hyung Joon; Oh, Yoon Seok; Kim, Ingyu; Kim, Hanbit; Jeon, Byeong Jo; Haam, So Young; Park, Ju-Young; Lee, Suk Ho; Kim, Kee Hoon; Chung, Jae-Ho; Park, Jae-Hoon

    2012-02-01

    We find the realization of large converse magnetoelectric (ME) effects at room temperature in a multiferroic hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62 μB/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be described by an effective free energy with a distinct set of ME coefficients. *These authors contributed equally to this work.

  9. Electric Field Control of Nonvolatile Four-State Magnetization at Room Temperature

    NASA Astrophysics Data System (ADS)

    Chun, Sae Hwan; Chai, Yi Sheng; Jeon, Byung-Gu; Kim, Hyung Joon; Oh, Yoon Seok; Kim, Ingyu; Kim, Hanbit; Jeon, Byeong Jo; Haam, So Young; Park, Ju-Young; Lee, Suk Ho; Chung, Jae-Ho; Park, Jae-Hoon; Kim, Kee Hoon

    2012-04-01

    We find the realization of large converse magnetoelectric (ME) effects at room temperature in a magnetoelectric hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200ps/m. The modulation of magnetization then reaches up to 0.62μB/f.u. in an electric field of 1.14MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients.

  10. Electric field control of nonvolatile four-state magnetization at room temperature.

    PubMed

    Chun, Sae Hwan; Chai, Yi Sheng; Jeon, Byung-Gu; Kim, Hyung Joon; Oh, Yoon Seok; Kim, Ingyu; Kim, Hanbit; Jeon, Byeong Jo; Haam, So Young; Park, Ju-Young; Lee, Suk Ho; Chung, Jae-Ho; Park, Jae-Hoon; Kim, Kee Hoon

    2012-04-27

    We find the realization of large converse magnetoelectric (ME) effects at room temperature in a magnetoelectric hexaferrite Ba0.52Sr2.48Co2Fe24O41 single crystal, in which rapid change of electric polarization in low magnetic fields (about 5 mT) is coined to a large ME susceptibility of 3200 ps/m. The modulation of magnetization then reaches up to 0.62μ(B)/f.u. in an electric field of 1.14 MV/m. We find further that four ME states induced by different ME poling exhibit unique, nonvolatile magnetization versus electric field curves, which can be approximately described by an effective free energy with a distinct set of ME coefficients.

  11. Magnetic refrigeration at room temperature - from magnetocaloric materials to a prototype

    NASA Astrophysics Data System (ADS)

    Theil Kuhn, L.; Pryds, N.; Bahl, C. R. H.; Smith, A.

    2011-07-01

    Based on the magnetocaloric effect, magnetic refrigeration at room temperature has for the past decade been a promising, environmentally friendly new energy technology predicted to have a significantly higher efficiency than the present conventional methods. However, so far only a few prototype refrigeration machines have been presented worldwide and there are still many scientific and technological challenges to be overcome. We report here on the MagCool project, which spans all the way from basic materials studies to the construction of a prototype. Emphasis has been on ceramic magnetocaloric materials, their shaping and graded composition for technological use. Modelling the performance of a permanent magnet with optimum use of the flux and relatively low weight, and designing and constructing a prototype continuous magnetic refrigeration device have also been major tasks in the project.

  12. Atomic magnetic gradiometer for room temperature high sensitivity magnetic field detection

    DOEpatents

    Xu,Shoujun; Lowery, Thomas L.; Budker, Dmitry; Yashchuk, Valeriy V.; Wemmer, David E.; Pines, Alexander

    2009-08-11

    A laser-based atomic magnetometer (LBAM) apparatus measures magnetic fields, comprising: a plurality of polarization detector cells to detect magnetic fields; a laser source optically coupled to the polarization detector cells; and a signal detector that measures the laser source after being coupled to the polarization detector cells, which may be alkali cells. A single polarization cell may be used for nuclear magnetic resonance (NMR) by prepolarizing the nuclear spins of an analyte, encoding spectroscopic and/or spatial information, and detecting NMR signals from the analyte with a laser-based atomic magnetometer to form NMR spectra and/or magnetic resonance images (MRI). There is no need of a magnetic field or cryogenics in the detection step, as it is detected through the LBAM.

  13. Quasirelativistic theory for the magnetic shielding constant. III. Quasirelativistic second-order Møller-Plesset perturbation theory and its application to tellurium compounds.

    PubMed

    Fukuda, Ryoichi; Nakatsuji, Hiroshi

    2005-07-22

    The quasirelativistic (QR) generalized unrestricted Hartree-Fock method for the magnetic shielding constant [R. Fukuda, M. Hada, and H. Nakatsuji, J. Chem. Phys. 118, 1015 (2003); R. Fukuda, M. Hada, and H. Nakatsuji, J. Chem. Phys.118, 1027 (2003)] has been extended to include the electron correlation effect in the level of the second-order Møller-Plesset perturbation theory (MP2). We have implemented the energy gradient and finite-perturbation methods to calculate the magnetic shielding constant at the QR MP2 level and applied to the magnetic shielding constants and the NMR chemical shifts of 125Te nucleus in various tellurium compounds. The calculated magnetic shielding constants and NMR chemical shifts well reproduced the experimental values. The relations of the chemical shifts with the natures of ligands, and the tellurium oxidation states were investigated. The chemical shifts in different valence states were explained by the paramagnetic shielding and spin-orbit terms. The tellurium 5p electrons are the dominant origin of the chemical shifts in the Te I and Te II compounds and the chemical shifts were explained by the p-hole mechanism. The tellurium d electrons also play an important role in the chemical shifts of the hypervalent compounds.

  14. Towards a new class of heavy ion doped magnetic semiconductors for room temperature applications

    PubMed Central

    Lee, Juwon; Subramaniam, Nagarajan Ganapathi; Agnieszka Kowalik, Iwona; Nisar, Jawad; Lee, Jaechul; Kwon, Younghae; Lee, Jaechoon; Kang, Taewon; Peng, Xiangyang; Arvanitis, Dimitri; Ahuja, Rajeev

    2015-01-01

    The article presents, using Bi doped ZnO, an example of a heavy ion doped oxide semiconductor, highlighting a novel p-symmetry interaction of the electronic states to stabilize ferromagnetism. The study includes both ab initio theory and experiments, which yield clear evidence for above room temperature ferromagnetism. ZnBixO1−x thin films are grown using the pulsed laser deposition technique. The room temperature ferromagnetism finds its origin in the holes introduced by the Bi doping and the p-p coupling between Bi and the host atoms. A sizeable magnetic moment is measured by means of x-ray magnetic circular dichroism at the O K-edge, probing directly the spin polarization of the O(2p) states. This result is in agreement with the theoretical predictions and inductive magnetometry measurements. Ab initio calculations of the electronic and magnetic structure of ZnBixO1−x at various doping levels allow to trace the origin of the ferromagnetic character of this material. It appears, that the spin-orbit energy of the heavy ion Bi stabilizes the ferromagnetic phase. Thus, ZnBixO1−x doped with a heavy non-ferromagnetic element, such as Bi, is a credible example of a candidate material for a new class of compounds for spintronics applications, based on the spin polarization of the p states. PMID:26592564

  15. Towards a new class of heavy ion doped magnetic semiconductors for room temperature applications

    NASA Astrophysics Data System (ADS)

    Lee, Juwon; Subramaniam, Nagarajan Ganapathi; Agnieszka Kowalik, Iwona; Nisar, Jawad; Lee, Jaechul; Kwon, Younghae; Lee, Jaechoon; Kang, Taewon; Peng, Xiangyang; Arvanitis, Dimitri; Ahuja, Rajeev

    2015-11-01

    The article presents, using Bi doped ZnO, an example of a heavy ion doped oxide semiconductor, highlighting a novel p-symmetry interaction of the electronic states to stabilize ferromagnetism. The study includes both ab initio theory and experiments, which yield clear evidence for above room temperature ferromagnetism. ZnBixO1-x thin films are grown using the pulsed laser deposition technique. The room temperature ferromagnetism finds its origin in the holes introduced by the Bi doping and the p-p coupling between Bi and the host atoms. A sizeable magnetic moment is measured by means of x-ray magnetic circular dichroism at the O K-edge, probing directly the spin polarization of the O(2p) states. This result is in agreement with the theoretical predictions and inductive magnetometry measurements. Ab initio calculations of the electronic and magnetic structure of ZnBixO1-x at various doping levels allow to trace the origin of the ferromagnetic character of this material. It appears, that the spin-orbit energy of the heavy ion Bi stabilizes the ferromagnetic phase. Thus, ZnBixO1-x doped with a heavy non-ferromagnetic element, such as Bi, is a credible example of a candidate material for a new class of compounds for spintronics applications, based on the spin polarization of the p states.

  16. Design of a Laboratory Hall Thruster with Magnetically Shielded Channel Walls, Phase III: Comparison of Theory with Experiment

    NASA Technical Reports Server (NTRS)

    Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard R.; Goebel, Dan M.

    2012-01-01

    A proof-of-principle effort to demonstrate a technique by which erosion of the acceleration channel in Hall thrusters of the magnetic-layer type can be eliminated has been completed. The first principles of the technique, now known as "magnetic shielding," were derived based on the findings of numerical simulations in 2-D axisymmetric geometry. The simulations, in turn, guided the modification of an existing 6-kW laboratory Hall thruster. This magnetically shielded (MS) thruster was then built and tested. Because neither theory nor experiment alone can validate fully the first principles of the technique, the objective of the 2-yr effort was twofold: (1) to demonstrate in the laboratory that the erosion rates can be reduced by >order of magnitude, and (2) to demonstrate that the near-wall plasma properties can be altered according to the theoretical predictions. This paper concludes the demonstration of magnetic shielding by reporting on a wide range of comparisons between results from numerical simulations and laboratory diagnostics. Collectively, we find that the comparisons validate the theory. Near the walls of the MS thruster, theory and experiment agree: (1) the plasma potential has been sustained at values near the discharge voltage, and (2) the electron temperature has been lowered by at least 2.5-3 times compared to the unshielded (US) thruster. Also, based on carbon deposition measurements, the erosion rates at the inner and outer walls of the MS thruster are found to be lower by at least 2300 and 1875 times, respectively. Erosion was so low along these walls that the rates were below the resolution of the profilometer. Using a sputtering yield model with an energy threshold of 25 V, the simulations predict a reduction of 600 at the MS inner wall. At the outer wall ion energies are computed to be below 25 V, for which case we set the erosion to zero in the simulations. When a 50-V threshold is used the computed ion energies are below the threshold at both

  17. Room Temperature Magnetically Ordered Polar Corundum GaFeO3 Displaying Magnetoelectric Coupling.

    PubMed

    Niu, Hongjun; Pitcher, Michael J; Corkett, Alex J; Ling, Sanliang; Mandal, Pranab; Zanella, Marco; Dawson, Karl; Stamenov, Plamen; Batuk, Dmitry; Abakumov, Artem M; Bull, Craig L; Smith, Ronald I; Murray, Claire A; Day, Sarah J; Slater, Ben; Cora, Furio; Claridge, John B; Rosseinsky, Matthew J

    2017-02-01

    The polar corundum structure type offers a route to new room temperature multiferroic materials, as the partial LiNbO3-type cation ordering that breaks inversion symmetry may be combined with long-range magnetic ordering of high spin d(5) cations above room temperature in the AFeO3 system. We report the synthesis of a polar corundum GaFeO3 by a high-pressure, high-temperature route and demonstrate that its polarity arises from partial LiNbO3-type cation ordering by complementary use of neutron, X-ray, and electron diffraction methods. In situ neutron diffraction shows that the polar corundum forms directly from AlFeO3-type GaFeO3 under the synthesis conditions. The A(3+)/Fe(3+) cations are shown to be more ordered in polar corundum GaFeO3 than in isostructural ScFeO3. This is explained by DFT calculations which indicate that the extent of ordering is dependent on the configurational entropy available to each system at the very different synthesis temperatures required to form their corundum structures. Polar corundum GaFeO3 exhibits weak ferromagnetism at room temperature that arises from its Fe2O3-like magnetic ordering, which persists to a temperature of 408 K. We demonstrate that the polarity and magnetization are coupled in this system with a measured linear magnetoelectric coupling coefficient of 0.057 ps/m. Such coupling is a prerequisite for potential applications of polar corundum materials in multiferroic/magnetoelectric devices.

  18. Local electrical control of magnetic order and orientation by ferroelastic domain arrangements just above room temperature

    PubMed Central

    Phillips, L. C.; Cherifi, R. O.; Ivanovskaya, V.; Zobelli, A.; Infante, I. C.; Jacquet, E.; Guiblin, N.; Ünal, A. A.; Kronast, F.; Dkhil, B.; Barthélémy, A.; Bibes, M.; Valencia, S.

    2015-01-01

    Ferroic materials (ferromagnetic, ferroelectric, ferroelastic) usually divide into domains with different orientations of their order parameter. Coupling between different ferroic systems creates new functionalities, for instance the electrical control of macroscopic magnetic properties including magnetization and coercive field. Here we show that ferroelastic domains can be used to control both magnetic order and magnetization direction at the nanoscale with a voltage. We use element-specific X-ray imaging to map the magnetic domains as a function of temperature and voltage in epitaxial FeRh on ferroelastic BaTiO3. Exploiting the nanoscale phase-separation of FeRh, we locally interconvert between ferromagnetic and antiferromagnetic states with a small electric field just above room temperature. Imaging and ab initio calculations show the antiferromagnetic phase of FeRh is favoured by compressive strain on c-oriented BaTiO3 domains, and the resultant magnetoelectric coupling is larger and more reversible than previously reported from macroscopic measurements. Our results emphasize the importance of nanoscale ferroic domain structure and the promise of first-order transition materials to achieve enhanced coupling in artificial multiferroics. PMID:25969926

  19. Investigating the emotional response to room acoustics: A functional magnetic resonance imaging study.

    PubMed

    Lawless, M S; Vigeant, M C

    2015-10-01

    While previous research has demonstrated the powerful influence of pleasant and unpleasant music on emotions, the present study utilizes functional magnetic resonance imaging (fMRI) to assess the positive and negative emotional responses as demonstrated in the brain when listening to music convolved with varying room acoustic conditions. During fMRI scans, subjects rated auralizations created in a simulated concert hall with varying reverberation times. The analysis detected activations in the dorsal striatum, a region associated with anticipation of reward, for two individuals for the highest rated stimulus, though no activations were found for regions associated with negative emotions in any subject.

  20. Influence of the shielding currents lengthscale and anisotropy effects on the magnetic flux profiles of high-temperature superconductors

    NASA Astrophysics Data System (ADS)

    Vanderbemden, P.; Lovchinov, V.

    2012-12-01

    The so-called "magnetic flux profile" AC inductive technique is a powerful method for determining the critical current density Jc of bulk superconductors. In this work we aim at reporting analytical expressions for magnetic flux profiles of superconducting rectangular samples exhibiting a critical current density anisotropy. The results are used for examining the error resulting from approximating a rectangular cross-section by an "infinite cylinder" or "infinite slab" geometry. It is found that such approximations can lead to an artificial curvature of the flux profiles and errors of 10%-20% in the determination of Jc. Next, the effects of how planar defects (cracks, platelet boundaries,...) affect the magnetic flux profile signal are discussed. It is found that the magnetic flux profiles are much sensitive to the lengthscale of shielding currents, thereby providing means of investigation of the typical size of induced current loops in bulk superconductors. Finally some illustrative flux profile data measured on a bulk, large grain melt-processed YBCO single domain exhibiting Jc anisotropy are presented and discussed in relation with theoretical predictions.

  1. Extremely strong room-temperature transient photocurrent-detected magnetic resonance in organic devices

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Liu, Rui; Cai, Min; Shinar, Ruth; Shinar, Joseph

    2012-12-01

    An extremely strong room-temperature photocurrent- (PC- or IPC-) detected magnetic resonance (PCDMR) that elucidates transport and trapping phenomena in organic devices, in particular solar cells, is described. When monitoring the transient PCDMR in indium tin oxide (ITO)/poly(2-methoxy-5-(2'-ethyl)-hexoxy-1,4-phenylenevinylene) (MEH-PPV)/Al devices, where the MEH-PPV film was baked overnight at 100 °C in O2, it is observed that |ΔIPC/IPC| peaks at values ≫1, where ΔIPC is the change in IPC induced by magnetic resonance conditions. Importantly, ΔIPC and IPC are of different origin. The mechanism most likely responsible for this effect is the spin-dependent formation of spinless bipolarons adjacent to negatively charged deep traps, apparently induced in particular by oxygen centers, to form trions.

  2. Calculation of binary magnetic properties and potential energy curve in xenon dimer: second virial coefficient of (129)Xe nuclear shielding.

    PubMed

    Hanni, Matti; Lantto, Perttu; Runeberg, Nino; Jokisaari, Jukka; Vaara, Juha

    2004-09-22

    Quantum chemical calculations of the nuclear shielding tensor, the nuclear quadrupole coupling tensor, and the spin-rotation tensor are reported for the Xe dimer using ab initio quantum chemical methods. The binary chemical shift delta, the anisotropy of the shielding tensor Delta sigma, the nuclear quadrupole coupling tensor component along the internuclear axis chi( parallel ), and the spin-rotation constant C( perpendicular ) are presented as a function of internuclear distance. The basis set superposition error is approximately corrected for by using the counterpoise correction (CP) method. Electron correlation effects are systematically studied via the Hartree-Fock, complete active space self-consistent field, second-order Møller-Plesset many-body perturbation, and coupled-cluster singles and doubles (CCSD) theories, the last one without and with noniterative triples, at the nonrelativistic all-electron level. We also report a high-quality theoretical interatomic potential for the Xe dimer, gained using the relativistic effective potential/core polarization potential scheme. These calculations used valence basis set of cc-pVQZ quality supplemented with a set of midbond functions. The second virial coefficient of Xe nuclear shielding, which is probably the experimentally best-characterized intermolecular interaction effect in nuclear magnetic resonance spectroscopy, is computed as a function of temperature, and compared to experiment and earlier theoretical results. The best results for the second virial coefficient, obtained using the CCSD(CP) binary chemical shift curve and either our best theoretical potential or the empirical potentials from the literature, are in good agreement with experiment. Zero-point vibrational corrections of delta, Delta sigma, chi (parallel), and C (perpendicular) in the nu=0, J=0 rovibrational ground state of the xenon dimer are also reported.

  3. Estimation of isotropic nuclear magnetic shieldings in the CCSD(T) and MP2 complete basis set limit using affordable correlation calculations.

    PubMed

    Kupka, Teobald; Stachów, Michał; Kaminsky, Jakub; Sauer, Stephan P A

    2013-08-01

    A linear correlation between isotropic nuclear magnetic shielding constants for seven model molecules (CH2 O, H2 O, HF, F2 , HCN, SiH4 and H2 S) calculated with 37 methods (34 density functionals, RHF, MP2 and CCSD(T)), with affordable pcS-2 basis set and corresponding complete basis set results, estimated from calculations with the family of polarization-consistent pcS-n basis sets is reported. This dependence was also supported by inspection of profiles of deviation between CBS estimated nuclear shieldings and shieldings obtained with the significantly smaller basis sets pcS-2 and aug-cc-pVTZ-J for the selected set of 37 calculation methods. It was possible to formulate a practical approach of estimating the values of isotropic nuclear magnetic shielding constants at the CCSD(T)/CBS and MP2/CBS levels from affordable CCSD(T)/pcS-2, MP2/pcS-2 and DFT/CBS calculations with pcS-n basis sets. The proposed method leads to a fairly accurate estimation of nuclear magnetic shieldings and considerable saving of computational efforts.

  4. Performance and Facility Background Pressure Characterization Tests of NASAs 12.5-kW Hall Effect Rocket with Magnetic Shielding Thruster

    NASA Technical Reports Server (NTRS)

    Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Shastry, Rohit; Thomas, Robert; Yim, John; Herman, Daniel; Williams, George; Myers, James; Hofer, Richard; Mikellides, Ioannis; Sekerak, Michael; Polk, James

    2015-01-01

    NASA's Space Technology Mission Directorate (STMD) Solar Electric Propulsion Technology Demonstration Mission (SEP/TDM) project is funding the development of a 12.5-kW Hall thruster system to support future NASA missions. The thruster designated Hall Effect Rocket with Magnetic Shielding (HERMeS) is a 12.5-kW Hall thruster with magnetic shielding incorporating a centrally mounted cathode. HERMeS was designed and modeled by a NASA GRC and JPL team and was fabricated and tested in vacuum facility 5 (VF5) at NASA GRC. Tests at NASA GRC were performed with the Technology Development Unit 1 (TDU1) thruster. TDU1's magnetic shielding topology was confirmed by measurement of anode potential and low electron temperature along the discharge chamber walls. Thermal characterization tests indicated that during full power thruster operation at peak magnetic field strength, the various thruster component temperatures were below prescribed maximum allowable limits. Performance characterization tests demonstrated the thruster's wide throttling range and found that the thruster can achieve a peak thruster efficiency of 63% at 12.5 kW 500 V and can attain a specific impulse of 3,000 s at 12.5 kW and a discharge voltage of 800 V. Facility background pressure variation tests revealed that the performance, operational characteristics, and magnetic shielding effectiveness of the TDU1 design were mostly insensitive to increases in background pressure.

  5. Characterization of ZnO:Co particles prepared by hydrothermal method for room temperature magnetism

    NASA Astrophysics Data System (ADS)

    Peng, Yingzi; Huo, Dexuan; He, Haiping; Li, Yuan; Li, Lingwei; Wang, Huawen; Qian, Zhenghong

    2012-03-01

    ZnO based diluted magnetic semiconductor particles (ZnO:Co) have been grown using a hydrothermal method with good crystallinity. The atomic percentage of Co presented in the specimen is about 0.01. Based on the x-ray diffraction and high-resolution transition electron, Co is found to be incorporated into ZnO lattice without evidence of obvious Co precipitates. However, from photoluminescence (PL) spectra in the range of 1.94 -3.45 eV, a strong broad emission centered around 600 nm (2.07 eV) in the visible range as well as a relatively weak peak at 2.81 eV are observed, indicating the presence of Co impurities. Moreover, intrinsic emissions such as DOX suggest that at least some Co have been doped into ZnO lattice, substituting for Zn2+ ions. The PL results further confirm the substitution of Zn2+ ions by Co, which leads to the changes of the electronic band structures. Magnetism could be realized at room temperature for the ZnO:Co nanoparticles under our experimental conditions although with low coercivity. The field-cooled and zero-field-cooled curves can be explained as a result of competition between the ferromagnetic and the antiferromagnetic ordering in the ZnO:Co nanoparticles. Combining the results from PL and magnetism characterization, it is reasonable to think that both doped Co in the ZnO lattice and Co impurities contribute to magnetism in ZnO:Co nanoparticles at room temperature.

  6. Magnetic ordering in relation to the room-temperature magnetoelectric effect of Sr3Co2Fe24O41.

    PubMed

    Soda, Minoru; Ishikura, Taishi; Nakamura, Hiroyuki; Wakabayashi, Yusuke; Kimura, Tsuyoshi

    2011-02-25

    The origin of a room-temperature magnetoelectric (ME) effect has been examined by means of neutron powder diffraction measurements for a Z-type hexaferrite Sr(3)Co(2)Fe(24)O(41). The temperature and magnetic-field dependence of the electric polarization P and several magnetic Bragg reflections show that a commensurate magnetic order with a (0,0,1) propagation vector has an intimate connection with the ME effect. The room-temperature ME effect can be understood in terms of the appearance of P which is induced by a transverse conical spin structure through the inverse Dzyaloshinskii-Moriya mechanism in analogy with Y-type hexaferrites.

  7. Negative ion beam injection apparatus with magnetic shield and electron removal means

    DOEpatents

    Anderson, Oscar A.; Chan, Chun F.; Leung, Ka-Ngo

    1994-01-01

    A negative ion source is constructed to produce H.sup.- ions without using Cesium. A high percentage of secondary electrons that typically accompany the extracted H.sup.- are trapped and eliminated from the beam by permanent magnets in the initial stage of acceleration. Penetration of the magnetic field from the permanent magnets into the ion source is minimized. This reduces the destructive effect the magnetic field could have on negative ion production and extraction from the source. A beam expansion section in the extractor results in a strongly converged final beam.

  8. Cryogenic Design of a Large Superconducting Magnet for Astro-particle Shielding on Deep Space Travel Missions

    NASA Astrophysics Data System (ADS)

    Bruce, Romain; Baudouy, Bertrand

    The Space Radiation Superconducting Shield (SR2S) European project aims at studying a large superconducting toroid magnet to protect the human habitat from the ionizing radiations coming from Galactic Cosmic Ray during long term missions in deep space. Titanium clad MgB2 conductor is used to afford a bending power greater than 5 T.m at 10 K. A specific cryogenic design is needed to cool down this 10 m long and 12.8 m in diameter magnet. A passive cooling system, using a V-groove sunshield, is considered to reduce the heat flux coming from the Sun or Mars. An active configuration, using pulse tube cryocoolers, will be linked to the 80 K thermal screen intercepting most of the heat fluxes coming from the human habitat. The toroid magnet will be connected also to cryocoolers to absorb the few watts reaching its surface. Two kinds of thermal link are being considered to absorb the heat on the 80 K thermal screen. The first one is active, with a pump circulating helium gas in a network of exchange tubes. The second one is passive using long cryogenic pulse heat pipe (PHP) with the evaporator on the surface of the thermal screen and the condenser attached to the pulse tube.

  9. Discriminating Hepatocellular Carcinoma in Rats Using a High-Tc SQUID Detected Nuclear Resonance Spectrometer in a Magnetic Shielding Box

    PubMed Central

    Huang, Kai-Wen; Chen, Hsin-Hsien; Yang, Hong-Chang; Horng, Herng-Er; Liao, Shu-Hsien; Yang, Shieh Yueh; Chieh, Jen-Jie; Wang, Li-Ming

    2012-01-01

    In this study, we report the spin-lattice relaxation rate of hepatocellular carcinoma (HCC) and normal liver tissue in rats using a high-Tc superconducting quantum interference device (SQUID) based nuclear magnetic resonance (NMR) spectrometer. The resonance spectrometer used for discriminating liver tumors in rats via the difference in longitudinal relaxation time in low magnetic fields was set up in a compact and portable magnetic shielding box. The frequency-domain NMR signals of HCC tissues and normal liver tissues were analyzed to study their respective longitudinal relaxation rate T1−1. The T1−1 of liver tissues for ten normal rats and ten cancerous rats were investigated respectively. The averaged T1−1 value of normal liver tissue was (6.41±0.66) s−1, and the averaged T1−1 value of cancerous tissue was (3.38±0.15) s−1. The ratio of T1−1 for normal liver tissues and cancerous liver tissues of the rats investigated is estimated to be 1.9. Since this significant statistical difference, the T1−1 value can be used to distinguish the HCC tissues from normal liver tissues. This method of examining liver and tumor tissues has the advantages of being convenient, easy to operate, and stable. PMID:23071710

  10. Discriminating hepatocellular carcinoma in rats using a high-Tc SQUID detected nuclear resonance spectrometer in a magnetic shielding box.

    PubMed

    Huang, Kai-Wen; Chen, Hsin-Hsien; Yang, Hong-Chang; Horng, Herng-Er; Liao, Shu-Hsien; Yang, Shieh Yueh; Chieh, Jen-Jie; Wang, Li-Ming

    2012-01-01

    In this study, we report the spin-lattice relaxation rate of hepatocellular carcinoma (HCC) and normal liver tissue in rats using a high-T(c) superconducting quantum interference device (SQUID) based nuclear magnetic resonance (NMR) spectrometer. The resonance spectrometer used for discriminating liver tumors in rats via the difference in longitudinal relaxation time in low magnetic fields was set up in a compact and portable magnetic shielding box. The frequency-domain NMR signals of HCC tissues and normal liver tissues were analyzed to study their respective longitudinal relaxation rate T(1) (-1). The T(1) (-1) of liver tissues for ten normal rats and ten cancerous rats were investigated respectively. The averaged T(1) (-1) value of normal liver tissue was (6.41±0.66) s(-1), and the averaged T(1) (-1) value of cancerous tissue was (3.38±0.15) s(-1). The ratio of T(1) (-1) for normal liver tissues and cancerous liver tissues of the rats investigated is estimated to be 1.9. Since this significant statistical difference, the T(1) (-1) value can be used to distinguish the HCC tissues from normal liver tissues. This method of examining liver and tumor tissues has the advantages of being convenient, easy to operate, and stable.

  11. Oxygen-vacancy-induced room-temperature magnetization in lamellar V2O5 thin films

    NASA Astrophysics Data System (ADS)

    Cezar, A. B.; Graff, I. L.; Varalda, J.; Schreiner, W. H.; Mosca, D. H.

    2014-10-01

    In this work, we study the local atomic and electronic structures as well as oxygen-vacancy-induced magnetic properties of electrodeposited V2O5 films. Unlike stoichiometric V2O5, which is a diamagnetic lamellar semiconductor, our oxygen-defective V2O5 films are ferromagnetic at room-temperature and their saturation magnetization decreases with air exposure time. X-ray absorption spectroscopy was used to monitor the aging effect on these films, revealing that freshly-made samples exhibit only local crystalline order, whereas the aged ones undoubtedly show an enhancement of crystallinity and coordination symmetry. The mean number of oxygen atoms around V tends to increase, indicating a decrease of oxygen vacancies with time. Concurrently with the decrease of oxygen vacancies, a loss of saturation magnetization is also observed. Hence, it can be concluded that the ferromagnetism of the V2O5 films originates from a vacancy-induced mechanism, confirming the universality of this class of ferromagnetism.

  12. Use of Second Generation Coated Conductors for Efficient Shielding of dc Magnetic Fields (Postprint)

    DTIC Science & Technology

    2010-07-15

    Similar to Ref. 15, along the center line of each 150 mm long section a 1 mm wide, 124 mm long slit was milled leaving a superconducting film in the form of...layer of superconducting film, can attenuate an external magnetic field of up to 5 mT by more than an order of magnitude. For comparison purposes...appears to be especially promising for the realization of large scale high-Tc superconducting screens. 15. SUBJECT TERMS magnetic screens, current

  13. Possible cryptic tectono-magnetic fabrics in `post-tectonic' granitoid plutons of the Canadian Shield

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham J.; Kehlenbeck, Manfred M.

    1996-01-01

    Two late Archean granitic plutons forcefully intruded and thermally metamorphosed Archean schists. Feldspar magacrysts aligned concentrically with the margins during inflation. Substantial tectonic deformation never affected the plutons. Nevertheless, both plutons show the same, consistently oriented, cryptic magnetic fabric revealed by anisotropy of low field susceptibility (AMS) from 134 samples. They have an NE-SW vertical magnetic foliation and a magnetic lineation trending 060/15. Eigenvalues of the orientation distribution of principal susceptibilities show that the magnetic fabrics have almost identical strengths, orientations and symmetry in both plutons. We propose a post-magmatic reactivation of the earlier regional tectonic shortening. This imparted a 'cryptic tectonic' magnetic fabric on the plutons that overprinted the magmatic AMS fabric in most outcrops. The plutons' AMS fabrics are subparallel to the much older schistosity of the country rocks. Because multidomain magnetite provides > 99% of the low field susceptibility of the rocks, it controls the AMS. However, we see no alignment of the magnetite grains. Thus, magnetic anisotropy may be due to stress alignment of intragranular domain walls and not controlled by grain shape, as usually assumed for magnetite.

  14. Electric control of magnon frequencies and magnetic moment of bismuth ferrite thin films at room temperature

    PubMed Central

    Kumar, Ashok; Scott, J. F.; Katiyar, R. S.

    2011-01-01

    Here, we report the tuning of room-temperature magnon frequencies from 473 GHz to 402 GHz (14%) and magnetic moment from 4 to 18 emu∕cm3 at 100 Oe under the application of external electric fields (E) across interdigital electrodes in BiFeO3 (BFO) thin films. A decrease in magnon frequencies and increase in phonon frequencies were observed with Magnon and phonon Raman intensities are asymmetric with polarity, decreasing with positive E (+E) and increasing with negative E (−E) where polarity is with respect to in-plane polarization P. The magnetoelectric coupling (α) is proved to be linear and a rather isotropic α = 8.5 × 10−12 sm−1. PMID:21901050

  15. Electric control of magnon frequencies and magnetic moment of bismuth ferrite thin films at room temperature.

    PubMed

    Kumar, Ashok; Scott, J F; Katiyar, R S

    2011-08-08

    Here, we report the tuning of room-temperature magnon frequencies from 473 GHz to 402 GHz (14%) and magnetic moment from 4 to 18 emu∕cm(3) at 100 Oe under the application of external electric fields (E) across interdigital electrodes in BiFeO(3) (BFO) thin films. A decrease in magnon frequencies and increase in phonon frequencies were observed with Magnon and phonon Raman intensities are asymmetric with polarity, decreasing with positive E (+E) and increasing with negative E (-E) where polarity is with respect to in-plane polarization P. The magnetoelectric coupling (α) is proved to be linear and a rather isotropic α = 8.5 × 10(-12) sm(-1).

  16. Optimized shielding design for the time-resolved Magnetic Recoil Spectrometer (MRSt) on the NIF

    NASA Astrophysics Data System (ADS)

    Wink, C.; Frenje, J.; Gatu Johnson, M.; Li, C. K.; Seguin, F.; Petrasso, R.; Hilsabeck, T.; Bionta, R.; Khater, H.

    2016-10-01

    To meet the goals for the MRSt to measure the neutron spectrum at the NIF with a time resolution of 20 ps and an accuracy of 5%, a S/B >5 for the down-scattered neutron measurement is required. As the MRSt-detector design consists of a pulse-dilation drift tube with a CsI photocathode positioned at the focal plane of the spectrometer and a microchannel plate (MCP) for signal gain, the S/B requirement can be met if the number of secondary electrons (SE) produced by neutron and γ-ray background in these components is reduced 50-100 times. It has been shown in ref. that the SE generated by the neutron and γ-ray background in the CsI is insignificant and won't affect the MRSt measurement. However, the MCP poses a greater S/B challenge due to higher background sensitivities. In this paper, we discuss an MRSt SE generation model, which includes the CsI photocathode and MCP, and the MRSt shielding design required to reduce the MCP background to the required level for a down-scattered neutron measurement. This work was supported in part by DOE (NNSA, NLUF) and LLNL.

  17. Carpenter in White Room

    NASA Technical Reports Server (NTRS)

    1962-01-01

    Inside Hangar S at the White Room Facility at Cape Canaveral, Florida, Mercury astronaut M. Scott Carpenter examines the honeycomb protective material on the main pressure bulkhead (heat shield) of his Mercury capsule nicknamed 'Aurora 7.'

  18. Observation of room-temperature magnetic skyrmions and their current-driven dynamics in ultrathin metallic ferromagnets

    NASA Astrophysics Data System (ADS)

    Woo, Seonghoon; Litzius, Kai; Krüger, Benjamin; Im, Mi-Young; Caretta, Lucas; Richter, Kornel; Mann, Maxwell; Krone, Andrea; Reeve, Robert M.; Weigand, Markus; Agrawal, Parnika; Lemesh, Ivan; Mawass, Mohamad-Assaad; Fischer, Peter; Kläui, Mathias; Beach, Geoffrey S. D.

    2016-05-01

    Magnetic skyrmions are topologically protected spin textures that exhibit fascinating physical behaviours and large potential in highly energy-efficient spintronic device applications. The main obstacles so far are that skyrmions have been observed in only a few exotic materials and at low temperatures, and fast current-driven motion of individual skyrmions has not yet been achieved. Here, we report the observation of stable magnetic skyrmions at room temperature in ultrathin transition metal ferromagnets with magnetic transmission soft X-ray microscopy. We demonstrate the ability to generate stable skyrmion lattices and drive trains of individual skyrmions by short current pulses along a magnetic racetrack at speeds exceeding 100 m s-1 as required for applications. Our findings provide experimental evidence of recent predictions and open the door to room-temperature skyrmion spintronics in robust thin-film heterostructures.

  19. Extraordinary high dielectric constant, electrical and magnetic properties of ferrite nanoparticles at room temperature

    NASA Astrophysics Data System (ADS)

    Batoo, Khalid Mujasam; Mir, Feroz Ahmed; Abd El-sadek, M.-S.; Shahabuddin, Md.; Ahmed, Niyaz

    2013-11-01

    Nanoparticles of spinel ferrites of basic composition Ni1- x Co x Fe2O4 (0.0 ≤ x ≤ 0.05) were synthesized through modified co-precipitation method, and were characterized for structural, transport electrical and magnetic properties using XRD, HRTEM, FTIR, LCR meter and VSM techniques, respectively. XRD analysis showed that all the samples are single-phase cubic spinel in structure. The average crystallite sizes of the nanoparticles were found between 30 nm to 45 nm. Real and imaginary parts of the impedance ( Z' and Z″) suggested coexistence of two relaxation regimes: one was introduced by electrode polarization, while the other was attributed to the coeffect of grain and grain boundary effects. The dielectric constant of the samples was found very high, which showed non-Debye relaxation phenomena, while conductivity of the samples exhibited a two-segment behavior with frequency. The room temperature M-H curves suggested that the samples exhibit supermagnetism, and the saturation magnetization increases with increasing Co2+ ion substitution.

  20. Magsat investigation. [Canadian shield

    NASA Technical Reports Server (NTRS)

    Hall, D. H. (Principal Investigator)

    1980-01-01

    A computer program was prepared for modeling segments of the Earth's crust allowing for heterogeneity in magnetization in calculating the Earth's field at Magsat heights. This permits investigation of a large number of possible models in assessing the magnetic signatures of subprovinces of the Canadian shield. The fit between the model field and observed fields is optimized in a semi-automatic procedure.

  1. Magnetic shielding of walls from the unmagnetized ion beam in a Hall thruster

    SciTech Connect

    Mikellides, Ioannis G.; Katz, Ira; Hofer, Richard R.; Goebel, Dan M.

    2013-01-14

    We demonstrate by numerical simulations and experiments that the unmagnetized ion beam formed in a Hall thruster can be controlled by an applied magnetic field in a manner that reduces by 2-3 orders of magnitude deleterious ion bombardment of the containing walls. The suppression of wall erosion in Hall thrusters to such low levels has remained elusive for decades.

  2. Construction of three-dimensional graphene interfaces into carbon fiber textiles for increasing deposition of nickel nanoparticles: flexible hierarchical magnetic textile composites for strong electromagnetic shielding.

    PubMed

    Bian, Xing-Ming; Liu, Lin; Li, Hai-Bing; Wang, Chan-Yuan; Xie, Qing; Zhao, Quan-Liang; Bi, Song; Hou, Zhi-Ling

    2017-01-27

    Since manipulating electromagnetic waves with electromagnetic active materials for environmental and electric engineering is a significant task, here a novel prototype is reported by introducing reduced graphene oxide (RGO) interfaces in carbon fiber (CF) networks for a hierarchical carbon fiber/reduced graphene oxide/nickel (CF-RGO-Ni) composite textile. Upon charaterizations of the microscopic morphologies, electrical and magnetic properties, the presence of three-dimensional RGO interfaces and bifunctional nickel nanoparticles substantially influences the related physical properties in the resulting hierarchical composite textiles. Eletromagnetic interference (EMI) shielding performance suggests that the hierarchical composite textiles hold a strong shielding effectiveness greater than 61 dB, showing greater advantages than conventional polymeric and foamy shielding composites. As a polymer-free lightweight structure, flexible CF-RGO-Ni composites of all electromagnetic active components offer unique understanding of the multi-scale and multiple mechanisms in electromagnetic energy consumption. Such a novel prototype of shielding structures along with convenient technology highlight a strategy to achieve high-performance EMI shielding, coupled with a universal approach for preparing advanced lightweight composites with graphene interfaces.

  3. Construction of three-dimensional graphene interfaces into carbon fiber textiles for increasing deposition of nickel nanoparticles: flexible hierarchical magnetic textile composites for strong electromagnetic shielding

    NASA Astrophysics Data System (ADS)

    Bian, Xing-Ming; Liu, Lin; Li, Hai-Bing; Wang, Chan-Yuan; Xie, Qing; Zhao, Quan-Liang; Bi, Song; Hou, Zhi-Ling

    2017-01-01

    Since manipulating electromagnetic waves with electromagnetic active materials for environmental and electric engineering is a significant task, here a novel prototype is reported by introducing reduced graphene oxide (RGO) interfaces in carbon fiber (CF) networks for a hierarchical carbon fiber/reduced graphene oxide/nickel (CF-RGO-Ni) composite textile. Upon charaterizations of the microscopic morphologies, electrical and magnetic properties, the presence of three-dimensional RGO interfaces and bifunctional nickel nanoparticles substantially influences the related physical properties in the resulting hierarchical composite textiles. Eletromagnetic interference (EMI) shielding performance suggests that the hierarchical composite textiles hold a strong shielding effectiveness greater than 61 dB, showing greater advantages than conventional polymeric and foamy shielding composites. As a polymer-free lightweight structure, flexible CF-RGO-Ni composites of all electromagnetic active components offer unique understanding of the multi-scale and multiple mechanisms in electromagnetic energy consumption. Such a novel prototype of shielding structures along with convenient technology highlight a strategy to achieve high-performance EMI shielding, coupled with a universal approach for preparing advanced lightweight composites with graphene interfaces.

  4. Angular dependence of direct current decay in a closed YBCO double-pancake coil under external AC magnetic field and reduction by magnetic shielding

    NASA Astrophysics Data System (ADS)

    Geng, J.; Zhang, H.; Li, C.; Zhang, X.; Shen, B.; Coombs, T. A.

    2017-03-01

    High T c superconducting (HTS) coils are ideal candidates in the use of high field magnets. HTS coils carrying a direct current, however, suffer a non-negligible loss when they are exposed to an external AC magnetic field. Although this phenomenon is well known, no study concerning AC magnetic field angular dependence of direct current decay has ever been shown. In this work, we experimentally investigate the direct current decay characteristics in a closed double pancake coil made of a YBCO coated conductor under external AC field. AC field of different angles with respect to the coil plane is applied. Results show that the current decay rate presents a strong angular dependence. The fastest decay occurs when the field is parallel to the coil plane, in which case the surface of the tape in the outermost layer experiences most flux variation. To reduce the decay rate, we propose wrapping superconducting tapes around the outermost layer of the coil to shield external AC field. This method significantly reduces direct current decay rate under parallel field, without affecting the perpendicular self-field of the coil.

  5. Radiation Storm vs. The Magnetic Shield: Superheroes of Magnetism & Space Weather Education - A Model for Teacher Professional Development Workshops

    NASA Astrophysics Data System (ADS)

    Russell, R. M.; Johnson, R. M.

    2010-12-01

    Magnetic and electric fields and phenomena play important roles in various situations in astronomy, planetary science, and Earth science. Students often lack an intuitive sense of electromagnetic phenomena, and therefore struggle with the complexities of planetary and stellar magnetic fields. Hands-on magnetism activities can provide students with an intuitive grasp of the basics of magnetism, preparing them for more challenging conceptual studies of magnetic phenomena. For the past six years, we have been presenting a professional development workshop for teachers covering the topics of magnetism and space weather. The workshop, which has been conducted more than 20 times for a range of audiences, blends together several simple hands-on activities, background information on space weather and geomagnetism, a collection of images, animations, and interactives that illustrate important concepts, and guidance about specific links between these topics and national science education standards. These workshops have been very well-received, and have consistently been rated highly by participants in surveys. We believe the methods used in these workshops can be applied to other topics in science education and to astronomy and Earth science education specifically. In this presentation, we will describe our magnetism and space weather workshop, including some of the hands-on activities. We will describe successful aspects of the workshop and comment on ways we think this approach could be replicated for other topics. We will also display some of the interactives, graphics, and animations shown during the workshops. Resources have been added to the workshop over the years in response to recurring questions from teachers; we will comment on this process and how it might be applied to other topics. The activities and extensive background content used or referenced in the workshop are available for free on the Windows to the Universe web site (www.windows2universe.org). Hands on

  6. Actively driven thermal radiation shield

    DOEpatents

    Madden, Norman W.; Cork, Christopher P.; Becker, John A.; Knapp, David A.

    2002-01-01

    A thermal radiation shield for cooled portable gamma-ray spectrometers. The thermal radiation shield is located intermediate the vacuum enclosure and detector enclosure, is actively driven, and is useful in reducing the heat load to mechanical cooler and additionally extends the lifetime of the mechanical cooler. The thermal shield is electrically-powered and is particularly useful for portable solid-state gamma-ray detectors or spectrometers that dramatically reduces the cooling power requirements. For example, the operating shield at 260K (40K below room temperature) will decrease the thermal radiation load to the detector by 50%, which makes possible portable battery operation for a mechanically cooled Ge spectrometer.

  7. Archean uplift of a subprovince boundary in the Canadian Shield, revealed by magnetic fabrics

    NASA Astrophysics Data System (ADS)

    Borradaile, Graham J.; Stewart, R. Alex; Werner, Tomasz

    1993-11-01

    A high strain zone, reported elsewhere as a subprovince or tectonic-terrane boundary, shows evidence of uplift during a penetrative D 1 event. Some outcrops reveal this by conventional L-S petrofabric observations. However, all outcrops permit measurements of the anisotropy of low field magnetic susceptibility (AMS) which here records the preferred crystallographic orientation of chlorite, biotite and amphibole. Furthermore, anisotropy of anhysteretic magnetic remanence (AARM) reflects the preferred orientation of ferromagnetic grains (magnetite and pyrrhotite). All three types of fabric show that the rocks were shortened in a north-south direction, perpendicular to the terrane boundary, and stretched upwards in a nearly coaxial strain history. A few anomalous magnetic fabrics may indicate some late D 1 subhorizontal E-W extension, compatible with transpression along the boundary. We conclude that this boundary is a zone of high strain associated with the uplift of the high-grade plutonic rocks of the Winnipeg River subprovince, with only slight evidence of minor components of late transpression during the penetrative D 1 fabrics.

  8. Active shielding to reduce low frequency disturbances in direct current near biomagnetic measurements

    NASA Astrophysics Data System (ADS)

    Platzek, D.; Nowak, H.; Giessler, F.; Röther, J.; Eiselt, M.

    1999-05-01

    Measurements of dc near biomagnetic fields are disturbed by low frequency noise that is not reduced sufficiently by most of the magnetically shielded rooms or gradiometers. For this reason an active shielding system has been developed at the Biomagnetic Center of the University of Jena. This work describes the principle of the active shielding system and demonstrates its properties concerning the attenuation of disturbing fields, frequency range, and some applications in biomedical measurements. We achieved a reduction of external low frequency magnetic fields by more than 50 dB and an attenuation of the field gradient by about 25 dB. This active shielding enables measurements of near dc biomagnetic fields in investigations of periinfarct depolarizations after ischemic stroke and spreading depression in migraine patients.

  9. Micromagnetic modeling of the shielding properties of nanoscale ferromagnetic layers

    NASA Astrophysics Data System (ADS)

    Iskandarova, I. M.; Knizhnik, A. A.; Popkov, A. F.; Potapkin, B. V.; Stainer, Q.; Lombard, L.; Mackay, K.

    2016-09-01

    Ferromagnetic shields are widely used to concentrate magnetic fields in a target region of space. Such shields are also used in spintronic nanodevices such as magnetic random access memory and magnetic logic devices. However, the shielding properties of nanostructured shields can differ considerably from those of macroscopic samples. In this work, we investigate the shielding properties of nanostructured NiFe layers around a current line using a finite element micromagnetic model. We find that thin ferromagnetic layers demonstrate saturation of magnetization under an external magnetic field, which reduces the shielding efficiency. Moreover, we show that the shielding properties of nanoscale ferromagnetic layers strongly depend on the uniformity of the layer thickness. Magnetic anisotropy in ultrathin ferromagnetic layers can also influence their shielding efficiency. In addition, we show that domain walls in nanoscale ferromagnetic shields can induce large increases and decreases in the generated magnetic field. Therefore, ferromagnetic shields for spintronic nanodevices require careful design and precise fabrication.

  10. Role of Spin-Dependent Terms in the Relationship among Nuclear Spin-Rotation and NMR Magnetic Shielding Tensors.

    PubMed

    Aucar, I Agustín; Gomez, Sergio S; Giribet, Claudia G; Aucar, Gustavo A

    2016-12-15

    The broadly accepted procedure to obtain the experimental absolute scale of NMR magnetic shieldings, σ, is well-known for nonheavy atom-containing molecules. It was uncovered more than 40 years ago by the works of Ramsey and Flygare. They found a quite accurate relationship among σ and the nuclear spin-rotation constants. Its relativistic extension was very recently proposed, although it has an intrinsic weakness because a new SO-S two-component term needs to be considered. We show how to overcome this problem. We found that (νY(S) - νY(atom,S)) generalizes the SO-S term, where νY(S) = ⟨⟨[((r - rY) × α)/(|r - rY|(3))]; S((4))⟩⟩, r - rY is the electron position with respect to the position of nucleus Y, and S((4)) is the four-component total electron spin. When including this new term, one finds that the best of our relativistic Flygare-like models fits quite well with the results of the most accurate method available at the moment. We also show that the difference among the parallel component of σ(Xe) in XeF2 and σ(Xe) of the free atom is almost completely described by that new term.

  11. Room temperature dielectric and magnetic properties of Gd and Ti co-doped BiFeO{sub 3} ceramics

    SciTech Connect

    Basith, M. A. E-mail: arima@yz.yamagata-u.ac.jp; Kurni, O.; Alam, M. S.; Sinha, B. L.; Ahmmad, Bashir E-mail: arima@yz.yamagata-u.ac.jp

    2014-01-14

    Room temperature dielectric and magnetic properties of BiFeO{sub 3} samples, co-doped with magnetic Gd and non-magnetic Ti in place of Bi and Fe, respectively, were reported. The nominal compositions of Bi{sub 0.9}Gd{sub 0.1}Fe{sub 1–x}Ti{sub x}O{sub 3} (x = 0.00-0.25) ceramics were synthesized by conventional solid state reaction technique. X-ray diffraction patterns revealed that the substitution of Fe by Ti induces a phase transition from rhombohedral to orthorhombic at x > 0.20. Morphological studies demonstrated that the average grain size was reduced from ∼1.5 μm to ∼200 nm with the increase in Ti content. Due to Ti substitution, the dielectric constant was stable over a wide range of high frequencies (30 kHz to 20 MHz) by suppressing the dispersion at low frequencies. The dielectric properties of the compounds are associated with their improved morphologies and reduced leakage current densities probably due to the lower concentration of oxygen vacancies in the compositions. Magnetic properties of Bi{sub 0.9}Gd{sub 0.1}Fe{sub 1–x}Ti{sub x}O{sub 3} (x = 0.00-0.25) ceramics measured at room temperature were enhanced with Ti substitution up to 20% compared to that of pure BiFeO{sub 3} and Ti undoped Bi{sub 0.9}Gd{sub 0.1}FeO{sub 3} samples. The enhanced magnetic properties might be attributed to the substitution induced suppression of spiral spin structure of BiFeO{sub 3}. An asymmetric shifts both in the field and magnetization axes of magnetization versus magnetic field curves was observed. This indicates the presence of exchange bias effect in these compounds notably at room temperature.

  12. High-efficiency resonant amplification of weak magnetic fields for single spin magnetometry at room temperature

    NASA Astrophysics Data System (ADS)

    Trifunovic, Luka; Pedrocchi, Fabio L.; Hoffman, Silas; Maletinsky, Patrick; Yacoby, Amir; Loss, Daniel

    2015-06-01

    Magnetic resonance techniques not only provide powerful imaging tools that have revolutionized medicine, but they have a wide spectrum of applications in other fields of science such as biology, chemistry, neuroscience and physics. However, current state-of-the-art magnetometers are unable to detect a single nuclear spin unless the tip-to-sample separation is made sufficiently small. Here, we demonstrate theoretically that by placing a ferromagnetic particle between a nitrogen-vacancy magnetometer and a target spin, the magnetometer sensitivity is improved dramatically. Using materials and techniques that are already experimentally available, our proposed set-up is sensitive enough to detect a single nuclear spin within ten milliseconds of data acquisition at room temperature. The sensitivity is practically unchanged when the ferromagnet surface to the target spin separation is smaller than the ferromagnet lateral dimensions; typically about a tenth of a micrometre. This scheme further benefits when used for nitrogen-vacancy ensemble measurements, enhancing sensitivity by an additional three orders of magnitude.

  13. Understanding and optimizing microemulsions with magnetic room temperature ionic liquids (MRTILs).

    PubMed

    Klee, Andreas; Prevost, Sylvain; Gasser, Urs; Gradzielski, Michael

    2015-03-12

    Nonaqueous microemulsions containing the magnetic room temperature ionic liquid (MRTIL) bmimFeCl4 as polar phase were studied with respect to their macroscopic phase behavior and structure by means of small angle neutron scattering (SANS). The phase behavior was studied in detail for different alcohols as cosurfactant and different oils as nonpolar phase and mainly by varying the chain length of the used ionic surfactant (CnmimCl with n = 14, 16, 18). In general, phase behavior and structural ordering in the mesophases were found to be comparable to water systems where with increasing content of MRTIL the microemulsions seems to become less and less structured leading to a rough and softer interface with less long-range ordering. The extent of structuring increases with increasing chain length of the surfactant. However, the pure surfactant is not able to form microemulsions and a rather large amount of alcohol is required for stabilization, where the effectiveness of the alcohol increases with increasing chain length of the alcohol. From this comprehensive investigation systematic trends can be deduced in order to formulate correspondingly structured microemulsions with MRTIL as polar phase.

  14. Performance, Facility Pressure Effects, and Stability Characterization Tests of NASA's Hall Effect Rocket with Magnetic Shielding Thruster

    NASA Technical Reports Server (NTRS)

    Kamhawi, Hani; Huang, Wensheng; Haag, Thomas; Yim, John; Herman, Daniel; Peterson, Peter Y.; Williams, George J.; Gilland, James; Hofer, Richard; Mikellides, Ioannis

    2016-01-01

    NASA's Hall Effect Rocket with Magnetic Shielding (HERMeS) 12.5 kW Technology Demonstration Unit-1 (TDU-1) has been the subject of extensive technology maturation in preparation for flight system development. Part of the technology maturation effort included experimental evaluation of the TDU-1 thruster with conducting and dielectric front pole cover materials in two different electrical configurations. A graphite front magnetic pole cover thruster configuration with the thruster body electrically tied to cathode, and an alumina front pole cover thruster configuration with the thruster body floating were evaluated. Both configurations were also evaluated at different facility background pressure conditions to evaluate background pressure effects on thruster operation. Performance characterization tests found that higher thruster performance was attained with the graphite front pole cover configuration with the thruster electrically tied to cathode. A total thrust efficiency of 68% and a total specific impulse of 2,820 s was demonstrated at a discharge voltage of 600 V and a discharge power of 12.5 kW. Thruster stability regimes were characterized with respect to the thruster discharge current oscillations and with maps of the discharge current-voltage-magnetic field (IVB). Analysis of TDU-1 discharge current waveforms found that lower normalized discharge current peak-to-peak and root mean square magnitudes were attained when the thruster was electrically floated with alumina front pole covers. Background pressure effects characterization tests indicated that the thruster performance and stability were mostly invariant to changes in the facility background pressure for vacuum chamber pressure below 1×10-5 Torr-Xe (for thruster flow rates of 20.5 mg/s). Power spectral density analysis of the discharge current waveforms showed that increasing the vacuum chamber background pressure resulted in a higher discharge current dominant breathing mode frequency. Finally, IVB

  15. {sup 33}S hyperfine interactions in H{sub 2}S and SO{sub 2} and revision of the sulfur nuclear magnetic shielding scale

    SciTech Connect

    Helgaker, Trygve; Gauss, Jürgen; Cazzoli, Gabriele Puzzarini, Cristina

    2013-12-28

    Using the Lamb-dip technique, the hyperfine structure in the rotational spectra of H{sub 2}{sup 33}S and {sup 33}SO{sub 2} has been resolved and the corresponding parameters—that is, the sulfur quadrupole-coupling and spin–rotation tensors—were determined. The experimental parameters are in good agreement with results from high-level coupled-cluster calculations, provided that up to quadruple excitations are considered in the cluster operator, sufficiently large basis sets are used, and vibrational corrections are accounted for. The {sup 33}S spin-rotation tensor for H{sub 2}S has been used to establish a new sulfur nuclear magnetic shielding scale, combining the paramagnetic part of the shielding as obtained from the spin–rotation tensor with a calculated value for the diamagnetic part as well as computed vibrational and temperature corrections. The value of 716(5) ppm obtained in this way for the sulfur shielding of H{sub 2}S is in good agreement with results from high-accuracy quantum-chemical calculations but leads to a shielding scale that is about 28 ppm lower than the one suggested previously in the literature, based on the {sup 33}S spin-rotation constant of OCS.

  16. Design of the precast, post-tensioned concrete shielding structure for the TFTR neutral beam test cell

    SciTech Connect

    Kaminsky, E.L.; Nilsson, E.T.

    1981-01-01

    At the TFTR facility, the Neutral Beam Test Cell is a room separated from the TFTR Cell by a 4-foot-thick concrete wall and devoted to testing the neutral beam injector. The function of the shielding structure is to protect personnel from radiation casued by pulsing the injector. The distance from the TFTR device to the injector is large enough to permit use of magnetic materials in the shielding structure, and the neutron flux levels are small enough so that ordinary concrete of moderate thickness may be employed. Radiation considerations are not discussed in this paper, which is devoted to a description of the structural design of the shield.

  17. Minimizing magnetic fields for precision experiments

    SciTech Connect

    Altarev, I.; Fierlinger, P.; Lins, T.; Marino, M. G.; Nießen, B.; Petzoldt, G.; Reisner, M.; Stuiber, S. Sturm, M.; Taggart Singh, J.; Taubenheim, B.; Rohrer, H. K.; Schläpfer, U.

    2015-06-21

    An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

  18. Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions.

    PubMed

    Yuasa, Shinji; Nagahama, Taro; Fukushima, Akio; Suzuki, Yoshishige; Ando, Koji

    2004-12-01

    The tunnel magnetoresistance (TMR) effect in magnetic tunnel junctions (MTJs) is the key to developing magnetoresistive random-access-memory (MRAM), magnetic sensors and novel programmable logic devices. Conventional MTJs with an amorphous aluminium oxide tunnel barrier, which have been extensively studied for device applications, exhibit a magnetoresistance ratio up to 70% at room temperature. This low magnetoresistance seriously limits the feasibility of spintronics devices. Here, we report a giant MR ratio up to 180% at room temperature in single-crystal Fe/MgO/Fe MTJs. The origin of this enormous TMR effect is coherent spin-polarized tunnelling, where the symmetry of electron wave functions plays an important role. Moreover, we observed that their tunnel magnetoresistance oscillates as a function of tunnel barrier thickness, indicating that coherency of wave functions is conserved across the tunnel barrier. The coherent TMR effect is a key to making spintronic devices with novel quantum-mechanical functions, and to developing gigabit-scale MRAM.

  19. Ferromagnetism at room temperature with a large magnetic moment in anatase V-doped TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Hong, Nguyen Hoa; Sakai, Joe; Hassini, Awatef

    2004-04-01

    V-doped TiO2 thin films were grown by laser ablation on LaAlO3 substrates. In the chosen range of the growth conditions, all V:TiO2 films have an anatase structure and exhibit semiconducting and ferromagnetic behaviors at room temperature. V:TiO2 films have a giant magnetic moment and they seem to be far better ferromagnetic than Co/Fe/Ni-doped TiO2 films. This study has proved that a few percent of V substituting for Ti in TiO2 can result in a potential diluted magnetic semiconductor.

  20. Room-temperature decay and light reactivation of high-Tc ferromagnetism in an oxide-diluted magnetic semiconductor.

    PubMed

    Pan, Dengyu; Wan, Jianguo; Xu, Guoliang; Lv, Liya; Wu, Yujie; Min, Han; Liu, Junming; Wang, Guanghou

    2006-10-04

    We present a novel route for manipulation of the ferromagnetic order in Co-doped TiO2 using UV laser irradiation. The ferromagnetic order of the nanocrystal films decays with aging in air at room temperature, which can be reactivated and enhanced by UV irradiation, whereas the coercive force reduces with irradiation time. Photoinduced trapped electrons were suggested to induce the ferromagnetic order. We believe that light manipulation is a general method for tuning the magnetic properties of oxide-based diluted magnetic semiconductors, which can find practical applications in future integrated magneto-optical nanoelectronics.

  1. Theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis-, and trans-1,2-difluoroethylenes

    SciTech Connect

    Nozirov, Farhod E-mail: farhod.nozirov@gmail.com; Stachów, Michał; Kupka, Teobald E-mail: farhod.nozirov@gmail.com

    2014-04-14

    A theoretical prediction of nuclear magnetic shieldings and indirect spin-spin coupling constants in 1,1-, cis- and trans-1,2-difluoroethylenes is reported. The results obtained using density functional theory (DFT) combined with large basis sets and gauge-independent atomic orbital calculations were critically compared with experiment and conventional, higher level correlated electronic structure methods. Accurate structural, vibrational, and NMR parameters of difluoroethylenes were obtained using several density functionals combined with dedicated basis sets. B3LYP/6-311++G(3df,2pd) optimized structures of difluoroethylenes closely reproduced experimental geometries and earlier reported benchmark coupled cluster results, while BLYP/6-311++G(3df,2pd) produced accurate harmonic vibrational frequencies. The most accurate vibrations were obtained using B3LYP/6-311++G(3df,2pd) with correction for anharmonicity. Becke half and half (BHandH) density functional predicted more accurate {sup 19}F isotropic shieldings and van Voorhis and Scuseria's τ-dependent gradient-corrected correlation functional yielded better carbon shieldings than B3LYP. A surprisingly good performance of Hartree-Fock (HF) method in predicting nuclear shieldings in these molecules was observed. Inclusion of zero-point vibrational correction markedly improved agreement with experiment for nuclear shieldings calculated by HF, MP2, CCSD, and CCSD(T) methods but worsened the DFT results. The threefold improvement in accuracy when predicting {sup 2}J(FF) in 1,1-difluoroethylene for BHandH density functional compared to B3LYP was observed (the deviations from experiment were −46 vs. −115 Hz)

  2. Magneto-caloric effect of FexZryB100-x-y metallic ribbons for room temperature magnetic refrigeration

    NASA Astrophysics Data System (ADS)

    Guo, D. Q.; Chan, K. C.; Xia, L.; Yu, P.

    2017-02-01

    Among various amorphous magnetic materials, even though Fe-based materials do not have high magnetocaloric effect (MCE), their advantages of tunable Curie temperature (TC) and low cost have attracted considerable attention in regard to room temperature magnetic refrigeration applications. With the aim of enhancing the MCE, the influence of boron addition on Fe-based amorphous materials was investigated in this study. Fe94-xZr6Bx (x=5, 6, 8 and 10), Fe91-yZr9By (y=3, 4, 5, 6, 8 and 10) and Fe89-zZr11Bz (z=3, 4, 5, 6, 8 and 10) specimens were made in ribbon form and their magnetocaloric effect was investigated. The Curie temperature (TC) of all three series of ribbons underwent an almost linear increase, and the peak magnetic entropy change, | Δ SMpeak | (obtained in a magnetic field of 1.5 T), generally increases with increasing boron content. The results further show that the Fe86Zr9B5 ribbon exhibits a relatively large | Δ SMpeak | value of 1.13 J/kgK at 330 K and a large refrigerant capacity value of 135.6 J/kg under 1.5 T. On the basis of these results, although there is still much scope for improvement before totally replacing the conventional cooling method, the Fe-based amorphous ribbon can be seen as a promising magnetocaloric material for room temperature magnetic refrigeration applications.

  3. Thiol-capped ZnO nanowire/nanotube arrays with tunable magnetic properties at room temperature.

    PubMed

    Deng, Su-Zi; Fan, Hai-Ming; Wang, Miao; Zheng, Min-Rui; Yi, Jia-Bao; Wu, Rong-Qin; Tan, Hui-Ru; Sow, Chorng-Haur; Ding, Jun; Feng, Yuan-Ping; Loh, Kian-Ping

    2010-01-26

    The present study reports room-temperature ferromagnetic behaviors in three-dimensional (3D)-aligned thiol-capped single-crystalline ZnO nanowire (NW) and nanotube (NT) arrays as well as polycrystalline ZnO NT arrays. Besides the observation of height-dependent saturation magnetization, a much higher M(s) of 166 microemu cm(-2) has been found in NTs compared to NWs (36 microemu cm(-2)) due to larger surface area in ZnO NTs, indicating morphology-dependent magnetic properties in ZnO NW/NT systems. Density functional calculations have revealed that the origin of ferromagnetism is mainly attributed to spin-polarized 3p electrons in S sites and, therefore, has a strong correlation with Zn-S bond anisotropy. The preferential magnetization direction of both single-crystalline NTs and NWs lies perpendicular to the tube/wire axis due to the aligned high anisotropy orientation of the Zn-S bonds on the lateral (100) face of ZnO NWs and NTs. Polycrystalline ZnO NTs, however, exhibit a preferential magnetization direction parallel to the tube axis which is ascribed to shape anisotropy dominating the magnetic response. Our results demonstrate the interplay of morphology, dimensions, and crystallinity on spin alignment and magnetic anisotropy in a 3D semiconductor nanosystem with interfacial magnetism.

  4. THEMIS discovers holes in Earth's solar shield

    NASA Video Gallery

    This animation shows the latest findings from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission. Earth's magnetic field; which shields our planet from severe ...

  5. Flexible Cable Providing EMI Shielding

    DTIC Science & Technology

    1999-06-07

    shielding the electronic 25 equipment by enclosing it in shielded rooms and cabinets, filling 1 any gaps therein with conductive gaskets, and also by...are found in U.S. 15 Patent Nos. 4,948,922 and 4,93 7,128 which disclose conductive 16 elastic gaskets used to fill gaps between openings in shielded...matrix binder which is filled with 5 particles of a high permeability iron-based alloy. The 6 conductive property of the matrix binder provides

  6. Modular shield

    DOEpatents

    Snyder, Keith W.

    2002-01-01

    A modular system for containing projectiles has a sheet of material including at least a polycarbonate layer held by a metal frame having a straight frame member corresponding to each straight edge of the sheet. Each frame member has a U-shaped shield channel covering and holding a straight edge of the sheet and an adjacent U-shaped clamp channel rigidly held against the shield channel. A flexible gasket separates each sheet edge from its respective shield channel; and each frame member is fastened to each adjacent frame member only by clamps extending between adjacent clamp channels.

  7. Imaging of room-temperature ferromagnetic nano-domains at the surface of a non-magnetic oxide

    NASA Astrophysics Data System (ADS)

    Taniuchi, T.; Motoyui, Y.; Morozumi, K.; Rödel, T. C.; Fortuna, F.; Santander-Syro, A. F.; Shin, S.

    2016-06-01

    Two-dimensional electron gases at oxide surfaces or interfaces show exotic ordered states of matter, like superconductivity, magnetism or spin-polarized states, and are a promising platform for alternative oxide-based electronics. Here we directly image a dense population of randomly distributed ferromagnetic domains of ~40 nm typical sizes at room temperature at the oxygen-deficient surface of SrTiO3, a non-magnetic transparent insulator in the bulk. We use laser-based photoemission electron microscopy, an experimental technique that gives selective spin detection of the surface carriers, even in bulk insulators, with a high spatial resolution of 2.6 nm. We furthermore find that the Curie temperature in this system is as high as 900 K. These findings open perspectives for applications in nano-domain magnetism and spintronics using oxide-based devices, for instance through the nano-engineering of oxygen vacancies at surfaces or interfaces of transition-metal oxides.

  8. Highly Efficient Extraction of Phenolic Compounds by Use of Magnetic Room Temperature Ionic Liquids for Environmental Remediation

    PubMed Central

    Deng, Ning; Li, Min; Zhao, Lijie; Lu, Chengfei; de Rooy, Sergio L.; Warner, Isiah M.

    2011-01-01

    A hydrophobic magnetic room temperature ionic liquid (MRTIL), trihexyltetradecylphosphonium tetrachloroferrate(III) ([3C6PC14][FeCl4]), was synthesized from trihexyltetradecylphosphonium chloride and FeCl3·6H2O. This MRTIL was investigated as a possible separation agent for solvent extraction of phenolic compounds from aqueous solution. Due to its strong paramagnetism, [3C6PC14][FeCl4] responds to an external neodymium magnet, which was employed in the design of a novel magnetic extraction technique. The conditions for extraction, including extraction time, volume ratio between MRTIL and aqueous phase, pH of aqueous solution, and structures of phenolic compounds were investigated and optimized. The magnetic extraction of phenols achieved equilibrium in 20 min and the phenolic compounds were found to have higher distribution ratios under acidic conditions. In addition, it was observed that phenols containing a greater number of chlorine or nitro substitutents exhibited higher distribution ratios. For example, the distribution ratio of phenol (DPh) was 107. In contrast, 3,5-dichlorophenol distribution ratio (D3,5-DCP) had a much higher value of 6372 under identical extraction conditions. When compared with four selected traditional non-magnetic room temperature ionic liquids, our [3C6PC14][FeCl4] exhibited significantly higher extraction efficiency under the same experimental conditions used in this work. Pentachlorophenol, a major component in the contaminated soil sample obtained from a superfund site, was successfully extracted and removed by use of [3C6PC14][FeCl4] with high extraction efficiency. Pentachlorophenol concentration was dramatically reduced from 7.8 μg.mL−1 to 0.2 μg.mL−1 after the magnetic extraction by use of [3C6PC14][FeCl4]. PMID:21783320

  9. Magnetic properties and magnetocaloric effect at room temperature of Ni50- x Ag x Mn37Sn13 alloys

    NASA Astrophysics Data System (ADS)

    Thanh, Tran Dang; Mai, Nguyen Thi; Dan, Nguyen Huy; Phan, The-Long; Yu, Seong-Cho

    2014-11-01

    In this work, we present a detailed study of the magnetic properties and the magnetocaloric effect at room temperature of Ni50- x Ag x Mn37Sn13 alloys with x = 1, 2, and 4, which were prepared by using an arc-melting method. Experimental results reveal that a partial replacement of Ag for Ni leads to a decrease in the anti-FM phase in the alloys. In addition, the martensitic-austenitic phase transition shifts towards lower temperature and is broaded. The Curie temperature ( T C A ) for the austenitic phase also shifts toward to lower temperature, but not by much. The Curie temperature was found to be 308, 305, and 298 K for x = 1, 2, and 4, respectively. The magnetic entropy change (Δ S m ) of the samples was calculated by using isothermal magnetization data. Under an applied magnetic field change of 10 kOe, the maximum value of Δ S m (|Δ S max |) was achieved at around room temperature and did not change much (~0.8 J·kg-1·K-1) with increasing Ag-doping concentration. Particularly, the M 2 vs. H/ M curves prove that all the samples exhibited a second-order magnetic phase transition. Based on Landau's phase-transition theory and careful analyses of the magnetic data around the T C A , we have determined the critical parameters β, γ, δ, and T C . The results show that the β values are located between those expected for the 3D-Heisenberg model ( β = 0.365) and mean-field theory ( β = 0.5). Such a result proves the coexistence of short-range and long-range ferromagnetic interactions in Ni50- x Ag x Mn37Sn13 alloys. The nature of the changes in the critical parameters and the |Δ S max | is thoroughly discussed by means of structural analyses.

  10. REACTOR SHIELD

    DOEpatents

    Wigner, E.P.; Ohlinger, L.E.; Young, G.J.; Weinberg, A.M.

    1959-02-17

    Radiation shield construction is described for a nuclear reactor. The shield is comprised of a plurality of steel plates arranged in parallel spaced relationship within a peripheral shell. Reactor coolant inlet tubes extend at right angles through the plates and baffles are arranged between the plates at right angles thereto and extend between the tubes to create a series of zigzag channels between the plates for the circulation of coolant fluid through the shield. The shield may be divided into two main sections; an inner section adjacent the reactor container and an outer section spaced therefrom. Coolant through the first section may be circulated at a faster rate than coolant circulated through the outer section since the area closest to the reactor container is at a higher temperature and is more radioactive. The two sections may have separate cooling systems to prevent the coolant in the outer section from mixing with the more contaminated coolant in the inner section.

  11. Improved room-temperature-selectivity between Nd and Fe in Nd recovery from Nd-Fe-B magnet

    SciTech Connect

    Kataoka, Y.; Kitagawa, J.; Ono, T.; Tsubota, M.

    2015-11-15

    The sustainable society requires the recycling of rare metals. Rare earth Nd is one of rare metals, accompanying huge consumption especially in Nd-Fe-B magnets. Although the wet process using acid is in practical use in the in-plant recycle of sludge, higher selectivity between Nd and Fe at room temperature is desired. We have proposed a pretreatment of corrosion before the dissolution into HCl and the oxalic acid precipitation. The corrosion produces γ-FeOOH and a Nd hydroxide, which have high selectivity for HCl solution at room temperature. Nd can be recovered as Mn{sub 2}O{sub 3}-type Nd{sub 2}O{sub 3}. The estimated recovery-ratio of Nd reaches to 97%.

  12. Improved room-temperature-selectivity between Nd and Fe in Nd recovery from Nd-Fe-B magnet

    NASA Astrophysics Data System (ADS)

    Kataoka, Y.; Ono, T.; Tsubota, M.; Kitagawa, J.

    2015-11-01

    The sustainable society requires the recycling of rare metals. Rare earth Nd is one of rare metals, accompanying huge consumption especially in Nd-Fe-B magnets. Although the wet process using acid is in practical use in the in-plant recycle of sludge, higher selectivity between Nd and Fe at room temperature is desired. We have proposed a pretreatment of corrosion before the dissolution into HCl and the oxalic acid precipitation. The corrosion produces γ-FeOOH and a Nd hydroxide, which have high selectivity for HCl solution at room temperature. Nd can be recovered as Mn2O3-type Nd2O3. The estimated recovery-ratio of Nd reaches to 97%.

  13. Synthesis, sustained release properties of magnetically functionalized organic-inorganic materials: Amoxicillin anions intercalated magnetic layered double hydroxides via calcined precursors at room temperature

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Liu, Qi; Zhang, Guangchun; Li, Zhanshuang; Yang, Piaoping; Jing, Xiaoyan; Zhang, Milin; Liu, Tianfu; Jiang, Zhaohua

    2009-09-01

    Zinc-aluminum-carbonate-layered double hydroxides (ZnAl-CO 3-LDHs), loaded with magnetic substrates (Fe 3O 4), were prepared for sustained drug-targeting delivery. From the X-ray diffraction results, it was found that the magnetic substrates were successfully incorporated with LDHs and highly dispersed in the hydrotalcite structure. After intercalation with an antibiotic drug (amoxicillin) by using a calcinations-reconstruction method, the basal spacing of layered double hydroxides increased from 7.51 Å to 12.35 Å, indicating that amoxicillin was successfully intercalated into the interlay space of LDHs as a monolayer. Furthermore, in vitro drug release experiments in pH 7.4 phosphate buffer solution (PBS) showed sustained release profiles with amoxicillin as a model drug. Magnetic measurements revealed that the composite possessed paramagnetic properties at room temperature.

  14. The hyperfine structure in the rotational spectra of D2(17)O and HD(17)O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen.

    PubMed

    Puzzarini, Cristina; Cazzoli, Gabriele; Harding, Michael E; Vázquez, Juana; Gauss, Jürgen

    2015-03-28

    Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing (17)O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined (17)O spin-rotation constants of D2 (17)O and HD(17)O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H2 (17)O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)].

  15. Shielding requirements in helical tomotherapy

    NASA Astrophysics Data System (ADS)

    Baechler, S.; Bochud, F. O.; Verellen, D.; Moeckli, R.

    2007-08-01

    Helical tomotherapy is a relatively new intensity-modulated radiation therapy (IMRT) treatment for which room shielding has to be reassessed for the following reasons. The beam-on-time needed to deliver a given target dose is increased and leads to a weekly workload of typically one order of magnitude higher than that for conventional radiation therapy. The special configuration of tomotherapy units does not allow the use of standard shielding calculation methods. A conventional linear accelerator must be shielded for primary, leakage and scatter photon radiations. For tomotherapy, primary radiation is no longer the main shielding issue since a beam stop is mounted on the gantry directly opposite the source. On the other hand, due to the longer irradiation time, the accelerator head leakage becomes a major concern. An analytical model based on geometric considerations has been developed to determine leakage radiation levels throughout the room for continuous gantry rotation. Compared to leakage radiation, scatter radiation is a minor contribution. Since tomotherapy units operate at a nominal energy of 6 MV, neutron production is negligible. This work proposes a synthetic and conservative model for calculating shielding requirements for the Hi-Art II TomoTherapy unit. Finally, the required concrete shielding thickness is given for different positions of interest.

  16. Shielding requirements in helical tomotherapy.

    PubMed

    Baechler, S; Bochud, F O; Verellen, D; Moeckli, R

    2007-08-21

    Helical tomotherapy is a relatively new intensity-modulated radiation therapy (IMRT) treatment for which room shielding has to be reassessed for the following reasons. The beam-on-time needed to deliver a given target dose is increased and leads to a weekly workload of typically one order of magnitude higher than that for conventional radiation therapy. The special configuration of tomotherapy units does not allow the use of standard shielding calculation methods. A conventional linear accelerator must be shielded for primary, leakage and scatter photon radiations. For tomotherapy, primary radiation is no longer the main shielding issue since a beam stop is mounted on the gantry directly opposite the source. On the other hand, due to the longer irradiation time, the accelerator head leakage becomes a major concern. An analytical model based on geometric considerations has been developed to determine leakage radiation levels throughout the room for continuous gantry rotation. Compared to leakage radiation, scatter radiation is a minor contribution. Since tomotherapy units operate at a nominal energy of 6 MV, neutron production is negligible. This work proposes a synthetic and conservative model for calculating shielding requirements for the Hi-Art II TomoTherapy unit. Finally, the required concrete shielding thickness is given for different positions of interest.

  17. Room-temperature ferromagnetism observed in Nd-doped In2O3 dilute magnetic semiconducting nanowires

    NASA Astrophysics Data System (ADS)

    Lv, Zhanpeng; Zhang, Junran; Niu, Wei; Zhang, Minhao; Song, Li; Zhu, Hairong; Wang, Xuefeng

    2016-09-01

    Nd-doped In2O3 nanowires were fabricated by an Au-catalyzed chemical vapor deposition method. Nd atoms were successfully doped into the In2O3 host lattice structure, as revealed by energy dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, and x-ray diffraction. Robust room temperature ferromagnetism was observed in Nd-doped In2O3 nanowires, which was attributed to the long-range-mediated magnetization among Nd3+-vacancy complexes through percolation-bound magnetic polarons. Project supported by the National Natural Science Foundation of China (Grant No. 11274003), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, and the Fundamental Research Funds for the Central Universities, China.

  18. Zero-field magnetic resonance of the photo-excited triplet state of pentacene at room temperature

    NASA Astrophysics Data System (ADS)

    Yang, Tran-Chin; Sloop, David J.; Weissman, S. I.; Lin, Tien-Sung

    2000-12-01

    The pulsed EPR free induction decay (FID) signals of the photo-excited pentacene triplet state are reported for three mixed crystals at room temperature: pentacene-h14 in p-terphenyl, pentacene-h14 in benzoic acid, and pentacene-d14 in p-terphenyl. The recorded FID signals have relatively long decay times of about four microseconds, presumably due to the reduced hyperfine interactions in the zero magnetic field. The time domain FID signals transform to spectral components typically narrower than 500 kHz, allowing us to determine the pentacene triplet zero field splitting parameters to better accuracy than previously reported. Further, a new experimental technique using the high speed magnetic field jumping capability enables us to examine the anisotropic hyperfine and quadrupole interactions.

  19. Reversible strain control of magnetic anisotropy in magnetoelectric heterostructures at room temperature

    PubMed Central

    Staruch, Margo; Gopman, Daniel B.; Iunin, Yury L.; Shull, Robert D.; Cheng, Shu Fan; Bussmann, Konrad; Finkel, Peter

    2016-01-01

    The ability to tune both magnetic and electric properties in magnetoelectric (ME) composite heterostructures is crucial for multiple transduction applications including energy harvesting or magnetic field sensing, or other transduction devices. While large ME coupling achieved through interfacial strain-induced rotation of magnetic anisotropy in magnetostrictive/piezoelectric multiferroic heterostructures has been demonstrated, there are presently certain restrictions for achieving a full control of magnetism in an extensive operational dynamic range, limiting practical realization of this effect. Here, we demonstrate the possibility of generating substantial reversible anisotropy changes through induced interfacial strains driven by applied electric fields in magnetostrictive thin films deposited on (0 1 1)-oriented domain-engineered ternary relaxor ferroelectric single crystals with extended temperature and voltage ranges as compared to binary relaxors. We show, through a combination of angular magnetization and magneto-optical domain imaging measurements, that a 90° in-plane rotation of the magnetic anisotropy and propagation of magnetic domains with low applied electric fields under zero electric field bias are realized. To our knowledge, the present value attained for converse magnetoelectric coupling coefficient is the highest achieved in the linear piezoelectric regime and expected to be stable for a wide temperature range, thus representing a step towards practical ME transduction devices. PMID:27869152

  20. Reversible strain control of magnetic anisotropy in magnetoelectric heterostructures at room temperature.

    PubMed

    Staruch, Margo; Gopman, Daniel B; Iunin, Yury L; Shull, Robert D; Cheng, Shu Fan; Bussmann, Konrad; Finkel, Peter

    2016-11-21

    The ability to tune both magnetic and electric properties in magnetoelectric (ME) composite heterostructures is crucial for multiple transduction applications including energy harvesting or magnetic field sensing, or other transduction devices. While large ME coupling achieved through interfacial strain-induced rotation of magnetic anisotropy in magnetostrictive/piezoelectric multiferroic heterostructures has been demonstrated, there are presently certain restrictions for achieving a full control of magnetism in an extensive operational dynamic range, limiting practical realization of this effect. Here, we demonstrate the possibility of generating substantial reversible anisotropy changes through induced interfacial strains driven by applied electric fields in magnetostrictive thin films deposited on (0 1 1)-oriented domain-engineered ternary relaxor ferroelectric single crystals with extended temperature and voltage ranges as compared to binary relaxors. We show, through a combination of angular magnetization and magneto-optical domain imaging measurements, that a 90° in-plane rotation of the magnetic anisotropy and propagation of magnetic domains with low applied electric fields under zero electric field bias are realized. To our knowledge, the present value attained for converse magnetoelectric coupling coefficient is the highest achieved in the linear piezoelectric regime and expected to be stable for a wide temperature range, thus representing a step towards practical ME transduction devices.

  1. Reversible strain control of magnetic anisotropy in magnetoelectric heterostructures at room temperature

    NASA Astrophysics Data System (ADS)

    Staruch, Margo; Gopman, Daniel B.; Iunin, Yury L.; Shull, Robert D.; Cheng, Shu Fan; Bussmann, Konrad; Finkel, Peter

    2016-11-01

    The ability to tune both magnetic and electric properties in magnetoelectric (ME) composite heterostructures is crucial for multiple transduction applications including energy harvesting or magnetic field sensing, or other transduction devices. While large ME coupling achieved through interfacial strain-induced rotation of magnetic anisotropy in magnetostrictive/piezoelectric multiferroic heterostructures has been demonstrated, there are presently certain restrictions for achieving a full control of magnetism in an extensive operational dynamic range, limiting practical realization of this effect. Here, we demonstrate the possibility of generating substantial reversible anisotropy changes through induced interfacial strains driven by applied electric fields in magnetostrictive thin films deposited on (0 1 1)-oriented domain-engineered ternary relaxor ferroelectric single crystals with extended temperature and voltage ranges as compared to binary relaxors. We show, through a combination of angular magnetization and magneto-optical domain imaging measurements, that a 90° in-plane rotation of the magnetic anisotropy and propagation of magnetic domains with low applied electric fields under zero electric field bias are realized. To our knowledge, the present value attained for converse magnetoelectric coupling coefficient is the highest achieved in the linear piezoelectric regime and expected to be stable for a wide temperature range, thus representing a step towards practical ME transduction devices.

  2. Cobalt-doped anatase TiO2: A room temperature dilute magnetic dielectric material

    NASA Astrophysics Data System (ADS)

    Griffin, K. A.; Pakhomov, A. B.; Wang, C. M.; Heald, S. M.; Krishnan, Kannan M.

    2005-05-01

    We experimentally investigate the room temperature ferromagnetism observed in insulating Co doped anatase TiO2 thin films grown by sputter deposition. The Co was uniformly incorporated in the lattice as Co(II) with no evidence of Co metal. A series of annealing treatments were carried out to optimize the ferromagnetic ordering and a saturation moment of 1.1μB/Co atom at 300 K was obtained with UHV annealing at 450 °C. Both as-deposited and annealed films were highly insulating at room temperature. Results show that the ferromagnetism is strongly dependent on the number and distribution of oxygen vacancies in the Co:TiO2 lattice.

  3. Absolute shielding scales for Al, Ga, and In and revised nuclear magnetic dipole moments of {sup 27}Al, {sup 69}Ga, {sup 71}Ga, {sup 113}In, and {sup 115}In nuclei

    SciTech Connect

    Antušek, A. Holka, F.

    2015-08-21

    We present coupled cluster calculations of NMR shielding constants of aluminum, gallium, and indium in water-ion clusters. In addition, relativistic and dynamical corrections and the influence of the second solvation shell are evaluated. The final NMR shielding constants define new absolute shielding scales, 600.0 ± 4.1 ppm, 2044.4 ± 31.4 ppm, and 4507.7 ± 63.7 ppm for aluminum, gallium, and indium, respectively. The nuclear magnetic dipole moments for {sup 27}Al, {sup 69}Ga, {sup 71}Ga, {sup 113}In, and {sup 115}In isotopes are corrected by combining the computed shielding constants with experimental NMR frequencies. The absolute magnitude of the correction increases along the series and for indium isotopes it reaches approximately −8.0 × 10{sup −3} of the nuclear magneton.

  4. Near fifty percent sodium substituted lanthanum manganites—A potential magnetic refrigerant for room temperature applications

    SciTech Connect

    Sethulakshmi, N.; Anantharaman, M. R.; Al-Omari, I. A.; Suresh, K. G.

    2014-03-03

    Nearly half of lanthanum sites in lanthanum manganites were substituted with monovalent ion-sodium and the compound possessed distorted orthorhombic structure. Ferromagnetic ordering at 300 K and the magnetic isotherms at different temperature ranges were analyzed for estimating magnetic entropy variation. Magnetic entropy change of 1.5 J·kg{sup −1}·K{sup −1} was observed near 300 K. An appreciable magnetocaloric effect was also observed for a wide range of temperatures near 300 K for small magnetic field variation. Heat capacity was measured for temperatures lower than 300 K and the adiabatic temperature change increases with increase in temperature with a maximum of 0.62 K at 280 K.

  5. Shielding effectiveness of multiple-shield cables with arbitrary terminations via transmission line analysis

    DOE PAGES

    Campione, Salvatore; Basilio, Lorena I.; Warne, Larry Kevin; ...

    2016-06-25

    Our paper reports on a transmission-line model for calculating the shielding effectiveness of multiple-shield cables with arbitrary terminations. Since the shields are not perfect conductors and apertures in the shields permit external magnetic and electric fields to penetrate into the interior regions of the cable, we use this model to estimate the effects of the outer shield current and voltage (associated with the external excitation and boundary conditions associated with the external conductor) on the inner conductor current and voltage. It is commonly believed that increasing the number of shields of a cable will improve the shielding performance. But thismore » is not always the case, and a cable with multiple shields may perform similar to or worse than a cable with a single shield. Furthermore, we want to shed more light on these situations, which represent the main focus of this paper.« less

  6. Shielding effectiveness of multiple-shield cables with arbitrary terminations via transmission line analysis

    SciTech Connect

    Campione, Salvatore; Basilio, Lorena I.; Warne, Larry Kevin; Hudson, Howard Gerald; Langston, William L.

    2016-06-25

    Our paper reports on a transmission-line model for calculating the shielding effectiveness of multiple-shield cables with arbitrary terminations. Since the shields are not perfect conductors and apertures in the shields permit external magnetic and electric fields to penetrate into the interior regions of the cable, we use this model to estimate the effects of the outer shield current and voltage (associated with the external excitation and boundary conditions associated with the external conductor) on the inner conductor current and voltage. It is commonly believed that increasing the number of shields of a cable will improve the shielding performance. But this is not always the case, and a cable with multiple shields may perform similar to or worse than a cable with a single shield. Furthermore, we want to shed more light on these situations, which represent the main focus of this paper.

  7. Experimental analysis of the magnetic field shielding and trapping properties of bulk melt-processed YBa 2Cu 3O 7-δ

    NASA Astrophysics Data System (ADS)

    Jiang, X. H.; Astill, D. M.; Lo, W.; Cardwell, D. A.; Coombs, T. A.; Campbell, A. M.; Larsen, J. G.

    1995-02-01

    A scanning Hall probe has been used to map the distributions of magnetic field in melt-processed YBa 2Cu 3O 7-δ (YBCO) discs prepared by seeded and controlled molten-zone techniques. Both shielded and trapped fields were studied as a function of applied magnetic field for each speciment. A clear four-fold symmetry has been observed in the field distribution of the seeded melt-processed sample, suggesting that there are two planes in the disc which exhibit a weak response to an applied field. Similar magnetic properties were observed for the molten-zone processed sample and attributed to the presence of cracks in the specimen. It was found that the applied field required to saturate each sample was much higher than the maximum observed trapped field, in contradiction to the Bean model for a slab geometry. This effect, which is probably due to the plate geometry of the specimens and the variation of critical current density with magnetic field, has implications for practical applications of bulk melt-processed YBCO.

  8. Thermocouple shield

    DOEpatents

    Ripley, Edward B.

    2009-11-24

    A thermocouple shield for use in radio frequency fields. In some embodiments the shield includes an electrically conductive tube that houses a standard thermocouple having a thermocouple junction. The electrically conductive tube protects the thermocouple from damage by an RF (including microwave) field and mitigates erroneous temperature readings due to the microwave or RF field. The thermocouple may be surrounded by a ceramic sheath to further protect the thermocouple. The ceramic sheath is generally formed from a material that is transparent to the wavelength of the microwave or RF energy. The microwave transparency property precludes heating of the ceramic sheath due to microwave coupling, which could affect the accuracy of temperature measurements. The ceramic sheath material is typically an electrically insulating material. The electrically insulative properties of the ceramic sheath help avert electrical arcing, which could damage the thermocouple junction. The electrically conductive tube is generally disposed around the thermocouple junction and disposed around at least a portion of the ceramic sheath. The concepts of the thermocouple shield may be incorporated into an integrated shielded thermocouple assembly.

  9. Closed-cycle cryocooled SQUID system with superconductive shield for biomagnetism

    NASA Astrophysics Data System (ADS)

    Yu, Kwon Kyu; Lee, Yong Ho; Lee, Seong Joo; Shim, Jeong Hyun; Hwang, Seong min; Kim, Jin Mok; Kwon, Hyuckchan; Kim, Kiwoong

    2014-10-01

    We developed a cryocooled SQUID system with which human magnetocardiogram (MCG) and possibly magnetoenceparogram (MEG) can be measured. To reduce cyclic magnetic noises originating from the regenerator of the cold heads of the cryocooler, a superconductive shield (99.5% Pb) was used to protect the SQUID sensors, and a ferromagnetic shield (78% Ni alloy) was used to screen the cold head. In addition, the SQUID sensors’ chamber was placed at a distance of 1.8 m from the cold head chamber to install the cold-head chamber outside the magnetically shielded room (MSR) for future development. The loss in cooling power due to the increased distance was compensated by increasing the number of thermal rods, and thus the SQUID sensor and superconductive shield could be refrigerated to 4.8 K and 5 K, respectively. The superconductive shield successfully rejected thermal noise emitted from metallic blocks used to improve thermal conduction. The noise of the SQUID system was 3 fT/Hz1/2, and the cyclic magnetic noise could be reduced to 1.7 pT. We could obtain a clear MCG signal while the entire cryogenics was in operation without any special digital processing.

  10. Dynamic in situ observation of voltage-driven repeatable magnetization reversal at room temperature.

    PubMed

    Gao, Ya; Hu, Jia-Mian; Nelson, C T; Yang, T N; Shen, Y; Chen, L Q; Ramesh, R; Nan, C W

    2016-03-31

    Purely voltage-driven, repeatable magnetization reversal provides a tantalizing potential for the development of spintronic devices with a minimum amount of power consumption. Substantial progress has been made in this subject especially on magnetic/ferroelectric heterostructures. Here, we report the in situ observation of such phenomenon in a NiFe thin film grown directly on a rhombohedral Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PMN-PT) ferroelectric crystal. Under a cyclic voltage applied perpendicular to the PMN-PT without a magnetic field, the local magnetization of NiFe can be repetitively reversed through an out-of-plane excursion and then back into the plane. Using phase field simulations we interpret magnetization reversal as a synergistic effect of the metastable ferroelastic switching in the PMN-PT and an electrically rotatable local exchange bias field arising from the heterogeneously distributed NiO clusters at the interface.

  11. Dynamic in situ observation of voltage-driven repeatable magnetization reversal at room temperature

    NASA Astrophysics Data System (ADS)

    Gao, Ya; Hu, Jia-Mian; Nelson, C. T.; Yang, T. N.; Shen, Y.; Chen, L. Q.; Ramesh, R.; Nan, C. W.

    2016-03-01

    Purely voltage-driven, repeatable magnetization reversal provides a tantalizing potential for the development of spintronic devices with a minimum amount of power consumption. Substantial progress has been made in this subject especially on magnetic/ferroelectric heterostructures. Here, we report the in situ observation of such phenomenon in a NiFe thin film grown directly on a rhombohedral Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PMN-PT) ferroelectric crystal. Under a cyclic voltage applied perpendicular to the PMN-PT without a magnetic field, the local magnetization of NiFe can be repetitively reversed through an out-of-plane excursion and then back into the plane. Using phase field simulations we interpret magnetization reversal as a synergistic effect of the metastable ferroelastic switching in the PMN-PT and an electrically rotatable local exchange bias field arising from the heterogeneously distributed NiO clusters at the interface.

  12. Dynamic in situ observation of voltage-driven repeatable magnetization reversal at room temperature

    PubMed Central

    Gao, Ya; Hu, Jia-Mian; Nelson, C. T.; Yang, T. N.; Shen, Y.; Chen, L. Q.; Ramesh, R.; Nan, C. W.

    2016-01-01

    Purely voltage-driven, repeatable magnetization reversal provides a tantalizing potential for the development of spintronic devices with a minimum amount of power consumption. Substantial progress has been made in this subject especially on magnetic/ferroelectric heterostructures. Here, we report the in situ observation of such phenomenon in a NiFe thin film grown directly on a rhombohedral Pb(Mg1/3Nb2/3)0.7Ti0.3O3(PMN-PT) ferroelectric crystal. Under a cyclic voltage applied perpendicular to the PMN-PT without a magnetic field, the local magnetization of NiFe can be repetitively reversed through an out-of-plane excursion and then back into the plane. Using phase field simulations we interpret magnetization reversal as a synergistic effect of the metastable ferroelastic switching in the PMN-PT and an electrically rotatable local exchange bias field arising from the heterogeneously distributed NiO clusters at the interface. PMID:27029464

  13. Paleoproterozoic structural frame of the Yetti domain (Eglab shield, Algeria): Emplacement conditions of the Tinguicht late pluton from magnetic fabric study

    NASA Astrophysics Data System (ADS)

    Merabet, Nacer-eddine; Mahdjoub, Yamina; Henry, Bernard; Abtout, Abdeslam; Maouche, Said; Kahoui, Mohamed; Lamali, Atmane; Ayache, Mohamed

    2016-02-01

    The Tinguicht pluton is part of the ˜2.07 Ga post-collisional magmatic suites that intruded the Yetti Paleoproterozoic volcano-sedimentary series of the western part of the Eglab Shield (West African Craton). It represents one of the most recent units of these suites. This pluton, with a NW-SE elliptic shape, is unfoliated, and its deformational structures are practically restricted to fracturing and faulting. New structural, microstructural and aeromagnetic data are presented in order to analyze in particular the relationship between the Tinguicht pluton emplacement and the related NNW-SSE major mega-shear zone, separating the Yetti and Eglab domains. To constrain the context of the regional post-collisional evolution of the Eglab shield, a structural analysis was performed by mapping the magnetic structures (foliation and lineation) using AMS. The combination of the results of all the used approaches leads to a new and enriched image of this granitic pluton and of its tectonic emplacement context. The elliptic shape of the granitic body and the AMS strain pattern are consistent with the presence of a NNW-SSE major structure. NNW-SSE is also one of the major directions highlighted by the aeromagnetic data. This study thus evidences the role of the pre-existing major shear zones in controlling emplacement of post-collisional Paleoproterozoic plutons like Tinguicht, as shown for Drissa pluton in the Eglab domain earlier.

  14. Nanogranular metallic Fe oxygen deficient TiO2-δ composite films: a room temperature, highly carrier polarized magnetic semiconductor

    NASA Astrophysics Data System (ADS)

    Yoon, S. D.; Widom, A.; Miller, K. E.; McHenry, M. E.; Vittoria, C.; Harris, V. G.

    2008-05-01

    Nanogranular metallic iron (Fe) and titanium dioxide (TiO2-δ) were sequentially deposited on (100) lanthanum aluminate (LaAlO3) substrates in a low oxygen chamber pressure using a pulsed laser ablation deposition (PLD) technique. By sequential deposition, ≈10 nm diameter metallic Fe spherical grains were suspended within a TiO2-δ matrix. The films show ferromagnetic behavior with a saturation magnetization of 3100 G at room temperature. Our estimate of the saturation magnetization based on the size and distribution of the Fe spheres agreed with the measured value. The film composite structure was characterized as a p-type magnetic semiconductor at 300 K with a carrier density of the order of ≈1022 cm-3. The hole carriers were excited at the interface between the nanogranular Fe and TiO2-δ matrix, similar to holes excited in the metal/n-type semiconductor interface commonly observed in metal-oxide-semiconductor (MOS) devices. From the large anomalous Hall effect measured in these films, we observed that the holes at the interface were strongly spin polarized. Structure and magnetotransport properties suggested that these PLD films have potential spintronics applications.

  15. Oxygen-vacancy-induced room-temperature magnetization in lamellar V{sub 2}O{sub 5} thin films

    SciTech Connect

    Cezar, A. B.; Graff, I. L. Varalda, J.; Schreiner, W. H.; Mosca, D. H.

    2014-10-28

    In this work, we study the local atomic and electronic structures as well as oxygen-vacancy-induced magnetic properties of electrodeposited V{sub 2}O{sub 5} films. Unlike stoichiometric V{sub 2}O{sub 5}, which is a diamagnetic lamellar semiconductor, our oxygen-defective V{sub 2}O{sub 5} films are ferromagnetic at room-temperature and their saturation magnetization decreases with air exposure time. X-ray absorption spectroscopy was used to monitor the aging effect on these films, revealing that freshly-made samples exhibit only local crystalline order, whereas the aged ones undoubtedly show an enhancement of crystallinity and coordination symmetry. The mean number of oxygen atoms around V tends to increase, indicating a decrease of oxygen vacancies with time. Concurrently with the decrease of oxygen vacancies, a loss of saturation magnetization is also observed. Hence, it can be concluded that the ferromagnetism of the V{sub 2}O{sub 5} films originates from a vacancy-induced mechanism, confirming the universality of this class of ferromagnetism.

  16. Imaging of room-temperature ferromagnetic nano-domains at the surface of a non-magnetic oxide.

    PubMed

    Taniuchi, T; Motoyui, Y; Morozumi, K; Rödel, T C; Fortuna, F; Santander-Syro, A F; Shin, S

    2016-06-10

    Two-dimensional electron gases at oxide surfaces or interfaces show exotic ordered states of matter, like superconductivity, magnetism or spin-polarized states, and are a promising platform for alternative oxide-based electronics. Here we directly image a dense population of randomly distributed ferromagnetic domains of ∼40 nm typical sizes at room temperature at the oxygen-deficient surface of SrTiO3, a non-magnetic transparent insulator in the bulk. We use laser-based photoemission electron microscopy, an experimental technique that gives selective spin detection of the surface carriers, even in bulk insulators, with a high spatial resolution of 2.6 nm. We furthermore find that the Curie temperature in this system is as high as 900 K. These findings open perspectives for applications in nano-domain magnetism and spintronics using oxide-based devices, for instance through the nano-engineering of oxygen vacancies at surfaces or interfaces of transition-metal oxides.

  17. Imaging of room-temperature ferromagnetic nano-domains at the surface of a non-magnetic oxide

    PubMed Central

    Taniuchi, T.; Motoyui, Y.; Morozumi, K.; Rödel, T. C.; Fortuna, F.; Santander-Syro, A. F.; Shin, S.

    2016-01-01

    Two-dimensional electron gases at oxide surfaces or interfaces show exotic ordered states of matter, like superconductivity, magnetism or spin-polarized states, and are a promising platform for alternative oxide-based electronics. Here we directly image a dense population of randomly distributed ferromagnetic domains of ∼40 nm typical sizes at room temperature at the oxygen-deficient surface of SrTiO3, a non-magnetic transparent insulator in the bulk. We use laser-based photoemission electron microscopy, an experimental technique that gives selective spin detection of the surface carriers, even in bulk insulators, with a high spatial resolution of 2.6 nm. We furthermore find that the Curie temperature in this system is as high as 900 K. These findings open perspectives for applications in nano-domain magnetism and spintronics using oxide-based devices, for instance through the nano-engineering of oxygen vacancies at surfaces or interfaces of transition-metal oxides. PMID:27283225

  18. Preparation of Soft Magnetic Fe-Ni-Pb-B Alloy Nanoparticles by Room Temperature Solid-Solid Reaction

    PubMed Central

    Zhong, Qin

    2013-01-01

    The Fe-Ni-Pb-B alloy nanoparticles was prepared by a solid-solid chemical reaction of ferric trichloride, nickel chloride, lead acetate, and potassium borohydride powders at room temperature. The research results of the ICP and thermal analysis indicate that the resultants are composed of iron, nickel, lead, boron, and PVP, and the component of the alloy is connected with the mole ratio of potassium borohydride and the metal salts. The TEM images show that the resultants are ultrafine and spherical particles, and the particle size is about a diameter of 25 nm. The largest saturation magnetization value of the 21.18 emu g−1 is obtained in the Fe-Ni-Pb-B alloy. The mechanism of the preparation reaction for the Fe-Ni-Pb-B multicomponent alloys is discussed. PMID:24348196

  19. Carboxylate-based molecular magnet: One path toward achieving stable quantum correlations at room temperature

    SciTech Connect

    Cruz, C.; Soares-Pinto, D. O.; Brandão, P.; dos Santos, A. M.; Reis, M. S.

    2016-03-07

    The control of quantum correlations in solid-state systems by means of material engineering is a broad avenue to be explored, since it makes possible steps toward the limits of quantum mechanics and the design of novel materials with applications on emerging quantum technologies. This letter explores the potential of molecular magnets to be prototypes of materials for quantum information technology in this context. More precisely, we engineered a material and from its geometric quantum discord we found significant quantum correlations up to 9540 K (even without entanglement); and, a pure singlet state occupied up to around 80 K (above liquid nitrogen temperature), additionally. Our results could only be achieved due to the carboxylate group promoting a metal-to-metal huge magnetic interaction.

  20. Carboxylate-based molecular magnet: One path toward achieving stable quantum correlations at room temperature

    DOE PAGES

    Cruz, C.; Soares-Pinto, D. O.; Brandão, P.; ...

    2016-03-07

    The control of quantum correlations in solid-state systems by means of material engineering is a broad avenue to be explored, since it makes possible steps toward the limits of quantum mechanics and the design of novel materials with applications on emerging quantum technologies. This letter explores the potential of molecular magnets to be prototypes of materials for quantum information technology in this context. More precisely, we engineered a material and from its geometric quantum discord we found significant quantum correlations up to 9540 K (even without entanglement); and, a pure singlet state occupied up to around 80 K (above liquidmore » nitrogen temperature), additionally. Our results could only be achieved due to the carboxylate group promoting a metal-to-metal huge magnetic interaction.« less

  1. Carboxylate-based molecular magnet: One path toward achieving stable quantum correlations at room temperature

    NASA Astrophysics Data System (ADS)

    Cruz, C.; Soares-Pinto, D. O.; Brandão, P.; dos Santos, A. M.; Reis, M. S.

    2016-02-01

    The control of quantum correlations in solid-state systems by means of material engineering is a broad avenue to be explored, since it makes possible steps toward the limits of quantum mechanics and the design of novel materials with applications on emerging quantum technologies. In this context, this letter explores the potential of molecular magnets to be prototypes of materials for quantum information technology. More precisely, we engineered a material and from its geometric quantum discord we found significant quantum correlations up to 9540 K (even without entanglement); and, in addition, a pure singlet state occupied up to around 80 K (above liquid nitrogen temperature). These results could only be achieved due to the carboxylate group promoting a metal-to-metal huge magnetic interaction.

  2. Electric field-induced tuning of magnetism in PbFe{sub 0.5}Nb{sub 0.5}O{sub 3} at room temperature

    SciTech Connect

    Rayaprol, S. E-mail: brangadi@gmail.com; Mukherjee, S.; Kaushik, S. D.; Matteppanavar, S.; Angadi, B. E-mail: brangadi@gmail.com

    2015-08-07

    We study the influence of electrical poling, carried out at room temperature, on the structure and magnetism of Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} by analyzing the differences observed in structural and magnetic properties before and after the electrical poling. The changes observed in magnetization of Pb(Fe{sub 0.5}Nb{sub 0.5})O{sub 3} before and after electrical poling exhibit considerably strong converse magnetoelectric effect at room temperature. In addition, the strengthening of Fe/Nb-O bond due to electrical poling is discussed on the basis of Raman spectral studies and analysis of neutron diffraction patterns. The potential tunability of magnetization with electrical poling can be an ideal tool for realization of application potential of this multiferroic material.

  3. Thermal plasma processed ferro-magnetically ordered face-centered cubic iron at room temperature

    SciTech Connect

    Raut, Suyog A.; Kanhe, Nilesh S.; Bhoraskar, S. V.; Mathe, V. L.; Das, A. K.

    2014-10-28

    Here, we report tailor made phase of iron nanoparticles using homogeneous gas phase condensation process via thermal plasma route. It was observed that crystal lattice of nano-crystalline iron changes as a function of operating parameters of the plasma reactor. In the present investigation iron nanoparticles have been synthesized in presence of argon at operating pressures of 125–1000 Torr and fixed plasma input DC power of 6 kW. It was possible to obtain pure fcc, pure bcc as well as the mixed phases for iron nanoparticles in powder form as a function of operating pressure. The as synthesized product was characterized for understanding the structural and magnetic properties by using X-ray diffraction, vibrating sample magnetometer, and Mössbauer spectroscopy. The data reveal that fcc phase is ferromagnetically ordered with high spin state, which is unusual whereas bcc phase is found to be ferromagnetic as usual. Finally, the structural and magnetic properties are co-related.

  4. Impact of Fe on structural modification and room temperature magnetic ordering in BaTiO3

    NASA Astrophysics Data System (ADS)

    Rajan, Soumya; Gazzali, P. M. Mohammed; Chandrasekaran, G.

    2017-01-01

    Ba1 - xFexTiO3 (x = 0, 0.005, 0.01) polycrystalline ceramics are prepared using solid state reaction method. Structural studies through XRD, Raman and XPS confirm single tetragonal phase for BaTiO3 whereas a structural disorder tends to intervene with the introduction of smaller Fe ions which reduces the tolerance factor and tetragonality ratio. Grain size of the samples is estimated using SEM micrographs with ImageJ software and chemical composition is confirmed using EDX spectra. Raman spectra measured in the temperature range of 303 K to 573 K showers light on the structural phase transition exploiting a significant disappearance of the 306 cm- 1 mode. Further, structural analyses suggest the entry of Fe into the B-site upon increasing its concentration in BaTiO3. The dopant sensitive modes lying at around 640 cm- 1 and 650 cm- 1 are assigned to lattice strain. A reduction in ferroelectric to paraelectric transition temperature is observed with a transformation from diffused type to normal ferroelectric upon the increased Fe content. The oxidation state of Fe in the BaTiO3 lattice has been decided using EPR Spectra precisely. Room temperature magnetic ordering is observed in Fe substituted BaTiO3 using PPMS. The coexistence of ferroelectric and magnetic ordering is established in the present study for optimized Fe substituted BaTiO3.

  5. Room temperature ferroelectricity in one-dimensional single chain molecular magnets [{M(Δ)M(Λ)}(ox)2(phen)2]n (M = Fe and Mn)

    NASA Astrophysics Data System (ADS)

    Bhatt, Pramod; Mukadam, M. D.; Meena, S. S.; Mishra, S. K.; Mittal, R.; Sastry, P. U.; Mandal, B. P.; Yusuf, S. M.

    2017-03-01

    The ferroelectric materials are mainly focused on pure inorganic oxides; however, the organic molecule based materials have recently attracted great attention because of their multifunctional properties. The mixing of oxalate and phenanthroline ligands with metal ions (Fe or Mn) at room temperature followed by hydrothermal treatment results in the formation of one-dimensional single chain molecular magnets which exhibit room temperature dielectric and ferroelectric behavior. The compounds are chiral in nature, and exhibit a ferroelectric behavior, attributed to the polar point group C2, in which they crystallized. The compounds are also associated with a dielectric loss and thus a relaxation process. The observed electric dipole moment, essential for a ferroelectricity, has been understood quantitatively in terms of lattice distortions at two different lattice sites within the crystal structure. The studied single chain molecular magnetic materials with room temperature ferroelectric and dielectric properties could be of great technological importance in non-volatile memory elements, and high-performance insulators.

  6. Read/write head having a GMR sensor biased by permanent magnets located between the GMR and the pole shields

    DOEpatents

    Yuan, Samuel W.; Rottmayer, Robert Earl; Carey, Matthew J.

    1999-01-01

    A compact read/write head having a biased giant magnetoresistive sensor. Permanent magnet films are placed adjacent to the giant magnetoresistive sensor operating in the current-perpendicular-to the-plane (Cpp) mode and spaced with respect to the sensor by conducting films. These permanent magnet films provide a magnetic bias. The bias field is substantial and fairly uniform across sensor height. Biasing of the giant magnetoresistive sensor provides distinguishable response to the rising and falling edges of a recorded pulse on an adjacent recording medium, improves the linearity of the response, and helps to reduce noise. This read/write head is much simpler to fabricate and pattern and provides an enhanced uniformity of the bias field throughout the sensor.

  7. Initial progress in the first wall, blanket, and shield Engineering Test Program for magnetically confined fusion-power reactors

    SciTech Connect

    Herman, H.; Baker, C.C.; Maroni, V.A.

    1981-10-01

    The first wall/blanket/shield (FW/B/S) Engineering Test Program (ETP) progressed from the planning stage into implementation during July, 1981. The program, generic in nature, comprises four Test Program Elements (TPE's), the emphasis of which is on defining the performance parameters for the Fusion Engineering Device (FED) and the major fusion device to follow FED. These elements are: (1) nonnuclear thermal-hydraulic and thermomechanical testing of first wall and component facsimiles with emphasis on surface heat loads and heat transient (i.e., plasma disruption) effects; (2) nonnuclear and nuclear testing of FW/B/S components and assemblies with emphasis on bulk (nuclear) heating effects, integrated FW/B/S hydraulics and mechanics, blanket coolant system transients, and nuclear benchmarks; (3) FW/B/S electromagnetic and eddy current effects testing, including pulsed field penetration, torque and force restraint, electromagnetic materials, liquid metal MHD effects and the like; and (4) FW/B/S Assembly, Maintenance and Repair (AMR) studies focusing on generic AMR criteria, with the objective of preparing an AMR designers guidebook; also, development of rapid remote assembly/disassembly joint system technology, leak detection and remote handling methods.

  8. Quantum electrodynamics effects on NMR magnetic shielding constants of He-like and Be-like atomic systems

    NASA Astrophysics Data System (ADS)

    Gimenez, Carlos A.; Kozioł, Karol; Aucar, Gustavo A.

    2016-03-01

    NMR shielding constants for He- and Be-like atomic systems of Ne, Ar, Kr, Xe, and Rn have been calculated at the random-phase-approximation level of approach, including an estimation of QED corrections within the polarization propagator formalism. We show that QED effects enhance electron correlation when Z becomes heavier, which happens with relativistic effects, and also that QED effects become smaller when going from more to less ionized systems. We studied two- and four-electron systems. Then such studies could easily be generalized to other many-electron systems. Results of calculations with our relatively simple model, which includes QED and electron correlation effects on the same theoretical grounds, have a summarized error in the range from 10% (for Ne) up to 24% (for Rn), so that our accuracy is a little lower than for calculations on H-like systems. Our findings should stimulate the development and/or the application of more rigorous formalisms to get more accurate QED corrections to response properties in many-electron systems.

  9. Electrical bistability around room temperature in an unprecedented one-dimensional coordination magnetic polymer.

    PubMed

    Amo-Ochoa, Pilar; Delgado, Esther; Gómez-García, Carlos J; Hernández, Diego; Hernández, Elisa; Martin, Avelino; Zamora, Félix

    2013-05-20

    The synthesis, crystal structure, and physical properties of an unprecedented one-dimensional (1D) coordination polymer containing [Fe2(S2C6H2Cl2)4](2-) entities bridged by dicationic [K2(μ-H2O)2(THF)4](2+) units are described. The magnetic properties show that the title compound presents pairwise Fe-Fe antiferromagnetic interactions that can be well reproduced with a S = 1/2 dimer model with an exchange coupling, J = -23 cm(-1). The electrical conductivity measurements show that the title compound is a semiconductor with an activation energy of about 290 meV and two different transitions, both with large hysteresis of about 60 and 30 K at 260-320 K and 350-380 K, respectively. These two transitions are assumed to be due to slight structural changes in the cation-anion interactions. Differential Scanning Calorimetry confirms the presence of both transitions. This compound represents the first sample of a coordination polymer showing electrical bistability.

  10. D0 Silicon Upgrade: Muon Shield Conceptual Design Report

    SciTech Connect

    Stredde, Herman J.; /Fermilab

    1996-05-14

    The nominal overall dimensions are 71-inch high x 71-inch wide x 144-inch long and has a 25-inch square hole throughout. The shield consists of three different materials, steel (inner most section), polycarbonate (central section) and lead (outer most section). The material thicknesses are, steel=15-inch, poly=6-inch and lead=2-inch. The estimated weight is {approx}69 tons. The shield is centered about the Tev beam line and the 25-inch square hole provides clearance to the low Beta quad, which is nominally 20-inch square. During beamline operation, the shield is in contact with Samus magnet core at the detector end and with the Main Ring shield wall on the MR side (with some small clearance {approx}2-inch-3-inch). The need for the clearance will be discussed later. The shield support structure consists steel structural members appropriately sized for loads encountered in the design. The structure must not only support the shield but, must be designed for rolling the entire assembly into position in the collision hall. It must provide for cylinders to lift the assembly, Hilman rollers and also connections for moving the entire assembly. The movement is considered to be similar to that with which the calorimeters were moved from the clean room to the sidewalk staging area, i.e. hydraulic cylinder and chain (see dwg. 3740.000-ME294017,3 sheets). This method will be used for the East to West motion and a hydraulic scheme will be used for any North-South motion. Since the shield is 144-inch long and the sidewalk structural support is {approx}96-inch, there is a section of the shield that is cantilevered (48-inch). Further, the EF toroid must open {approx}40+ inch for access to the detector during operations and this requires that the shield or some part of it must also move. This conceptual design suggests that the shield be designed in two pieces axially. These two pieces are identical in cross section but, the lengths are divided into 48-inch nearest EF and 96-inch

  11. Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment

    NASA Technical Reports Server (NTRS)

    Rojdev, Kristina; Christiansen, Eric

    2013-01-01

    Deep space missions must contend with a harsh radiation environment Impacts to crew and electronics. Need to invest in multifunctionality for spacecraft optimization. MMOD shield. Goals: Increase radiation mitigation potential. Retain overall MMOD shielding performance.

  12. Room-temperature switching of magnetic hysteresis by reversible single-crystal-to-single-crystal solvent exchange in imidazole-inspired Fe(ii) complexes.

    PubMed

    Huang, Wei; Shen, Fuxing; Zhang, Ming; Wu, Dayu; Pan, Feifei; Sato, Osamu

    2016-10-14

    The recent upsurge in molecular magnetism reflects its application in the areas of sensors and molecular switches. Thermal hysteresis is crucial to the molecular bistability and information storage, a wide hysteresis near room temperature is expected to be of practical sense for the molecular compound. In this work, spin crossover iron(ii) complexes [Fe(Liq)2](BF4)2·(CH3CH2)2O (1-Et2O) and [Fe(Liq)2](BF4)2·3H2O (1-3H2O) were prepared and structurally and magnetically analysed. The single-crystal-to-single-crystal (SCSC) solvation transformation and the influence on the crystal structures and magnetic hysteresis were investigated in an etherification-hydration cycle. At room temperature, X-ray diffraction experiments indicated a transformation from one crystal (1-Et2O, P21212) to another crystal (1-3H2O, P212121) upon humidity exposure and reversible recovery of its crystallinity upon exposure to ether vapor. The etherified phase 1-Et2O exhibits room temperature spin crossover (T1/2 = 305 K) but negligible thermal hysteresis, however the hydrated phase 1-3H2O exhibits the apparent hysteresis loop (T1/2↑ = 346 K, T1/2↓ = 326 K) which expands to room temperature. This effect is associated with the change of intermolecular cooperativity in the etherification-hydration recyclability.

  13. Fast Room Temperature Very Low Field-Magnetic Resonance Imaging System Compatible with MagnetoEncephaloGraphy Environment

    PubMed Central

    Galante, Angelo; Sinibaldi, Raffaele; Conti, Allegra; De Luca, Cinzia; Catallo, Nadia; Sebastiani, Piero; Pizzella, Vittorio; Romani, Gian Luca; Sotgiu, Antonello; Della Penna, Stefania

    2015-01-01

    In recent years, ultra-low field (ULF)-MRI is being given more and more attention, due to the possibility of integrating ULF-MRI and Magnetoencephalography (MEG) in the same device. Despite the signal-to-noise ratio (SNR) reduction, there are several advantages to operating at ULF, including increased tissue contrast, reduced cost and weight of the scanners, the potential to image patients that are not compatible with clinical scanners, and the opportunity to integrate different imaging modalities. The majority of ULF-MRI systems are based, until now, on magnetic field pulsed techniques for increasing SNR, using SQUID based detectors with Larmor frequencies in the kHz range. Although promising results were recently obtained with such systems, it is an open question whether similar SNR and reduced acquisition time can be achieved with simpler devices. In this work a room-temperature, MEG-compatible very-low field (VLF)-MRI device working in the range of several hundred kHz without sample pre-polarization is presented. This preserves many advantages of ULF-MRI, but for equivalent imaging conditions and SNR we achieve reduced imaging time based on preliminary results using phantoms and ex-vivo rabbits heads. PMID:26630172

  14. Magnetic-field-dependent spin decoherence and dephasing in room-temperature CdSe nanocrystal quantum dots

    NASA Astrophysics Data System (ADS)

    Fumani, A. Khastehdel; Berezovsky, J.

    2013-10-01

    We perform and analyze a series of time-resolved Faraday rotation measurements of coherent spin dynamics in a room-temperature ensemble of CdSe nanocrystal quantum dots (NCQDs) to study the decoherence and dephasing mechanisms that limit the transverse spin lifetime. Coherent spin lifetimes on the order of nanoseconds have been previously observed in CdSe NCQDs, but the presence of multiple components with distinct dynamics and strong inhomogeneous dephasing have made it difficult to study the relevant spin decay mechanisms quantitatively. Here, we obtain reliable fitting results by ensuring that cross-correlations between model parameters are minimized for the parameters of interest. Furthermore, we characterize the morphological inhomogeneity of the NCQD ensemble using transmission electron microscopy to constrain the model parameters that specify inhomogeneous dephasing. We find that g-factor inhomogeneity-induced dephasing (gID) is not sufficient to explain the magnetic-field-dependent decay of the spin signal. We propose an additional decoherence mechanism arising from rapid transitions between the fine structure states of the exciton referred to as fine-structure decoherence (FSD). By including both gID and FSD in the model, excellent fits are obtained to the data, including a prominent short-time-scale feature, which has typically been excluded from the fits in previous work.

  15. Structural characterization, solvent effects on nuclear magnetic shielding tensors, experimental and theoretical DFT studies on the vibrational and NMR spectra of 3-(acrylamido)phenylboronic acid

    NASA Astrophysics Data System (ADS)

    Alver, Özgür; Kaya, Mehmet Fatih; Dikmen, Gökhan

    2015-12-01

    Structural elucidation of 3-(acrylamido)phenylboronic acid (C9H10BNO3) was carried out with 1H, 13C and HETCOR NMR techniques. Solvent effects on nuclear magnetic shielding tensors were examined with deuterated dimethyl sulfoxide, acetone, methanol and water solvents. The correct order of appearance of carbon and hydrogen atoms on NMR scale from highest magnetic field region to the lowest one were investigated using different types of theoretical levels and the details of the levels were presented in this study. Stable structural conformers and vibrational band analysis of the title molecule (C9H10BNO3) were studied both experimental and theoretical viewpoints using FT-IR, Raman spectroscopic methods and density functional theory (DFT). FT-IR and Raman spectra were obtained in the region of 4000-400 cm-1, and 3700-10 cm-1, respectively. Becke-3-Lee-Yang-Parr (B3LYP) hybrid density functional theory method with 6-31++G(d, p) basis set was included in the search for optimized structures and vibrational wavenumbers. Experimental and theoretical results show that after application of a suitable scaling factor density functional B3LYP method resulted in acceptable results for predicting vibrational wavenumbers except OH and NH stretching modes which is most likely arising from increasing unharmonicity in the high wave number region and possible intra and inter molecular interaction at OH edges those of which are not fully taken into consideration in theoretical processes. To make a more quantitative vibrational assignments, potential energy distribution (PED) values were calculated using VEDA 4 (Vibrational Energy Distribution Analysis) program.

  16. Free-standing and single-crystalline Fe(1-x)Mn(x)Si nanowires with room-temperature ferromagnetism and excellent magnetic response.

    PubMed

    Hung, Min-Hsiu; Wang, Chiu-Yen; Tang, Jianshi; Lin, Ching-Chun; Hou, Te-Chien; Jiang, Xiaowei; Wang, Kang L; Chen, Lih-Juann

    2012-06-26

    High-aspect-ratio Fe(1-x)Mn(x)Si nanowires with room-temperature ferromagnetism were synthesized by a chemical vapor deposition (CVD) method in one step. This is the first report of ternary silicide nanowires using magnetic Mn ions to partially replace metal sites in the host matrix. Here we report the excellent magnetic characteristics of Fe(1-x)Mn(x)Si nanowires, which exhibit strong ferromagnetism at room temperature and high magnetoresistance (MR) variation. As-synthesized Fe(1-x)Mn(x)Si nanowires show a hyperbranched morphology and a spin-disorder behavior. The strong spin interaction in Fe(1-x)Mn(x)Si nanowires, induced by the substitution of Fe sublattices for magnetic Mn ions, was revealed in the hysteresis loops. The magnetization versus magnetic field (M-H) curves of Fe(1-x)Mn(x)Si nanowires are much less sensitive to the temperature variation from 10 to 300 K than those of FeSi nanowires. Remarkably, the excellent MR performance, -41.6% at 25 K with a magnetic field of 9 T, was demonstrated in an individual Fe(0.88)Mn(0.12)Si nanowire.

  17. Radiation shielding of astronauts in interplanetary flights: the CREAM surveyor to Mars and the magnetic lens system for a spaceship.

    PubMed

    Spillantini, P; Taccetti, F; Papini, P; Rossi, L; Casolino, M

    2001-01-01

    The radiation absorbed by astronauts during interplanetary flights is mainly due to cosmic rays of solar origin (SCR). In the most powerful solar flares the dose absorbed in few hours can exceed that cumulated in one year of exposition to the galactic component of cosmic rays (GCR). At energies above the minimum one needed to cross the walls of the spaceship there are extrapolations and guesses, but no data, on the angular distribution of SCR's, an information that is necessary for establishing whatever defence strategy. It was therefore proposed of sending to Mars a measurement device, that should continuously collect data during the travel, and possibly also in the orbit around Mars and on the Mars surface. The device should identify the particle and privilege the completeness in the measurement of its parameters. In fact the high energy electrons travel at speed of the light and could be used in the and future dangerous proton component. Also the much less abundant but individually more dangerous ions should be identified. The device should indeed include a magnetic spectrometer and a high granularity range telescope, and a good time of flight measurement. ASI is supporting an assessment study of a possible mission of such a device on board of the 2005 probe to Mars. A parallel technical study is also in progress to define the workable techniques and the possible configurations of a system of magnetic lenses for protecting the crew of a spaceship.

  18. Advanced Multifunctional MMOD Shield: Radiation Shielding Assessment

    NASA Technical Reports Server (NTRS)

    Rojdev, Kristina; Christiansen, Eric

    2011-01-01

    As NASA is looking to explore further into deep space, multifunctional materials are a necessity for decreasing complexity and mass. One area where multifunctional materials could be extremely beneficial is in the micrometeoroid orbital debris (MMOD) shield. A typical MMOD shield on the International Space Station (ISS) is a stuffed whipple shield consisting of multiple layers. One of those layers is the thermal blanket, or multi-layer insulation (MLI). By increasing the MMOD effectiveness of MLI blankets, while still preserving their thermal capabilities, could allow for a less massive MMOD shield. Thus, a study was conducted to evaluate concept MLI blankets for MMOD shields. In conjunction, these MLI blankets and the subsequent MMOD shields were also evaluated for their radiation shielding effectiveness towards protecting crew. These concepts were evaluated against the ISS MLI blankets and the ISS MMOD shield, which acted as the baseline. These radiation shielding assessments were performed using the high charge and energy transport software (HZETRN). This software is based on a one-dimensional formula of the Boltzmann transport equation with a straight-ahead approximation. Each configuration was evaluated against the following environments to provide a diverse view of radiation shielding effectiveness in most space environments within the heliosphere: August 1972 solar particle event, October 1989 solar particle event, 1982 galactic cosmic ray environment (during solar maximum), 1987 galactic cosmic ray environment (during solar minimum), and a low earth orbit environment in 1970 that corresponded to an altitude of 400 km and inclination of 51.6 . Both the absorbed dose and the dose equivalent were analyzed, but the focus of the discussion was on the dose equivalent since the data is most concerned with radiation shielding of the crew. The following paper outlines the evaluations performed and discusses the results and conclusions of this evaluation for

  19. Space reactor shielding fabrication

    NASA Technical Reports Server (NTRS)

    Welch, F. H.

    1972-01-01

    The fabrication of space reactor neutron shielding by a melting and casting process utilizing lithium hydride is described. The first neutron shield fabricated is a large pancake shape 86 inches in diameter, containing about 1700 pounds of lithium hydride. This shield, fabricated by the unique melting and casting process, is the largest lithium hydride shield ever built.

  20. Assessment of Alphamagnetic Spectrometer (AMS) Upper Experiment Structural Configuration Shielding Effectiveness Associated with Change from Cryo-Cooled Magnet to Permanent Magnet

    NASA Technical Reports Server (NTRS)

    Scully, Robert

    2012-01-01

    In the spring of 2010, the Alpha Magnetic Spectrometer 2 (AMS-02) underwent a series of system level electromagnetic interference control measurements, followed by thermal vacuum testing. Shortly after completion of the thermal vacuum testing, the project decided to remove the cryogenically cooled superconducting magnet, and replace it with the original permanent magnet design employed in the earlier AMS- 01 assembly. Doing so necessitated several structural changes, as well as removal or modification of numerous electronic and thermal control devices and systems. At this stage, the project was rapidly approaching key milestone dates for hardware completion and delivery for launch, and had little time for additional testing or assessment of any impact to the electromagnetic signature of the AMS-02. Therefore, an analytical assessment of the radiated emissions behavioural changes associated with the system changes was requested.

  1. Room-Temperature Ferromagnetism of Cu-Doped ZnO Films Probed by Soft X-Ray Magnetic Circular Dichroism

    SciTech Connect

    Herng, T.S.; Ku, W.; Qi, D.-C.; Berlijn, T.; Yi, J.B.; Yang, K.S.; Dai, Y.; Feng, Y.P.; Santoso, I.; Sanchez-Hanke, C.; Gao, X.Y.; Wee, A.T.S.; Ding, J.; Rusydi, A.

    2010-11-08

    We report direct evidence of room-temperature ferromagnetic ordering in O-deficient ZnO:Cu films by using soft x-ray magnetic circular dichroism and x-ray absorption. Our measurements have revealed unambiguously two distinct features of Cu atoms associated with (i) magnetically ordered Cu ions present only in the oxygen-deficient samples and (ii) magnetically disordered regular Cu{sup 2+} ions present in all the samples. We find that a sufficient amount of both oxygen vacancies (V{sub O}) and Cu impurities is essential to the observed ferromagnetism, and a non-negligible portion of Cu impurities is uninvolved in the magnetic order. Based on first-principles calculations, we propose a microscopic 'indirect double-exchange' model, in which alignments of localized large moments of Cu in the vicinity of the V{sub O} are mediated by the large-sized vacancy orbitals.

  2. Rotational spectra, potential function, Born Oppenheimer breakdown and magnetic shielding of SiSe and SiTe

    NASA Astrophysics Data System (ADS)

    Giuliano, Barbara M.; Bizzocchi, Luca; Grabow, Jens-Uwe

    2008-09-01

    The pure rotational spectra of 18 isotopic species of SiSe (8) and SiTe (10) have been measured in their X1Σ + electronic state with a pulsed-jet resonator Fourier transform microwave spectrometer. The molecules were prepared by a combined DC discharge/laser ablation technique and stabilised in a supersonic jet of Ar. Global multi-isotopologue analyses yielded spectroscopic Dunham parameters Y01, Y11, Y21, Y31 and Y02 for both species, as well as effective Born-Oppenheimer breakdown (BOB) coefficients δ01 for Si, Se and Te. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X1Σ + electronic state of both SiSe and SiTe. Additionally, the magnetic hyperfine interactions produced by the uneven mass number A nuclei 29Si, 77Se and 125Te were observed, yielding first determinations of the corresponding nuclear spin-rotation coupling constants.

  3. The rotational spectra, potential function, Born-Oppenheimer breakdown, and magnetic shielding of SnSe and SnTe.

    PubMed

    Bizzocchi, Luca; Giuliano, Barbara M; Hess, Mareike; Grabow, Jens-Uwe

    2007-03-21

    The pure rotational spectra of 27 isotopic species of SnSe and SnTe have been measured in the frequency range of 5-24 GHz using a Fabry-Perot-type resonator pulsed-jet Fourier-transform microwave spectrometer. Gaseous samples of both chalcogenides were prepared by laser ablation of suitable target rods and were stabilized in supersonic jets of Ar. Global multi-isotopolog analyses of all available high-resolution data produced spectroscopic Dunham parameters Y01, Y11, Y21, Y31, Y02, and Y12 for both species, as well as Born-Oppenheimer breakdown (BOB) coefficients delta01 for Sn, Se, and Te. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X 1Sigma+ electronic state of both SnSe and SnTe. Additionally, the magnetic hyperfine interaction produced by the dipolar nuclei 119Sn, 117Sn, 77Se, and 125Te was observed, yielding first determinations of the corresponding spin-rotation coupling constants.

  4. The rotational spectra, potential function, Born-Oppenheimer breakdown, and magnetic shielding of SnSe and SnTe

    NASA Astrophysics Data System (ADS)

    Bizzocchi, Luca; Giuliano, Barbara M.; Hess, Mareike; Grabow, Jens-Uwe

    2007-03-01

    The pure rotational spectra of 27 isotopic species of SnSe and SnTe have been measured in the frequency range of 5-24GHz using a Fabry-Pérot-type resonator pulsed-jet Fourier-transform microwave spectrometer. Gaseous samples of both chalcogenides were prepared by laser ablation of suitable target rods and were stabilized in supersonic jets of Ar. Global multi-isotopolog analyses of all available high-resolution data produced spectroscopic Dunham parameters Y01, Y11, Y21, Y31, Y02, and Y12 for both species, as well as Born-Oppenheimer breakdown (BOB) coefficients δ01 for Sn, Se, and Te. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the XΣ+1 electronic state of both SnSe and SnTe. Additionally, the magnetic hyperfine interaction produced by the dipolar nuclei Sn119, Sn117, Se77, and Te125 was observed, yielding first determinations of the corresponding spin-rotation coupling constants.

  5. 13. WEIGHING ROOM Fish were lifted up from tower by ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    13. WEIGHING ROOM Fish were lifted up from tower by conveyor, controlled by buttons above the two sets of vertical electrical conduits. They entered the weighing room through the shielded window on the left (shielding missing from the window on the right), were weighed and then transported to the holding tanks. - Hovden Cannery, 886 Cannery Row, Monterey, Monterey County, CA

  6. Investigation of multiferroicity, spin-phonon coupling, and unusual magnetic ordering close to room temperature in LuMn0.5Fe0.5O3

    NASA Astrophysics Data System (ADS)

    Sarkar, Tanushree; Manna, Kaustuv; Elizabeth, Suja; Anil Kumar, P. S.

    2017-02-01

    We report the detailed experimental characteristics of LuMn0.5Fe0.5O3 synthesized by the wet chemical method and proclaim it as a new member of the multiferroic family. The compound stabilizes in P63cm crystal symmetry. It exhibits a spin re-orientation transition at TSR and an antiferromagnetic transition at TN. In addition, our magnetization vs. temperature data reveals an extra broad maximum close to room temperature; unseen in earlier studies. By invoking the compatible nature of the magnetic exchange path in P63cm symmetry, we have argued that the origin lies in the intraplane short-range spin ordering. Heat capacity is measured and analysed to elucidate the magnetic entropy. Though long-range antiferromagnetic ordering vanishes at TN ˜ 103 K, we find the experimental magnetic entropy calculated till 200 K is less by a significant amount from the value of theoretical spin randomization magnetic entropy; further supporting the existence of spin ordering beyond TN and even above 200 K. While the specific heat data and phonon modes of Raman spectra show a signature of spin-phonon coupling at TSR and TN both, dielectric anomaly indicating a magnetoelectric effect is seen only at TN. Piezoresponse force microscopy and ferroelectric hysteresis loop measurement confirm the room-temperature weak ferroelectricity with a saturation polarization value 0.007 μC/cm2 and low coercive field. Furthermore high-temperature dielectric characteristics reveal the ferroelectric transition at around 900 K and exhibit Maxwell-Wagner type relaxation. The present work serves as a bridge between h-RMnO3 and rare earth ferrite RFeO3. It assumes significance in the light of recent research developments in hexagonal RFeO3 (mainly h-LuFeO3) in the context of room-temperature multiferroicity and magnetoelectricity.

  7. Large magnetic response in (Bi4Nd)Ti3(Fe0.5Co0.5)O15 ceramic at room-temperature

    NASA Astrophysics Data System (ADS)

    Yang, F. J.; Su, P.; Wei, C.; Chen, X. Q.; Yang, C. P.; Cao, W. Q.

    2011-12-01

    Ceramics of Nd/Co co-substituted Bi5Ti3FeO15, i.e., (Bi4Nd)Ti3(Fe0.5Co0.5)O15 were prepared by the conventional solid-state reaction method. The X-ray diffraction pattern demonstrates that the sample of the layered perovskite phase was successfully obtained, even if little Bi-deficient pyrochlore Bi2Ti2O7 also existed. The ferroelectric and magnetic Curie temperatures were determined to be 1077 K and 497 K, respectively. The multiferroic property of the sample at room temperature was demonstrated by ferroelectric and magnetic measurements. Remarkably, by Nd/Co co-substituting, the sample exhibited large magnetic response with 2Mr = 330 memu/g and 2Hc = 562 Oe at applied magnetic field of 8 kOe at room temperature. The present work suggests the possibility of doped Bi5Ti3FeO15 as a potential multiferroic.

  8. Verification of antiferromagnetic exchange coupling at room temperature using polar magneto-optic Kerr effect in thin EuS/Co multilayers with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Goschew, A.; Scott, M.; Fumagalli, P.

    2016-08-01

    We report on magneto-optic Kerr measurements in polar geometry carried out on a series of thin Co/EuS multilayers on suitable Co/Pd-multilayer substrates. Thin Co/EuS multilayers of a few nanometers individual layer thickness usually have their magnetization in plane. Co/Pd multilayers introduce a perpendicular magnetic anisotropy in the Co/EuS layers deposited on top, thus making it possible to measure magneto-optic signals in the polar geometry in remanence in order to study exchange coupling. Magneto-optic Kerr-effect spectra and hysteresis loops were recorded in the visible and ultraviolet photon-energy range at room temperature. The EuS contribution to the magneto-optic signal is extracted at 4.1 eV by combining hysteresis loops measured at different photon energies with polar magneto-optic Kerr-effect spectra recorded in remanence and in an applied magnetic field of 2.2 T. The extracted EuS signal shows clear signs of antiferromagnetic coupling of the Eu magnetic moments to the Co layers. This implies that the ordering temperature of at least a fraction of the EuS layers is above room temperature proving that magneto-optic Kerr-effect spectroscopy can be used here as a quasi-element-specific method.

  9. Meteoroid/Debris Shielding

    NASA Technical Reports Server (NTRS)

    Christiansen, Eric L.

    2003-01-01

    This report provides innovative, low-weight shielding solutions for spacecraft and the ballistic limit equations that define the shield's performance in the meteoroid/debris environment. Analyses and hypervelocity impact testing results are described that have been used in developing the shields and equations. Spacecraft shielding design and operational practices described in this report are used to provide effective spacecraft protection from meteoroid and debris impacts. Specific shield applications for the International Space Station (ISS), Space Shuttle Orbiter and the CONTOUR (Comet Nucleus Tour) space probe are provided. Whipple, Multi-Shock and Stuffed Whipple shield applications are described.

  10. RadShield: semiautomated shielding design using a floor plan driven graphical user interface.

    PubMed

    DeLorenzo, Matthew C; Wu, Dee H; Yang, Kai; Rutel, Isaac B

    2016-09-01

    The purpose of this study was to introduce and describe the development of RadShield, a Java-based graphical user interface (GUI), which provides a base design that uniquely performs thorough, spatially distributed calculations at many points and reports the maximum air-kerma rate and barrier thickness for each barrier pursuant to NCRP Report 147 methodology. Semiautomated shielding design calculations are validated by two approaches: a geometry-based approach and a manual approach. A series of geometry-based equations were derived giving the maximum air-kerma rate magnitude and location through a first derivative root finding approach. The second approach consisted of comparing RadShield results with those found by manual shielding design by an American Board of Radiology (ABR)-certified medical physicist for two clinical room situations: two adjacent catheterization labs, and a radiographic and fluoroscopic (R&F) exam room. RadShield's efficacy in finding the maximum air-kerma rate was compared against the geometry-based approach and the overall shielding recommendations by RadShield were compared against the medical physicist's shielding results. Percentage errors between the geometry-based approach and RadShield's approach in finding the magnitude and location of the maximum air-kerma rate was within 0.00124% and 14 mm. RadShield's barrier thickness calculations were found to be within 0.156 mm lead (Pb) and 0.150 mm lead (Pb) for the adjacent catheterization labs and R&F room examples, respectively. However, within the R&F room example, differences in locating the most sensitive calculation point on the floor plan for one of the barriers was not considered in the medical physicist's calculation and was revealed by the RadShield calculations. RadShield is shown to accurately find the maximum values of air-kerma rate and barrier thickness using NCRP Report 147 methodology. Visual inspection alone of the 2D X-ray exam distribution by a medical physicist may not

  11. RadShield: semiautomated shielding design using a floor plan driven graphical user interface.

    PubMed

    DeLorenzo, Matthew C; Wu, Dee H; Yang, Kai; Rutel, Isaac B

    2016-09-08

    The purpose of this study was to introduce and describe the development of RadShield, a Java-based graphical user interface (GUI), which provides a base design that uniquely performs thorough, spatially distributed calculations at many points and reports the maximum air-kerma rate and barrier thickness for each barrier pursuant to NCRP Report 147 methodology. Semiautomated shielding design calculations are validated by two approaches: a geometry-based approach and a manual approach. A series of geometry-based equations were derived giv-ing the maximum air-kerma rate magnitude and location through a first derivative root finding approach. The second approach consisted of comparing RadShield results with those found by manual shielding design by an American Board of Radiology (ABR)-certified medical physicist for two clinical room situations: two adjacent catheterization labs, and a radiographic and fluoroscopic (R&F) exam room. RadShield's efficacy in finding the maximum air-kerma rate was compared against the geometry-based approach and the overall shielding recommendations by RadShield were compared against the medical physicist's shielding results. Percentage errors between the geometry-based approach and RadShield's approach in finding the magnitude and location of the maximum air-kerma rate was within 0.00124% and 14 mm. RadShield's barrier thickness calculations were found to be within 0.156 mm lead (Pb) and 0.150 mm lead (Pb) for the adjacent catheteriza-tion labs and R&F room examples, respectively. However, within the R&F room example, differences in locating the most sensitive calculation point on the floor plan for one of the barriers was not considered in the medical physicist's calculation and was revealed by the RadShield calculations. RadShield is shown to accurately find the maximum values of air-kerma rate and barrier thickness using NCRP Report 147 methodology. Visual inspection alone of the 2D X-ray exam distribution by a medical physicist may not

  12. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Room-Temperature Anisotropic Ferromagnetism in Fe-Doped In2O3 Heteroepitaxial Films

    NASA Astrophysics Data System (ADS)

    Xing, Peng-Fei; Chen, Yan-Xue; Tang, Min-Jian; Yan, Shi-Shen; Liu, Guo-Lei; Mei, Liang-Mo; Jiao, Jun

    2009-11-01

    Fe-doped In2O3 films are grown epitaxially on YSZ (100) substrates by pulsed laser deposition. The in-situ reflection high-energy electron diffraction, the atomic force microscopy, and the x-ray diffraction patterns show that the films have a well defined cubic structure epitaxially oriented in the (100) direction. Room temperature ferromagnetism is observed by an alternating gradient magnetometer. Strong perpendicular magnetic anisotropy with a remnant magnetization ratio of 0.83 and a coercivity of 2.5kOe is revealed. Both the structural and the magnetic measurements suggest that this ferromagnetism is an intrinsic property deriving from the spin-orbit coupling between the diluted Fe atoms.

  13. Room-temperature ferromagnetism in Zn{sub 1-x}Co{sub x}O magnetic semiconductors prepared by sputtering

    SciTech Connect

    Dinia, A.; Schmerber, G.; Meny, C.; Pierron-Bohnes, V.; Beaurepaire, E.

    2005-06-15

    We have used magnetron cosputtering to grow Zn{sub 1-x}Co{sub x}O magnetic dilute semiconductors. The growth has been performed on SiO{sub 2}/Si and Al{sub 2}O{sub 3}(0001) substrates. The Co concentration has been varied between 0.1 and 0.25 and the substrate temperature between room temperature and 600 deg. C. X-ray diffraction analysis has shown that for the films grown on Si substrates the structural quality of the film is improved by increasing the growth temperature and/or postgrowth annealing. The films are textured with c axis of the wurtzite structure along the growth direction. However, for the films grown on Al{sub 2}O{sub 3} substrate quasi-epitaxial films have been obtained for 600 deg. C substrate temperature. Magnetization measurements have shown that the ferromagnetism is directly correlated to the structural quality and appears by increasing the growth temperature and/or postgrowth annealing. Moreover, for the highly textured film a clear magnetic perpendicular anisotropy has been evidenced with the easy magnetization axis along the growth direction. To evidence the intrinsic nature of the ferromagnetism in the films, transmission optical measurements have been used. They show three absorption bands that are characteristics of d-d transitions of tetrahedrally coordinated Co{sup 2+}. This has been supported by nuclear magnetic resonance and magnetic thermal variation.

  14. Enhanced Whipple Shield

    NASA Technical Reports Server (NTRS)

    Crews, Jeanne L. (Inventor); Christiansen, Eric L. (Inventor); Williamsen, Joel E. (Inventor); Robinson, Jennifer R. (Inventor); Nolen, Angela M. (Inventor)

    1997-01-01

    A hypervelocity impact (HVI) Whipple Shield and a method for shielding a wall from penetration by high velocity particle impacts where the Whipple Shield is comprised of spaced apart inner and outer metal sheets or walls with an intermediate cloth barrier arrangement comprised of ceramic cloth and high strength cloth which are interrelated by ballistic formulae.

  15. NEUTRONIC REACTOR SHIELD

    DOEpatents

    Fermi, E.; Zinn, W.H.

    1957-09-24

    The reactor radiation shield material is comprised of alternate layers of iron-containing material and compressed cellulosic material, such as masonite. The shielding material may be prefabricated in the form of blocks, which can be stacked together in ary desired fashion to form an effective shield.

  16. Ion beam thruster shield

    NASA Technical Reports Server (NTRS)

    Power, J. L. (Inventor)

    1976-01-01

    An ion thruster beam shield is provided that comprises a cylindrical housing that extends downstream from the ion thruster and a plurality of annular vanes which are spaced along the length of the housing, and extend inwardly from the interior wall of the housing. The shield intercepts and stops all charge exchange and beam ions, neutral propellant, and sputter products formed due to the interaction of beam and shield emanating from the ion thruster outside of a fixed conical angle from the thruster axis. Further, the shield prevents the sputter products formed during the operation of the engine from escaping the interior volume of the shield.

  17. Band-edge exciton transitions in (Ga 1- xMn x)N diluted magnetic semiconductor films with above room temperature ferromagnetic transition

    NASA Astrophysics Data System (ADS)

    Jeon, H. C.; Kang, T. W.; Kim, T. W.; Cho, Y. H.

    2006-06-01

    (Ga 1- xMn x)N thin films grown on GaN buffer layers by using molecular beam epitaxy were investigated with the goal of producing diluted magnetic semiconductors (DMSs) with band-edge exciton transitions for applications in optomagnetic devices. The magnetization curve as a function of the magnetic field at 5 K indicated that ferromagnetism existed in the (Ga 1- xMn x)N thin films, and the magnetization curve as a function of the temperature showed that the ferromagnetic transition temperature of the (Ga 1- xMn x)N thin film was above room temperature. Photoluminescence and photoluminescence excitation spectra showed that band-edge exciton transitions in (Ga 1- xMn x)N thin films appeared. These results indicate that the (Ga 1- xMn x)N DMSs with a magnetic single phase hold promise for potential applications in spin optoelectronic devices in the blue region of the spectrum.

  18. Influence of pulsating magnetic field on softening behavior of cold rolled AISI 4340 steel at room temperature

    SciTech Connect

    Prasad, S.N.; Singh, P.N.; Singh, V.

    1996-06-15

    The mechanical behavior of a ferromagnetic material is influenced by presence of magnetic field. The rate of stress relaxation in nickel increases by a.c. magnetic field of 11 Oersted (Oe) and 60 Hz. The application of 800 Oe steady magnetic field accelerates the process of creeping in high purity iron. The purpose of the present investigation was to examine the influence of pulsating magnetic field of 942 Oe, produced by a.c. current (50Hz), on the softening behavior of AISI 4340 steel, cold rolled to 20, 60, and 80%.

  19. Magnetic properties of nitrogen-doped ZrO2: Theoretical evidence of absence of room temperature ferromagnetism

    NASA Astrophysics Data System (ADS)

    Albanese, Elisa; Leccese, Mirko; di Valentin, Cristiana; Pacchioni, Gianfranco

    2016-08-01

    N-dopants in bulk monoclinic ZrO2 and their magnetic interactions have been investigated by DFT calculations, using the B3LYP hybrid functional. The electronic and magnetic properties of the paramagnetic N species, substitutionals and interstitials, are discussed. Their thermodynamic stability has been estimated as a function of the oxygen partial pressure. At 300 K, N prefers interstitial sites at any range of oxygen pressure, while at higher temperatures (700–1000 K), oxygen poor-conditions facilitate substitutional dopants. We have considered the interaction of two N defects in various positions in order to investigate the possible occurrence of ferromagnetic ordering. A very small magnetic coupling constant has been calculated for several 2N-ZrO2 configurations, thus demonstrating that magnetic ordering can be achieved only at very low temperatures, well below liquid nitrogen. Furthermore, when N atoms replace O at different sites, resulting in slightly different positions of the corresponding N 2p levels, a direct charge transfer can occur between the two dopants with consequent quenching of the magnetic moment. Another mechanism that contributes to the quenching of the N magnetic moments is the interplay with oxygen vacancies. These effects contribute to reduce the concentration of magnetic impurities, thus limiting the possibility to establish magnetic ordering.

  20. Magnetic properties of nitrogen-doped ZrO2: Theoretical evidence of absence of room temperature ferromagnetism

    PubMed Central

    Albanese, Elisa; Leccese, Mirko; Di Valentin, Cristiana; Pacchioni, Gianfranco

    2016-01-01

    N-dopants in bulk monoclinic ZrO2 and their magnetic interactions have been investigated by DFT calculations, using the B3LYP hybrid functional. The electronic and magnetic properties of the paramagnetic N species, substitutionals and interstitials, are discussed. Their thermodynamic stability has been estimated as a function of the oxygen partial pressure. At 300 K, N prefers interstitial sites at any range of oxygen pressure, while at higher temperatures (700–1000 K), oxygen poor-conditions facilitate substitutional dopants. We have considered the interaction of two N defects in various positions in order to investigate the possible occurrence of ferromagnetic ordering. A very small magnetic coupling constant has been calculated for several 2N-ZrO2 configurations, thus demonstrating that magnetic ordering can be achieved only at very low temperatures, well below liquid nitrogen. Furthermore, when N atoms replace O at different sites, resulting in slightly different positions of the corresponding N 2p levels, a direct charge transfer can occur between the two dopants with consequent quenching of the magnetic moment. Another mechanism that contributes to the quenching of the N magnetic moments is the interplay with oxygen vacancies. These effects contribute to reduce the concentration of magnetic impurities, thus limiting the possibility to establish magnetic ordering. PMID:27527493

  1. Room-temperature solid-state maser.

    PubMed

    Oxborrow, Mark; Breeze, Jonathan D; Alford, Neil M

    2012-08-16

    The invention of the laser has resulted in many innovations, and the device has become ubiquitous. However, the maser, which amplifies microwave radiation rather than visible light, has not had as large an impact, despite being instrumental in the laser's birth. The maser's relative obscurity has mainly been due to the inconvenience of the operating conditions needed for its various realizations: atomic and free-electron masers require vacuum chambers and pumping; and solid-state masers, although they excel as low-noise amplifiers and are occasionally incorporated in ultrastable oscillators, typically require cryogenic refrigeration. Most realizations of masers also require strong magnets, magnetic shielding or both. Overcoming these various obstacles would pave the way for improvements such as more-sensitive chemical assays, more-precise determinations of biomolecular structure and function, and more-accurate medical diagnostics (including tomography) based on enhanced magnetic resonance spectrometers incorporating maser amplifiers and oscillators. Here we report the experimental demonstration of a solid-state maser operating at room temperature in pulsed mode. It works on a laboratory bench, in air, in the terrestrial magnetic field and amplifies at around 1.45 gigahertz. In contrast to the cryogenic ruby maser, in our maser the gain medium is an organic mixed molecular crystal, p-terphenyl doped with pentacene, the latter being photo-excited by yellow light. The maser's pumping mechanism exploits spin-selective molecular intersystem crossing into pentacene's triplet ground state. When configured as an oscillator, the solid-state maser's measured output power of around -10 decibel milliwatts is approximately 100 million times greater than that of an atomic hydrogen maser, which oscillates at a similar frequency (about 1.42 gigahertz). By exploiting the high levels of spin polarization readily generated by intersystem crossing in photo-excited pentacene and other

  2. The role of the exchange-correlation response kernel and scaling corrections in relativistic density functional nuclear magnetic shielding calculations with the zeroth-order regular approximation

    NASA Astrophysics Data System (ADS)

    Autschbach, Jochen

    2013-09-01

    The relativistic NMR module of the Amsterdam Density Functional (ADF) package, which is frequently utilised in studies of heavy atom NMR chemical shifts, is extended to calculate a hitherto neglected term from the response of the exchange-correlation (XC) potential. The term vanishes in the absence of spin-orbit coupling. Further, corrections to the shielding arising from scaling factors in the zeroth-order regular approximation (zora) relativistic framework are investigated. The XC response markedly improves calculated proton chemical shifts for hydrogen halides. Mercury chemical shifts for mercury dihalides are also noticeably altered. Contributions from density-gradient dependent terms in the response kernel contribute about 30-40%. New fully relativistic density functional theory (DFT) benchmark data are compared with zora and literature reference values. In line with previous work, it is found that absolute shielding constants for Hg are not accurately predicted with zora. However, chemical shifts agree well with fully relativistic calculations. The application of 'scaled-zora' scaling factors deteriorates the shielding constants and is therefore not recommended. The scaling hardly affects chemical shifts. zora calculations are not suitable for absolute shielding of heavy atoms but they can be used safely for chemical shifts in most application scenarios.

  3. Electromagnetic and Stress Analyses of the ITER Equatorial Thermal Shield

    NASA Astrophysics Data System (ADS)

    Lei, Mingzhun; Song, Yuntao; Wang, Songke; Wang, Xianwei

    2013-08-01

    The ITER equatorial thermal shield is located inside the cryostat and outside the vacuum vessel, and its purpose is to provide a thermal shield from hot components to the superconducting magnets. Electromagnetic analysis of the equatorial thermal shield was performed using the ANSYS code, because electromagnetic load was one of the main loads. The 40° sector finite element model was established including the vacuum vessel, equatorial thermal shield, and superconducting magnets. The main purpose of this analysis was to investigate the eddy current and electromagnetic force in the equatorial thermal shield during plasma disruption. Stress analysis was implemented under the electromagnetic load. The results show that the equatorial thermal shield can accommodate the calculated electromagnetic loads.

  4. Predictions for Radiation Shielding Materials

    NASA Technical Reports Server (NTRS)

    Kiefer, Richard L.

    2002-01-01

    Radiation from galactic cosmic rays (GCR) and solar particle events (SPE) is a serious hazard to humans and electronic instruments during space travel, particularly on prolonged missions outside the Earth s magnetic fields. Galactic cosmic radiation (GCR) is composed of approx. 98% nucleons and approx. 2% electrons and positrons. Although cosmic ray heavy ions are 1-2% of the fluence, these energetic heavy nuclei (HZE) contribute 50% of the long-term dose. These unusually high specific ionizations pose a significant health hazard acting as carcinogens and also causing microelectronics damage inside spacecraft and high-flying aircraft. These HZE ions are of concern for radiation protection and radiation shielding technology, because gross rearrangements and mutations and deletions in DNA are expected. Calculations have shown that HZE particles have a strong preference for interaction with light nuclei. The best shield for this radiation would be liquid hydrogen, which is totally impractical. For this reason, hydrogen-containing polymers make the most effective practical shields. Shielding is required during missions in Earth orbit and possibly for frequent flying at high altitude because of the broad GCR spectrum and during a passage into deep space and LunarMars habitation because of the protracted exposure encountered on a long space mission. An additional hazard comes from solar particle events (SPEs) which are mostly energetic protons that can produce heavy ion secondaries as well as neutrons in materials. These events occur at unpredictable times and can deliver a potentially lethal dose within several hours to an unshielded human. Radiation protection for humans requires safety in short-term missions and maintaining career exposure limits within acceptable levels on future long-term exploration missions. The selection of shield materials can alter the protection of humans by an order of magnitude. If improperly selected, shielding materials can actually

  5. Room-temperature magnetic topological Weyl fermion and nodal line semimetal states in half-metallic Heusler Co2TiX (X=Si, Ge, or Sn)

    PubMed Central

    Chang, Guoqing; Xu, Su-Yang; Zheng, Hao; Singh, Bahadur; Hsu, Chuang-Han; Bian, Guang; Alidoust, Nasser; Belopolski, Ilya; Sanchez, Daniel S.; Zhang, Songtian; Lin, Hsin; Hasan, M. Zahid

    2016-01-01

    Topological semimetals (TSMs) including Weyl semimetals and nodal-line semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature. PMID:27974837

  6. 80% tunneling magnetoresistance at room temperature for thin Al-O barrier magnetic tunnel junction with CoFeB as free and reference layers

    NASA Astrophysics Data System (ADS)

    Wei, H. X.; Qin, Q. H.; Ma, M.; Sharif, R.; Han, X. F.

    2007-05-01

    Magnetic tunnel junctions (MTJs) with structures of Ta(5)/Cu(10)/Ta(5)/Ir21Mn79(10)/Co75Fe25(2)/Ru(0.75)/Co40Fe40B20(3)/Al(0.6)-O /Co40Fe40B20(2.5)/Ta(3)/Ru(7) (units in nanometers) were deposited via ultrahigh vacuum magnetron sputtering (ULVAC). Microscale ring-type magnetic tunnel junctions (RMTJs) with an outer radius of 2μm and an inner radius of 1μm were patterned using standard UV lithography combined with ion milling. Both reference and free layers were Co40Fe40B20 and a very thin Al-O (0.6nm) barrier layer was used. Tunneling magnetoresistances (TMRs) of up to 81% at room temperature and 107% at 4.2K were observed. These RMTJs with high TMR and low coercivity, of about 26Oe, combined with the ring-type geometry, which greatly reduces stray magnetic field, are ideal for certain magnetic field sensor applications.

  7. Room-temperature magnetic topological Weyl fermion and nodal line semimetal states in half-metallic Heusler Co2TiX (X=Si, Ge, or Sn)

    NASA Astrophysics Data System (ADS)

    Chang, Guoqing; Xu, Su-Yang; Zheng, Hao; Singh, Bahadur; Hsu, Chuang-Han; Bian, Guang; Alidoust, Nasser; Belopolski, Ilya; Sanchez, Daniel S.; Zhang, Songtian; Lin, Hsin; Hasan, M. Zahid

    2016-12-01

    Topological semimetals (TSMs) including Weyl semimetals and nodal-line semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.

  8. Room-temperature magnetic topological Weyl fermion and nodal line semimetal states in half-metallic Heusler Co2TiX (X=Si, Ge, or Sn).

    PubMed

    Chang, Guoqing; Xu, Su-Yang; Zheng, Hao; Singh, Bahadur; Hsu, Chuang-Han; Bian, Guang; Alidoust, Nasser; Belopolski, Ilya; Sanchez, Daniel S; Zhang, Songtian; Lin, Hsin; Hasan, M Zahid

    2016-12-15

    Topological semimetals (TSMs) including Weyl semimetals and nodal-line semimetals are expected to open the next frontier of condensed matter and materials science. Although the first inversion breaking Weyl semimetal was recently discovered in TaAs, its magnetic counterparts, i.e., the time-reversal breaking Weyl and nodal line semimetals, remain elusive. They are predicted to exhibit exotic properties distinct from the inversion breaking TSMs including TaAs. In this paper, we identify the magnetic topological semimetal states in the ferromagnetic half-metal compounds Co2TiX (X = Si, Ge, or Sn) with Curie temperatures higher than 350 K. Our first-principles band structure calculations show that, in the absence of spin-orbit coupling, Co2TiX features three topological nodal lines. The inclusion of spin-orbit coupling gives rise to Weyl nodes, whose momentum space locations can be controlled as a function of the magnetization direction. Our results not only open the door for the experimental realization of topological semimetal states in magnetic materials at room temperature, but also suggest potential applications such as unusual anomalous Hall effect in engineered monolayers of the Co2TiX compounds at high temperature.

  9. The hyperfine structure in the rotational spectra of D{sub 2}{sup 17}O and HD{sup 17}O: Confirmation of the absolute nuclear magnetic shielding scale for oxygen

    SciTech Connect

    Puzzarini, Cristina Cazzoli, Gabriele; Harding, Michael E.; Vázquez, Juana; Gauss, Jürgen

    2015-03-28

    Guided by theoretical predictions, the hyperfine structures of the rotational spectra of mono- and bideuterated-water containing {sup 17}O have been experimentally investigated. To reach sub-Doppler resolution, required to resolve the hyperfine structure due to deuterium quadrupole coupling as well as to spin-rotation (SR) and dipolar spin-spin couplings, the Lamb-dip technique has been employed. The experimental investigation and in particular, the spectral analysis have been supported by high-level quantum-chemical computations employing coupled-cluster techniques and, for the first time, a complete experimental determination of the hyperfine parameters involved was possible. The experimentally determined {sup 17}O spin-rotation constants of D{sub 2}{sup 17}O and HD{sup 17}O were used to derive the paramagnetic part of the corresponding nuclear magnetic shielding constants. Together with the computed diamagnetic contributions as well as the vibrational and temperature corrections, the latter constants have been employed to confirm the oxygen nuclear magnetic shielding scale, recently established on the basis of spin-rotation data for H{sub 2}{sup 17}O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)].

  10. Magneto-optical controlled transmittance alteration of PbS quantum dots by moderately applied magnetic fields at room temperature

    SciTech Connect

    Singh, Akhilesh K.; Barik, Puspendu; Ullrich, Bruno E-mail: bruno.ullrich@yahoo.com

    2014-12-15

    We observed changes of the transmitted monochromatic light passing through a colloidal PbS quantum dot film on glass owing to an applied moderate (smaller than 1 T) magnetic field under ambient conditions. The observed alterations show a square dependence on the magnetic field increase that cannot be achieved with bulk semiconductors. The findings point to so far not recognized application potentials of quantum dots.

  11. Magneto-optical controlled transmittance alteration of PbS quantum dots by moderately applied magnetic fields at room temperature

    NASA Astrophysics Data System (ADS)

    Singh, Akhilesh K.; Barik, Puspendu; Ullrich, Bruno

    2014-12-01

    We observed changes of the transmitted monochromatic light passing through a colloidal PbS quantum dot film on glass owing to an applied moderate (smaller than 1 T) magnetic field under ambient conditions. The observed alterations show a square dependence on the magnetic field increase that cannot be achieved with bulk semiconductors. The findings point to so far not recognized application potentials of quantum dots.

  12. Cable shield connecting device

    DOEpatents

    Silva, Frank A.

    1979-01-01

    A cable shield connecting device for installation on a high voltage cable of the type having a metallic shield, the device including a relatively conformable, looped metal bar for placement around a bared portion of the metallic shield to extend circumferentially around a major portion of the circumference of the metallic shield while being spaced radially therefrom, a plurality of relatively flexible metallic fingers affixed to the bar, projecting from the bar in an axial direction and spaced circumferentially along the bar, each finger being attached to the metallic shield at a portion located remote from the bar to make electrical contact with the metallic shield, and a connecting conductor integral with the bar.

  13. Relativistic calculation of nuclear magnetic shielding tensor using the regular approximation to the normalized elimination of the small component. III. Introduction of gauge-including atomic orbitals and a finite-size nuclear model

    NASA Astrophysics Data System (ADS)

    Hamaya, S.; Maeda, H.; Funaki, M.; Fukui, H.

    2008-12-01

    The relativistic calculation of nuclear magnetic shielding tensors in hydrogen halides is performed using the second-order regular approximation to the normalized elimination of the small component (SORA-NESC) method with the inclusion of the perturbation terms from the metric operator. This computational scheme is denoted as SORA-Met. The SORA-Met calculation yields anisotropies, Δσ =σ∥-σ⊥, for the halogen nuclei in hydrogen halides that are too small. In the NESC theory, the small component of the spinor is combined to the large component via the operator σ⃗ṡπ⃗U/2c, in which π⃗=p⃗+A⃗, U is a nonunitary transformation operator, and c ≅137.036 a.u. is the velocity of light. The operator U depends on the vector potential A⃗ (i.e., the magnetic perturbations in the system) with the leading order c-2 and the magnetic perturbation terms of U contribute to the Hamiltonian and metric operators of the system in the leading order c-4. It is shown that the small Δσ for halogen nuclei found in our previous studies is related to the neglect of the U(0,1) perturbation operator of U, which is independent of the external magnetic field and of the first order with respect to the nuclear magnetic dipole moment. Introduction of gauge-including atomic orbitals and a finite-size nuclear model is also discussed.

  14. Relativistic calculation of nuclear magnetic shielding tensor using the regular approximation to the normalized elimination of the small component. III. Introduction of gauge-including atomic orbitals and a finite-size nuclear model.

    PubMed

    Hamaya, S; Maeda, H; Funaki, M; Fukui, H

    2008-12-14

    The relativistic calculation of nuclear magnetic shielding tensors in hydrogen halides is performed using the second-order regular approximation to the normalized elimination of the small component (SORA-NESC) method with the inclusion of the perturbation terms from the metric operator. This computational scheme is denoted as SORA-Met. The SORA-Met calculation yields anisotropies, Delta sigma = sigma(parallel) - sigma(perpendicular), for the halogen nuclei in hydrogen halides that are too small. In the NESC theory, the small component of the spinor is combined to the large component via the operator sigma x piU/2c, in which pi = p + A, U is a nonunitary transformation operator, and c approximately = 137.036 a.u. is the velocity of light. The operator U depends on the vector potential A (i.e., the magnetic perturbations in the system) with the leading order c(-2) and the magnetic perturbation terms of U contribute to the Hamiltonian and metric operators of the system in the leading order c(-4). It is shown that the small Delta sigma for halogen nuclei found in our previous studies is related to the neglect of the U(0,1) perturbation operator of U, which is independent of the external magnetic field and of the first order with respect to the nuclear magnetic dipole moment. Introduction of gauge-including atomic orbitals and a finite-size nuclear model is also discussed.

  15. Analysis of the effect of different absorber materials and loading on the shielding effectiveness of a metallic enclosure

    NASA Astrophysics Data System (ADS)

    Parr, S.; Karcoon, H.; Dickmann, S.; Rambousky, R.

    2015-11-01

    Metallic rooms as part of a complex system, like a ship, are necessarily connected electromagnetically via apertures and cables to the outside. Therefore, their electromagnetic shielding effectiveness (SE) is limited by ventilation openings, cable feed-throughs and door gaps. Thus, electronic equipment inside these rooms is susceptible to outer electromagnetic threats like IEM (Intentional Electromagnetic Interference). Dielectric or magnetic absorber inside such a screened room can be used in order to prevent the SE from collapsing at the resonant frequencies. In this contribution, the effect of different available absorber materials is compared, as well as other properties like weight and workability. Furthermore, parameter variations of the absorber as well as the effect of loading in form of metallic and dielectric structures on the SE are analyzed.

  16. RADIATION SHIELDING DEVICE

    DOEpatents

    Wigner, E.P.; Young, G.J.

    1958-09-23

    ABS>A radiation shield that is suitable for the protection of personnel from both gamma rays and nentrons is described. The shield is comprised of a hollow wall and an aggregate consisting of iron and water in approximately equal amounts by volume substantially filling the wall. A means is provided to circulate the water through the wall to cool the shield when in use.

  17. Room temperature magnetic ordering, enhanced magnetization and exchange bias of GdMnO3 nanoparticles in (GdMnO3)0.70(CoFe2O4)0.30

    NASA Astrophysics Data System (ADS)

    Mitra, A.; Mahapatra, A. S.; Mallick, A.; Chakrabarti, P. K.

    2017-02-01

    Nanoparticles of GdMnO3 (GMO) are prepared by sol-gel method. To enhance the magnetic property and also to obtain the magnetic ordering at room temperature (RT), nanoparticles of GMO are incorporated in the matrix of CoFe2O4 (CFO). Desired crystallographic phases of CFO, GMO and GMO-CFO are confirmed by analyzing X-ray diffractrograms (XRD) using Rietveld method. The average size of nanoparticles and their distribution, crystallographic phase, nanocrystallinity etc. are studied by high-resolution transmission electron microscope (HRTEM). Magnetic hysteresis loops (M-H) of GMO-CFO under zero field cooled (ZFC) and field cooled (FC) conditions are observed at different temperatures down to 5 K. Magnetization vs. temperature (M-T) under ZFC and FC conditions are also recorded. Interestingly, exchange bias (EB) is found at low temperature which suggests the encapsulation of the ferromagnetic (FM) nanoparticles of GMO by the ferrimagnetic nanoparticles of CFO below 100 K. Enhanced magnetization, EB effect and RT magnetic ordering of GMO-CFO would be interesting for both theoretical and experimental investigations.

  18. A Launch Requirements Trade Study for Active Space Radiation Shielding for Long Duration Human Missions

    NASA Technical Reports Server (NTRS)

    Singleterry, Robert C., Jr.; Bollweg, Ken; Martin, Trent; Westover, Shayne; Battiston, Roberto; Burger, William J.; Meinke, Rainer

    2015-01-01

    A trade study for an active shielding concept based on magnetic fields in a solenoid configuration versus mass based shielding was developed. Monte Carlo simulations were used to estimate the radiation exposure for two values of the magnetic field strength and the mass of the magnetic shield configuration. For each field strength, results were reported for the magnetic region shielding (end caps ignored) and total region shielding (end caps included but no magnetic field protection) configurations. A value of 15 cSv was chosen to be the maximum exposure for an astronaut. The radiation dose estimate over the total shield region configuration cannot be used at this time without a better understanding of the material and mass present in the end cap regions through a detailed vehicle design. The magnetic shield region configuration, assuming the end cap regions contribute zero exposure, can be launched on a single Space Launch System rocket and up to a two year mission can be supported. The magnetic shield region configuration results in two versus nine launches for a comparable mass based shielding configuration. The active shielding approach is clearly more mass efficient because of the reduced number of launches than the mass based shielding for long duration missions.

  19. Room Acoustics

    NASA Astrophysics Data System (ADS)

    Kuttruff, Heinrich; Mommertz, Eckard

    The traditional task of room acoustics is to create or formulate conditions which ensure the best possible propagation of sound in a room from a sound source to a listener. Thus, objects of room acoustics are in particular assembly halls of all kinds, such as auditoria and lecture halls, conference rooms, theaters, concert halls or churches. Already at this point, it has to be pointed out that these conditions essentially depend on the question if speech or music should be transmitted; in the first case, the criterion for transmission quality is good speech intelligibility, in the other case, however, the success of room-acoustical efforts depends on other factors that cannot be quantified that easily, not least it also depends on the hearing habits of the listeners. In any case, absolutely "good acoustics" of a room do not exist.

  20. INTOR radiation shielding for personnel access

    SciTech Connect

    Gohar, Y.; Abdou, M.

    1981-01-01

    The INTOR reactor shield system consists of the blanket, bulk shield, penetration shield, component shield, and biological shield. The bulk shield consists of two parts: (a) the inboard shield; and (b) the outboard shield. The distinction between the different components of the shield system is essential to satisfy the different design constraints and achieve various objectives.

  1. Magnetic Field R&D for the neutron EDM experiment at TRIUMF

    NASA Astrophysics Data System (ADS)

    Mammei, Russell R.

    2014-09-01

    The neutron EDM experiment at TRIUMF aims to constrain the EDM with a precision of 1 ×10-27 e-cm by 2018. The experiment will use a spallation ultracold neutron (UCN) source employing superfluid helium coupled to a room-temperature EDM apparatus. In the previous best experiment, conducted at ILL, effects related to magnetic field homogeneity and instability were found to dominate the systematic error. This presentation will cover our R&D efforts on passive and active magnetic shielding, magnetic field generation within shielded volumes, and precision magnetometry. The neutron EDM experiment at TRIUMF aims to constrain the EDM with a precision of 1 ×10-27 e-cm by 2018. The experiment will use a spallation ultracold neutron (UCN) source employing superfluid helium coupled to a room-temperature EDM apparatus. In the previous best experiment, conducted at ILL, effects related to magnetic field homogeneity and instability were found to dominate the systematic error. This presentation will cover our R&D efforts on passive and active magnetic shielding, magnetic field generation within shielded volumes, and precision magnetometry. Supported by the Canada Foundation for Innovation, the Natural Sciences and Engineering Research Council of Canada, and the Canada Research Chairs program.

  2. Magnetic properties of epitaxial Fe{sub 3}O{sub 4} films with various crystal orientations and tunnel magnetoresistance effect at room temperature

    SciTech Connect

    Nagahama, Taro Matsuda, Yuya; Tate, Kazuya; Kawai, Tomohiro; Takahashi, Nozomi; Hiratani, Shungo; Watanabe, Yusuke; Yanase, Takashi; Shimada, Toshihiro

    2014-09-08

    Fe{sub 3}O{sub 4} is a ferrimagnetic spinel ferrite that exhibits electric conductivity at room temperature (RT). Although the material has been predicted to be a half metal according to ab-initio calculations, magnetic tunnel junctions (MTJs) with Fe{sub 3}O{sub 4} electrodes have demonstrated a small tunnel magnetoresistance (TMR) effect. Not even the sign of the tunnel magnetoresistance ratio has been experimentally established. Here, we report on the magnetic properties of epitaxial Fe{sub 3}O{sub 4} films with various crystal orientations. The films exhibited apparent crystal orientation dependence on hysteresis curves. In particular, Fe{sub 3}O{sub 4}(110) films exhibited in-plane uniaxial magnetic anisotropy. With respect to the squareness of hysteresis, Fe{sub 3}O{sub 4} (111) demonstrated the largest squareness. Furthermore, we fabricated MTJs with Fe{sub 3}O{sub 4}(110) electrodes and obtained a TMR effect of −12% at RT. The negative TMR ratio corresponded to the negative spin polarization of Fe{sub 3}O{sub 4} predicted from band calculations.

  3. Influence of interstitial Mn on magnetism in the room-temperature ferromagnet Mn1+δSb

    DOE PAGES

    Taylor, Alice E.; Berlijn, Tom; Hahn, Steven E.; ...

    2015-06-15

    We repormore » t elastic and inelastic neutron scattering measurements of the high-TC ferromagnet Mn1+δSb. Measurements were performed on a large, TC = 434 K, single crystal with interstitial Mn content of δ ≈ 0.13. The neutron diffraction results reveal that the interstitial Mn has a magnetic moment, and that it is aligned antiparallel to the main Mn moment. We perform density functional theory calculations including the interstitial Mn, and find the interstitial to be magnetic in agreement with the diffraction data. The inelastic neutron scattering measurements reveal two features in the magnetic dynamics: i) a spin-wave-like dispersion emanating from ferromagnetic Bragg positions (H K 2n), and ii) a broad, non-dispersive signal centered at forbidden Bragg positions (H K 2n+1). The inelastic spectrum cannot be modeled by simple linear spin-wave theory calculations, and appears to be significantly altered by the presence of the interstitial Mn ions. Finally, the results show that the influence of the interstitial Mn on the magnetic state in this system is more important than previously understood.« less

  4. Manipulation of magnetism in perpendicularly magnetized Heusler alloy Co2FeAl0.5Si0.5 by electric-field at room temperature

    NASA Astrophysics Data System (ADS)

    Wang, H. L.; Wu, Y.; Yu, H. J.; Jiang, Y.; Zhao, J. H.

    2016-09-01

    The electrical manipulation of magnetic properties in perpendicularly magnetized Co2FeAl0.5Si0.5 ultra-thin films has been investigated. An electric-field is applied by utilizing either a solid-state dielectric HfO2 film or an ionic gel film as the gate insulator in the form of a field effect parallel capacitor. Obvious changes of the coercive field and Curie temperature (˜24 K) by gating voltage are observed for a 0.8 nm thick film, while a clear change of the magnetic anisotropy is obtained for the 1.1 nm thick one. The experimental results have been attributed to both the electric-field-induced modulation of carrier density near the interface and the oxidation-reduction effect inside the magnetic films.

  5. NEUTRONIC REACTOR SHIELDING

    DOEpatents

    Borst, L.B.

    1961-07-11

    A special hydrogenous concrete shielding for reactors is described. In addition to Portland cement and water, the concrete essentially comprises 30 to 60% by weight barytes aggregate for enhanced attenuation of fast neutrons. The biological shields of AEC's Oak Ridge Graphite Reactor and Materials Testing Reactor are particular embodiments.

  6. TFCX shielding optimization

    SciTech Connect

    Yang, S.; Gohar, Y.

    1985-01-01

    Design analyses and tradeoff studies for the bulk shield of the Tokamak Fusion Core Experiment (TFCX) were performed. Several shielding options were considered to lower the capital cost of the shielding system. Optimization analyses were carried out to reduce the nuclear responses in the TF coils and the dose equivalent in the reactor hall one day after shutdown. Two TFCX designs with different toroidal field (TF) coil configurations were considered during this work. The materials for the shield were selected based upon tradeoff studies and the results from the previous design studies. The main shielding materials are water, concrete, and steel balls (Fe1422 or Nitronic 33). Small amounts of boron carbide and lead are employed to reduce activation, nuclear heating in the TF coils, and dose equivalent after shutdown.

  7. Analytic Ballistic Performance Model of Whipple Shields

    NASA Technical Reports Server (NTRS)

    Miller, J. E.; Bjorkman, M. D.; Christiansen, E. L.; Ryan, S. J.

    2015-01-01

    The dual-wall, Whipple shield is the shield of choice for lightweight, long-duration flight. The shield uses an initial sacrificial wall to initiate fragmentation and melt an impacting threat that expands over a void before hitting a subsequent shield wall of a critical component. The key parameters to this type of shield are the rear wall and its mass which stops the debris, as well as the minimum shock wave strength generated by the threat particle impact of the sacrificial wall and the amount of room that is available for expansion. Ensuring the shock wave strength is sufficiently high to achieve large scale fragmentation/melt of the threat particle enables the expansion of the threat and reduces the momentum flux of the debris on the rear wall. Three key factors in the shock wave strength achieved are the thickness of the sacrificial wall relative to the characteristic dimension of the impacting particle, the density and material cohesion contrast of the sacrificial wall relative to the threat particle and the impact speed. The mass of the rear wall and the sacrificial wall are desirable to minimize for launch costs making it important to have an understanding of the effects of density contrast and impact speed. An analytic model is developed here, to describe the influence of these three key factors. In addition this paper develops a description of a fourth key parameter related to fragmentation and its role in establishing the onset of projectile expansion.

  8. Heat Shield in Pieces

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image from NASA's Mars Exploration Rover Opportunity shows the remains of the rover's heat shield, broken into two key pieces, the main piece on the left side and a broken-off flank piece near the middle of the image. The heat shield impact site is identified by the circle of red dust on the right side of the picture. In this view, Opportunity is approximately 20 meters (66 feet) away from the heat shield, which protected it while hurtling through the martian atmosphere.

    In the far left of the image, a meteorite called 'Heat Shield Rock,' sits nearby, The Sun is reflecting off the silver-colored underside of the internal thermal blankets of the heat shield.

    The rover spent 36 sols investigating how the severe heating during entry through the atmosphere affected the heat shield. The most obvious is the fact that the heat shield inverted upon impact.

    This is an approximately true-color rendering of the scene acquired around 1:22 p.m. local solar time on Opportunity sol 324 (Dec. 21, 2004) in an image mosaic using panoramic filters at wavelengths of 750, 530, and 430 nanometers.

  9. Shielding against galactic cosmic rays

    NASA Technical Reports Server (NTRS)

    Schimmerling, W.; Wilson, J. W.; Nealy, J. E.; Thibeault, S. A.; Cucinotta, F. A.; Shinn, J. L.; Kim, M.; Kiefer, R.

    1996-01-01

    Ions of galactic origin are modified but not attenuated by the presence of shielding materials. Indeed, the number of particles and the absorbed energy behind most shield materials increases as a function of shield thickness. The modification of the galactic cosmic ray composition upon interaction with shielding is the only effective means of providing astronaut protection. This modification is intimately conntected with the shield transport porperties and is a strong function of shield composition. The systematic behavior of the shield properites in terms of microscopic energy absorption events will be discussed. The shield effectiveness is examined with respect to convectional protection practice and in terms of a biological endpoint: the efficiency for reduction of the probability of transformation of shielded C3H1OT1/2 mouse cells. The relative advantage of developing new shielding technologies is discussed in terms of a shield performance as related to biological effect and the resulting uncertainty in estimating astronaut risk.

  10. Low-field magnetic resonance imaging of gases

    SciTech Connect

    Schmidt, D.M.; Espy, M.A.

    1998-11-01

    This is the final report of a six-month, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The main goal of this project was to develop the capability to conduct low-field magnetic resonance imaging of hyper-polarized noble gas nuclei and of thermally polarized protons in water. The authors constructed a versatile low-field NMR system using a SQUID gradiometer detector inside a magnetically shielded room. This device has sufficient low-field sensitivity to detect the small signals associated with NMR at low magnetic fields.

  11. What Is Radiation Shielding?

    NASA Video Gallery

    Kerry Lee, NASA Orion radiation system manager, explains how radiation shielding is used to block harmful particles coming into the spacecraft without producing secondary particles that can cause e...

  12. Adhesive particle shielding

    DOEpatents

    Klebanoff, Leonard Elliott; Rader, Daniel John; Walton, Christopher; Folta, James

    2009-01-06

    An efficient device for capturing fast moving particles has an adhesive particle shield that includes (i) a mounting panel and (ii) a film that is attached to the mounting panel wherein the outer surface of the film has an adhesive coating disposed thereon to capture particles contacting the outer surface. The shield can be employed to maintain a substantially particle free environment such as in photolithographic systems having critical surfaces, such as wafers, masks, and optics and in the tools used to make these components, that are sensitive to particle contamination. The shield can be portable to be positioned in hard-to-reach areas of a photolithography machine. The adhesive particle shield can incorporate cooling means to attract particles via the thermophoresis effect.

  13. Crash-Resistant Shield

    NASA Technical Reports Server (NTRS)

    Bixler, Charles H.

    1990-01-01

    Impact-resistant shield designed to consist of aluminum honeycomb structure sandwiched between inner and outer aluminum skins. Intended to protect radioisotope thermoelectric generator of spacecraft from impact with ground or water after free fall from upper atmosphere. Designed to absorb impact energy by buckling, while inner and outer skins designed to protect against shrapnel, overpressure, and impact loads. Concept of shield applicable to crashproof compartments for ground vehicles and aircraft.

  14. Memory's Room.

    ERIC Educational Resources Information Center

    Carruthers, Mary

    1999-01-01

    Describes the Liberal Arts Studiolo from the Ducal Palace at Guibbio, Italy. Discusses how the room's design and decoration mirrors its educational uses. Notes that the object of education was to provide the young person with a kind of mental library of materials that could be drawn upon quickly. (RS)

  15. Electrodynamic Dust Shield Demonstrator

    NASA Technical Reports Server (NTRS)

    Stankie, Charles G.

    2013-01-01

    The objective of the project was to design and manufacture a device to demonstrate a new technology developed by NASA's Electrostatics and Surface Physics Laboratory. The technology itself is a system which uses magnetic principles to remove regolith dust from its surface. This project was to create an enclosure that will be used to demonstrate the effectiveness of the invention to The Office of the Chief Technologist. ONE of the most important challenges of space exploration is actually caused by something very small and seemingly insignificant. Dust in space, most notably on the moon and Mars, has caused many unforeseen issues. Dirt and dust on Earth, while a nuisance, can be easily cleaned and kept at bay. However, there is considerably less weathering and erosion in space. As a result, the microscopic particles are extremely rough and abrasive. They are also electrostatically charged, so they cling to everything they make contact with. This was first noted to be a major problem during the Apollo missions. Dust would stick to the spacesuits, and could not be wiped off as predicted. Dust was brought back into the spacecraft, and was even inhaled by astronauts. This is a major health hazard. Atmospheric storms and other events can also cause dust to coat surfaces of spacecraft. This can cause abrasive damage to the craft. The coating can also reduce the effectiveness of thermal insulation and solar panels.' A group of engineers at Kennedy Space Center's Electrostatics and Surface Physics Laboratory have developed a new technology, called the Electrodynamic Dust Shield, to help alleviate these problems. It is based off of the electric curtain concept developed at NASA in 1967. "The EDS is an active dust mitigation technology that uses traveling electric fields to transport electrostatically charged dust particles along surfaces. To generate the traveling electric fields, the EDS consists of a multilayer dielectric coating with an embedded thin electrode grid

  16. Shields-1, A SmallSat Radiation Shielding Technology Demonstration

    NASA Technical Reports Server (NTRS)

    Thomsen, D. Laurence, III; Kim, Wousik; Cutler, James W.

    2015-01-01

    The NASA Langley Research Center Shields CubeSat initiative is to develop a configurable platform that would allow lower cost access to Space for materials durability experiments, and to foster a pathway for both emerging and commercial-off-the-shelf (COTS) radiation shielding technologies to gain spaceflight heritage in a relevant environment. The Shields-1 will be Langleys' first CubeSat platform to carry out this mission. Radiation shielding tests on Shields-1 are planned for the expected severe radiation environment in a geotransfer orbit (GTO), where advertised commercial rideshare opportunities and CubeSat missions exist, such as Exploration Mission 1 (EM-1). To meet this objective, atomic number (Z) graded radiation shields (Zshields) have been developed. The Z-shield properties have been estimated, using the Space Environment Information System (SPENVIS) radiation shielding computational modeling, to have 30% increased shielding effectiveness of electrons, at half the thickness of a corresponding single layer of aluminum. The Shields-1 research payload will be made with the Z-graded radiation shields of varying thicknesses to create dose-depth curves to be compared with baseline materials. Additionally, Shields-1 demonstrates an engineered Z-grade radiation shielding vault protecting the systems' electronic boards. The radiation shielding materials' performances will be characterized using total ionizing dose sensors. Completion of these experiments is expected to raise the technology readiness levels (TRLs) of the tested atomic number (Z) graded materials. The most significant contribution of the Z-shields for the SmallSat community will be that it enables cost effective shielding for small satellite systems, with significant volume constraints, while increasing the operational lifetime of ionizing radiation sensitive components. These results are anticipated to increase the development of CubeSat hardware design for increased mission lifetimes, and enable

  17. Shielded, Automated Umbilical Mechanism

    NASA Technical Reports Server (NTRS)

    Barron, Daniel R.; Morrill, Brion F.; Jasulaitis, Vytas

    1995-01-01

    Umbilical mechanism automatically connects and disconnects various fluid couplings and/or electrical contacts while shielding mating parts from debris. Reacts mating and demating loads internally, without additional supporting structures. All functions - extension of plug, mating, and movement of debris shields - actuated by single motor. If mechanism jams or fails at any point in sequence, override feature in drive train allows manual operation. Designed for service in outer space, where its shields protect against micrometeoroids, debris, ultraviolet radiation, and atomic oxygen. Used on Earth to connect or disconnect fluid or electrical utilities in harsh environments like those of nuclear powerplants or undersea construction sites, or in presence of radioactive, chemical, or biological hazards, for example.

  18. Radiation shielding composition

    DOEpatents

    Quapp, W.J.; Lessing, P.A.

    1998-07-28

    A composition is disclosed for use as a radiation shield. The shield is a concrete product containing a stable uranium aggregate for attenuating gamma rays and a neutron absorbing component, the uranium aggregate and neutron absorbing component being present in the concrete product in sufficient amounts to provide a concrete having a density between about 4 and about 15 grams/cm{sup 3} and which will at a predetermined thickness, attenuate gamma rays and absorb neutrons from a radioactive material of projected gamma ray and neutron emissions over a determined time period. The composition is preferably in the form of a container for storing radioactive materials that emit gamma rays and neutrons. The concrete container preferably comprises a metal liner and/or a metal outer shell. The resulting radiation shielding container has the potential of being structurally sound, stable over a long period of time, and, if desired, readily mobile. 5 figs.

  19. Radiation shielding composition

    DOEpatents

    Quapp, William J.; Lessing, Paul A.

    2000-12-26

    A composition for use as a radiation shield. The shield is a concrete product containing a stable uranium aggregate for attenuating gamma rays and a neutron absorbing component, the uranium aggregate and neutron absorbing component being present in the concrete product in sufficient amounts to provide a concrete having a density between about 4 and about 15 grams/cm.sup.3 and which will at a predetermined thickness, attenuate gamma rays and absorb neutrons from a radioactive material of projected gamma ray and neutron emissions over a determined time period. The composition is preferably in the form of a container for storing radioactive materials that emit gamma rays and neutrons. The concrete container preferably comprises a metal liner and/or a metal outer shell. The resulting radiation shielding container has the potential of being structurally sound, stable over a long period of time, and, if desired, readily mobile.

  20. Radiation shielding composition

    DOEpatents

    Quapp, William J.; Lessing, Paul A.

    1998-01-01

    A composition for use as a radiation shield. The shield is a concrete product containing a stable uranium aggregate for attenuating gamma rays and a neutron absorbing component, the uranium aggregate and neutron absorbing component being present in the concrete product in sufficient amounts to provide a concrete having a density between about 4 and about 15 grams/cm.sup.3 and which will at a predetermined thickness, attenuate gamma rays and absorb neutrons from a radioactive material of projected gamma ray and neutron emissions over a determined time period. The composition is preferably in the form of a container for storing radioactive materials that emit gamma rays and neutrons. The concrete container preferably comprises a metal liner and/or a metal outer shell. The resulting radiation shielding container has the potential of being structurally sound, stable over a long period of time, and, if desired, readily mobile.

  1. Space station MMOD shielding

    NASA Astrophysics Data System (ADS)

    Christiansen, Eric L.; Nagy, Kornel; Lear, Dana M.; Prior, Thomas G.

    2009-10-01

    This paper describes the International Space Station (ISS) micro-meteoroid orbital debris (MMOD) impact shielding including the requirements for protection as well as technical approaches to meeting the requirements. Current activities in providing MMOD protection for ISS are described, including efforts to augment MMOD protection by adding shields on-orbit. Another activity is to observe MMOD impact damage on ISS elements and returned hardware, and to compare the observed damage with predicted damage using Bumper code risk assessment software. A conclusion of this paper is that ISS will be protected adequately from MMOD impact after completing augmentation of ISS shielding for service module, and after improving MMOD protection for Soyuz and Progress vehicles. Another conclusion is that impact damage observed to the ISS mini-pressurized logistics module matches the distribution of impacts predicted by Bumper code.

  2. Opportunity's Heat Shield Scene

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image from NASA's Mars Exploration Rover Opportunity reveals the scene of the rover's heat shield impact. In this view, Opportunity is approximately 130 meters (427 feet) away from the device that protected it while hurtling through the martian atmosphere.

    The rover spent 36 sols investigating how the severe heating during entry through the atmosphere affected the heat shield. The most obvious is the fact that the heat shield inverted upon impact.

    This is the panoramic camera team's best current attempt at generating a true-color view of what this scene would look like if viewed by a human on Mars. It was generated from a mathematical combination of six calibrated, left-eye panoramic camera images acquired around 1:50 p.m. local solar time on Opportunity's sol 322 (Dec. 19, 2004) using filters ranging in wavelengths from 430 to 750 nanometers.

  3. LPT. Shield test facility (TAN645 and 646). Sections show relationships ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LPT. Shield test facility (TAN-645 and -646). Sections show relationships among control rooms, coupling station, counting rooms, pools, equipment rooms, data room and other areas. Ralph M. Parsons 1229-17 ANP/GE-6-645-A-4. April 1957. Approved by INEEL Classification Office for public release. INEEL index code no. 037-0645/0646-00-693-107350 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  4. Shielding Structures for Interplanetary Human Mission

    NASA Astrophysics Data System (ADS)

    Tracino, Emanuele; Lobascio, Cesare

    2012-07-01

    Since the end of Apollo missions, human spaceflight has been limited to the Low Earth Orbit (LEO), inside the protective magnetic field of the Earth, because astronauts are, to the largest degree, protected from the harsh radiation environment of the interplanetary space. However, this situation will change when space exploration missions beyond LEO will become the real challenge of the human exploration program. The feasibility of these missions in the solar system is thus strongly connected to the capability to mitigate the radiation-induced biological effects on the crew during the journey and the permanence on the intended planet surface. Inside the International Space Station (ISS), the volumes in which the crew spends most of the time, namely the crew quarters are the only parts that implement dedicated additional radiation shielding made of polyethylene tiles designed for mitigating SPE effects. Furthermore, specific radiation shielding materials are often added to the described configuration to shield crew quarters or the entire habitat example of these materials are polyethylene, liquid hydrogen, etc. but, increasing the size of the exploration vehicles to bring humans beyond LEO, and without the magnetosphere protection, such approach is unsustainable because the mass involved is a huge limiting factor with the actual launcher engine technology. Moreover, shielding against GCR with materials that have a low probability of nuclear interactions and in parallel a high ionizing energy loss is not always the best solution. In particular there is the risk to increase the LET of ions arriving at the spacecraft shell, increasing their Radio-Biological Effectiveness. Besides, the production of secondary nuclei by projectile and target fragmentation is an important issue when performing an engineering assessment of materials to be used for radiation shielding. The goal of this work is to analyze different shielding solutions to increase as much as possible the

  5. Glove box shield

    DOEpatents

    Brackenbush, Larry W.; Hoenes, Glenn R.

    1981-01-01

    According to the present invention, a shield for a glove box housing radioactive material is comprised of spaced apart clamping members which maintain three overlapping flaps in place therebetween. There is a central flap and two side flaps, the side flaps overlapping at the interior edges thereof and the central flap extending past the intersection of the side flaps in order to insure that the shield is always closed when the user withdraws his hand from the glove box. Lead loaded neoprene rubber is the preferred material for the three flaps, the extent of lead loading depending upon the radiation levels within the glove box.

  6. Glove box shield

    DOEpatents

    Brackenbush, L.W.; Hoenes, G.R.

    A shield for a glove box housing radioactive material is comprised of spaced apart clamping members which maintain three overlapping flaps in place therebetween. There is a central flap and two side flaps, the side flaps overlapping at the interior edges thereof and the central flap extending past the intersection of the side flaps in order to insure that the shield is always closed when the user wthdraws his hand from the glove box. Lead loaded neoprene rubber is the preferred material for the three flaps, the extent of lead loading depending upon the radiation levels within the glove box.

  7. Composition for radiation shielding

    DOEpatents

    Kronberg, James W.

    1994-01-01

    A composition for use as a radiation shield. The shield has a depleted urum core for absorbing gamma rays and a bismuth coating for preventing chemical corrosion and absorbing gamma rays. Alternatively, a sheet of gadolinium may be positioned between the uranium core and the bismuth coating for absorbing neutrons. The composition is preferably in the form of a container for storing materials that emit radiation such as gamma rays and neutrons. The container is preferably formed by casting bismuth around a pre-formed uranium container having a gadolinium sheeting, and allowing the bismuth to cool. The resulting container is a structurally sound, corrosion-resistant, radiation-absorbing container.

  8. Hinged Shields for Machine Tools

    NASA Technical Reports Server (NTRS)

    Lallande, J. B.; Poland, W. W.; Tull, S.

    1985-01-01

    Flaps guard against flying chips, but fold away for tool setup. Clear plastic shield in position to intercept flying chips from machine tool and retracted to give operator access to workpiece. Machine shops readily make such shields for own use.

  9. Efficacy of Cosmic Ray Shields

    NASA Astrophysics Data System (ADS)

    Rhodes, Nicholas

    2015-10-01

    This research involved testing various types of shielding with a self-constructed Berkeley style cosmic ray detector, in order to evaluate the materials of each type of shielding's effectiveness at blocking cosmic rays and the cost- and size-efficiency of the shields as well. The detector was constructed, then tested for functionality and reliability. Following confirmation, the detector was then used at three different locations to observe it altitude or atmospheric conditions had any effect on the effectiveness of certain shields. Multiple types of shielding were tested with the detector, including combinations of several shields, primarily aluminum, high-iron steel, polyethylene plastic, water, lead, and a lead-alternative radiation shield utilized in radiology. These tests regarding both the base effectiveness and the overall efficiency of shields is designed to support future space exploratory missions where the risk of exposure to possibly lethal amounts of cosmic rays for crew and the damage caused to unshielded electronics are of serious concern.

  10. Lightweight Shield Against Space Debris

    NASA Technical Reports Server (NTRS)

    Redmon, John W., Jr.; Lawson, Bobby E.; Miller, Andre E.; Cobb, W. E.

    1992-01-01

    Report presents concept for lightweight, deployable shield protecting orbiting spacecraft against meteoroids and debris, and functions as barrier to conductive and radiative losses of heat. Shield made in four segments providing 360 degree coverage of cylindrical space-station module.

  11. Lightweight blast shield

    SciTech Connect

    Mixon, Larry C.; Snyder, George W.; Hill, Scott D.; Johnson, Gregory L.; Wlodarski, J. Frank; von Spakovsky, Alexis P.; Emerson, John D.; Cole, James M.; Tipton, John P.

    1991-01-01

    A tandem warhead missile arrangement that has a composite material housing structure with a first warhead mounted at one end and a second warhead mounted near another end of the composite structure with a dome shaped composite material blast shield mounted between the warheads to protect the second warhead from the blast of the first warhead.

  12. Electrostatic space radiation shielding

    NASA Astrophysics Data System (ADS)

    Tripathi, Ram K.; Wilson, John W.; Youngquist, Robert C.

    2008-09-01

    For the success of NASA’s new vision for space exploration to Moon, Mars and beyond, exposures from the hazards of severe space radiation in deep space long duration missions is ‘a must solve’ problem. The payload penalty demands a very stringent requirement on the design of the spacecrafts for human deep space missions. The exploration beyond low Earth orbit (LEO) to enable routine access of space will require protection from the hazards of the accumulated exposures of space radiation, Galactic Cosmic Rays (GCR) and Solar Particle Events (SPE), and minimizing the production of secondary radiation is a great advantage. There is a need to look to new horizons for newer technologies. The present investigation revisits electrostatic active radiation shielding and explores the feasibility of using the electrostatic shielding in concert with the state-of-the-art materials shielding and protection technologies. The full space radiation environment has been used, for the first time, to explore the feasibility of electrostatic shielding. The goal is to repel enough positive charge ions so that they miss the spacecraft without attracting thermal electrons. Conclusions are drawn for the future directions of space radiation protection.

  13. Neutron fluxes in radiotherapy rooms.

    PubMed

    Agosteo, S; Foglio Para, A; Maggioni, B

    1993-01-01

    The spatial distribution of the neutron flux, originated in an electron accelerator therapy room when energies above the threshold of (y,n) and (e,e'n) reactions are employed, is physically due to a direct flux, coming from the accelerator head, and to a flux diffused from the walls. In this work, the flux is described to a high degree of approximation by a set of functions whose spatial behavior is univocally determined by the angular distributions of the neutrons emitted from the shield of the accelerator head and diffused from the walls. The analytical results are verified with an extended series of Monte Carlo simulations obtained with the MCNP code.

  14. Flexible Multi-Shock Shield

    NASA Technical Reports Server (NTRS)

    Christiansen, Eric L. (Inventor); Crews, Jeanne L. (Inventor)

    2005-01-01

    Flexible multi-shock shield system and method are disclosed for defending against hypervelocity particles. The flexible multi-shock shield system and method may include a number of flexible bumpers or shield layers spaced apart by one or more resilient support layers, all of which may be encapsulated in a protective cover. Fasteners associated with the protective cover allow the flexible multi-shock shield to be secured to the surface of a structure to be protected.

  15. SSC environmental radiation shielding

    SciTech Connect

    Jackson, J.D.

    1987-07-01

    The environmental radiation shielding requirements of the SSC have been evaluated using currently available computational tools that incorporate the well known processes of energy loss and degradation of high energy particles into Monte Carlo computer codes. These tools permit determination of isodose contours in the matter surrounding a source point and therefore the specification of minimum thicknesses or extents of shielding in order to assure annual dose equivalents less than some specified design amount. For the general public the annual dose equivalent specified in the design is 10 millirem, small compared to the dose from naturally occurring radiation. The types of radiation fall into two classes for the purposes of shielding determinations-hadrons and muons. The sources of radiation at the SSC of concern for the surrounding environment are the interaction regions, the specially designed beam dumps into which the beams are dumped from time to time, and beam clean-up regions where stops remove the beam halo in order to reduce experimental backgrounds. A final, unlikely source of radiation considered is the accidental loss of the full beam at some point around the ring. Conservative choices of a luminosity of 10{sup 34} cm{sup {minus}2}s{sup {minus}1} and a beam current three times design have been made in calculating the required shielding and boundaries of the facility. In addition to determination of minimum distances for the annual dose equivalents, the question of possible radioactivity produced in nearby wells or in municipal water supplies is addressed. The designed shielding distances and beam dumps are such that the induced radioactivity in ground water is safely smaller than the levels permitted by EPA and international agencies.

  16. Spacecraft Electrostatic Radiation Shielding

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This project analyzed the feasibility of placing an electrostatic field around a spacecraft to provide a shield against radiation. The concept was originally proposed in the 1960s and tested on a spacecraft by the Soviet Union in the 1970s. Such tests and analyses showed that this concept is not only feasible but operational. The problem though is that most of this work was aimed at protection from 10- to 100-MeV radiation. We now appreciate that the real problem is 1- to 2-GeV radiation. So, the question is one of scaling, in both energy and size. Can electrostatic shielding be made to work at these high energy levels and can it protect an entire vehicle? After significant analysis and consideration, an electrostatic shield configuration was proposed. The selected architecture was a torus, charged to a high negative voltage, surrounding the vehicle, and a set of positively charged spheres. Van de Graaff generators were proposed as the mechanism to move charge from the vehicle to the torus to generate the fields necessary to protect the spacecraft. This design minimized complexity, residual charge, and structural forces and resolved several concerns raised during the internal critical review. But, it still is not clear if such a system is costeffective or feasible, even though several studies have indicated usefulness for radiation protection at energies lower than that of the galactic cosmic rays. Constructing such a system will require power supplies that can generate voltages 10 times that of the state of the art. Of more concern is the difficulty of maintaining the proper net charge on the entire structure and ensuring that its interaction with solar wind will not cause rapid discharge. Yet, if these concerns can be resolved, such a scheme may provide significant radiation shielding to future vehicles, without the excessive weight or complexity of other active shielding techniques.

  17. The 'Room within a Room' Concept for Monitored Warhead Dismantlement

    SciTech Connect

    Tanner, Jennifer E.; Benz, Jacob M.; White, Helen; McOmish, Sarah; Allen, Keir; Tolk, Keith; Weeks, George E.

    2014-12-01

    Over the past 10 years, US and UK experts have engaged in a technical collaboration with the aim of improving scientific and technological abilities in support of potential future nuclear arms control and non-proliferation agreements. In 2011 a monitored dismantlement exercise provided an opportunity to develop and test potential monitoring technologies and approaches. The exercise followed a simulated nuclear object through a dismantlement process and looked to explore, with a level of realism, issues surrounding device and material monitoring, chain of custody, authentication and certification of equipment, data management and managed access. This paper focuses on the development and deployment of the ‘room-within-a-room’ system, which was designed to maintain chain of custody during disassembly operations. A key challenge for any verification regime operating within a nuclear weapon complex is to provide the monitoring party with the opportunity to gather sufficient evidence, whilst protecting sensitive or proliferative information held by the host. The requirement to address both monitoring and host party concerns led to a dual function design which: • Created a controlled boundary around the disassembly process area which could provide evidence of unauthorised diversion activities. • Shielded sensitive disassembly operations from monitoring party observation. The deployed room-within-a-room was an integrated system which combined a number of chain of custody technologies (i.e. cameras, tamper indicating panels and enclosures, seals, unique identifiers and radiation portals) and supporting deployment procedures. This paper discusses the bounding aims and constraints identified by the monitoring and host parties with respect to the disassembly phase, the design of the room-within-a-room system, lessons learned during deployment, conclusions and potential areas of future work. Overall it was agreed that the room-within-a-room approach was effective but

  18. Shielding of substations against direct lightning strokes by shield wires

    SciTech Connect

    Chowdhuri, P. )

    1994-01-01

    A new analysis for shielding outdoor substations against direct lightning strokes by shield wires is proposed. The basic assumption of this proposed method is that any lightning stroke which penetrates the shields will cause damage. The second assumption is that a certain level of risk of failure must be accepted, such as one or two failures per 100 years. The proposed method, using electrogeometric model, was applied to design shield wires for two outdoor substations: (1) 161-kV/69-kV station, and (2) 500-kV/161-kV station. The results of the proposed method were also compared with the shielding data of two other substations.

  19. Noise modeling from high-permeability shields using Kirchhoff equations

    SciTech Connect

    Sandin, Henrik J; Volegov, Petr L; Espy, Michelle A; Matlashov, Andrei N; Savukov, Igor M; Schultz, Larry J

    2010-01-01

    Progress in the development of high-sensitivity magnetic-field measurements has stimulated interest in understanding magnetic noise of conductive materials, especially of magnetic shields (DC or rf) based on high-permeability materials and/or high-conductivity materials. For example, SQUIDs and atomic magnetometers have been used in many experiments with mu-metal shields, and additionally SQUID systems frequently have rf shielding based on thin conductive materials. Typical existing approaches to modeling noise only work with simple shield and sensor geometries while common experimental setups today consist of multiple sensor systems arbitrary shapes and complex shield geometries. With complex sensor arrays used in, for example, MEG and Ultra Low Field MRI studies the knowledge of the noise correlation between sensors is as important as the knowledge of the noise itself. This is crucial for incorporating efficient noise cancelation schemes for the system. We developed an approach that allows us to calculate the Johnson noise for any geometrically shaped shield and multiple sensor systems. The approach uses a fraction of the processing power of other approaches and with a multiple sensor system our approach not only calculates the noise for each sensor but it also calculates the noise correlation matrix between sensors. Here we will show the algorithm and examples where it can be implemented.

  20. Review of active radiation shielding developments

    NASA Astrophysics Data System (ADS)

    Battiston, Roberto

    The radiation risk due to ionizing particles is a critical issue for long duration manned space missions. The ionization losses in the materials of the spacecraft provide passive shielding effectively stopping low energy particles. However, the estimates of the material required to obtain an acceptable level of radiation result in a prohibitive mass. Active electromagnetic shields, which deflect the charged particles, have been considered as an alternative solution. During the last 10 years the interest in this area has grown. A study of active magnetic shielding based on high-temperature superconductors (HTS) was initiated in an ESA study in 2010, continued in the context of the NASA Innovative Advanced Concepts (NIAC) programs (2011-2014) as well as within a dedicated FP7 EU program, SR2S (2013-2015). The aim of these effort was to provide a realistic evaluation of the possibilities based on current technology levels as well extrapolating to reasonable technology advances expected during the next decade. The different configurations considered were assessed in terms of their technical feasibility and shielding efficiency. We present here a status report of the ongoing work and some preliminary results.

  1. Basement utility room (room 24; air handling room), near the ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Basement utility room (room 24; air handling room), near the west end of the combat operations center, looking southwest towards fan system one, air ducts, and walk-in filter rooms. The exterior equipment well is visible at the left - March Air Force Base, Strategic Air Command, Combat Operations Center, 5220 Riverside Drive, Moreno Valley, Riverside County, CA

  2. Roof Shield for Advance and Retreat Mining

    NASA Technical Reports Server (NTRS)

    Lewis, E. V.

    1985-01-01

    Shield sections change their configuration to suit mining mode. Articulation cylinders raise rear shield to advance position, and locking cylinders hold it there. To change to retreat position articulation cylinders lower shield. Locking pins at edge of outermost shield plate latch shield to chock base. Shield accommodates roof heights ranging from 36 to 60 inches (0.9 to 1.52 meters).

  3. A Historically Significant Shield for In Vivo Measurements

    SciTech Connect

    Lynch, Timothy P.

    2007-08-01

    Due to the ubiquitous nature of ionizing radiation, in vivo measurement systems designed to measure low levels of radionuclides in people are usually enclosed within a high density shield. Lead, steel, earth, and water are just some of the materials that have been and are being used to shield the detectors from radiations of cosmic, atmospheric, and terrestrial origin. At many Department of Energy sites, the counting room shields are constructed of pre-world War II steel to reduce the background levels to achieve measurements with low minimum detectable activities (MDA). This is one example of what is commonly called low background steel in the in vivo industry vernacular. The name arises from the fact the steel was manufactured prior to the beginning of atmospheric testing of nuclear weapons in the 1940s. Consequently, the steel is not likely to be contaminated with fission or activation products from fallout. For high energy photons (600 keV shielding significantly reduces the background levels. This is the story "swords-to-plowshare" of the unique steel that now forms a shielded room used at the In Vivo Radioassay and Research Facility (IVRRF) in Richland, Washington.

  4. Clinical uses of collagen shields.

    PubMed

    Poland, D E; Kaufman, H E

    1988-09-01

    Collagen shields immersed in tobramycin solution for one minute were applied to one eye each of 60 patients who had had cataract extraction, penetrating keratoplasty, or epikeratophakia or who had nonsurgical epithelial healing problems. The shields were well tolerated; one patient had the shield removed and one patient lost the shield in the early postoperative period. The surgical patients showed more rapid healing of epithelial defects after surgery with the use of the collagen shield. Patients with acute nonsurgical epithelial problems, such as contact lens abrasions and recurrent erosion, responded to the use of the collagen shield with improved healing. Patients with chronic epithelial defects responded poorly, presumably because underlying abnormalities in Bowman's layer prevented epithelial growth in the area of the defect. No infections were noted in any of the patients. The collagen shields appear to promote enhanced healing in patients with postsurgical and acute epithelial defects and to provide adequate antibiotic prophylaxis against infection in these vulnerable eyes.

  5. Composition for radiation shielding

    DOEpatents

    Kronberg, J.W.

    1994-08-02

    A composition for use as a radiation shield is disclosed. The shield has a depleted uranium core for absorbing gamma rays and a bismuth coating for preventing chemical corrosion and absorbing gamma rays. Alternatively, a sheet of gadolinium may be positioned between the uranium core and the bismuth coating for absorbing neutrons. The composition is preferably in the form of a container for storing materials that emit radiation such as gamma rays and neutrons. The container is preferably formed by casting bismuth around a pre-formed uranium container having a gadolinium sheeting, and allowing the bismuth to cool. The resulting container is a structurally sound, corrosion-resistant, radiation-absorbing container. 2 figs.

  6. Gas shielding apparatus

    DOEpatents

    Brandt, D.

    1984-06-05

    An apparatus for preventing oxidation by uniformly distributing inert shielding gas over the weld area of workpieces such as pipes being welded together. The apparatus comprises a chamber and a gas introduction element. The chamber has an annular top wall, an annular bottom wall, an inner side wall and an outer side wall connecting the top and bottom walls. One side wall is a screen and the other has a portion defining an orifice. The gas introduction element has a portion which encloses the orifice and can be one or more pipes. The gas introduction element is in fluid communication with the chamber and introduces inert shielding gas into the chamber. The inert gas leaves the chamber through the screen side wall and is dispersed evenly over the weld area.

  7. Gas shielding apparatus

    DOEpatents

    Brandt, Daniel

    1985-01-01

    An apparatus for preventing oxidation by uniformly distributing inert shielding gas over the weld area of workpieces such as pipes being welded together. The apparatus comprises a chamber and a gas introduction element. The chamber has an annular top wall, an annular bottom wall, an inner side wall and an outer side wall connecting the top and bottom walls. One side wall is a screen and the other has a portion defining an orifice. The gas introduction element has a portion which encloses the orifice and can be one or more pipes. The gas introduction element is in fluid communication with the chamber and introduces inert shielding gas into the chamber. The inert gas leaves the chamber through the screen side wall and is dispersed evenly over the weld area.

  8. Gas shielding apparatus

    DOEpatents

    Brandt, D.

    1985-12-31

    An apparatus is disclosed for preventing oxidation by uniformly distributing inert shielding gas over the weld area of workpieces such as pipes being welded together. The apparatus comprises a chamber and a gas introduction element. The chamber has an annular top wall, an annular bottom wall, an inner side wall and an outer side wall connecting the top and bottom walls. One side wall is a screen and the other has a portion defining an orifice. The gas introduction element has a portion which encloses the orifice and can be one or more pipes. The gas introduction element is in fluid communication with the chamber and introduces inert shielding gas into the chamber. The inert gas leaves the chamber through the screen side wall and is dispersed evenly over the weld area. 3 figs.

  9. Project BioShield

    DTIC Science & Technology

    2005-06-10

    to Congress. Expedited Peer Review . The Project BioShield Act of 2004 authorizes the HHS Secretary to use an expedited award process, rather than the...normal peer review process, for grants, contracts, and cooperative agreements related to biomedical countermeasure R&D activity, if the Secretary... peer review process will reduce the quality of the research.6 Peer review is designed to maximize the chances that only proposals with the greatest

  10. Project BioShield

    DTIC Science & Technology

    2006-09-27

    Expedited Peer Review . The Project BioShield Act of 2004 authorizes the HHS Secretary to use an expedited award process, rather than the normal peer ...such awards, or to many, will depend on what needs the Secretary deems pressing. Some scientists have expressed concerns that an expedited peer review process...will reduce the quality of the research.6 Peer review is designed to maximize the chances that only proposals with the greatest scientific

  11. MTR, TRA603. BASEMENT FLOOR PLAN. REACTOR SHIELDING, CANAL AND RABBIT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MTR, TRA-603. BASEMENT FLOOR PLAN. REACTOR SHIELDING, CANAL AND RABBIT CANAL, DEEP WELL STORAGE. DECONTAMINATION ROOM, VAULT, MONITOR ROOM, OFFICE, STAIRWAYS. BLAW-KNOX 3150-803-1, 7/1950. INL INDEX NO. 531-0603-00-098-100560, REV. 6. - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  12. Skylab Solar Shield

    NASA Technical Reports Server (NTRS)

    1973-01-01

    A sail like sunshade for possible use as a sunscreen for the Skylab Orbital Workshop (OWS) is shown being fabricated in the GE Building across the street from Johnson Space Center, Houston Texas. Three people help the steamstress feed the material through the sewing machine. The three-layered sunshade will be composed of a top layer of aluminized mylar, a middle layer of laminated nylon ripstop, and a bottom layer of thin nylon. Working on the sunshade are from left to right: Dale Gentry, Elizabeth Gauldin, Alyene Baker, and James H. Barnett Jr. Mrs. Baker, a GE employee, operates the double needle Singer sewing machine. Barnett is head of the Crew Equipment Development Section of JSC Crew Systems Division. Mrs. Gauldin is also with the Crew Systems Division. Gentry works for GE. The work shown here is part of the crash program underway to prepare a sunshield for Skylab to replace the orginal shield which was lost when Skylab 1 was launched on May 14, 1973. The improvised solar shield selected to be used will be carried to Earth orbit by the Skylab 2 crewman who will then deploy the reflective parasol to shade part of the OWS from the hot rays of the sun. Loss of the orginal sun shield has caused an overheating problem. in the Orbital Work Shop.

  13. Crumpled Heat Shield

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Phoenix Mars Lander's Surface Stereo Imager took this image of the spacecraft's crumpled heat shield on Sept. 16, 2008, the 111th Martian day of the mission.

    The 2-1/2 meter (about 8-1/2 feet) heat shield landed southeast of Phoenix, about halfway between the spacecraft and its backshell/parachute. The backshell/parachute touched ground 300 meters (1,000 ft) to the south of the lander.

    The dark area to the right of the heat shield is the 'bounce mark' it made on impact with the Red Planet. This image is the highest-resolution image that will likely be taken by the lander, and is part of the 1,500-image 'Happily Ever After' panorama.

    The Phoenix mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is led by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  14. Pure rotational spectra of PbSe and PbTe: potential function, Born-Oppenheimer breakdown, field shift effect and magnetic shielding.

    PubMed

    Giuliano, Barbara M; Bizzocchi, Luca; Cooke, Stephen; Banser, Deike; Hess, Mareike; Fritzsche, Juliane; Grabow, Jens-Uwe

    2008-04-21

    The pure rotational spectra of 41 isotopic species of PbSe and PbTe have been measured in their X 1Sigma+ electronic state with a resonator pulsed-jet Fourier transform microwave spectrometer. The molecules were prepared by laser ablation of suitable target rods and stabilised in supersonic jets of noble gas. Global multi-isotopologue analyses yielded spectroscopic Dunham parameters Y01, Y11, Y21, Y31, Y02, and Y12 for both species, as well as effective Born-Oppenheimer breakdown (BOB) coefficients delta01 for Pb, Se and Te. Unusual large values of the BOB parameters for Pb have been rationalized in terms of finite nuclear size (field shift) effect. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X 1Sigma+ electronic state of both PbSe and PbTe. Additionally, the magnetic hyperfine interactions produced by the uneven mass number A nuclei 207Pb, 77Se, 123Te, and 125Te were observed, yielding first determinations of the corresponding nuclear spin-rotation coupling constants.

  15. Large magnetic response in (Bi{sub 4}Nd)Ti{sub 3}(Fe{sub 0.5}Co{sub 0.5})O{sub 15} ceramic at room-temperature

    SciTech Connect

    Yang, F. J.; Su, P.; Wei, C.; Chen, X. Q.; Yang, C. P.; Cao, W. Q.

    2011-12-15

    Ceramics of Nd/Co co-substituted Bi{sub 5}Ti{sub 3}FeO{sub 15}, i.e., (Bi{sub 4}Nd)Ti{sub 3}(Fe{sub 0.5}Co{sub 0.5})O{sub 15} were prepared by the conventional solid-state reaction method. The X-ray diffraction pattern demonstrates that the sample of the layered perovskite phase was successfully obtained, even if little Bi-deficient pyrochlore Bi{sub 2}Ti{sub 2}O{sub 7} also existed. The ferroelectric and magnetic Curie temperatures were determined to be 1077 K and 497 K, respectively. The multiferroic property of the sample at room temperature was demonstrated by ferroelectric and magnetic measurements. Remarkably, by Nd/Co co-substituting, the sample exhibited large magnetic response with 2M{sub r} = 330 memu/g and 2H{sub c} = 562 Oe at applied magnetic field of 8 kOe at room temperature. The present work suggests the possibility of doped Bi{sub 5}Ti{sub 3}FeO{sub 15} as a potential multiferroic.

  16. Overview of active methods for shielding spacecraft from energetic space radiation.

    PubMed

    Townsend, L W

    2001-01-01

    During the 1960's and into the early 1970's, investigations were conducted related to the feasibility of using active radiation shielding methods, such as afforded by electromagnetic fields, as alternatives to passive, bulk material shielding to attenuate space radiations. These active concepts fall into four categories: (1) electrostatic fields; (2) plasma shields; (3) confined magnetic fields; and (4) unconfined magnetic fields. In nearly all of these investigations, consideration was given only to shielding against protons or electrons, or both. During the 1980's and 1990's there were additional studies related to proton shielding and some new studies regarding the efficacy of using active methods to shield from the high energy heavy ion (HZE particle) component of the galactic cosmic ray spectrum. In this overview, each concept category is reviewed and its applicability and limitations for the various types of space radiations are described. Recommendations for future research on this topic are made.

  17. Photoneutron production in the primary barriers of medical accelerator rooms.

    PubMed

    McGinley, P H

    1992-04-01

    Several radiation surveys, at medical linear accelerator facilities where lead or steel had been used with concrete to fabricate the primary barriers, revealed the existence of a sizable neutron field outside the shielding. This neutron field is produced by photoneutrons generated in the metal portion of the shield when the primary x-ray beam is aimed at the barrier. A method was developed to calculate the neutron dose-equivalent rate expected outside a primary shield when it is irradiated by a high-energy x-ray beam. It was found that the minimum photoneutron dose was produced when the metal part of the shield was positioned inside the treatment room in front of the concrete and also by using steel in place of lead. A thickness of less than or equal to 17 cm of metal on the inner surface of the shield produced only a slight increase in the neutron dose equivalent outside the barrier.

  18. Justification for Shielded Receiver Tube Additional Lead Shielding

    SciTech Connect

    BOGER, R.M.

    2000-04-11

    In order to reduce high radiation dose rates encountered when core sampling some radioactive waste tanks the addition of 240 lbs. of lead shielding is being considered to the shielded receiver tube on core sample trucks No.1, No.3 and No.4. The lead shielding is 4 inch diameter x 1/2 inch thick half rounds that have been installed around the SR tube over its' full length. Using three unreleased but independently reviewed structural analyses HNF-6018 justifies the addition of the lead shielding.

  19. Space mapping method for the design of passive shields

    NASA Astrophysics Data System (ADS)

    Sergeant, Peter; Dupré, Luc; Melkebeek, Jan

    2006-04-01

    The aim of the paper is to find the optimal geometry of a passive shield for the reduction of the magnetic stray field of an axisymmetric induction heater. For the optimization, a space mapping algorithm is used that requires two models. The first is an accurate model with a high computational effort as it contains finite element models. The second is less accurate, but it has a low computational effort as it uses an analytical model: the shield is replaced by a number of mutually coupled coils. The currents in the shield are found by solving an electrical circuit. Space mapping combines both models to obtain the optimal passive shield fast and accurately. The presented optimization technique is compared with gradient, simplex, and genetic algorithms.

  20. Barium ferrite decorated reduced graphene oxide nanocomposite for effective electromagnetic interference shielding.

    PubMed

    Verma, Meenakshi; Singh, Avanish Pratap; Sambyal, Pradeep; Singh, Bhanu Pratap; Dhawan, S K; Choudhary, Veena

    2015-01-21

    There is an increased interest in the development of high performance microwave shielding materials against electromagnetic pollution in recent years. Barium ferrite decorated reduced graphene oxide (BaFe12O19@RGO) nanocomposite was synthesized by a high energy ball milling technique and its electromagnetic properties were investigated in the frequency range of 12.4-18 GHz (Ku band). The results showed that barium ferrite (BaFe12O19) nanoparticles with an average particle size of 20-30 nm were well distributed and firmly anchored onto the surface of the reduced graphene oxide sheets. The obtained nanocomposite exhibited a saturation magnetization of 18.1 emu g(-1) at room temperature. The presence of BaFe12O19 nanoparticles in the nanocomposite enhances the space charge polarization, natural resonance, multiple scattering and the effective anisotropy energy leading to a high electromagnetic interference shielding effectiveness of 32 dB (∼99.9% attenuation) at a critical thickness of 3 mm. The results suggested that the as-prepared BaFe12O19@RGO nanocomposite showed great potential as an effective candidate for a new type of microwave absorbing material.

  1. Desert Shield/Storm Logistics

    DTIC Science & Technology

    1993-04-15

    Wc This document may not be retee for open publiarion until it has bm deaed by the Vproprnite military service or gmeanen agency. DESERT SHIELD /STORM...capture what had occurred during Operations DESERT SHIELD and STORM, the commanders of the Division Support Command of the 24th Infantry Division...Mechanized) held a ful. day of discussion centering on what occurted during Operation DESERT STORM and its preceding operation, DESERT SHIELD . The entire

  2. Balloonlike Shields Against Fast Projectiles

    NASA Technical Reports Server (NTRS)

    Rucker, Michelle A.

    1993-01-01

    Report proposes use of flexible gas-filled or liquid-filled pouches to shield spacecraft against impacts by small meteoroids and orbiting debris traveling at speeds approximately greater than 2 km/s. Shields made in various forms reminiscent of balloons, pillows, air mattresses, or sealed-air-bubble packing material. Serve as lightweight, easily installed alternatives to heavier, rigid shields made of space aluminum sheets custom-designed and attached to spacecraft only with great difficulty and expense.

  3. Watching a disappearing shield

    SciTech Connect

    Stolarski, R.S.

    1988-10-01

    The remote-sensing techniques used to monitor atmospheric ozone levels are reviewed, and recent results are discussed. The importance of the ozone layer as a shield for UV radiation is stressed, and the impact of human activities generating ozone-destroying compounds is considered. Ground-based, airborne, balloon-borne, and satellite remote-sensing methods are shown to complement each other to provide both global coverage and detailed structural information. Data obtained with the Nimbus-7 TOMS and solar-backscatter UV instruments are presented in graphs and briefly characterized.

  4. Spacecraft ceramic protective shield

    NASA Technical Reports Server (NTRS)

    Larriva, Rene F. (Inventor); Nelson, Anne (M.); Czechanski, James G. (Inventor); Poff, Ray E. (Inventor)

    1995-01-01

    A low areal density protective shield apparatus, and method for making same, for protecting spacecraft structures from impact with hypervelocity objects, including a bumper member comprising a bumper ceramic layer, a bumper shock attenuator layer, and a bumper confining layer. The bumper ceramic layer can be SiC or B.sub.4 C; the bumper shock attenuator layer can be zirconia felt; and the bumper confining layer can be aluminum. A base armor member can be spaced from the bumper member and a ceramic fiber-based curtain can be positioned between the bumper and base armor members.

  5. 15. ROOMS 48 AND 49, LOOKING SOUTH FROM ENTRANCE TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. ROOMS 48 AND 49, LOOKING SOUTH FROM ENTRANCE TO ROOM 47. THE OAK CABINETS ARE USED TO STORE ROCK CORE SAMPLES. - U.S. Geological Survey, Rock Magnetics Laboratory, 345 Middlefield Road, Menlo Park, San Mateo County, CA

  6. Hypervelocity impact shield

    NASA Technical Reports Server (NTRS)

    Cour-Palais, Burton G. (Inventor); Crews, Jeanne Lee (Inventor)

    1991-01-01

    A hypervelocity impact shield and method for protecting a wall structure, such as a spacecraft wall, from impact with particles of debris having densities of about 2.7 g/cu cm and impact velocities up to 16 km/s are disclosed. The shield comprises a stack of ultra thin sheets of impactor disrupting material supported and arranged by support means in spaced relationship to one another and mounted to cover the wall in a position for intercepting the particles. The sheets are of a number and spacing such that the impacting particle and the resulting particulates of the impacting particle and sheet material are successively impact-shocked to a thermal state of total melt and/or vaporization to a degree as precludes perforation of the wall. The ratio of individual sheet thickness to the theoretical diameter of particles of debris which may be of spherical form is in the range of 0.03 to 0.05. The spacing between adjacent sheets is such that the debris cloud plume of liquid and vapor resulting from an impacting particle penetrating a sheet does not puncture the next adjacent sheet prior to the arrival thereat of fragment particulates of sheet material and the debris particle produced by a previous impact.

  7. PBF Cubicle 13. Shield wall details illustrate shielding technique of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    PBF Cubicle 13. Shield wall details illustrate shielding technique of stepped penetrations and brick layout scheme for valve stem extension sleeve. Aerojet Nuclear Company. Date: May 1976. INEEL index no. 761-0620-00-400-195280 - Idaho National Engineering Laboratory, SPERT-I & Power Burst Facility Area, Scoville, Butte County, ID

  8. Drip Shield Emplacement Gantry Concept

    SciTech Connect

    Silva, R.A.; Cron, J.

    2000-03-29

    This design analysis has shown that, on a conceptual level, the emplacement of drip shields is feasible with current technology and equipment. A plan for drip shield emplacement was presented using a Drip Shield Transporter, a Drip Shield Emplacement Gantry, a locomotive, and a Drip Shield Gantry Carrier. The use of a Drip Shield Emplacement Gantry as an emplacement concept results in a system that is simple, reliable, and interfaces with the numerous other exising repository systems. Using the Waste Emplacement/Retrieval System design as a basis for the drip shield emplacement concept proved to simplify the system by using existing equipment, such as the gantry carrier, locomotive, Electrical and Control systems, and many other systems, structures, and components. Restricted working envelopes for the Drip Shield Emplacement System require further consideration and must be addressed to show that the emplacement operations can be performed as the repository design evolves. Section 6.1 describes how the Drip Shield Emplacement System may use existing equipment. Depending on the length of time between the conclusion of waste emplacement and the commencement of drip shield emplacement, this equipment could include the locomotives, the gantry carrier, and the electrical, control, and rail systems. If the exisiting equipment is selected for use in the Drip Shield Emplacement System, then the length of time after the final stages of waste emplacement and start of drip shield emplacement may pose a concern for the life cycle of the system (e.g., reliability, maintainability, availability, etc.). Further investigation should be performed to consider the use of existing equipment for drip shield emplacement operations. Further investigation will also be needed regarding the interfaces and heat transfer and thermal effects aspects. The conceptual design also requires further design development. Although the findings of this analysis are accurate for the assumptions made

  9. Radiation Shielding Optimization on Mars

    NASA Technical Reports Server (NTRS)

    Slaba, Tony C.; Mertens, Chris J.; Blattnig, Steve R.

    2013-01-01

    Future space missions to Mars will require radiation shielding to be optimized for deep space transit and an extended stay on the surface. In deep space, increased shielding levels and material optimization will reduce the exposure from most solar particle events (SPE) but are less effective at shielding against galactic cosmic rays (GCR). On the surface, the shielding provided by the Martian atmosphere greatly reduces the exposure from most SPE, and long-term GCR exposure is a primary concern. Previous work has shown that in deep space, additional shielding of common materials such as aluminum or polyethylene does not significantly reduce the GCR exposure. In this work, it is shown that on the Martian surface, almost any amount of aluminum shielding increases exposure levels for humans. The increased exposure levels are attributed to neutron production in the shield and Martian regolith as well as the electromagnetic cascade induced in the Martian atmosphere. This result is significant for optimization of vehicle and shield designs intended for the surface of Mars.

  10. Reflective Shields for Artificial Satellites

    NASA Technical Reports Server (NTRS)

    Bouquet, F. L.

    1986-01-01

    Report proposes reflective shield that protects spacecraft from radiant energy. Also gives some protection against particle beams and cosmic rays. Conceptual shield essentially advanced version of decorative multifaceted mirror balls often hung over dance floors. Mirror facets disperse radiant energy in many directions.

  11. Lunar Surface Reactor Shielding Study

    NASA Technical Reports Server (NTRS)

    King, Shawn; Lipinksi, Ronald; McAlpine, William

    2006-01-01

    Nuclear reactor system could provide power to support a long term human exploration to the moon. Such a system would require shielding to protect astronauts from its emitted radiations. Shielding studies have been performed for a Gas Cooled Reactor (GCR) system because it is considered to be the most suitable nuclear reactor system available for lunar exploration, based on its tolerance of oxidizing lunar regolith and its good conversion efficiency (Wright, 2003). The goals of the shielding studies were to provide optimal material shielding configuration that reduces the dose (rem) to the required level in order to protect astronauts, and to estimate the mass of regolith that would provide an equivalent protective effect if it were used as the shielding material. All calculations were performed using MCNPX code, a Monte Carlo transport code.

  12. Portable convertible blast effects shield

    DOEpatents

    Pastrnak, John W.; Hollaway, Rocky; Henning, Carl D.; Deteresa, Steve; Grundler, Walter; Hagler, Lisle B.; Kokko, Edwin; Switzer, Vernon A.

    2011-03-15

    A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more frusto-conically-tapered telescoping rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration by the friction fit of adjacent pairs of frusto-conically-tapered rings to each other.

  13. Portable convertible blast effects shield

    DOEpatents

    Pastrnak, John W.; Hollaway, Rocky; Henning, Carl D.; Deteresa, Steve; Grundler, Walter; Hagler, Lisle B.; Kokko, Edwin; Switzer, Vernon A

    2007-05-22

    A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more telescoping cylindrical rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration, such as by click locks.

  14. Portable convertible blast effects shield

    SciTech Connect

    Pastrnak, John W.; Hollaway, Rocky; Henning, Carl D.; Deteresa, Steve; Grundler, Walter; Hagler,; Lisle B.; Kokko, Edwin; Switzer, Vernon A

    2010-10-26

    A rapidly deployable portable convertible blast effects shield/ballistic shield includes a set two or more telescoping cylindrical rings operably connected to each other to convert between a telescopically-collapsed configuration for storage and transport, and a telescopically-extended upright configuration forming an expanded inner volume. In a first embodiment, the upright configuration provides blast effects shielding, such as against blast pressures, shrapnel, and/or fire balls. And in a second embodiment, the upright configuration provides ballistic shielding, such as against incoming weapons fire, shrapnel, etc. Each ring has a high-strength material construction, such as a composite fiber and matrix material, capable of substantially inhibiting blast effects and impinging projectiles from passing through the shield. And the set of rings are releasably securable to each other in the telescopically-extended upright configuration, such as by click locks.

  15. Welding shield for coupling heaters

    DOEpatents

    Menotti, James Louis

    2010-03-09

    Systems for coupling end portions of two elongated heater portions and methods of using such systems to treat a subsurface formation are described herein. A system may include a holding system configured to hold end portions of the two elongated heater portions so that the end portions are abutted together or located near each other; a shield for enclosing the end portions, and one or more inert gas inlets configured to provide at least one inert gas to flush the system with inert gas during welding of the end portions. The shield may be configured to inhibit oxidation during welding that joins the end portions together. The shield may include a hinged door that, when closed, is configured to at least partially isolate the interior of the shield from the atmosphere. The hinged door, when open, is configured to allow access to the interior of the shield.

  16. Silica heat shield sizing

    NASA Technical Reports Server (NTRS)

    Ebbesmeyer, L. H.; Christensen, H. E.

    1975-01-01

    The sensitivity of silica heat shield requirements to gap width, tile edge radius, and heat transfer distribution within tile gaps was investigated. A two-dimensional thermal model was modified and used to determine the effect of two dimensional heat transfer distributions at high temperature reusable surface insulation edges on shuttle thermal protection system (TPS) requirements. The sensitivity of TPS requirements to coating thickness, emissivity, substructure thickness, and changes in gap heating for several locations on shuttle was also studied. An inverse solution technique was applied to temperature data obtained in the Ames 20 MW turbulent duct in order to examine the effect of tile edge radius on TPS requirements. The derived heating values were then used to predict TPS requirements. Results show that increasing tile radius reduces TPS requirements.

  17. NEUTRON SHIELDING STRUCTURE

    DOEpatents

    Mattingly, J.T.

    1962-09-25

    A lightweight neutron shielding structure comprises a honeycomb core which is filled with a neutron absorbing powder. The honeycomb core is faced with parallel planar facing sheets to form a lightweight rigid unit. Suitable absorber powders are selected from among the following: B, B/sub 4/C, B/sub 2/O/ sub 3/, CaB/sub 6/, Li/sub 2/CO3, LiOH, LiBO/sub 2/, Li/s ub 2/O. The facing sheets are constructed of a neutron moderating material, so that fast neutrons will be moderated while traversing the facing sheets, and ultimately be absorbed by the absorber powder in the honeycomb. Beryllium is a preferred moderator material for use in the facing sheets. The advantage of the structure is that it combines the rigidity and light weight of a honeycomb construction with the neutron absorption properties of boron and lithium. (AEC)

  18. Green synthesis of the Cu/Fe3O4 nanoparticles using Morinda morindoides leaf aqueous extract: A highly efficient magnetically separable catalyst for the reduction of organic dyes in aqueous medium at room temperature

    NASA Astrophysics Data System (ADS)

    Nasrollahzadeh, Mahmoud; Atarod, Monireh; Sajadi, S. Mohammad

    2016-02-01

    This paper reports the green and in-situ preparation of the Cu/Fe3O4 magnetic nanocatalyst synthesized using Morinda morindoides leaf extract without stabilizers or surfactants. The catalyst was characterized by XRD, SEM, EDS, UV-visible, TEM, VSM and TGA-DTA. The catalytic performance of the resulting nanocatalyst was examined for the reduction of 4-nitrophenol (4-NP), Congo red (CR) and Rhodamine B (RhB) in an environmental friendly medium at room temperature. The catalyst was recovered using an external magnet and reused several times without appreciable loss of its catalytic activity. In addition, the stability of the recycled catalyst has been proved by SEM and EDS techniques.

  19. Adverse shielding of the heating field and high ohmic loss introduced by electrostatic shields employed in radio-frequency heating of plasma

    SciTech Connect

    Faulconer, D.W.

    1983-07-01

    The electrostatic shields now commonly employed to shield antennas in the heating of plasma in the ion cyclotron frequency range are shown to reduce the specific radiation resistance of a long narrow antenna in the presence of plasma by a significant factor (on the order of 2/3 for a typical double-array shield) due to the effect of magnetic shielding of the magnetosonic polarization. An allied change in antenna specific inductance is also found. These effects are shown to diminish with increase in antenna width and should pose no major problem for the wide antennas projected for use in fusion experiments. In addition to the foregoing effects which are not ohmically dissipative in essence, electrostatic shields are also shown to introduce surprisingly high ohmic loss, this being of potential importance in shield design. The dependences of the above magnetic and ohmic phenomena on shield parameters are given and a shield design minimizing them is presented. Their repercussion on coupling efficiency and on the excitation voltage necessary for a given power flux from the antenna is discussed.

  20. Lunar Surface Reactor Shielding Study

    SciTech Connect

    Kang, Shawn; McAlpine, William; Lipinski, Ronald

    2006-01-20

    A nuclear reactor system could provide power to support long term human exploration of the moon. Such a system would require shielding to protect astronauts from its emitted radiations. Shielding studies have been performed for a Gas Cooled Reactor system because it is considered to be the most suitable nuclear reactor system available for lunar exploration, based on its tolerance of oxidizing lunar regolith and its good conversion efficiency. The goals of the shielding studies were to determine a material shielding configuration that reduces the dose (rem) to the required level in order to protect astronauts, and to estimate the mass of regolith that would provide an equivalent protective effect if it were used as the shielding material. All calculations were performed using MCNPX, a Monte Carlo transport code. Lithium hydride must be kept between 600 K and 700 K to prevent excessive swelling from large amounts of gamma or neutron irradiation. The issue is that radiation damage causes separation of the lithium and the hydrogen, resulting in lithium metal and hydrogen gas. The proposed design uses a layer of B4C to reduce the combined neutron and gamma dose to below 0.5Grads before the LiH is introduced. Below 0.5Grads the swelling in LiH is small (less than about 1%) for all temperatures. This approach causes the shield to be heavier than if the B4C were replaced by LiH, but it makes the shield much more robust and reliable.

  1. Optimized Shielding and Fabrication Techniques for TiN and Al Microwave Resonators

    NASA Astrophysics Data System (ADS)

    Kreikebaum, John Mark; Kim, Eunseong; Livingston, William; Dove, Allison; Calusine, Gregory; Hover, David; Rosenberg, Danna; Oliver, William; Siddiqi, Irfan

    We present a systematic study of the effects of shielding and packaging on the internal quality factor (Qi) of Al and TiN microwave resonators designed for use in qubit readout. Surprisingly, Qi =1.3x106 TiN samples investigated at 100 mK exhibited no significant changes in linewidth when operated without magnetic shielding and in an open cryo-package. In contrast, Al resonators showed systematic improvement in Qi with each successive shield. Measurements were performed in an adiabatic demagnetization refrigerator, where typical ambient fields of 0.2 mT are present at the sample stage. We discuss the effect of 100 mK and 500 mK Cu radiation shields and cryoperm magnetic shielding on resonator Q as a function of temperature and input power in samples prepared with a variety of surface treatments, fabrication recipes, and embedding circuits. This research was supported by the ARO and IARPA.

  2. X-band frequency response and electromagnetic interference shielding in multiferroic BiFeO3 nanomaterials

    NASA Astrophysics Data System (ADS)

    Reshi, Hilal Ahmad; Singh, Avanish Pratap; Pillai, Shreeja; Para, Touseef Ahmad; Dhawan, S. K.; Shelke, Vilas

    2016-10-01

    The presence of electric dipoles, magnetic dipoles and mobile charges is a prerequisite for electromagnetic interference (EMI) shielding materials. Here, we demonstrate that multiferroic compound with incipient ensemble of electric and magnetic dipoles can perform as an EMI shielding material. We synthesized single phase BiFeO3 nanomaterial and studied complex electromagnetic properties in an X-band frequency region. A shielding effectiveness up to 11 dB with a major contribution from absorption was observed in the BiFeO3 nanomaterials. An auxiliary functionality of radiation shielding is revealed in the multiferroic BiFeO3 compound.

  3. New Materials for EMI Shielding

    NASA Technical Reports Server (NTRS)

    Gaier, James R.

    1999-01-01

    Graphite fibers intercalated with bromine or similar mixed halogen compounds have substantially lower resistivity than their pristine counterparts, and thus should exhibit higher shielding effectiveness against electromagnetic interference. The mechanical and thermal properties are nearly unaffected, and the shielding of high energy x-rays and gamma rays is substantially increased. Characterization of the resistivity of the composite materials is subtle, but it is clear that the composite resistivity is substantially lowered. Shielding effectiveness calculations utilizing a simple rule of mixtures model yields results that are consistent with available data on these materials.

  4. NEUTRON ABSORPTION AND SHIELDING DEVICE

    DOEpatents

    Axelrad, I.R.

    1960-06-21

    A neutron absorption and shielding device is described which is adapted for mounting in a radiation shielding wall surrounding a radioactive area through which instrumentation leads and the like may safely pass without permitting gamma or neutron radiation to pass to the exterior. The shielding device comprises a container having at least one nonrectilinear tube or passageway means extending therethrough, which is adapted to contain instrumentation leads or the like, a layer of a substance capable of absorbing gamma rays, and a solid resinous composition adapted to attenuate fast-moving neutrons and capture slow- moving or thermal neutrons.

  5. Room temperature ferromagnetism with large magnetic moment at low field in rare-earth-doped BiFeO₃ thin films.

    PubMed

    Kim, Tae-Young; Hong, Nguyen Hoa; Sugawara, T; Raghavender, A T; Kurisu, M

    2013-05-22

    Thin films of rare earth (RE)-doped BiFeO3 (where RE=Sm, Ho, Pr and Nd) were grown on LaAlO3 substrates by using the pulsed laser deposition technique. All the films show a single phase of rhombohedral structure with space group R3c. The saturated magnetization in the Ho- and Sm-doped films is much larger than the values reported in the literature, and is observed at quite a low field of 0.2 T. For Ho and Sm doping, the magnetization increases as the film becomes thinner, suggesting that the observed magnetism is mostly due to a surface effect. In the case of Nd doping, even though the thin film has a large magnetic moment, the mechanism seems to be different.

  6. Understanding the magnetic interaction between intrinsic defects and impurity ions in room-temperature ferromagnetic Mg1-x Fe x O thin films

    NASA Astrophysics Data System (ADS)

    Kapilashrami, Mukes; Wang, Yung Jui; Li, Xin; Glans, Per-Anders; Fang, Mei; Riazanova, Anastasia V.; Belova, Lyubov M.; Rao, K. V.; Luo, Yi; Barbiellini, Bernardo; Lin, Hsin; Markiewicz, Robert; Bansil, Arun; Hussain, Zahid; Guo, Jinghua

    2016-04-01

    Understanding the nature and characteristics of the intrinsic defects and impurities in the dielectric barrier separating the ferromagnetic electrodes in a magnetic tunneling junction is of great importance for understanding the often observed ‘barrier-breakdown’ therein. In this connection, we present herein systematic experimental (SQUID and synchrotron-radiation-based x-ray absorption spectroscopy) and computational studies on the electronic and magnetic properties of Mg1-x Fe x O thin films. Our studies reveal: (i) defect aggregates comprised of basic and trimer units (Fe impurity coupled to 1 or 2 Mg vacancies) and (ii) existence of two competing magnetic orders, defect- and dopant-induced, with spin densities aligning anti-parallel if the trimer is present in the oxide matrix. These findings open up new avenues for designing tunneling barriers with high endurance and tunneling effect upon tuning the concentration/distribution of the two magnetic orders.

  7. Shielding synchrotron light sources: Advantages of circular shield walls tunnels

    SciTech Connect

    Kramer, S. L.; Ghosh, V. J.; Breitfeller, M.

    2016-04-26

    Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produce significantly higher neutron component dose to the experimental floor than lower energy injection and ramped operations. High energy neutrons produced in the forward direction from thin target beam losses are a major component of the dose rate outside the shield walls of the tunnel. The convention has been to provide thicker 90° ratchet walls to reduce this dose to the beam line users. We present an alternate circular shield wall design, which naturally and cost effectively increases the path length for this forward radiation in the shield wall and thereby substantially decreasing the dose rate for these beam losses. Here, this shield wall design will greatly reduce the dose rate to the users working near the front end optical components but will challenge the beam line designers to effectively utilize the longer length of beam line penetration in the shield wall. Additional advantages of the circular shield wall tunnel are that it's simpler to construct, allows greater access to the insertion devices and the upstream in tunnel beam line components, as well as reducing the volume of concrete and therefore the cost of the shield wall.

  8. Shielding synchrotron light sources: Advantages of circular shield walls tunnels

    DOE PAGES

    Kramer, S. L.; Ghosh, V. J.; Breitfeller, M.

    2016-04-26

    Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produce significantly higher neutron component dose to the experimental floor than lower energy injection and ramped operations. High energy neutrons producedmore » in the forward direction from thin target beam losses are a major component of the dose rate outside the shield walls of the tunnel. The convention has been to provide thicker 90° ratchet walls to reduce this dose to the beam line users. We present an alternate circular shield wall design, which naturally and cost effectively increases the path length for this forward radiation in the shield wall and thereby substantially decreasing the dose rate for these beam losses. Here, this shield wall design will greatly reduce the dose rate to the users working near the front end optical components but will challenge the beam line designers to effectively utilize the longer length of beam line penetration in the shield wall. Additional advantages of the circular shield wall tunnel are that it's simpler to construct, allows greater access to the insertion devices and the upstream in tunnel beam line components, as well as reducing the volume of concrete and therefore the cost of the shield wall.« less

  9. Shielding synchrotron light sources: Advantages of circular shield walls tunnels

    NASA Astrophysics Data System (ADS)

    Kramer, S. L.; Ghosh, V. J.; Breitfeller, M.

    2016-08-01

    Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produce significantly higher neutron component dose to the experimental floor than lower energy injection and ramped operations. High energy neutrons produced in the forward direction from thin target beam losses are a major component of the dose rate outside the shield walls of the tunnel. The convention has been to provide thicker 90° ratchet walls to reduce this dose to the beam line users. We present an alternate circular shield wall design, which naturally and cost effectively increases the path length for this forward radiation in the shield wall and thereby substantially decreasing the dose rate for these beam losses. This shield wall design will greatly reduce the dose rate to the users working near the front end optical components but will challenge the beam line designers to effectively utilize the longer length of beam line penetration in the shield wall. Additional advantages of the circular shield wall tunnel are that it's simpler to construct, allows greater access to the insertion devices and the upstream in tunnel beam line components, as well as reducing the volume of concrete and therefore the cost of the shield wall.

  10. Locker Room Talk.

    ERIC Educational Resources Information Center

    Fickes, Michael

    1999-01-01

    Examines the trends in college and university sports and recreation center locker rooms as envisioned by a specialist. Features of the modern locker room and the different levels of locker room design are explained. Final comments discuss whether college and university facility managers are inclined to move to high-end locker rooms. (GR)

  11. Radiation shielding for neutron guides

    NASA Astrophysics Data System (ADS)

    Ersez, T.; Braoudakis, G.; Osborn, J. C.

    2006-11-01

    Models of the neutron guide shielding for the out of bunker guides on the thermal and cold neutron beam lines of the OPAL Reactor (ANSTO) were constructed using the Monte Carlo code MCNP 4B. The neutrons that were not reflected inside the guides but were absorbed by the supermirror (SM) layers were noted to be a significant source of gammas. Gammas also arise from neutrons absorbed by the B, Si, Na and K contained in the glass. The proposed shielding design has produced compact shielding assemblies. These arrangements are consistent with safety requirements, floor load limits, and cost constraints. To verify the design a prototype was assembled consisting of 120 mm thick Pb(96%)Sb(4%) walls resting on a concrete block. There was good agreement between experimental measurements and calculated dose rates for bulk shield regions.

  12. Structural/Radiation-Shielding Epoxies

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Smith, Joseph G.; Hinkley, Jeffrey; Blattnig, Steve; Delozier, Donavon M.; Watson, Kent A.; Ghose, Sayata

    2009-01-01

    A development effort was directed toward formulating epoxy resins that are useful both as structural materials and as shielding against heavy-ion radiation. Hydrogen is recognized as the best element for absorbing heavy-ion radiation, and high-hydrogen-content polymers are now in use as shielding materials. However, high-hydrogen-content polymers (e.g. polyethylene) are typically not good structural materials. In contrast, aromatic polymers, which contain smaller amounts of hydrogen, often have the strength necessary for structural materials. Accordingly, the present development effort is based on the concept that an ideal structural/ heavy-ion-radiation-shielding material would be a polymer that contains sufficient hydrogen (e.g., in the form of aliphatic molecular groups) for radiation shielding and has sufficient aromatic content for structural integrity.

  13. Heat Shield Flank Close Up

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image from NASA's Mars Exploration Rover Opportunity features an up-close view of the flank piece of the rover's broken heat shield.

    The rover spent 36 sols investigating how the severe heating during entry through the atmosphere affected the heat shield. The most obvious is the fact that the heat shield inverted upon impact. Overall, engineers were interested in evaluating the performance of the heat shield's thermal protection system.

    This is the the panormamic camera team's best current attempt at generating a 'true color' view of what this scene would look like if viewed by a human on Mars. It was generated from a mathematical combination of six calibrated, left-eye panoramic camera images acquired around 3:07 p.m. local solar time on Opportunity's sol 331 (Dec. 28, 2004) using filters ranging in wavelengths from 430 to 750 nanometers.

  14. Composite Aerogel Multifoil Protective Shielding

    NASA Technical Reports Server (NTRS)

    Jones, Steven M.

    2013-01-01

    New technologies are needed to survive the temperatures, radiation, and hypervelocity particles that exploration spacecraft encounter. Multilayer insulations (MLIs) have been used on many spacecraft as thermal insulation. Other materials and composites have been used as micrometeorite shielding or radiation shielding. However, no material composite has been developed and employed as a combined thermal insulation, micrometeorite, and radiation shielding. By replacing the scrims that have been used to separate the foil layers in MLIs with various aerogels, and by using a variety of different metal foils, the overall protective performance of MLIs can be greatly expanded to act as thermal insulation, radiation shielding, and hypervelocity particle shielding. Aerogels are highly porous, low-density solids that are produced by the gelation of metal alkoxides and supercritical drying. Aerogels have been flown in NASA missions as a hypervelocity particle capture medium (Stardust) and as thermal insulation (2003 MER). Composite aerogel multifoil protective shielding would be used to provide thermal insulation, while also shielding spacecraft or components from radiation and hypervelocity particle impacts. Multiple layers of foil separated by aerogel would act as a thermal barrier by preventing the transport of heat energy through the composite. The silica aerogel would act as a convective and conductive thermal barrier, while the titania powder and metal foils would absorb and reflect the radiative heat. It would also capture small hypervelocity particles, such as micrometeorites, since it would be a stuffed, multi-shock Whipple shield. The metal foil layers would slow and break up the impacting particles, while the aerogel layers would convert the kinetic energy of the particles to thermal and mechanical energy and stop the particles.

  15. Thermal neutron shield and method of manufacture

    DOEpatents

    Metzger, Bert Clayton; Brindza, Paul Daniel

    2014-03-04

    A thermal neutron shield comprising boron shielding panels with a high percentage of the element Boron. The panel is least 46% Boron by weight which maximizes the effectiveness of the shielding against thermal neutrons. The accompanying method discloses the manufacture of boron shielding panels which includes enriching the pre-cursor mixture with varying grit sizes of Boron Carbide.

  16. Room temperature ferroelectric and magnetic investigations and detailed phase analysis of Aurivillius phase Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Co{sub 0.3}O{sub 15} thin films

    SciTech Connect

    Keeney, Lynette; Kulkarni, Santosh; Deepak, Nitin; Schmidt, Michael; Petkov, Nikolay; Zhang, Panfeng F.; Roy, Saibal; Pemble, Martyn E.; Whatmore, Roger W.; Cavill, Stuart

    2012-09-01

    Aurivillius phase Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Co{sub 0.3}O{sub 15} (BTF7C3O) thin films on {alpha}-quartz substrates were fabricated by a chemical solution deposition method and the room temperature ferroelectric and magnetic properties of this candidate multiferroic were compared with those of thin films of Mn{sup 3+} substituted, Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Mn{sub 0.3}O{sub 15} (BTF7M3O). Vertical and lateral piezoresponse force microscopy (PFM) measurements of the films conclusively demonstrate that BTF7C3O and BTF7M3O thin films are piezoelectric and ferroelectric at room temperature, with the major polarization vector in the lateral plane of the films. No net magnetization was observed for the in-plane superconducting quantum interference device (SQUID) magnetometry measurements of BTF7M3O thin films. In contrast, SQUID measurements of the BTF7C3O films clearly demonstrated ferromagnetic behavior, with a remanent magnetization, B{sub r}, of 6.37 emu/cm{sup 3} (or 804 memu/g), remanent moment = 4.99 Multiplication-Sign 10{sup -5} emu. The BTF7C3O films were scrutinized by x-ray diffraction, high resolution transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive x-ray analysis mapping to assess the prospect of the observed multiferroic properties being intrinsic to the main phase. The results of extensive micro-structural phase analysis demonstrated that the BTF7C3O films comprised of a 3.95% Fe/Co-rich spinel phase, likely CoFe{sub 2-x}Ti{sub x}O{sub 4}, which would account for the observed magnetic moment in the films. Additionally, x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) imaging confirmed that the majority of magnetic response arises from the Fe sites of Fe/Co-rich spinel phase inclusions. While the magnetic contribution from the main phase could not be determined by the XMCD-PEEM images, these data however imply that the Bi{sub 5}Ti{sub 3}Fe{sub 0.7}Co{sub 0.3}O{sub 15} thin

  17. Neutronic reactor thermal shield

    DOEpatents

    Lowe, Paul E.

    1976-06-15

    1. The combination with a plurality of parallel horizontal members arranged in horizontal and vertical rows, the spacing of the members in all horizontal rows being equal throughout, the spacing of the members in all vertical rows being equal throughout; of a shield for a nuclear reactor comprising two layers of rectangular blocks through which the members pass generally perpendicularly to the layers, each block in each layer having for one of the members an opening equally spaced from vertical sides of the block and located closer to the top of the block than the bottom thereof, whereby gravity tends to make each block rotate about the associated member to a position in which the vertical sides of the block are truly vertical, the openings in all the blocks of one layer having one equal spacing from the tops of the blocks, the openings in all the blocks of the other layer having one equal spacing from the tops of the blocks, which spacing is different from the corresponding spacing in the said one layer, all the blocks of both layers having the same vertical dimension or length, the blocks of both layers consisting of relatively wide blocks and relatively narrow blocks, all the narrow blocks having the same horizontal dimension or width which is less than the horizontal dimension or width of the wide blocks, which is the same throughout, each layer consisting of vertical rows of narrow blocks and wide blocks alternating with one another, each vertical row of narrow blocks of each layer being covered by a vertical row of wide blocks of the other layer which wide blocks receive the same vertical row of members as the said each vertical row of narrow blocks, whereby the rectangular perimeters of each block of each layer is completely out of register with that of each block in the other layer.

  18. Novel room temperature ferromagnetic semiconductors

    SciTech Connect

    Gupta, Amita

    2004-06-01

    Today's information world, bits of data are processed by semiconductor chips, and stored in the magnetic disk drives. But tomorrow's information technology may see magnetism (spin) and semiconductivity (charge) combined in one 'spintronic' device that exploits both charge and 'spin' to carry data (the best of two worlds). Spintronic devices such as spin valve transistors, spin light emitting diodes, non-volatile memory, logic devices, optical isolators and ultra-fast optical switches are some of the areas of interest for introducing the ferromagnetic properties at room temperature in a semiconductor to make it multifunctional. The potential advantages of such spintronic devices will be higher speed, greater efficiency, and better stability at a reduced power consumption. This Thesis contains two main topics: In-depth understanding of magnetism in Mn doped ZnO, and our search and identification of at least six new above room temperature ferromagnetic semiconductors. Both complex doped ZnO based new materials, as well as a number of nonoxides like phosphides, and sulfides suitably doped with Mn or Cu are shown to give rise to ferromagnetism above room temperature. Some of the highlights of this work are discovery of room temperature ferromagnetism in: (1) ZnO:Mn (paper in Nature Materials, Oct issue, 2003); (2) ZnO doped with Cu (containing no magnetic elements in it); (3) GaP doped with Cu (again containing no magnetic elements in it); (4) Enhancement of Magnetization by Cu co-doping in ZnO:Mn; (5) CdS doped with Mn, and a few others not reported in this thesis. We discuss in detail the first observation of ferromagnetism above room temperature in the form of powder, bulk pellets, in 2-3 mu-m thick transparent pulsed laser deposited films of the Mn (<4 at. percent) doped ZnO. High-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS) spectra recorded from 2 to 200nm areas showed homogeneous distribution of Mn substituting

  19. Physical analysis of the shielding capacity for a lightweight apron designed for shielding low intensity scattering X-rays

    NASA Astrophysics Data System (ADS)

    Kim, Seon Chil; Choi, Jeong Ryeol; Jeon, Byeong Kyou

    2016-07-01

    The purpose of this paper is to develop a lightweight apron that will be used for shielding low intensity radiation in medical imaging radiography room and to apply it to a custom-made effective shielding. The quality of existing aprons made for protecting our bodies from direct radiation are improved so that they are suitable for scattered X-rays. Textiles that prevent bodies from radiation are made by combining barium sulfate and liquid silicon. These materials have the function of shielding radiation in a manner like lead. Three kinds of textiles are produced. The thicknesses of each textile are 0.15 mm, 0.21 mm, and 0.29 mm and the corresponding lead equivalents are 0.039 mmPb, 0.095 mmPb, 0.22 mmPb for each. The rate of shielding space scattering rays are 80% from the distance of 0.5 m, 86% from 1.0 m, and 97% from 1.5 m. If we intend to approach with the purpose of shielding scattering X-rays and low intensity radiations, it is possible to reduce the weight of the apron to be 1/5 compared to that of the existing lead aprons whose weight is typically more than 4 kg. We confirm, therefore, that it is possible to produce lightweight aprons that are used for the purpose of shielding low dose radiations.

  20. Physical analysis of the shielding capacity for a lightweight apron designed for shielding low intensity scattering X-rays

    PubMed Central

    Kim, Seon Chil; Choi, Jeong Ryeol; Jeon, Byeong Kyou

    2016-01-01

    The purpose of this paper is to develop a lightweight apron that will be used for shielding low intensity radiation in medical imaging radiography room and to apply it to a custom-made effective shielding. The quality of existing aprons made for protecting our bodies from direct radiation are improved so that they are suitable for scattered X-rays. Textiles that prevent bodies from radiation are made by combining barium sulfate and liquid silicon. These materials have the function of shielding radiation in a manner like lead. Three kinds of textiles are produced. The thicknesses of each textile are 0.15 mm, 0.21 mm, and 0.29 mm and the corresponding lead equivalents are 0.039 mmPb, 0.095 mmPb, 0.22 mmPb for each. The rate of shielding space scattering rays are 80% from the distance of 0.5 m, 86% from 1.0 m, and 97% from 1.5 m. If we intend to approach with the purpose of shielding scattering X-rays and low intensity radiations, it is possible to reduce the weight of the apron to be 1/5 compared to that of the existing lead aprons whose weight is typically more than 4 kg. We confirm, therefore, that it is possible to produce lightweight aprons that are used for the purpose of shielding low dose radiations. PMID:27461510

  1. Physical analysis of the shielding capacity for a lightweight apron designed for shielding low intensity scattering X-rays.

    PubMed

    Kim, Seon Chil; Choi, Jeong Ryeol; Jeon, Byeong Kyou

    2016-07-27

    The purpose of this paper is to develop a lightweight apron that will be used for shielding low intensity radiation in medical imaging radiography room and to apply it to a custom-made effective shielding. The quality of existing aprons made for protecting our bodies from direct radiation are improved so that they are suitable for scattered X-rays. Textiles that prevent bodies from radiation are made by combining barium sulfate and liquid silicon. These materials have the function of shielding radiation in a manner like lead. Three kinds of textiles are produced. The thicknesses of each textile are 0.15 mm, 0.21 mm, and 0.29 mm and the corresponding lead equivalents are 0.039 mmPb, 0.095 mmPb, 0.22 mmPb for each. The rate of shielding space scattering rays are 80% from the distance of 0.5 m, 86% from 1.0 m, and 97% from 1.5 m. If we intend to approach with the purpose of shielding scattering X-rays and low intensity radiations, it is possible to reduce the weight of the apron to be 1/5 compared to that of the existing lead aprons whose weight is typically more than 4 kg. We confirm, therefore, that it is possible to produce lightweight aprons that are used for the purpose of shielding low dose radiations.

  2. Accelerator-based validation of shielding codes

    SciTech Connect

    Zeitlin, Cary; Heilbronn, Lawrence; Miller, Jack; Wilson, John W.

    2002-08-12

    The space radiation environment poses risks to astronaut health from a diverse set of sources, ranging from low-energy protons and electrons to highly-charged, high-energy atomic nuclei and their associated fragmentation products, including neutrons. The low-energy protons and electrons are the source of most of the radiation dose to Shuttle and ISS crews, while the more energetic particles that comprise the Galactic Cosmic Radiation (protons, He, and heavier nuclei up to Fe) will be the dominant source for crews on long-duration missions outside the earth's magnetic field. Because of this diversity of sources, a broad ground-based experimental effort is required to validate the transport and shielding calculations used to predict doses and dose-equivalents under various mission scenarios. The experimental program of the LBNL group, described here, focuses principally on measurements of charged particle and neutron production in high-energy heavy-ion fragmentation. Other aspects of the program include measurements of the shielding provided by candidate spacesuit materials against low-energy protons (particularly relevant to extra-vehicular activities in low-earth orbit), and the depth-dose relations in tissue for higher-energy protons. The heavy-ion experiments are performed at the Brookhaven National Laboratory's Alternating Gradient Synchrotron and the Heavy-Ion Medical Accelerator in Chiba in Japan. Proton experiments are performed at the Lawrence Berkeley National Laboratory's 88'' Cyclotron with a 55 MeV beam, and at the Loma Linda University Proton Facility with 100 to 250 MeV beam energies. The experimental results are an important component of the overall shielding program, as they allow for simple, well-controlled tests of the models developed to handle the more complex radiation environment in space.

  3. A&M. TAN607. Shield wall sections and details around hot shop ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    A&M. TAN-607. Shield wall sections and details around hot shop and special equipment room, showing taper, crane rail elevations, and elevation for biparting door (door no. 301) in wall between hot shop and special equipment room. Ralph M. Parsons 902-3-ANP-607-S 138. Date: December 1952. Approved by INEEL Classification Office for public release. INEEL index code no. 034-0607-62-963-106782 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  4. Shielding in biology and biophysics: Methodology, dosimetry, interpretation

    NASA Astrophysics Data System (ADS)

    Vladimirsky, B. M.; Temuryants, N. A.

    2016-12-01

    An interdisciplinary review of the publications on the shielding of organisms by different materials is presented. The authors show that some discrepancies between the results of different researchers might be attributed to methodological reasons, including purely biological (neglect of rhythms) and technical (specific features of the design or material of the screen) ones. In some cases, an important factor is the instability of control indices due to the variations in space weather. According to the modern concept of biological exposure to microdoses, any isolation of a biological object by any material necessarily leads to several simultaneous changes in environmental parameters, and this undermines the principle of "all other conditions being equal" in the classical differential scheme of an experiment. The shielding effects of water solution are universally recognized and their influence is to be observed for all organisms. Data on the exposure of living organisms to weak combined magnetic fields and on the influence of space weather enabled the development of theoretical models generally explaining the effect of shielding for bioorganisms. Ferromagnetic shielding results in changes of both the static magnetic field and the field of radio waves within the area protected by the screen. When screens are nonmagnetic, changes are due to the isolation from the radio waves. In both cases, some contribution to the fluctuations of measured parameters can be made by variations in the level of ionizing radiation.

  5. Spin-rotation and NMR shielding constants in HCl

    SciTech Connect

    Jaszuński, Michał; Repisky, Michal; Demissie, Taye B.; Komorovsky, Stanislav; Malkin, Elena; Ruud, Kenneth; Garbacz, Piotr; Jackowski, Karol; Makulski, Włodzimierz

    2013-12-21

    The spin-rotation and nuclear magnetic shielding constants are analysed for both nuclei in the HCl molecule. Nonrelativistic ab initio calculations at the CCSD(T) level of approximation show that it is essential to include relativistic effects to obtain spin-rotation constants consistent with accurate experimental data. Our best estimates for the spin-rotation constants of {sup 1}H{sup 35}Cl are C{sub Cl}  = −53.914 kHz and C{sub H}  = 42.672 kHz (for the lowest rovibrational level). For the chlorine shielding constant, the ab initio value computed including the relativistic corrections, σ(Cl) = 976.202 ppm, provides a new absolute shielding scale; for hydrogen we find σ(H) = 31.403 ppm (both at 300 K). Combining the theoretical results with our new gas-phase NMR experimental data allows us to improve the accuracy of the magnetic dipole moments of both chlorine isotopes. For the hydrogen shielding constant, including relativistic effects yields better agreement between experimental and computed values.

  6. Spin-rotation and NMR shielding constants in HCl

    NASA Astrophysics Data System (ADS)

    Jaszuński, Michał; Repisky, Michal; Demissie, Taye B.; Komorovsky, Stanislav; Malkin, Elena; Ruud, Kenneth; Garbacz, Piotr; Jackowski, Karol; Makulski, Włodzimierz

    2013-12-01

    The spin-rotation and nuclear magnetic shielding constants are analysed for both nuclei in the HCl molecule. Nonrelativistic ab initio calculations at the CCSD(T) level of approximation show that it is essential to include relativistic effects to obtain spin-rotation constants consistent with accurate experimental data. Our best estimates for the spin-rotation constants of 1H35Cl are CCl = -53.914 kHz and CH = 42.672 kHz (for the lowest rovibrational level). For the chlorine shielding constant, the ab initio value computed including the relativistic corrections, σ(Cl) = 976.202 ppm, provides a new absolute shielding scale; for hydrogen we find σ(H) = 31.403 ppm (both at 300 K). Combining the theoretical results with our new gas-phase NMR experimental data allows us to improve the accuracy of the magnetic dipole moments of both chlorine isotopes. For the hydrogen shielding constant, including relativistic effects yields better agreement between experimental and computed values.

  7. Magnetic and electrical properties on possible room temperature hybrid multiferroic BaTiO3/La2/3Sr1/3MnO3

    NASA Astrophysics Data System (ADS)

    Ordoñez, John Edward; Gómez, María Elena; Lopera Muñoz, Wilson; Prieto, Pedro Antonio; Thin Film Group Team; Center of Excellence on Novel Materials-CENM, Cali, Colombia Team

    2015-03-01

    We addressed to deposit the ferromagnetic phase of the La1-xSrxMnO3 and the ferroelectric BaTiO3 for possible hybrid multiferroic heterostructure. We have optimized the growth parameters for depositing BaTiO3(BTO) / La2/3Ca1/3MnO3(LCMO) / (001) SrTiO3 by sputtering RF and DC, respectively, in pure oxygen atmosphere and a substrate temperature of 830°C. Keeping fixed the magnetic layer thickness (tLSMO = 40 nm) and varying the thickness of the ferroelectric layer (tBTO = 20, 40, 80, 100 nm). We want to point out the influence of the thicknesses ratio (tBTO/tLSMO) on electrical and magnetic properties. From x-ray diffraction (XRD) analysis, we found the bragg peaks for LSMO maintain its position but BTO peak shift to lower Bragg angle indicating a strained BTO film. Magnetization and polarization measurements indicate a possible multiferroic behavior in the bilayers. Hysteresis loop measurements of bilayers show ferromagnetic behavior. Authors thank Instituto de Nanociencia de Aragón, Zaragoza, Spain. Work partially supported by COLCIENCIAS-UNIVALLE Project 110656933104 Contract No. 2013-0002, CI 7917 and CI 7978.

  8. Final Focus Shielding Designs for Modern Heavy-Ion Fusion Power Plant Designs

    SciTech Connect

    Latkowski, J F; Meier, W R

    2000-07-05

    Recent work in heavy-ion fusion accelerators and final focusing systems shows a trend towards less current per beam, and thus, a greater number of beams. Final focusing magnets are susceptible to nuclear heating, radiation damage, and neutron activation. The trend towards more beams, however, means that there can be less shielding for each magnet, Excessive levels of nuclear heating may lead to magnet quench or an intolerable recirculating power for magnet cooling. High levels of radiation damage may result in short magnet lifetimes and low reliability. Finally, neutron activation of the magnet components may lead to difficulties in maintenance, recycling, and waste disposal. The present work expands upon previous, three-dimensional magnet shielding calculations for a modified version of the HYLIFE-I1 IFE power plant design. We present key magnet results as a function of the number of beams.

  9. Final focus shielding designs for modern heavy-ion fusion power plant designs

    NASA Astrophysics Data System (ADS)

    Latkowski, J. F.; Meier, W. R.

    2001-05-01

    Recent work in heavy-ion fusion accelerators and final focusing systems shows a trend towards less current per beam, and thus, a greater number of beams. Final focusing magnets are susceptible to nuclear heating, radiation damage, and neutron activation. The trend towards more beams, however, means that there can be less shielding for each magnet. Excessive levels of nuclear heating may lead to magnet quench or to an intolerable recirculating power for magnet cooling. High levels of radiation damage may result in short magnet lifetimes and low reliability. Finally, neutron activation of the magnet components may lead to difficulties in maintenance, recycling, and waste disposal. The present work expands upon previous, three-dimensional magnet shielding calculations for a modified version of the HYLIFE-II IFE power plant design. We present key magnet results as a function of the number of beams.

  10. Trailer shield assembly for a welding torch

    NASA Technical Reports Server (NTRS)

    Dyer, Gerald E. (Inventor)

    1989-01-01

    This invention relates generally to trailer shields for gas shielded arc welding torches, and more particularly to a trailer shield assembly provided with a shield gas manifold for providing an even dispersion of shield gas to the interior of the shield assembly, which generally encloses a joint being welded and a welding trailing portion of hot welded metal. The novelty of the invention lies in providing trailer shield with a manifold tube having a plurality of openings from which shield gas is distributed. A gas manifold region ahead of the torch is also provided with shield gas from a tube to protect metal preheated by the torch. Further novelty lies in constructing portions of sides and housing and portions of side walls of the guide of stainless steel screen having a tight mesh.

  11. Radiation shielding materials and containers incorporating same

    DOEpatents

    Mirsky, Steven M.; Krill, Stephen J.; Murray, Alexander P.

    2005-11-01

    An improved radiation shielding material and storage systems for radioactive materials incorporating the same. The PYRolytic Uranium Compound ("PYRUC") shielding material is preferably formed by heat and/or pressure treatment of a precursor material comprising microspheres of a uranium compound, such as uranium dioxide or uranium carbide, and a suitable binder. The PYRUC shielding material provides improved radiation shielding, thermal characteristic, cost and ease of use in comparison with other shielding materials. The shielding material can be used to form containment systems, container vessels, shielding structures, and containment storage areas, all of which can be used to house radioactive waste. The preferred shielding system is in the form of a container for storage, transportation, and disposal of radioactive waste. In addition, improved methods for preparing uranium dioxide and uranium carbide microspheres for use in the radiation shielding materials are also provided.

  12. Radiation Shielding Materials and Containers Incorporating Same

    DOEpatents

    Mirsky, Steven M.; Krill, Stephen J.; and Murray, Alexander P.

    2005-11-01

    An improved radiation shielding material and storage systems for radioactive materials incorporating the same. The PYRolytic Uranium Compound (''PYRUC'') shielding material is preferably formed by heat and/or pressure treatment of a precursor material comprising microspheres of a uranium compound, such as uranium dioxide or uranium carbide, and a suitable binder. The PYRUC shielding material provides improved radiation shielding, thermal characteristic, cost and ease of use in comparison with other shielding materials. The shielding material can be used to form containment systems, container vessels, shielding structures, and containment storage areas, all of which can be used to house radioactive waste. The preferred shielding system is in the form of a container for storage, transportation, and disposal of radioactive waste. In addition, improved methods for preparing uranium dioxide and uranium carbide microspheres for use in the radiation shielding materials are also provided.

  13. Freely oriented portable superconducting magnet

    DOEpatents

    Schmierer, Eric N.; Prenger, F. Coyne; Hill, Dallas D.

    2010-01-12

    A freely oriented portable superconducting magnet is disclosed. Coolant is supplied to the superconducting magnet from a repository separate from the magnet, enabling portability of the magnet. A plurality of support assemblies structurally anchor and thermally isolate the magnet within a thermal shield. A plurality of support assemblies structurally anchor and thermally isolate the thermal shield within a vacuum vessel. The support assemblies restrain movement of the magnet resulting from energizing and cooldown, as well as from changes in orientation, enabling the magnet to be freely orientable.

  14. CORROSION OF LEAD SHIELDING IN NUCLEAR MATERIALS PACKAGES

    SciTech Connect

    Subramanian, K; Kerry Dunn, K; Joseph Murphy, J

    2008-07-18

    Inspection of United States-Department of Energy (US-DOE) model 9975 nuclear materials shipping package revealed corrosion of the lead shielding that was induced by off-gas constituents from organic components in the package. Experiments were performed to determine the corrosion rate of lead when exposed to off-gas or degradation products of these organic materials. The results showed that the room temperature vulcanizing (RTV) sealant was the most corrosive organic species used in the construction of the packaging, followed by polyvinyl acetate (PVAc) glue. Fiberboard material, also used in the construction of the packaging induced corrosion to a much lesser extent than the PVAc glue and RTV sealant, and only in the presence of condensed water. The results indicated faster corrosion at temperatures higher than ambient and with condensed water. In light of these corrosion mechanisms, the lead shielding was sheathed in a stainless steel liner to mitigate against corrosion.

  15. Development of an improved toughness hyperpure silica reflective heat shield

    NASA Technical Reports Server (NTRS)

    Rusert, E. L.; Hackett, T. L.; Drennan, D. N.

    1979-01-01

    High purity three dimensionally woven silica-silica materials were evaluated for use as a tough reflective heat shield for planetary entry probes. A special weave design was selected to minimize light piping effects through the heat shield thickness. Various weave spacings were evaluated for densification efficiency with an 0.7 micron particle size high purity silica. Spectral hemispherical reflectance was measured from 0.2 to 2.5 microns at room temperature. Reflectance increases due to densification and purity of material were measured. Reflectance of 3D hyperpure silica was higher than 3D astroquartz silica for all wavelengths. Mechanical properties were measured in beam flexure and beam shear tests. Results indicated strengths lower than reported for slip cast fused silica. Low strengths were attributed to low densities achieved through vacuum impregnation.

  16. Evaluating passively shielded gradient coil configurations for optimal eddy current compensation

    NASA Astrophysics Data System (ADS)

    Sanchez Lopez, Hector; Poole, Michael; Crozier, Stuart

    2010-05-01

    In magnetic resonance imaging, rapidly switching magnetic fields are used to spatially encode the signal. The temporal change of these fields induces eddy currents in nearby conducting structures of the scanner. These eddy currents, in turn, generate a secondary magnetic field that opposes and distorts the desired gradient field. Eddy current compensation methods are generally applied assuming that the primary and secondary magnetic field gradients possess similar spatial characteristics in the imaging volume (field matching). In this work an optimization method is used to deform the shape of the coil support and/or a highly conductive passive shield in order to improve the field matching and reduce the inductive coupling between the gradient coil and the passive shield. Using the residual field after eddy current compensation as the objective function, the coil support and/or conducting surfaces were deformed to obtain passively shielded x- and z-gradient coils with improved field matching and eddy current compensation. Assuming a single frequency, quasi-static simulation, it was demonstrated that the residual field was reduced up to 24 times by reshaping the coil and passive shield surfaces due to the improved field matching. However, using transient analyses we showed that in the case of the passively shielded x-gradient coil the residual field may only be reduced by five times from a cylindrical coil configuration. A bulge shape is created in the conducting surface as a mechanism of matching the field and at the same time reducing the mutual inductive coupling between the coil and the passive shield. An actively shielded coil with control over the magnetic field produced by the induced current was used as a reference coil that produces the minimal residual field. The actively shielded gradient coil produces minimal residual field for short and long pulses in the transient analyses.

  17. Jet shielding of jet noise

    NASA Technical Reports Server (NTRS)

    Simonich, J. C.; Amiet, R. K.; Schlinker, R. H.

    1986-01-01

    An experimental and theoretical study was conducted to develop a validated first principle analysis for predicting the jet noise reduction achieved by shielding one jet exhaust flow with a second, closely spaced, identical jet flow. A generalized fuel jet noise analytical model was formulated in which the acoustic radiation from a source jet propagates through the velocity and temperature discontinuity of the adjacent shielding jet. Input variables to the prediction procedure include jet Mach number, spacing, temperature, diameter, and source frequency. Refraction, diffraction, and reflection effects, which control the dual jet directivity pattern, are incorporated in the theory. The analysis calculates the difference in sound pressure level between the dual jet configuration and the radiation field based on superimposing two independent jet noise directivity patterns. Jet shielding was found experimentally to reduce noise levels in the common plane of the dual jet system relative to the noise generated by two independent jets.

  18. Preliminary shielding assessment for the 100 MeV proton linac (KOMAC).

    PubMed

    Lee, Young-Ouk; Cho, Y S; Chang, J

    2005-01-01

    The Proton Engineering Frontier Project is building the Korea Multipurpose Accelerator Complex facilities from 2002 to 2012, which consists of a high-current 100 MeV proton linear accelerator and various beam-lines. This paper provides a preliminary estimate of the shielding required for the 20 mA proton linac and the beam-dump. For an accurate information on secondary neutron production from the guiding magnet and primary heat sink of the beam dump, proton-induced 63Cu and 65Cu cross section data were evaluated and applied to shielding calculations. The required thickness of the concrete was assessed by a simple line-of-sight model for the lateral shielding of the beam-line and the full shielding of the beam dump. Monte Carlo simulations were also performed using the MCNPX code to obtain the source term and attenuation coefficients for the three-dimensional lateral shielding model of the beam-line.

  19. U.S ITER : electromagnetic analysis of transient forces due to disrupted plasma currents on the ITER shield modules.

    SciTech Connect

    Kotulski, Joseph Daniel; Coats, Rebecca Sue; Pasik, Michael Francis

    2007-06-01

    This paper describes the electromagnetic analysis that has been completed using the OPERA-3d product to characterize the forces on the ITER shield modules as part of the conceptual design. These forces exist due to the interaction of the eddy currents induced in the shield modules and the large magnetic fields present in the tokamak.

  20. Monte Carlo simulations for the space radiation superconducting shield project (SR2S).

    PubMed

    Vuolo, M; Giraudo, M; Musenich, R; Calvelli, V; Ambroglini, F; Burger, W J; Battiston, R

    2016-02-01

    Astronauts on deep-space long-duration missions will be exposed for long time to galactic cosmic rays (GCR) and Solar Particle Events (SPE). The exposure to space radiation could lead to both acute and late effects in the crew members and well defined countermeasures do not exist nowadays. The simplest solution given by optimized passive shielding is not able to reduce the dose deposited by GCRs below the actual dose limits, therefore other solutions, such as active shielding employing superconducting magnetic fields, are under study. In the framework of the EU FP7 SR2S Project - Space Radiation Superconducting Shield--a toroidal magnetic system based on MgB2 superconductors has been analyzed through detailed Monte Carlo simulations using Geant4 interface GRAS. Spacecraft and magnets were modeled together with a simplified mechanical structure supporting the coils. Radiation transport through magnetic fields and materials was simulated for a deep-space mission scenario, considering for the first time the effect of secondary particles produced in the passage of space radiation through the active shielding and spacecraft structures. When modeling the structures supporting the active shielding systems and the habitat, the radiation protection efficiency of the magnetic field is severely decreasing compared to the one reported in previous studies, when only the magnetic field was modeled around the crew. This is due to the large production of secondary radiation taking place in the material surrounding the habitat.

  1. Monte Carlo simulations for the space radiation superconducting shield project (SR2S)

    NASA Astrophysics Data System (ADS)

    Vuolo, M.; Giraudo, M.; Musenich, R.; Calvelli, V.; Ambroglini, F.; Burger, W. J.; Battiston, R.

    2016-02-01

    Astronauts on deep-space long-duration missions will be exposed for long time to galactic cosmic rays (GCR) and Solar Particle Events (SPE). The exposure to space radiation could lead to both acute and late effects in the crew members and well defined countermeasures do not exist nowadays. The simplest solution given by optimized passive shielding is not able to reduce the dose deposited by GCRs below the actual dose limits, therefore other solutions, such as active shielding employing superconducting magnetic fields, are under study. In the framework of the EU FP7 SR2S Project - Space Radiation Superconducting Shield - a toroidal magnetic system based on MgB2 superconductors has been analyzed through detailed Monte Carlo simulations using Geant4 interface GRAS. Spacecraft and magnets were modeled together with a simplified mechanical structure supporting the coils. Radiation transport through magnetic fields and materials was simulated for a deep-space mission scenario, considering for the first time the effect of secondary particles produced in the passage of space radiation through the active shielding and spacecraft structures. When modeling the structures supporting the active shielding systems and the habitat, the radiation protection efficiency of the magnetic field is severely decreasing compared to the one reported in previous studies, when only the magnetic field was modeled around the crew. This is due to the large production of secondary radiation taking place in the material surrounding the habitat.

  2. Locker Room Design Trends.

    ERIC Educational Resources Information Center

    Wiens, Janet

    2001-01-01

    Examines how today's college and university athletic locker rooms have become sophisticated recruiting tools that rival many professional facilities. Locker room design and location and their level of furniture, finishes, and equipment are discussed as is the trend for more environmentally friendly locker rooms. (GR)

  3. On designing room sheilding for total-body irradiation

    SciTech Connect

    Barish, R.J.

    1996-05-01

    When designing shielding for total-body irradiation as an additional modality of treatment in an ordinary radiation therapy room, the extended treatment distance used for these patients greatly increases the workload because of the inverse-square factor. In a seeming contradiction to logic, for a facility with an exterior wall in the path of one lateral primary beam, and a restricted area behind the other primary wall, the overall shielding requirements are lower if the TBI patients are treated with the machine oriented toward the occupied interior. 4 refs.

  4. Review of DOE Planned Change Request for Shielded Containers for Remote-Handled Transuranic Waste

    EPA Pesticide Factsheets

    This report summarizes SC&A's review of the planned change request (PCR) submitted by DOE to EPA proposing the disposal of some remote-handled (RH) transuranic (TRU) waste in shielded containers on the floor of the disposal rooms at WIPP

  5. LPT. Shield test facility assembly and test building (TAN646), south ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LPT. Shield test facility assembly and test building (TAN-646), south facade. Camera facing north. High-bay section is pool room. Single-story section at right is control building (TAN-645). Small metal building is post-1970 addition. INEEL negative no. HD-40-7-3 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  6. LPT. Shield test facility (TAN645 and 646). Floor plan and ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LPT. Shield test facility (TAN-645 and -646). Floor plan and room names. Ralph M. Parsons 1229-17 ANP/GE-6-645-A-1. April 1957. Approved by INEEL Classification Office for public release. INEEL index code no. 037-0645/0646-00-693-107347 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  7. Fan-fold shielded electrical leads

    DOEpatents

    Rohatgi, Rajeev R.; Cowan, Thomas E.

    1996-01-01

    Fan-folded electrical leads made from copper cladded Kapton, for example, with the copper cladding on one side serving as a ground plane and the copper cladding on the other side being etched to form the leads. The Kapton is fan folded with the leads located at the bottom of the fan-folds. Electrical connections are made by partially opening the folds of the fan and soldering, for example, the connections directly to the ground plane and/or the lead. The fan folded arrangement produces a number of advantages, such as electrically shielding the leads from the environment, is totally non-magnetic, and has a very low thermal conductivity, while being easy to fabricate.

  8. Fan-fold shielded electrical leads

    DOEpatents

    Rohatgi, R.R.; Cowan, T.E.

    1996-06-11

    Disclosed are fan-folded electrical leads made from copper cladded Kapton, for example, with the copper cladding on one side serving as a ground plane and the copper cladding on the other side being etched to form the leads. The Kapton is fan folded with the leads located at the bottom of the fan-folds. Electrical connections are made by partially opening the folds of the fan and soldering, for example, the connections directly to the ground plane and/or the lead. The fan folded arrangement produces a number of advantages, such as electrically shielding the leads from the environment, is totally non-magnetic, and has a very low thermal conductivity, while being easy to fabricate. 3 figs.

  9. Active-passive gradient shielding for MRI acoustic noise reduction.

    PubMed

    Edelstein, William A; Kidane, Tesfaye K; Taracila, Victor; Baig, Tanvir N; Eagan, Timothy P; Cheng, Yu-Chung N; Brown, Robert W; Mallick, John A

    2005-05-01

    An important source of MRI acoustic noise-magnet cryostat warm-bore vibrations caused by eddy-current-induced forces-can be mitigated by a passive metal shield mounted on the outside of a vibration-isolated, vacuum-enclosed shielded gradient set. Finite-element (FE) calculations for a z-gradient indicate that a 2-mm-thick Cu layer wrapped on the gradient assembly can decrease mechanical power deposition in the warm bore and reduce warm-bore acoustic noise production by about 25 dB. Eliminating the conducting warm bore and other magnet parts as significant acoustic noise sources could lead to the development of truly quiet, fully functioning MRI systems with noise levels below 70 dB.

  10. Material characterisation and preliminary mechanical design for the HL-LHC shielded beam screens operating at cryogenic temperatures.

    NASA Astrophysics Data System (ADS)

    Garion, C.; Dufay-Chanat, L.; Koettig, T.; Machiocha, W.; Morrone, M.

    2015-12-01

    The High Luminosity LHC project (HL-LHC) aims at increasing the luminosity (rate of collisions) in the Large Hadron Collider (LHC) experiments by a factor of 10 beyond the original design value (from 300 to 3000 fb-1). It relies on new superconducting magnets, installed close to the interaction points, equipped with new beam screen. This component has to ensure the vacuum performance together with shielding the cold mass from physics debris and screening the cold bore cryogenic system from beam induced heating. The beam screen operates in the range 40-60 K whereas the magnet cold bore temperature is 1.9 K. A tungsten-based material is used to absorb the energy of particles. In this paper, measurements of the mechanical and physical properties of such tungsten material are shown at room and cryogenic temperature. In addition, the design and the thermal mechanical behaviour of the beam screen assembly are presented also. They include the heat transfer from the tungsten absorbers to the cooling pipes and the supporting system that has to minimise the heat inleak into the cold mass. The behaviour during a magnet quench is also presented.

  11. Shielding analysis for a heavy ion beam chamber with plasma channels for ion transport

    SciTech Connect

    Sawan, M.E.; Peterson, R.R.; Yu, S.

    2000-06-28

    Neutronics analysis has been performed to assess the shielding requirements for the insulators and final focusing magnets in a modified HYLIFE-II target chamber that utilizes pre-formed plasma channels for heavy ion beam transport. Using 65 cm thick Flibe jet assemblies provides adequate shielding for the electrical insulator units. Additional shielding is needed in front of the final focusing superconducting quadrupole magnets. A shield with a thickness varying between 45 and 90 cm needs to be provided in front of the quadrupole unit. The final laser mirrors located along the channel axis are in the direct line-of-sight of source neutrons. Neutronics calculations were performed to determine the constraints on the placement of these mirrors to be lifetime components.

  12. NMR shielding and spin-rotation constants in XCO (X = Ni, Pd, Pt) molecules

    NASA Astrophysics Data System (ADS)

    Demissie, Taye B.; Jaszuński, Michał; Malkin, Elena; Komorovský, Stanislav; Ruud, Kenneth

    2015-07-01

    Ab initio nonrelativistic and four-component relativistic DFT (density functional theory) methods are combined to study the spin-rotation and absolute nuclear magnetic resonance (NMR) shielding constants of group 10 transition metal monocarbonyls. Good agreement is obtained between the calculated and available experimental data for the spin-rotation constants and shielding spans for PdCO and PtCO. These data allow us to determine accurate absolute chemical shielding constants for all the nuclei, as well as for the unknown spin-rotation constants. We compare the four-component shielding constants with those obtained from the spin-orbit zeroth-order regular approximation, together with an assessment of the performance of different basis sets. For the first time, relativistically optimised basis sets for the heavy atoms used in the four-component calculations are shown to give converged results for both magnetic properties studied. We dedicate this article to the memory of Professor Nicholas C. Handy.

  13. Low-cost electromagnetic shielding using drywall composites: results of RFI (radio-frequency interference) testing of a shielding effectiveness. Final technical report

    SciTech Connect

    Williams, P.F.; Heyen, K.K.; McCormack, R.G.

    1987-10-01

    Because of developments in electronics technology, the need for electromagnetic shielding has increased. To reduce the cost of this shielding, new materials are needed. The U.S. Army Corps of Engineers, Fort Worth District (FWD), and the U.S. Army Construction Engineering Research Laboratory (USA-CERL) have developed composite materials that use standard, construction-grade, aluminum foil-backed gypsum board in combination with either a metal mesh or lead foil. Special seams for these composites were designed by U.S. Gypsum Company. USA-CERL evaluated the adequacy of each material and seam design by using radio-frequency antennas and receivers to measure its shielding effectiveness when mounted in the wall of a shielded room. These evaluations showed that the composite panels met the specified requirement of 60 decibels (dB) of shielding. The composites were also shown to be adequate for most communications security applications. However, the addition of a seam decreased shielding by as much as 10 dB.

  14. An outboard shield design for TIBER-II with potential for tritium self-sufficiency: Appendix A-1

    SciTech Connect

    Sawan, M.E.; Sviatoslavsky, I.N.

    1987-01-01

    The outboard breeding shield design for TIBER-II is described. The design allows for tritium self-sufficiency without compromising magnet protection, design simplicity, and the testing mission of the device. The shield consists of a beryllium pebble front zone backed by a steel pebble zone. The shield is cooled by an aqueous solution containing 16 g LiNO/sub 3/ per 100 cm/sup 3/. A double first wall is used to insure uniform cooling and minimize pressure. The design pressure for the outboard shield is 0.19 MPa and the coolant temperature is less than 75/sup 0/C. 6 refs., 5 figs., 3 tabs.

  15. Reliability-Based Electronics Shielding Design Tools

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; O'Neill, P. J.; Zang, T. A.; Pandolf, J. E.; Tripathi, R. K.; Koontz, Steven L.; Boeder, P.; Reddell, B.; Pankop, C.

    2007-01-01

    Shielding design on large human-rated systems allows minimization of radiation impact on electronic systems. Shielding design tools require adequate methods for evaluation of design layouts, guiding qualification testing, and adequate follow-up on final design evaluation.

  16. Rotary stripper for shielded and unshielded FCC

    NASA Technical Reports Server (NTRS)

    Angele, W.; Chambers, C. M.

    1971-01-01

    Rotary stripper removes narrow strips of insulation and shielding to any desired depth. Unshielded cables are stripped on both sides with one stroke, shielded cables are stripped in steps of different depths.

  17. Shielding and grounding in large detectors

    SciTech Connect

    Radeka, V.

    1998-09-01

    Prevention of electromagnetic interference (EMI), or ``noise pickup,`` is an important design aspect in large detectors in accelerator environments. Shielding effectiveness as a function of shield thickness and conductivity vs the type and frequency of the interference field is described. Noise induced in transmission lines by ground loop driven currents in the shield is evaluated and the importance of low shield resistance is emphasized. Some measures for prevention of ground loops and isolation of detector-readout systems are discussed.

  18. Tank Car Head Shield Fatigue Evaluation.

    DTIC Science & Technology

    1982-11-01

    shields and to record measurements which reflect the dynamic response of the head shield (and its attachments) and then to devise a method for...areas were instrumented for measuring strains. Other positions were also instrumented to obtain a breader understanding of the response of the shield ...center sill of four feet six inches, measured in a straight line between extreme edges; (ii) A minimum width at the top of shield of nine feet

  19. Analysis and Evaluation of Suppressive Shields

    DTIC Science & Technology

    1977-06-01

    resistance of the shield to fragment penetration, and 7. attenuation of thermal effects by the shield . Other aspects of the design include problems of entry...propellant, 2. methods to predict the thermal environment outside of a suppressive shield , 3. comparisons between measured and predicted pressures... SHIELDS by P. A. Co- x P. S. Westine CD J. J. Kulesz L.LJ E. D. Espurza c-.- January 1978 SOUTHWEST RESEARCH INSTITUTE Post Office Drawer 28510, 6220

  20. 21 CFR 880.5630 - Nipple shield.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Nipple shield. 880.5630 Section 880.5630 Food and... Nipple shield. (a) Identification. A nipple shield is a device consisting of a cover used to protect the nipple of a nursing woman. This generic device does not include nursing pads intended solely to...