Sample records for halbach magnet array

  1. Inverted Linear Halbach Array for Separation of Magnetic Nanoparticles

    PubMed Central

    Ijiri, Y.; Poudel, C.; Williams, P.S.; Moore, L.R.; Orita, T.; Zborowski, M.

    2014-01-01

    A linear array of Nd-Fe-B magnets has been designed and constructed in an inverted Halbach configuration for use in separating magnetic nanoparticles. The array provides a large region of relatively low magnetic field, yet high magnetic field gradient in agreement with finite element modeling calculations. The magnet assembly has been combined with a flow channel for magnetic nanoparticle suspensions, such that for an appropriate distance away from the assembly, nanoparticles of higher moment aggregate and accumulate against the channel wall, with lower moment nanoparticles flowing unaffected. The device is demonstrated for iron oxide nanoparticles with diameters of ~ 5 and 20 nm. In comparison to other approaches, the inverted Halbach array is more amenable to modeling and to scaling up to preparative quantities of particles. PMID:25382864

  2. Passive axial magnetic bearing with Halbach magnetized array in magnetically suspended control moment gyro application

    Microsoft Academic Search

    Sun Jinji; Ren Yuan; Fang Jiancheng

    2011-01-01

    The paper presents a special configuration of passive axial magnetic bearing with segmented Halbach magnetized array in magnetically suspended control moment gyro (MSCMG). Peculiarity of presented passive axial magnetic bearing is its ability to provide angular stiffness so that it can produce gyro moment when it is used in MSCMG. The MSCMG with this passive axial magnetic bearing can efficiently

  3. Experiments on Inductive Magnetic Levitation with a Circular Halbach Array

    NASA Astrophysics Data System (ADS)

    Bean, Ian; Goncz, Doug; Raymer, Austin; Specht, Jason; Zalles, Ricardo; Majewski, Walerian

    2013-03-01

    Using a ring Halbach array, we are investigating a repulsive levitating force and a drag force acting on the magnet from a ring of inductors rotating below the magnet. After measuring induced currents, voltages and magnetic fields in the individual inductors (in the form of short solenoids), we investigated the dependence of lift/drag forces on the speed of relative rotation. The ratio of lift to drag increases with the angular velocity, as expected from a related theory of the induction effects in a linear motion. We are experimenting with the shape and density of inductors, and their material, in an attempt to maximize the lift at a minimal velocity of rotation. Eventually this design could have applications as frictionless bearings or as frictionless gear in a wide range of systems, especially in machinery that cannot be easily accessed.

  4. Radial Halbach Magnetic Bearings

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2009-01-01

    Radial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Radial Halbach magnetic bearings are based on the same principle as that of axial Halbach magnetic bearings, differing in geometry as the names of these two types of bearings suggest. Both radial and axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control. Axial Halbach magnetic bearings were described in Axial Halbach Magnetic Bearings (LEW-18066-1), NASA Tech Briefs, Vol. 32, No. 7 (July 2008), page 85. In the remainder of this article, the description of the principle of operation from the cited prior article is recapitulated and updated to incorporate the present radial geometry. In simplest terms, the basic principle of levitation in an axial or radial Halbach magnetic bearing is that of the repulsive electromagnetic force between (1) a moving permanent magnet and (2) an electric current induced in a stationary electrical conductor by the motion of the magnetic field. An axial or radial Halbach bearing includes multiple permanent magnets arranged in a Halbach array ("Halbach array" is defined below) in a rotor and multiple conductors in the form of wire coils in a stator, all arranged so the rotary motion produces an axial or radial repulsion that is sufficient to levitate the rotor. A basic Halbach array (see Figure 1) consists of a row of permanent magnets, each oriented so that its magnetic field is at a right angle to that of the adjacent magnet, and the right-angle turns are sequenced so as to maximize the magnitude of the magnetic flux density on one side of the row while minimizing it on the opposite side. The advantage of this configuration is that it makes it possible to approach the theoretical maximum force per unit area that could be exerted by a given amount of permanent-magnet material. The configuration is named after physicist Klaus Halbach, who conceived it for use in particle accelerators. Halbach arrays have also been studied for use in magnetic-levitation ("maglev") railroad trains. In a radial Halbach magnetic bearing, the basic Halbach arrangement is modified into a symmetrical arrangement of sector-shaped permanent magnets mounted on the outer cylindrical surface of a drum rotor (see Figure 2). The magnets are oriented to concentrate the magnetic field on their radially outermost surface. The stator coils are mounted in a stator shell surrounding the rotor.

  5. A new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage.

    PubMed

    Choi, Young-Man; Lee, Moon G; Gweon, Dae-Gab; Jeong, Jaehwa

    2009-04-01

    Next-generation lithography requires a high precision stage, which is compatible with a high vacuum condition. A magnetic levitation stage with six degrees-of-freedom is considered state-of-the-art technology for a high vacuum condition. The noncontact characteristic of magnetic levitation enables high precision positioning as well as no particle generation. To position the stage against gravity, z-directional electromagnetic levitation mechanisms are widely used. However, if electromagnetic actuators for levitation are used, heat is inevitably generated, which deforms the structures and degrades accuracy of the stage. Thus, a gravity compensator is required. In this paper, we propose a new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage. The novel Halbach magnetic bearing exerts a force four times larger than a conventional magnetic bearing with the same volume. We also discuss the complementary characteristics of the two magnetic bearings. By modifying the height of the center magnet in a Halbach magnetic bearing, a performance compromise between levitating force density and force uniformity is obtained. The Halbach linear active magnetic bearing can be a good solution for magnetic levitation stages because of its large and uniform levitation force. PMID:19405690

  6. A new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage

    NASA Astrophysics Data System (ADS)

    Choi, Young-Man; Lee, Moon G.; Gweon, Dae-Gab; Jeong, Jaehwa

    2009-04-01

    Next-generation lithography requires a high precision stage, which is compatible with a high vacuum condition. A magnetic levitation stage with six degrees-of-freedom is considered state-of-the-art technology for a high vacuum condition. The noncontact characteristic of magnetic levitation enables high precision positioning as well as no particle generation. To position the stage against gravity, z-directional electromagnetic levitation mechanisms are widely used. However, if electromagnetic actuators for levitation are used, heat is inevitably generated, which deforms the structures and degrades accuracy of the stage. Thus, a gravity compensator is required. In this paper, we propose a new magnetic bearing using Halbach magnet arrays for a magnetic levitation stage. The novel Halbach magnetic bearing exerts a force four times larger than a conventional magnetic bearing with the same volume. We also discuss the complementary characteristics of the two magnetic bearings. By modifying the height of the center magnet in a Halbach magnetic bearing, a performance compromise between levitating force density and force uniformity is obtained. The Halbach linear active magnetic bearing can be a good solution for magnetic levitation stages because of its large and uniform levitation force.

  7. Halbach Magnetic Rotor Development

    NASA Technical Reports Server (NTRS)

    Gallo, Christopher A.

    2008-01-01

    The NASA John H. Glenn Research Center has a wealth of experience in Halbach array technology through the Fundamental Aeronautics Program. The goals of the program include improving aircraft efficiency, reliability, and safety. The concept of a Halbach magnetically levitated electric aircraft motor will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels, increase efficiency and reliability, reduce maintenance and decrease operating noise levels. Experimental hardware systems were developed in the GRC Engineering Development Division to validate the basic principles described herein and the theoretical work that was performed. A number of Halbach Magnetic rotors have been developed and tested under this program. A separate test hardware setup was developed to characterize each of the rotors. A second hardware setup was developed to test the levitation characteristics of the rotors. Each system focused around a unique Halbach array rotor. Each rotor required original design and fabrication techniques. A 4 in. diameter rotor was developed to test the radial levitation effects for use as a magnetic bearing. To show scalability from the 4 in. rotor, a 1 in. rotor was developed to also test radial levitation effects. The next rotor to be developed was 20 in. in diameter again to show scalability from the 4 in. rotor. An axial rotor was developed to determine the force that could be generated to position the rotor axially while it is rotating. With both radial and axial magnetic bearings, the rotor would be completely suspended magnetically. The purpose of this report is to document the development of a series of Halbach magnetic rotors to be used in testing. The design, fabrication and assembly of the rotors will be discussed as well as the hardware developed to test the rotors.

  8. Double dipolar halbach array for rheological measurements on magnetic fluids at variable magnetic flux density B

    NASA Astrophysics Data System (ADS)

    Barroso, V. C.; Raich, H.; Blümler, P.; Wilhelm, M.

    2009-02-01

    A new experimental setup for measuring rheological properties of magnetic fluids at variable magnetic flux density B with increased homogeneity is described. The proposed setup is mounted on a commercial strain-controlled ARES rotational rheometer. The magnetic flux is generated via two concentric Halbach cylindrical arrays made from permanent NdFeB magnets. The use of permanent magnets overcomes some of the disadvantages of electromagnets (e.g., excessive heating of the coils, formation of large radial stray fields, cost of electricity, cooling, etc). The performance of the new setup is tested for a magnetorheological fluid in both steady and oscillatory shear regimes.

  9. Analysis of the magnetic field and force of LSM with permanent magnet Halbach array and ironless coil

    Microsoft Academic Search

    Xiao Zhang; Yungang Li; Hengkun Liu

    2011-01-01

    The LSM, or linear synchronous motor, with permanent magnet Halbach array and ironless coil possesses the dominant advantages of direct linear movement and being energy-saving. To analytically investigate the characteristics of this innovative LSM, its magnetic field and magnetic force are analyzed in this work. Based on the magnetic field of a single surface current, the field of a single

  10. Axial Halbach Magnetic Bearings

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2008-01-01

    Axial Halbach magnetic bearings have been investigated as part of an effort to develop increasingly reliable noncontact bearings for future high-speed rotary machines that may be used in such applications as aircraft, industrial, and land-vehicle power systems and in some medical and scientific instrumentation systems. Axial Halbach magnetic bearings are passive in the sense that unlike most other magnetic bearings that have been developed in recent years, they effect stable magnetic levitation without need for complex active control.

  11. A comparison of two magnetic ultra-cold neutron trapping concepts using a Halbach-octupole array

    E-print Network

    K. Leung; S. Ivanov; F. Martin; F. Rosenau; M. Simson; O. Zimmer

    2015-03-17

    This paper describes a new magnetic trap for ultra-cold neutrons (UCNs) made from a 1.2 m long Halbach-octupole array of permanent magnets with an inner bore radius of 47 mm combined with an assembly of superconducting end coils and bias field solenoid. The use of the trap in a vertical, magneto-gravitational and a horizontal setup are compared in terms of the effective volume and ability to control key systematic effects that need to be addressed in high precision neutron lifetime measurements.

  12. The use of a linear Halbach array combined with a step-SPLITT channel for continuous sorting of magnetic species

    PubMed Central

    Hoyos, Mauricio; Moore, Lee; Williams, P. Stephen; Zborowski, Maciej

    2011-01-01

    The Quadrupole Magnetic Sorter (QMS), employing an annular flow channel concentric with the aperture of a quadrupole magnet, is well established for cell and particle separations. Here we propose a magnetic particle separator comprising a linear array of cylindrical magnets, analogous to the array proposed by Klaus Halbach, mated to a substantially improved form of parallel-plate SPLITT channel, known as the step-SPLITT channel. While the magnetic force and throughput are generally lower than for the QMS, the new separator has advantages in ease of fabrication and the ability to vary the magnetic force to suit the separands. Preliminary experiments yield results consistent with prediction and show promise regarding future separations of cells of biomedical interest. PMID:21399709

  13. Position sensor for linear synchronous motors employing halbach arrays

    DOEpatents

    Post, Richard Freeman

    2014-12-23

    A position sensor suitable for use in linear synchronous motor (LSM) drive systems employing Halbach arrays to create their magnetic fields is described. The system has several advantages over previously employed ones, especially in its simplicity and its freedom from being affected by weather conditions, accumulated dirt, or electrical interference from the LSM system itself.

  14. Halbach array DC motor/generator

    DOEpatents

    Merritt, Bernard T. (Livermore, CA); Dreifuerst, Gary R. (Livermore, CA); Post, Richard F. (Walnut Creek, CA)

    1998-01-01

    A new configuration of DC motor/generator is based on a Halbach array of permanent magnets. This motor does not use ferrous materials so that the only losses are winding losses and losses due to bearings and windage. An "inside-out" design is used as compared to a conventional motor/generator design. The rotating portion, i.e., the rotor, is on the outside of the machine. The stationary portion, i.e., the stator, is formed by the inside of the machine. The rotor contains an array of permanent magnets that provide a uniform field. The windings of the motor are placed in or on the stator. The stator windings are then "switched" or "commutated" to provide a DC motor/generator much the same as in a conventional DC motor. The commutation can be performed by mechanical means using brushes or by electronic means using switching circuits. The invention is useful in electric vehicles and adjustable speed DC drives.

  15. Halbach array DC motor/generator

    DOEpatents

    Merritt, B.T.; Dreifuerst, G.R.; Post, R.F.

    1998-01-06

    A new configuration of DC motor/generator is based on a Halbach array of permanent magnets. This motor does not use ferrous materials so that the only losses are winding losses and losses due to bearings and windage. An ``inside-out`` design is used as compared to a conventional motor/generator design. The rotating portion, i.e., the rotor, is on the outside of the machine. The stationary portion, i.e., the stator, is formed by the inside of the machine. The rotor contains an array of permanent magnets that provide a uniform field. The windings of the motor are placed in or on the stator. The stator windings are then ``switched`` or ``commutated`` to provide a DC motor/generator much the same as in a conventional DC motor. The commutation can be performed by mechanical means using brushes or by electronic means using switching circuits. The invention is useful in electric vehicles and adjustable speed DC drives. 17 figs.

  16. Energy harvesting from electric power lines employing the Halbach arrays

    NASA Astrophysics Data System (ADS)

    He, Wei; Li, Ping; Wen, Yumei; Zhang, Jitao; Lu, Caijiang; Yang, Aichao

    2013-10-01

    This paper proposes non-invasive energy harvesters to scavenge alternating magnetic field energy from electric power lines. The core body of a non-invasive energy harvester is a linear Halbach array, which is mounted on the free end of a piezoelectric cantilever beam. The Halbach array augments the magnetic flux density on the side of the array where the power line is placed and significantly lowers the magnetic field on the other side. Consequently, the magnetic coupling strength is enhanced and more alternating magnetic field energy from the current-carrying power line is converted into electrical energy. An analytical model is developed and the theoretical results verify the experimental results. A power of 566 ?W across a 196 k? resistor is generated from a single wire, and a power of 897 ?W across a 212 k? resistor is produced from a two-wire power cord carrying opposite currents at 10 A. The harvesters employing Halbach arrays for a single wire and a two-wire power cord, respectively, exhibit 3.9 and 3.2 times higher power densities than those of the harvesters employing conventional layouts of magnets. The proposed devices with strong response to the alternating currents are promising to be applied to electricity end-use environment in electric power systems.

  17. Development and Testing of a Radial Halbach Magnetic Bearing

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2006-01-01

    The NASA John H. Glenn Research Center has developed and tested a revolutionary Radial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Radial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Radial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical applications, manufacturing equipment, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Radial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

  18. Development and Testing of an Axial Halbach Magnetic Bearing

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.

    2006-01-01

    The NASA Glenn Research Center has developed and tested a revolutionary Axial Halbach Magnetic Bearing. The objective of this work is to develop a viable non-contact magnetic thrust bearing utilizing Halbach arrays for all-electric flight, and many other applications. This concept will help to reduce harmful emissions, reduce the Nation s dependence on fossil fuels and mitigate many of the concerns and limitations encountered in conventional axial bearings such as bearing wear, leaks, seals and friction loss. The Axial Halbach Magnetic Bearing is inherently stable and requires no active feedback control system or superconductivity as required in many magnetic bearing designs. The Axial Halbach Magnetic Bearing is useful for very high speed applications including turbines, instrumentation, medical systems, computer memory systems, and space power systems such as flywheels. Magnetic fields suspend and support a rotor assembly within a stator. Advanced technologies developed for particle accelerators, and currently under development for maglev trains and rocket launchers, served as the basis for this application. Experimental hardware was successfully designed and developed to validate the basic principles and analyses. The report concludes that the implementation of Axial Halbach Magnetic Bearings can provide significant improvements in rotational system performance and reliability.

  19. Optimal Halbach permanent magnet designs for maximally pulling and pushing nanoparticles

    E-print Network

    Shapiro, Benjamin

    Optimal Halbach permanent magnet designs for maximally pulling and pushing nanoparticles A. Sarwar targeting Optimal permanent magnet Nano-particle trapping Pushing nanoparticle Halbach array design a b to focus therapeutic nanoparticles to disease locations, the sharp fall off of magnetic fields and forces

  20. Rock magnetic applications of Halbach cylinders

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Vadeboin, F.; Clochard, L.

    2001-10-01

    Permanent magnet field sources made of NdFeB, in particular the Halbach cylinders, have not previously been used by rock magneticists. Here, their use is explored for determining saturation IRM (SIRM) and S ratio. An original "one-step" scheme is presented to obtain both parameters in one measurement and one operation of IRM acquisition using two crossed Halbach cylinders with 1.0 and 0.3 T fields. The first tests performed demonstrate the ability of Halbach cylinders to derive SIRM and S values over a wide range of coercivities using both the standard and the one-step schemes, although further improvements are needed in field homogeneity to achieve better precision. Other possible applications of Halbach cylinders are reviewed.

  1. Analytical Force Calculations for High-Precision Planar Actuator With Halbach Magnet Array

    Microsoft Academic Search

    Hao Jiang; Xueliang Huang; Gan Zhou; Yubin Wang; Zheng Wang

    2009-01-01

    In this paper, an analytical approach is presented to calculate the magnetic force between the mover and the stator of an electromagnetic planar actuator. The key is to use the coenergy method to calculate the force, in such a way that the stator current can be predicted properly to offer the accurate orientation and location for the real-time control of

  2. A two-pole Halbach permanent magnet guideway for high temperature superconducting Maglev vehicle

    NASA Astrophysics Data System (ADS)

    Jing, H.; Wang, J.; Wang, S.; Wang, L.; Liu, L.; Zheng, J.; Deng, Z.; Ma, G.; Zhang, Y.; Li, J.

    2007-10-01

    In order to improve the levitation performance of the high temperature superconducting (HTS) magnetic levitation (Maglev) vehicle, a two-pole Halbach array’s permanent magnet guideway (PMG) is proposed, which is called as Halbach PMG. The finite element method (FEM) calculations indicate that Halbach PMG has a wider high-field region than the present PMG of equal PM’s transverse section. The levitation force of bulk HTSCs with the present PMG and Halbach PMG are measured. The results show that at different levitation gaps, the force ratios based on the Halbach PMG are about 2.3 times larger than that on the present PMG, which greatly increases the load capability of the system. Therefore, both the numerical analysis and experimental results have confirmed that the Halbach PMG will further enhance the performance of the vehicle and it is possible to decrease the total numbers of onboard HTSCs, reducing overall costs. So based on the Halbach PMG, we further study the width ratios between HTSCs and PMG for making the better use of the onboard HTSCs. Some preliminary results are given. These results are important for further HTS Maglev vehicle system designs using Halbach PMG.

  3. Optimal Halbach permanent magnet designs for maximally pulling and pushing nanoparticles

    NASA Astrophysics Data System (ADS)

    Sarwar, A.; Nemirovski, A.; Shapiro, B.

    2012-03-01

    Optimization methods are presented to design Halbach arrays to maximize the forces applied on magnetic nanoparticles at deep tissue locations. In magnetic drug targeting, where magnets are used to focus therapeutic nanoparticles to disease locations, the sharp fall off of magnetic fields and forces with distances from magnets has limited the depth of targeting. Creating stronger forces at a depth by optimally designed Halbach arrays would allow treatment of a wider class of patients, e.g. patients with deeper tumors. The presented optimization methods are based on semi-definite quadratic programming, yield provably globally optimal Halbach designs in 2 and 3-dimensions, for maximal pull or push magnetic forces (stronger pull forces can collect nanoparticles against blood forces in deeper vessels; push forces can be used to inject particles into precise locations, e.g. into the inner ear). These Halbach designs, here tested in simulations of Maxwell's equations, significantly outperform benchmark magnets of the same size and strength. For example, a 3-dimensional 36 element 2000 cm 3 volume optimal Halbach design yields a 5× greater force at a 10 cm depth compared to a uniformly magnetized magnet of the same size and strength. The designed arrays should be feasible to construct, as they have a similar strength (?1 T), size (?2000 cm 3), and number of elements (?36) as previously demonstrated arrays, and retain good performance for reasonable manufacturing errors (element magnetization direction errors ?5°), thus yielding practical designs to improve magnetic drug targeting treatment depths.

  4. Optimal Halbach Permanent Magnet Designs for Maximally Pulling and Pushing Nanoparticles.

    PubMed

    Sarwar, A; Nemirovski, A; Shapiro, B

    2012-03-01

    Optimization methods are presented to design Halbach arrays to maximize the forces applied on magnetic nanoparticles at deep tissue locations. In magnetic drug targeting, where magnets are used to focus therapeutic nanoparticles to disease locations, the sharp fall off of magnetic fields and forces with distances from magnets has limited the depth of targeting. Creating stronger forces at depth by optimally designed Halbach arrays would allow treatment of a wider class of patients, e.g. patients with deeper tumors. The presented optimization methods are based on semi-definite quadratic programming, yield provably globally optimal Halbach designs in 2 and 3-dimensions, for maximal pull or push magnetic forces (stronger pull forces can collect nano-particles against blood forces in deeper vessels; push forces can be used to inject particles into precise locations, e.g. into the inner ear). These Halbach designs, here tested in simulations of Maxwell's equations, significantly outperform benchmark magnets of the same size and strength. For example, a 3-dimensional 36 element 2000 cm(3) volume optimal Halbach design yields a ×5 greater force at a 10 cm depth compared to a uniformly magnetized magnet of the same size and strength. The designed arrays should be feasible to construct, as they have a similar strength (? 1 Tesla), size (? 2000 cm(3)), and number of elements (? 36) as previously demonstrated arrays, and retain good performance for reasonable manufacturing errors (element magnetization direction errors ? 5°), thus yielding practical designs to improve magnetic drug targeting treatment depths. PMID:23335834

  5. Halbach array generator/motor having mechanically regulated output voltage and mechanical power output

    DOEpatents

    Post, Richard F.

    2005-06-14

    A motor/generator has its stationary portion, i.e., the stator, positioned concentrically within its rotatable element, i.e., the rotor, along the axis of rotation of the rotor. The rotor includes a Halbach array of magnets. The voltage and power outputs are regulated by varying the radial gap in between the stator windings and the rotating Halbach array. The gap is varied by extensible and retractable supports attached to the stator windings that can move the windings in a radial direction.

  6. Measurement of the Rheological Properties of Magnetorheological Fluids Using a Double Concentric Halbach Cylinder Array

    NASA Astrophysics Data System (ADS)

    Barroso, Vitor C.; Raich, Hanspeter; Blümler, Peter; Wilhelm, Manfred

    2008-07-01

    A new experimental setup for measuring rheological properties of magnetic fluids at variable magnetic flux density B with increased homogeneity is described. The proposed setup is mounted on a commercial strain-controlled ARES rotational rheometer. The magnetic flux is generated via two concentric Halbach cylindrical arrays made from permanent NdFeB magnets. The use of permanent magnets overcomes some of the disadvantages of electromagnets (e.g., excessive heating of the coils, formation of large radial stray fields, cost of electricity, cooling, etc). The performance of the new setup is tested for a magnetorheological fluid in both steady and oscillatory shear regimes.

  7. Design and Analysis of a Nested Halbach Permanent Magnet Magnetic Refrigerator

    E-print Network

    Victoria, University of

    Design and Analysis of a Nested Halbach Permanent Magnet Magnetic Refrigerator by Armando Tura BEng Committee Design and Analysis of a Nested Halbach Permanent Magnet Magnetic Refrigerator by Armando Tura with the potential to create efficient and compact refrigeration devices is an active magnetic regenerative

  8. Laboratory Scale Prototype of a Low-Speed Electrodynamic Levitation System Based on a Halbach Magnet Array

    ERIC Educational Resources Information Center

    Iniguez, J.; Raposo, V.

    2009-01-01

    In this paper we analyse the behaviour of a small-scale model of a magnetic levitation system based on the Inductrack concept. Drag and lift forces acting on our prototype, moving above a continuous copper track, are studied analytically following a simple low-speed approach. The experimental results are in good agreement with the theoretical…

  9. Magnetic field homogeneity perturbations in finite Halbach dipole magnets.

    PubMed

    Turek, Krzysztof; Liszkowski, Piotr

    2014-01-01

    Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z)-Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm. PMID:24316186

  10. Halbach array generator/motor having an automatically regulated output voltage and mechanical power output

    DOEpatents

    Post, Richard F.

    2005-02-22

    A motor/generator having its stationary portion, i.e., the stator, positioned concentrically within its rotatable element, i.e., the rotor, along its axis of rotation. The rotor includes a Halbach array. The stator windings are switched or commutated to provide a DC motor/generator much the same as in a conventional DC motor/generator. The voltage and power are automatically regulated by using centrifugal force to change the diameter of the rotor, and thereby vary the radial gap in between the stator and the rotating Halbach array, as a function of the angular velocity of the rotor.

  11. Development of Halbach magnet for portable NMR device

    NASA Astrophysics Data System (ADS)

    Do?an, N.; Topkaya, R.; Suba?i, H.; Yerli, Y.; Rameev, B.

    2009-03-01

    Nuclear magnetic resonance (NMR) has enormous potential for various applications in industry as the on-line or at-line test/control device of process environments. Advantage of NMR is its non-destructive nature, because it does not require the measurement probe to have a contact with the tested media. Despite of the recent progress in this direction, application of NMR in industry is still very limited. This is related to the technical and analytical complications of NMR as a method, and high cost of NMR analyzers available at the market. However in many applications, NMR is a very useful technique to test various products and to monitor quantitatively industrial processes. Fortunately usually there is no need in a high-field superconducting magnets to obtain the high-resolution spectra with the detailed information on chemical shifts and coupling-constant. NMR analyzers are designed to obtain the relaxation parameters by measuring the NMR spectra in the time domain rather than in frequency domain. Therefore it is possible to use small magnetic field (and low frequency of 2-60 MHz) in NMR systems, based on permanent magnet technology, which are specially designed for specific at-line and on-line process applications. In this work we present the permanent magnet system developed to use in the portative NMR devices. We discuss the experimental parameters of the designed Halbach magnet system and compare them with results of theoretical modelling.

  12. Three-Dimensional Field Solutions for Multi-Pole Cylindrical Halbach Arrays in an Axial Orientation

    NASA Technical Reports Server (NTRS)

    Thompson, William K.

    2006-01-01

    This article presents three-dimensional B field solutions for the cylindrical Halbach array in an axial orientation. This arrangement has applications in the design of axial motors and passive axial magnetic bearings and couplers. The analytical model described here assumes ideal magnets with fixed and uniform magnetization. The field component functions are expressed as sums of 2-D definite integrals that are easily computed by a number of mathematical analysis software packages. The analysis is verified with sample calculations and the results are compared to equivalent results from traditional finite-element analysis (FEA). The field solutions are then approximated for use in flux linkage and induced EMF calculations in nearby stator windings by expressing the field variance with angular displacement as pure sinusoidal function whose amplitude depends on radial and axial position. The primary advantage of numerical implementation of the analytical approach presented in the article is that it lends itself more readily to parametric analysis and design tradeoffs than traditional FEA models.

  13. Investigation of a 7-pole/6-slot Halbach-magnetized permanent-magnet linear alternator used for free-piston stirling engines

    NASA Astrophysics Data System (ADS)

    Zheng, Ping; Tong, Chengde; Zhao, Jing; Yu, Bin; Li, Lin; Bai, Jingang; Zhang, Lu

    2012-04-01

    This paper investigates a 7-pole/6-slot Halbach-magnetized permanent-magnet linear alternator used for free piston Stirling engines (FPSEs). Taking the advantages of Halbach array, a 1 kW prototype alternator is designed. Considering the rms value of electromotive force (EMF) and harmonic distortion, the optimal length ratio of the axial- and radial-magnetized permanent magnets and thicknesses of the permanent magnets are optimized by 2D finite element method. The alternator detent force, which is an important factor for smooth operation of FPSEs, is studied by optimizing slot tip and end tooth. The load and thermal performances of the final design are simulated. A prototype alternator was designed, built and tested. Experimental data indicated satisfactory design.

  14. Recent Development of Halbach Permanent Magnet Machines and Applications

    Microsoft Academic Search

    Z. Q. Zhu

    2007-01-01

    Halbach magnetised PM brushless machines are novel in that their magnetisation is self-shielding. They offer many attractive features, such as sinusoidal airgap field distribution and back-emf waveform, negligible cogging torque, potentially high airgap flux density and no need of rotor back-iron. Hence, they have recently attracted many research and development interests and extensive exploitation for their applications. This paper starts

  15. The art and science of magnet design: Selected notes of Klaus Halbach. Volume 2

    SciTech Connect

    NONE

    1995-02-01

    This volume contains a compilation of 57 notes written by Dr. Klaus Halbach selected from his collection of over 1650 such documents. It provides an historic snapshot of the evolution of magnet technology and related fields as the notes range from as early as 1965 to the present, and is intended to show the breadth of Dr. Halbach`s interest and ability that have long been an inspiration to his many friends and colleagues. As Halbach is an experimental physicist whose scientific interests span many areas, and who does his most innovative work with pencil and paper rather than at the workbench or with a computer, the vast majority of the notes in this volume were handwritten and their content varies greatly--some reflect original work or work for a specific project, while others are mere clarifications of mathematical calculations or design specifications. As the authors converted the notes to electronic form, some were superficially edited and corrected, while others were extensively re-written to reflect current knowledge and notation. The notes are organized under five categories which reflect their primary content: Beam Position Monitors, (bpm), Current Sheet Electron Magnets (csem), Magnet Theory, (thry), Undulators and Wigglers (u-w), and Miscellaneous (misc). Within the category, they are presented chronologically starting from the most recent note and working backwards in time.

  16. Torque Production in a Halbach Machine

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Gallo, Christopher A.; Thompson, William K.; Vrnak, Daniel R.

    2006-01-01

    The NASA John H. Glenn Research Center initiated the investigation of torque production in a Halbach machine for the Levitated Ducted Fan (LDF) Project to obtain empirical data in determining the feasibility of using a Halbach motor for the project. LDF is a breakthrough technology for "Electric Flight" with the development of a clean, quiet, electric propulsor system. Benefits include zero emissions, decreased dependence on fossil fuels, increased efficiency, increased reliability, reduced maintenance, and decreased operating noise levels. A commercial permanent magnet brushless motor rotor was tested with a custom stator. An innovative rotor utilizing a Halbach array was designed and developed to fit directly into the same stator. The magnets are oriented at 90deg to the adjacent magnet, which cancels the magnetic field on the inside of the rotor and strengthens the field on the outside of the rotor. A direct comparison of the commercial rotor and the Halbach rotor was made. In addition, various test models were designed and developed to validate the basic principles described, and the theoretical work that was performed. The report concludes that a Halbach array based motor can provide significant improvements in electric motor performance and reliability.

  17. A portable Halbach magnet that can be opened and closed without force: The NMR-CUFF

    NASA Astrophysics Data System (ADS)

    Windt, Carel W.; Soltner, Helmut; Dusschoten, Dagmar van; Blümler, Peter

    2011-01-01

    Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5 mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings.

  18. A portable Halbach magnet that can be opened and closed without force: the NMR-CUFF.

    PubMed

    Windt, Carel W; Soltner, Helmut; van Dusschoten, Dagmar; Blümler, Peter

    2011-01-01

    Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings. PMID:21036637

  19. Demonstration of Halbach-like magnets for improving microwave window power capacity

    NASA Astrophysics Data System (ADS)

    Chang, Chao; Liu, Yansheng; Ouyang, Xiaoping; Guo, Letian; Wu, Xiaolong; Sun, Xu; Wang, Limin

    2014-09-01

    The application of a resonant magnetic field to suppress the multipactor at the vacuum/dielectric interface of a high-power microwave window was theoretically proposed by Chang et al. [Appl. Phys. Lett. 96, 111502 (2010)] and the proof-of-principle was experimentally demonstrated by Chang et al. [Appl. Phys. Lett. 97, 141501 (2010)]. However, for transmitting gigawatt power, conventional large-scale magnets have the significant drawback of a nonuniform and heterogeneous B-field, which enhances the multipactor rather than suppresses it. The Halbach-like magnets for generating the transverse homogeneous B-field in a large scale are studied for suppressing the multipactor; the underlying physics in the particle-in-cell simulation was simulated, and the window breakdown threshold was significantly enhanced at multi-gigawatt.

  20. Relaxation-relaxation exchange experiments in porous media with portable Halbach-Magnets.

    NASA Astrophysics Data System (ADS)

    Haber, A.; Haber-Pohlmeier, S.; Casanova, F.; Blümich, B.

    2009-04-01

    Mobile NMR became a powerful tool following the development of portable NMR sensors for well logging. By now there are numerous applications of mobile NMR in materials analysis and chemical engineering where, for example, unique information about the structure, morphology and dynamics of polymers is obtained, and new opportunities are provided for geo-physical investigations [1]. In particular, dynamic information can be retrieved by two-dimensional Laplace exchange NMR, where the initial NMR relaxation environment is correlated with the final relaxation environment of molecules migrating from one environment to the other within a so-called NMR mixing time tm [2]. Relaxation-relaxation exchange experiments of water in inorganic porous media were performed at low and moderately inhomogeneous magnetic field with a simple, portable Halbach-Magnet. By conducting NMR transverse relaxation exchange experiments for several mixing times and converting the results to 2D T2 distributions (joint probability densities of transverse relaxation times T2) with the help of the inverse 2D Laplace Transformation (ILT), we obtained characteristic exchange times for different pore sizes. The results of first experiments on soil samples are reported, which reveal information about the complex pore structure of soil and the moisture content. References: 1. B. Blümich, J. Mauler, A. Haber, J. Perlo, E. Danieli, F. Casanova, Mobile NMR for Geo-Physical Analysis and Material Testing, Petroleum Science, xx (2009) xxx - xxx. 2. K. E. Washburn, P.T. Callaghan, Tracking pore to pore exchange using relaxation exchange spectroscopy, Phys. Rev. Lett. 97 (2006) 175502.

  1. Two dimensional exchange NMR experiments of natural porous media with portable Halbach-Magnets

    NASA Astrophysics Data System (ADS)

    Haber, Agnes; Haber-Pohlmeier, Sabina; Casanova, Federico; Blümich, Bernhard

    2010-05-01

    The characterization of pore space and connectivity in soils of different textures is one topic within Cluster A, Partial Project A1. For this purpose low field mobile NMR became a powerful tool following the development of portable NMR sensors for well logging. By now there are numerous applications of mobile NMR in materials analysis and chemical engineering where, for example, unique information about the structure, morphology and dynamics of polymers is obtained, and new opportunities are provided for geophysical investigations [1]. In particular, dynamic information can be retrieved by two-dimensional Laplace exchange NMR, where the initial NMR relaxation environment is correlated with the final relaxation environment of molecules migrating from one environment to the other within a so-called NMR mixing time tm [2]. Relaxation-relaxation exchange experiments were performed with saturated and un-saturated soil samples at low and moderately inhomogeneous magnetic field with a simple, portable Halbach-Magnet. By conducting NMR transverse relaxation exchange experiments for several mixing times and inverting the results to 2D T2 distributions (similar to joint probability densities of transverse relaxation times T2) with the help of inverse 2D Laplace Transformation (ILT), we observed characteristic exchange processes: Soils consisting mainly of silt and clay components show predominantly exchange between the smaller pores at mixing times of some milliseconds. In addition, there exists also weaker exchange with the larger pores observable for longer mixing time. In contrast to that fine sand exhibits 2D T2 distributions with no exchange processes which can be interpreted that water molecules move within pores of the same size class. These results will be compared to the exchange behaviour under unsaturated conditions. References: 1. B. Blümich, J. Mauler, A. Haber, J. Perlo, E. Danieli, F. Casanova, Mobile NMR for geophysical analysis and material testing, Petroleum Science 6 (2009) 1-7. 2. K. E. Washburn, P.T. Callaghan, Tracking pore to pore exchange using relaxation exchange spectroscopy, Phys. Rev. Lett. 97 (2006) 175502.

  2. Magnetic arrays

    DOEpatents

    Trumper, D.L.; Kim, W.; Williams, M.E.

    1997-05-20

    Electromagnet arrays are disclosed which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness. 12 figs.

  3. Magnetic arrays

    DOEpatents

    Trumper, David L. (Plaistow, NH); Kim, Won-jong (Cambridge, MA); Williams, Mark E. (Pelham, NH)

    1997-05-20

    Electromagnet arrays which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness.

  4. Inductrack magnet configuration

    DOEpatents

    Post, Richard Freeman

    2003-12-16

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track of windings is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  5. Inductrack magnet configuration

    DOEpatents

    Post, Richard Freeman

    2003-10-14

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track of windings is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  6. Passive magnetic bearing for a horizontal shaft

    DOEpatents

    Post, Richard F.

    2003-12-02

    A passive magnetic bearing is composed of a levitation element and a restorative element. The levitation element is composed of a pair of stationary arcuate ferromagnetic segments located within an annular radial-field magnet array. The magnet array is attached to the inner circumference of a hollow shaft end. An attractive force between the arcuate segments and the magnet array acts vertically to levitate the shaft, and also in a horizontal transverse direction to center the shaft. The restorative element is comprised of an annular Halbach array of magnets and a stationary annular circuit array located within the Halbach array. The Halbach array is attached to the inner circumference of the hollow shaft end. A repulsive force between the Halbach array and the circuit array increases inversely to the radial space between them, and thus acts to restore the shaft to its equilibrium axis of rotation when it is displaced therefrom.

  7. Optimization and improvement of Halbach cylinder design

    NASA Astrophysics Data System (ADS)

    Bjørk, R.; Bahl, C. R. H.; Smith, A.; Pryds, N.

    2008-07-01

    In this paper we describe the results of a parameter survey of a 16 segmented Halbach cylinder in three dimensions in which the parameters internal radius, rin, external radius, rex, and length, L, have been varied. Optimal values of rex and L were found for a Halbach cylinder with the least possible volume of magnets with a given mean flux density in the cylinder bore. The volume of the cylinder bore could also be significantly increased by only slightly increasing the volume of the magnets, for a fixed mean flux density. Placing additional blocks of magnets on the end faces of the Halbach cylinder also improved the mean flux density in the cylinder bore, especially so for short Halbach cylinders with large rex. Moreover, magnetic cooling as an application for Halbach cylinders was considered. A magnetic cooling quality parameter, ?cool, was introduced and results showed that this parameter was optimal for long Halbach cylinders with small rex. Using the previously mentioned additional blocks of magnets can improve the parameter by as much as 15% as well as improve the homogeneity of the field in the cylinder bore.

  8. Permanent Magnets Design and Magnetic Field Analysis of Multi-disc Coreless Permanent Magnet Synchronous Motor

    Microsoft Academic Search

    Xiao-yuan WANG; Fang ZHAO; Jing-juan DU; Li-xiao QI; Ren-yuan TANG

    2006-01-01

    This paper presents a new multi-disc coreless permanent magnet synchronous motor whose permanent magnets are arranged in the “Halbach array”. Unit motor combined structure is adopted to simplify processing technology of the motor. Airgap magnetic flux density is increased taking advantage of high remanence and coercive force of NdFeB permanent magnet material and high gathering magnetism function of Halbach array.

  9. Comparison of adjustable permanent magnetic field sources

    NASA Astrophysics Data System (ADS)

    Bjørk, R.; Bahl, C. R. H.; Smith, A.; Pryds, N.

    2010-11-01

    A permanent magnet assembly in which the flux density can be altered by a mechanical operation is often significantly smaller than comparable electromagnets and also requires no electrical power to operate. In this paper five permanent magnet designs in which the magnetic flux density can be altered are analyzed using numerical simulations, and compared based on the generated magnetic flux density in a sample volume and the amount of magnet material used. The designs are the concentric Halbach cylinder, the two half Halbach cylinders, the two linear Halbach arrays and the four and six rod mangle. The concentric Halbach cylinder design is found to be the best performing design, i.e. the design that provides the most magnetic flux density using the least amount of magnet material. A concentric Halbach cylinder has been constructed and the magnetic flux density, the homogeneity and the direction of the magnetic field are measured and compared with numerical simulation and a good agrement is found.

  10. Metamaterial anisotropic flux concentrators and magnetic arrays

    NASA Astrophysics Data System (ADS)

    Bjørk, R.; Smith, A.; Bahl, C. R. H.

    2013-08-01

    A metamaterial magnetic flux concentrator is investigated in detail in combination with a Halbach cylinder of infinite length. A general analytical solution to the field is determined and the magnetic figure of merit is determined for a Halbach cylinder with a flux concentrator. It is shown that an ideal flux concentrator will not change the figure of merit of a given magnet design, while the non-ideal will always lower it. The geometric parameters producing maximum figure of merit, i.e., the most efficient devices, are determined. The force and torque between two concentric Halbach cylinders with flux concentrators is determined and the maximum torque is found. Finally, the effect of non-ideal flux concentrators and the practical use of flux concentrators, as well as demagnetization issues, is discussed.

  11. Comparison of conventional and novel quadrupole drift tube magnets inspired by Klaus Halbach

    SciTech Connect

    Feinberg, B. [Lawrence Berkeley Lab., CA (United States)

    1995-02-01

    Quadrupole drift tube magnets for a heavy-ion linac provide a demanding application of magnet technology. A comparison is made of three different solutions to the problem of providing an adjustable high-field-strength quadrupole magnet in a small volume. A conventional tape-wound electromagnet quadrupole magnet (conventional) is compared with an adjustable permanent-magnet/iron quadrupole magnet (hybrid) and a laced permanent-magnet/iron/electromagnet (laced). Data is presented from magnets constructed for the SuperHILAC heavy-ion linear accelerator, and conclusions are drawn for various applications.

  12. Magnetic Fields and Forces in Permanent Magnet Levitated Bearings

    Microsoft Academic Search

    Kevin D. Bachovchin; James F. Hoburg; Richard F. Post

    2012-01-01

    Magnetic fields and magnetic forces from magnetic bearings made of circular Halbach permanent-magnet arrays are computed and analyzed. The magnetic fields are calculated using superposition of fields due to patches of magnetization charge at surfaces where the magnetization is discontinuous. The magnetic force from the magnetic bearing is computed using superposition of forces on each patch of magnetization charge. The

  13. Simulations of remanence and field distributions of permanent magnet array with rectangular cavity

    NASA Astrophysics Data System (ADS)

    Xu, X. N.; Lu, D. W.; Xu, X. B.; Zang, W. C.; Madireddi, Sesha

    2008-08-01

    The magnetic phenomena of a Halbach-type permanent magnet array under a strong self-field such as demagnetization, saturation, deflection, and rotation of remanence vectors occur deep in the interior of the magnets, and thus lead to an inhomogeneous field even for a hollow cylindrical permanent magnet array with circular cavity. Considering the anisotropic magnetization loops of commercially available permanent magnets, the self-consistent remanence and field distributions of a 16 piece hollow cylindrical permanent magnet array with rectangular cavity (HCPMARC) are presented here to simulate the magnetic phenomena inside the magnets. The field distribution of a HCPMARC can be modulated by array structure while keeping both the cross sectional areas of the cavity and the magnets constant. At the expense of field uniformity, a HCPMARC acquires greater center field uniformity than a HCPMACC does. Furthermore, we simulated the magnetization and field distributions for a yoked HCPMARC obtained by replacing the partial permanent magnets with soft ones on both magnetic poles of a yokeless HCPMARC. Such substitution always enhances field uniformity but depresses the center field. This, in turn, causes changes in the average magnitude of the field in the entire rectangular cavity.

  14. Permanent magnet array for the magnetic refrigerator

    NASA Astrophysics Data System (ADS)

    Lee, S. J.; Kenkel, J. M.; Pecharsky, V. K.; Jiles, D. C.

    2002-05-01

    Recent research into the development of magnetic refrigeration (MR) operating at room temperature has shown that it can provide a reliable, energy-efficient cooling system. To enhance the cooling power of the magnetic refrigerator, it is required to use a magnetic refrigerant material with large magnetocaloric effect (MCE) at the appropriate temperature. Most advanced magnetic refrigerant materials show largest MCE at high applied magnetic fields generated by a superconducting magnet. For application of MCE to air conditioners or household refrigerators, it is essential to develop a permanent magnet array to form a compact, strong, and energy-efficient magnetic field generator. Generating a magnetic field well above the remanence of a permanent magnet material is hard to achieve through conventional designs. A permanent magnet array based on a hollow cylindrical flux source is found to provide an appropriate geometry and magnetic field strength for MR applications.

  15. A Multi-axis Compact Positioner with a 6-coil Platen Moving Over a Superimposed Halbach Magnet Matrix

    E-print Network

    Nguyen, Vu Huy

    2012-07-16

    A multi-axis compact positioner is designed and implemented in this thesis. The single-moving-part positioner is designed to move in the magnetic field generated by a superimposed concentrated-field permanent magnet matrix. The compact positioner...

  16. High speed PM motor with hybrid magnetic bearing for kinetic energy storage

    Microsoft Academic Search

    D. Johnson; P. Pillay; M. Malengret

    2001-01-01

    This paper describes the design essentials of an external-rotor permanent magnet Halbach array motor with a hybrid magnetic bearing, intended for kinetic energy storage. The theoretical estimations are compared to finite element analysis as well as an approximated model using standard shape magnets. A dipole Balbach array produces a uniform flux distribution inside the cylindrical stator, where straight windings on

  17. Coherent magnetic semiconductor nanodot arrays

    PubMed Central

    2011-01-01

    In searching appropriate candidates of magnetic semiconductors compatible with mainstream Si technology for future spintronic devices, extensive attention has been focused on Mn-doped Ge magnetic semiconductors. Up to now, lack of reliable methods to obtain high-quality MnGe nanostructures with a desired shape and a good controllability has been a barrier to make these materials practically applicable for spintronic devices. Here, we report, for the first time, an innovative growth approach to produce self-assembled and coherent magnetic MnGe nanodot arrays with an excellent reproducibility. Magnetotransport experiments reveal that the nanodot arrays possess giant magneto-resistance associated with geometrical effects. The discovery of the MnGe nanodot arrays paves the way towards next-generation high-density magnetic memories and spintronic devices with low-power dissipation. PMID:21711627

  18. Magnetic forces between arrays of cylindrical permanent magnets

    Microsoft Academic Search

    D. Vokoun; G. Tomassetti; M. Beleggia; I. Stachiv

    2011-01-01

    Permanent magnet arrays are often employed in a broad range of applications: actuators, sensors, drug targeting and delivery systems, fabrication of self-assembled particles, just to name a few. An estimate of the magnetic forces in play between arrays is required to control devices and fabrication procedures. Here, we introduce analytical expressions for calculating the attraction force between two arrays of

  19. CHIP-SIZE MAGNETIC SENSOR ARRAYS

    Microsoft Academic Search

    Carl H. Smith; Robert W. Schneider

    2002-01-01

    Arrays of micron-sized magnetic sensors and sensor spacing on a single chip can be used to detect very small magnetic fields with high spatial resolution. These very small magnetic fields, or changes in magnetic fields, are associated with magnetic biosensors, non-destructive test\\/ inspection\\/evaluation, document validation including currency and credit cards and magnetic imaging. By using a silicon substrate, the signal

  20. Structure of One-Axis Controlled Repulsive Type Magnetic Bearing System With Surface Permanent Magnets Installed and Its Levitation and Rotation Tests

    Microsoft Academic Search

    Takahisa Ohji; Yoshiyuki Katsuda; Kenji Amei; Masaaki Sakui

    2011-01-01

    This paper deals with a new bearing structure of one-axis controlled repulsive type magnetic bearing system that has a motor function of a surface permanent magnet (SPM). We evaluated the magnetic bearing structures by using the 4-pole 4-segment type and 4-pole Halbach array, which were placed around cylindrical permanent magnet sets as field magnets. The comparison of magnetic flux density

  1. A bidirectional magnetic microactuator using electroplated permanent magnet arrays

    Microsoft Academic Search

    Hyoung J. Cho; Chong H. Ahn

    2002-01-01

    A novel bidirectional magnetic microactuator using electroplated permanent magnet arrays has been designed, fabricated and characterized. To realize a bidirectional microactuator, CoNiMnP-based permanent magnet arrays have been fabricated first on a silicon cantilever beam using a new electroplating technique. In the fabricated permanent magnets, the vertical coercivity and retentivity have been achieved up to 87.6 kA\\/m (1100 Oe) and 190

  2. Note: Manipulation of supersonic atomic beams with static magnetic fields

    NASA Astrophysics Data System (ADS)

    Gardner, Jamie; Castillo-Garza, Rodrigo; Raizen, Mark G.

    2013-09-01

    The inhomogeneous magnetic field of a permanent-magnet planar Halbach array is used to either deflect or to specularly reflect a supersonic beam of neutral atoms. Metastable neon and helium beams are tested to experimentally evaluate the performance of this array in a range of configurations. Results are compared with numerical simulations and the device is presented as a high precision tool for the manipulation of neutral atom beams.

  3. Improved Halbach sensor for NMR scanning of drill cores.

    PubMed

    Anferova, Sophia; Anferov, Vladimir; Arnold, Juliane; Talnishnikh, Elena; Voda, Mihai A; Kupferschläger, Klaus; Blümler, Peter; Clauser, Christoph; Blümich, Bernhard

    2007-05-01

    A lightweight Halbach magnet system for use in nuclear magnetic resonance (NMR) studies on drill cores was designed and built. It features an improved homogeneous magnetic field with a strength of 0.22 T and a maximum accessible sensitive volume. Additionally, it is furnished with a sliding table for automatic scans of cylindrical samples. This device is optimized for nondestructive online measurements of porosity and pore size distributions of water-saturated full cylindrical and split semicylindrical drill cores of different diameters. The porosity of core plugs with diameters from 20 to 80 mm can be measured routinely using exchangeable radiofrequency coils. Advanced NMR techniques that provide 2D T(1)-T(2) correlations with an average measurement time of 30 min and permeability estimates can be performed with a special insert suitable for small core plugs with diameter and length of 20 mm. PMID:17466767

  4. Three-Magnet Arrays for Unilateral Magnetic Resonance

    NASA Astrophysics Data System (ADS)

    Garcia Naranjo, Juan Carlos

    Unilateral Magnetic Resonance (UMR) has become, in different research areas, a powerful tool to interrogate samples of arbitrary size. The three-magnet array developed by the MRI Centre of the University of New Brunswick has features that make it a simple and robust approach for UMR. This thesis introduces a group of solutions to broaden the range of application of this design. Practical applications for non-destructive testing and reservoir core plug characterization are presented. We have shown that it is also possible to monitor the curing process of an epoxy/polyamidoamine system by employing a three-magnet array. A new version of the three-magnet array which features extended constant magnetic field gradients is also introduced. Constant gradients of more than 3 cm extent can be achieved in a very simple, compact and safe design. The application of the three-magnet array in combination with a solenoid as the RF probe for analysis of long core plugs has been presented. Core plugs of different diameter can be analyzed by simply changing the diameter of the RF probe employed for the measurement. Results of an initial survey of selective excitation in UMR are presented. The low SNR and inhomogeneities in the selective spot reduce the effectiveness of selective excitation for UMR.

  5. Passive magnetic bearing system

    DOEpatents

    Post, Richard F.

    2014-09-02

    An axial stabilizer for the rotor of a magnetic bearing provides external control of stiffness through switching in external inductances. External control also allows the stabilizer to become a part of a passive/active magnetic bearing system that requires no external source of power and no position sensor. Stabilizers for displacements transverse to the axis of rotation are provided that require only a single cylindrical Halbach array in its operation, and thus are especially suited for use in high rotation speed applications, such as flywheel energy storage systems. The elimination of the need of an inner cylindrical array solves the difficult mechanical problem of supplying support against centrifugal forces for the magnets of that array. Compensation is provided for the temperature variation of the strength of the magnetic fields of the permanent magnets in the levitating magnet arrays.

  6. Forces between arrays of permanent magnets of basic geometric shapes

    NASA Astrophysics Data System (ADS)

    Vokoun, D.; Beleggia, M.

    2014-01-01

    We provide formulas for evaluating the magnetic force between two permanent magnet arrays, regularly spaced over a square lattice. We focus on three basic shapes of magnets constituting the arrays: cylinder, sphere and rectangular prism. When the lattice parameter is large, the expressions can be used to calculate the force between two single magnets in a computationally efficient way. The calculations are validated experimentally by measuring the attraction force between two single permanent magnets, where we demonstrate a fair agreement within about 15%.

  7. Phase combination for self-cancellation of magnetic force in undulators

    NASA Astrophysics Data System (ADS)

    Kinjo, Ryota; Tanaka, Takashi

    2014-12-01

    A simple arrangement of undulator magnets having nearly zero magnetic force between the upper and lower magnet arrays is proposed, which significantly simplifies the mechanical structure of undulators. In this arrangement, each magnet array is divided into a number of sections, half of which are phase-shifted according to a particular rule without breaking the periodic condition required for the undulator field. Calculation results show that, when the gap over period is in practical range, more than or equal to 1 /18 , the magnetic force can be reduced down to less than 1 /50 of that in the Halbach undulator by applying the proposed scheme.

  8. The Inductrack Approach to Magnetic Levitation

    SciTech Connect

    Post, R.F.; Ryutov, D.D.

    2000-04-19

    Concepts developed during research on passive magnetic bearing systems at the Lawrence Livermore National Laboratory gave rise to a new approach to magnetic levitation, the Inductrack. A passive induced-current system employing permanent magnets on the moving vehicle, the Inductrack maximizes levitation forces by a combination of two elements. First, the permanent magnets on the vehicle are arranged in a ''Halbach array,'' a magnet configuration that optimally produces a periodic magnetic field below the array, while canceling the field above the array. Second, the track is made up of close-packed shorted electrical circuits. These circuits couple optimally to the magnetic field of the Halbach array. As a result, levitating forces of order 40 metric tonnes per square meter of Halbach array can be generated, using NdFeB magnets whose weight is a few percent of the levitated weight. Being an induced-current system, the levitation requires motion of the vehicle above a low transition speed. For maglev applications this speed is a few kilometers per hour, walking speed. At rest or in the station auxiliary wheels are needed. The Inductrack is thus fail-safe, that is, drive system failure would only result in the vehicle slowing down and finally settling on its auxiliary wheels. On the basis of theoretical analyses a small model vehicle and a 20-meter-long track was built and tested at speeds of order 12 meters per second. A second model, designed to achieve 10-g acceleration levels and much higher speeds, is under construction under NASA sponsorship, en route to the design of maglev-based launchers for rockets. Some of the presently perceived practical problems of implementing full-scale maglev systems based on the Inductrack concept will be discussed.

  9. Magnetic flux array for spontaneous magnetic reconnection experiments A. Kesich, J. Bonde, J. Egedal,a

    E-print Network

    Egedal, Jan

    Magnetic flux array for spontaneous magnetic reconnection experiments A. Kesich, J. Bonde, J; published online 24 June 2008 Experimental investigation of reconnection in magnetized plasmas relies on accurate characterization of the evolving magnetic fields. In experimental configurations where the plasma

  10. MRAM array with coupled soft-adjacent magnetic layer

    Microsoft Academic Search

    Yimin Guo; P. Wang; M.-M. Chen; C. Horng; T. Min; L. Hong; O. Voegeli; R. Tong; P. Chen; S. Le; J. Chen; T. Zhong; L. Yang; G. Liu; Y. Chen; S. Shi; K. Yang; D. Tsang

    2005-01-01

    Soft-adjacent magnetic layer (SAL) coupled MRAM arrays have been developed for high density, low current applications. Instead of using shape anisotropies, free layer elements have been used strongly coupled with their adjacent-soft magnetic bit lines, forming coupling anisotropies (perpendicular to bit line directions) on free layer elements to hold stored data. MRAM array test data show that the use of

  11. Novel microwave properties and "memory effect" in magnetic nanowire array

    NASA Astrophysics Data System (ADS)

    Kou, Xiaoming

    2011-12-01

    Ferromagnetic nanowire arrays embedded in insulating matrices have attracted great attention in recent years for their rich physics and potential as sensor and microwave applications. Magnetic nanowires made of 3d transitional metals or their alloys have the advantages of high saturation magnetizations, limited eddy current loss, and guaranteed microwave penetration due to nanometer size. The nanowire arrays can also have high ferromagnetic resonance (FMR) frequencies due to shape anisotropy. In this work, the following new phenomena of magnetic nanowire arrays are demonstrated and explained with a theoretical model. (1) A simple theoretical analysis indicates that high permeability is possible in nanowire arrays with the magnetocrystalline anisotropy comparable to the demagnetization energy and its easy axis perpendicular to the nanowire. With proper conditions, we have fabricated Co nanowire arrays with a crystalline easy axis perpendicular to the nanowire. For Co nanowire arrays with certain geometries, high permeability and low losses have been achieved. (2) Magnetic materials with tunable FMR are highly desirable in microwave devices. We demonstrate that the natural FMR of Ni90Fe10 nanowire array can be tuned continuously from 8.2 to 11.7 GHz by choosing different remanent state. Theoretical model based on dipolar interaction among nanowires has been developed to explain the observed phenomena. A double FMR feature caused by dipolar interaction in magnetic nanowire array was predicted and verified in Co nanowires. (3) A memory effect has also been demonstrated in magnetic nanowire arrays. The magnetic nanowire array has the ability to record the maximum magnetic field that the array has been exposed to after the field has been turned off. The origin of the memory effect is the strong magnetic dipole interaction among the nanowires. Based on the memory effect, a novel and extremely low cost EMP detection scheme is proposed. It has the potential to measure magnetic field pulses as high as a few hundred Oe without breaking down. In the proposed EMP detector, a magnetic field sensor is required to measure the surface field of the magnetic nanowire array. MgO based magnetic tunnel junction (MTJ) is one type of magnetic field sensors. We investigated the evolution of the magnetic transport properties as a function of short annealing time in MgO based MTJ junctions. It is found that the desired sensor behavior appears in samples annealed for 17 minutes. The result can be well fitted by using the superparamagnetism theory, suggesting the formation of superparamagnetic particles in the free layer during the high temperature annealing. The control of MTJ properties with annealing time is desirable in magnetic field sensor productions.

  12. Method of making a miniature scale periodic permanent magnet array and miniature scaled periodic permanent magnet array so formed

    Microsoft Academic Search

    Fred J. Cadieu; Tak D. Cheung

    1986-01-01

    A miniature scale periodic permanent magnet array is made from a magnetic material having a high intrinsic coercive force and a magnetic material having a low intrinsic coercive force by depositing alternating layers of the high and low intrinsic coercive force materials, exposing the layered structure to a strong film plane magnetic field to saturate the layers, applying a reverse

  13. A magnetic microstirrer and array for microfluidic mixing

    Microsoft Academic Search

    Liang-Hsuan Lu; Kee Suk Ryu; Chang Liu

    2002-01-01

    We report the development of a micromachined magnetic-bar micromixer for microscale fluid mixing in biological laboratory-on-a-chip applications. The mixer design is inspired by large scale magnetic bar mixers. A rotating magnetic field causes a single magnetic bar or an array of them to rotate rapidly within a fluid environment. A fabrication process of the magnetic bar mixer is developed. Results

  14. MRI RF array decoupling method with magnetic wall distributed filters.

    PubMed

    Connell, Ian R O; Gilbert, Kyle M; Abou-Khousa, Mohamed A; Menon, Ravi S

    2015-04-01

    Multi-channel radio-frequency (RF) transmit coil arrays have been developed to mitigate many of the RF challenges associated with ultra-high field ( ? 7T) magnetic resonance imaging (MRI). These arrays can be used for parallel RF transmission to produce spatially tailored RF excitation over the field of view. However, the realization of such arrays remains a challenge due to significant reactive interaction between the array coils, i.e., mutual coupling. In this paper, a novel bandstop filter ("magnetic wall") is used in an MRI RF transmit array to decouple individual coils. The proposed decoupling method is inspired by periodic resonator designs commonly used in frequency selective surfaces and is used as a distributed RF filter to suppress the transmission of RF energy between coils in an array. The decoupling of the magnetic wall (MW) is analyzed in terms of equivalent circuits that include terms for both magnetic and electric coupling for an arbitrary number of MW resonant conductors. Both frequency-and time-domain full-wave simulations were performed to analyze a specific MW structure. The performance of the proposed method is experimentally validated for both first-order coupling and higher-order coupling with a three-coil 7T array setup. Analysis and measurements confirm that the rejection band of the MW can be tuned to provide high isolation in the presence of cross coupling between RF array coils. PMID:25838388

  15. High-Field Gradient Permanent Micromagnets for Targeted Drug Delivery with Magnetic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Zablotskii, Vitalii; Pastor, José Martín; Larumbe, Silvia; Pérez-Landazábal, José Ignacio; Recarte, Vicente; Gómez-Polo, Cristina

    2010-12-01

    We analytically investigate several micromagnetic systems aimed at the optimization of drug and gene delivery processes and show their applicability to the controlled positioning of magnetic nanoparticles. The systems considered are: i) a square array of cylindrical microneedles, ii) a planar stepped array of magnets, and iii) a Halbach array of micromagnets. We calculate spatial distributions of force components acting on a magnetic nanoparticle and the field gradients produced by these magnetic configurations. These calculations show that array geometries tend to enhance the field gradients and forces that can be obtained from a given material. The benefits of the proposed micromagnetic systems—tunability, scalability, and ability of creation of magnetic flux distributions with high-gradient areas allowing precise focusing of magnetic nanoparticles (MNPs)—are also discussed.

  16. Selective actuation of arrays of carbon nanotubes using magnetic resonance.

    PubMed

    Volodin, Alexander; Santini, Claudia A; De Gendt, Stefan; Vereecken, Philippe M; Van Haesendonck, Chris

    2013-07-23

    We introduce the use of ferromagnetic resonance (FMR) to actuate mechanical resonances in as grown arrays of carbon nanotubes (CNTs) loaded with Ni particles (Ni-CNTs). This contactless method is closely related to the magnetic resonance force microscopy technique and provides spatial selectivity of actuation along the array. The Ni-CNT arrays are grown by chemical vapor deposition and are composed of homogeneous CNTs with uniform length (~600 nm) and almost equal diameter (~20 nm), which are loaded with Ni catalyst particles at their tips due to the tip growth mode. The vibrations of the Ni-CNTs are actuated by relying on the driving force that appears due to the FMR excited at about 2 GHz in the Ni particles (diameter ~100 nm). The Ni-CNT oscillations (frequency ~40 MHz) are detected mechanically by atomic force microscopy. The acquired oscillation images of the Ni-CNT uniform array reveal clear maxima in the spatial distribution of the oscillation amplitudes. We attribute these maxima to the "sensitive slices", i.e., the spatial regions of the Ni-CNT array where the FMR condition is met. Similar to magnetic resonance imaging, the sensitive slice is determined by the magnetic field gradient and moves along the Ni-CNT array as the applied magnetic field is ramped. Our excitation method does not require the presence of any additional microfabricated electrodes or coils near the CNTs and is particularly advantageous in cases where the traditional electrical actuation methods are not effective or cannot be implemented. The remote actuation can be effectively implemented also for arrays of other magnetic nanomechanical resonators. PMID:23742039

  17. Optimizing colloidal dispersity of magnetic nanoparticles based on magnetic separation with magnetic nanowires array

    NASA Astrophysics Data System (ADS)

    Sun, Jianfei; He, Miaomiao; Liu, Xuan; Gu, Ning

    2015-02-01

    Based on sharp geometry of Ni nanowires, we developed a novel high-gradient magnetic separator that was composed of a nanowires array and a uniform magnetic field. When suspension of magnetic nanoparticles (MNPs) flowed through it, the relatively large nanoparticles or clusters were removed from the suspension so that the size distribution can be improved. The separation resulted from magnetic force so that extra molecules or solvents were unnecessary to add. The performance was proved by scanned electron microscopy characterization and dynamic light scattering measurement. The improvement in magnetic colloidal dispersivity is important for the biomedical application of MNPs. Our results may also play a role in microfluidic application and nanoparticle-based detection.

  18. Magnetic nanoparticle assembly arrays prepared by hierarchical self-assembly on a patterned surface.

    PubMed

    Wen, Tianlong; Zhang, Dainan; Wen, Qiye; Zhang, Huaiwu; Liao, Yulong; Li, Qiang; Yang, Qinghui; Bai, Feiming; Zhong, Zhiyong

    2015-03-01

    Inverted pyramid hole arrays were fabricated by photolithography and used as templates to direct the growth of colloidal nanoparticle assemblies. Cobalt ferrite nanoparticles deposit in the holes to yield high quality pyramid magnetic nanoparticle assembly arrays by carefully controlling the evaporation of the carrier fluid. Magnetic measurements indicate that the pyramid magnetic nanoparticle assembly arrays preferentially magnetize perpendicular to the substrate. PMID:25712606

  19. Magnetic track array for efficient bead capture in microchannels.

    PubMed

    Abonnenc, Mélanie; Gassner, Anne-Laure; Morandini, Jacques; Josserand, Jacques; Girault, Hubert H

    2009-10-01

    Magnetism-based microsystems, as those dedicated to immunoaffinity separations or (bio)chemical reactions, take benefit of the large surface area-to-volume ratio provided by the immobilized magnetic beads, thus increasing the sensitivity of the analysis. As the sensitivity is directly linked to the efficiency of the magnetic bead capture, this paper presents a simple method to enhance the capture in a microchannel. Considering a microchannel surrounded by two rectangular permanent magnets of different length (L (m) = 2, 5, 10 mm) placed in attraction, it is shown that the amount of trapped beads is limited by the magnetic forces mainly located at the magnet edges. To overcome this limitation, a polyethylene terephthalate (PET) microchip with an integrated magnetic track array has been prototyped by laser photo-ablation. The magnetic force is therefore distributed all along the magnet length. It results in a multi-plug bead capture, observed by microscope imaging, with a magnetic force value locally enhanced. The relative amount of beads, and so the specific binding surface for further immunoassays, presents a significant increase of 300% for the largest magnets. The influence of the track geometry and relative permeability on the magnetic force was studied by numerical simulations, for the microchip operating with 2-mm-long magnets. PMID:19685235

  20. Revealing Cosmic Magnetism with the Square Kilometre Array

    Microsoft Academic Search

    Bryan M. Gaensler; Rainer Beck; Luigina Feretti; Wolfgang Reich

    2008-01-01

    The Square Kilometer Array (SKA) will be one of a suite of new, large telescopes for the 21 st century probing fundamental physics, the origin and evolution of the Universe, the structure of the Milky Way Galaxy, and the formation and distribution of planets. The evolution, structure and origin of magnetic fields are still open problems in physics and astrophysics.

  1. Fabrication of Metallic Magnetic Calorimeter X-ray Detector Arrays

    NASA Astrophysics Data System (ADS)

    Hsieh, W.-T.; Adams, J. A.; Bandler, S. R.; Beyer, J.; Denis, K. L.; Eguchi, H.; Figueroa-Feliciano, E.; Rotzinger, H.; Schneider, G. H.; Seidel, G. M.; Stevenson, T. R.; Travers, D. E.

    2008-04-01

    Microcalorimeters with metallic magnetic sensors show great promise for use in astronomical X-ray spectroscopy. We describe the design and fabrication of a lithographically patterned magnetic microcalorimeter. A paramagnetic AuEr film is sputter-deposited as the sensor, which is coupled to a low noise SQUID via a meander superconducting pickup loop used as an inductor. This inductor also provides the magnetic field bias to the sensor. The AuEr film is deposited over this meander such that the field created by a large current flowing in the loop magnetizes the sensor material. The use of thin film techniques in the fabrication of these magnetic sensors not only allows strong magnetic coupling between the sensor and the inductor, it also is scalable for array fabrication.

  2. Analysis and design optimization of ironless linear permanent magnet synchronous motors with non-overlapping concentrated windings for ultra-precision positioning system

    NASA Astrophysics Data System (ADS)

    Li, Liyi; Tang, Yongbin; Liu, Jiaxi; Chen, Qiming

    2013-01-01

    This paper presents the electromagnetic design of Ironless permanent magnet linear synchronous motor with non-overlapping concentrated windings based on the Equivalent Magnetizing Current(EMC) method. For one such motor structure we give analytical formulae for its magnetic field and thrust density and analyze to improve air-gap flux density and thrust density by varying motor design parameters. In order to minimize thrust ripple and improve thrust density, we analyze the superiority of ILPMLSM with Halbach magnet array and fractional-slot concentrated winding. The validity of the proposed technique is confirmed with 2-D Finite Element (FE) analysis.

  3. Magnetic interactions in Ni-Cu/Cu superlattice nanowire arrays

    NASA Astrophysics Data System (ADS)

    Robinson, A.; Schwarzacher, W.

    2003-05-01

    The remanent magnetization of Ni-Cu/Cu superlattice nanowires was investigated. Arrays of superlattice nanowires were prepared by template deposition through polycarbonate nanoporous membranes using a single electrolyte bath. The thicknesses of the nickel-rich layers (tNi) and copper layers (tCu) were independently controlled by monitoring the current during deposition. The wire diameter was determined by transmission electron microscopy imaging to be 80 nm. A study of the remanent magnetization at 20 K for a range of values of tNi and tCu reveals the existence of magnetic interactions within each array. It is noted that for an array with tNi of 200 Å, the strength of the interactions decreases with increasing tCu, indicating that the interactions are taking place between nickel layers. However the interaction strength appears to reach a minimum level, beyond which an increase in tCu does not correspond to a decrease in the interaction strength observed. A minimum interaction level is also observed for an array with tNi of 50 Å, for all values of tCu investigated.

  4. Microfabricated atomic vapor cell arrays for magnetic field measurements

    SciTech Connect

    Woetzel, S.; Schultze, V.; IJsselsteijn, R.; Schulz, T.; Anders, S.; Stolz, R.; Meyer, H.-G. [Institute of Photonic Technology, Albert-Einstein-Str. 9, D-07745 Jena (Germany)

    2011-03-15

    We describe a method for charging atomic vapor cells with cesium and buffer gas. By this, it is possible to adjust the buffer gas pressure in the cells with good accuracy. Furthermore, we present a new design of microfabricated vapor cell arrays, which combine silicon wafer based microfabrication and ultrasonic machining to achieve the arrays of thermally separated cells with 50 mm{sup 3} volume. With cells fabricated in the outlined way, intrinsic magnetic field sensitivities down to 300 fT/Hz{sup 1/2} are reached.

  5. About the Influence of the Magnetic Field Configuration on the Levitation Characteristics of the System Superconductor - Array of Magnets

    NASA Astrophysics Data System (ADS)

    Ermolaev, Yu. S.; Rudnev, I. A.

    2014-07-01

    Interaction of a superconductor with an array of magnets having different orientations of the magnetization vector is theoretically investigated. Based on a critical state model, the interaction force arising in the system superconductor - array of magnets is calculated by the method of finite elements. Optimal configurations of the magnetic system are established in which maximum values of both attractive and repulsive forces are created.

  6. Bistability in a Superconducting Al Thin Film Induced by Arrays of Fe-Nanodot Magnetic Vortices

    NASA Astrophysics Data System (ADS)

    Villegas, J. E.; Li, C.-P.; Schuller, Ivan K.

    2007-11-01

    A hybrid system, consisting of an array of Fe nanodots covered by a superconducting Al thin film, exhibits very unusual magnetotransport, including a giant hysteretic magnetoresistance with different reversible or irreversible regimes related to the magnetic state of the array. These effects originate from the magnetic fields produced by magnetic nanodots in the “magnetic vortex state.” This is a unique model system in which properties of a magnetic array are transferred into the superconductor.

  7. The Square Kilometre Array: A new probe of cosmic magnetism

    E-print Network

    Bryan M. Gaensler

    2006-03-02

    Magnetic fields are a fundamental part of many astrophysical phenomena, but the evolution, structure and origin of magnetic fields are still unresolved problems in physics and astrophysics. When and how were the first fields generated? Are present-day magnetic fields the result of standard dynamo action, or do they represent rapid or recent field amplification through other processes? What role do magnetic fields play in turbulence, cosmic ray acceleration and structure formation? I explain how the Square Kilometre Array (SKA), a next-generation radio telescope, can deliver stunning new data-sets that will address these currently unanswered issues. The foundation for these experiments will be an all-sky survey of rotation measures, in which Faraday rotation toward >10^7 background sources will provide a dense grid for probing magnetism in the Milky Way, nearby galaxies, and in distant galaxies, clusters and protogalaxies. Using these data, we can map out the evolution of magnetized structures from redshifts z > 3 to the present, can distinguish between different origins for seed magnetic fields in galaxies, and can develop a detailed model of the magnetic field geometry of the intergalactic medium and of the overall Universe. In addition, the SKA will certainly discover new magnetic phenomena beyond what we can currently predict or imagine.

  8. Levitation Force Investigation of Bulk HTSC Above Halbach PMG with Different Cross-Section Physical Dimensions by 3D-Modeling Numerical Method

    NASA Astrophysics Data System (ADS)

    Lu, Yiyun; Liu, Guoliang; Qin, Yujie

    2014-10-01

    The levitation force of a bulk high temperature superconductor (HTSC) over Halbach permanent magnet guideways (PMG) with different cross-section configuration is studied by numerical method. The Halbach PMG is composed of three host permanent magnets (HPMs) and two slave permanent magnets (SPMs). One cylindrical bulk HTSC with a diameter of 30 mm and height of 15 mm is used. The 3D-modeling is formulated by the H-method. The numerical resolving codes are practiced using finite element method (FEM). The E-J power law is used to describe the electric current nonlinear characteristics of bulk HTSC. By the method, the influence of the cross-section physical dimensions of Halbach PMG on the levitation forces of bulk HTSC levitated above the PMG is studied. The simulation results show that increasing the width of SPM ( can enhance the bulk HTSC levitation performance immediately under the condition of keeping the ratio of ( : the width of HPM) to between 1.6 and 1.8, the ratio of td (the height of the PMG) to between 1.2 and 1.4. By the method, the bulk HTSC better levitation performance can be expected.

  9. Magnetization Reversal in Arrays of Perpendicularly Magnetized Ultrathin Dots Coupled by Dipolar Interaction

    Microsoft Academic Search

    T. Aign; P. Meyer; S. Lemerle; J. P. Jamet; J. Ferré; V. Mathet; C. Chappert; J. Gierak; C. Vieu; F. Rousseaux; H. Launois; H. Bernas

    1998-01-01

    Arrays of micron size perpendicularly magnetized ultrathin Co dots with 20 nm separation were obtained using ion irradiation by a focused ion beam and studied by polar magneto-optical microscopy. Because irradiation induces easy nucleation regions along dot borders, magnetization reversal inside the dots under a perpendicular field is due only to domain wall propagation, driven by applied field and dipolar

  10. Magnetization Reversal Study of Geometrically Frustrated, Quasiperiodic Antidot Arrays

    NASA Astrophysics Data System (ADS)

    Woods, Justin; Bhat, Vinayak; Farmer, Barry; de Long, Lance; Hastings, Todd; Sklenar, Joseph; Ketterson, John

    2013-03-01

    We have used electron beam lithography to pattern quasiperiodic AD arrays in permalloy films of thickness 25 nm. Two five-fold rotationally symmetric Penrose tilings were fabricated with AD kites and darts having long (d1) and short edges (d2) equal to 1620 nm or 810 nm, and 1000 nm or 500 nm, respectively, with fixed Py line width of 100 nm. Two eight-fold Ammann tilings were patterned with square and rhomboid AD of edge lengths of 1000 nm or 2000 nm, resp. Magnetization reversal was studied at various angles between the in-plane, applied DC magnetic field H and the quasiperiodic array. We observed very reproducible hysteresis curves with low-field anomalies not present in our previous studies of periodic, square arrays of square-, circular- and diamond-shaped AD; e.g., for the Penrose tilings, we observed four reproducible knee anomalies (both for 81 H 331 Oe, and for -19 H -71 Oe). Micromagnetic simulations exhibit systematic evolution of domain walls (DW) in the hysteretic regime due to DW pinning by edges of the quasicrystalline pattern, which correlates DW evolution with observed features in magnetic hysteresis.

  11. Vibrational Properties of High- Superconductors Levitated Above a Bipolar Permanent Magnetic Guideway

    NASA Astrophysics Data System (ADS)

    Liu, Lu; Wang, Jiasu

    2014-05-01

    A bipolar permanent magnetic guideway (PMG) has a unique magnetic field distribution profile which may introduce a better levitation performance and stability to the high- superconducting (HTS) maglev system. The dynamic vibration properties of multiple YBCO bulks arranged into different arrays positioned above a bipolar PMG and free to levitate were investigated. The acceleration and resonance frequencies were experimentally measured, and the stiffness and damping coefficients were evaluated for dynamic stability. Results indicate that the levitation stiffness is closely related to the field-cooling-height and sample positioning. The damping ratio was found to be low and nonlinear for the Halbach bipolar HTS-PMG system.

  12. Magnetocaloric effect: permanent magnet array for generation of high magnetic fields

    NASA Astrophysics Data System (ADS)

    Lee, Seong-Jae; Kenkel, John; Jiles, David

    2002-03-01

    The magnetocaloric effect (MCE), the heating or cooling of magnetic materials in a magnetic field, is unusually large in the Gd_5(Si_xGe_1-x)4 alloy system. Normally the maximum in the MCE occurs at the Curie temperature (Tc) because the spin entropy change is a maximum. By suitable selection of the composition of this alloy system the Curie temperature can be changed over the range 25 K for x = 0 to 340 K for x =1, and the composition range around x = 0.5 exhibits the largest magnetocaloric effect. In order to increase the amount of heat exchanged the change in applied magnetic field should be as large as possible, and in this research values above 1.5 Tesla are suggested. We have studied a permanent magnet array based on NdFeB, which with a remanent magnetization of only 1.2 Tesla can still generate a magnetic flux density, or magnetic induction B of 2-3 Tesla. In order to generate the high magnetic induction in the absence of a power supply, a modified hollow cylindrical permanent magnet array (HCPMA) has been designed to produce the required strength of magnetic field. Soft magnetic materials including permalloy (NiFe) were used for focusing the magnetic field in the central region. The magnitude of the magnetic flux density at the center was about 2 Tesla. The magnitude and homogeneity of the magnetic field for this design are comparable with the conventional C-shaped yoke and HCPMA. This can be easily adapted for a low power rotary system in which the magnetocaloric material can be exposed alternately to high and low magnetic fields so that it can accept and reject heat from its surroundings.

  13. Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient

    PubMed Central

    Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

    2014-01-01

    Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

  14. Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient.

    PubMed

    Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

    2014-01-01

    Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

  15. Development of a magnetic nanoparticle susceptibility magnitude imaging array.

    PubMed

    Ficko, Bradley W; Nadar, Priyanka M; Hoopes, P Jack; Diamond, Solomon G

    2014-02-21

    There are several emerging diagnostic and therapeutic applications of magnetic nanoparticles (mNPs) in medicine. This study examines the potential for developing an mNP imager that meets these emerging clinical needs with a low cost imaging solution that uses arrays of digitally controlled drive coils in a multiple-frequency, continuous-wave operating mode and compensated fluxgate magnetometers. The design approach is described and a mathematical model is developed to support measurement and imaging. A prototype is used to demonstrate active compensation of up to 185 times the primary applied magnetic field, depth sensitivity up to 2.5 cm (p < 0.01), and linearity over five dilutions (R(2) > 0.98, p < 0.001). System frequency responses show distinguishable readouts for iron oxide mNPs with single magnetic domain core diameters of 10 and 40 nm, and multi-domain mNPs with a hydrodynamic diameter of 100 nm. Tomographic images show a contrast-to-noise ratio of 23 for 0.5 ml of 12.5 mg Fe ml(-1) mNPs at 1 cm depth. A demonstration involving the injection of mNPs into pork sausage shows the potential for use in biological systems. These results indicate that the proposed mNP imaging approach can potentially be extended to a larger array system with higher-resolution. PMID:24504184

  16. Development of a Magnetic Nanoparticle Susceptibility Magnitude Imaging Array

    PubMed Central

    Ficko, Bradley W.; Nadar, Priyanka M.; Hoopes, P. Jack; Diamond, Solomon G.

    2014-01-01

    There are several emerging diagnostic and therapeutic applications of magnetic nanoparticles (mNPs) in medicine. This study examines the potential for developing an mNP imager that meets these emerging clinical needs with a low cost imaging solution that uses arrays of digitally controlled drive coils in a multiple-frequency, continuous-wave operating mode and compensated fluxgate magnetometers. The design approach is described and a mathematical model is developed to support measurement and imaging. A prototype is used to demonstrate active compensation of up to 185 times the primary applied magnetic field, depth sensitivity up to 2.5 cm (p < 0.01), and linearity over 5 dilutions (R2 > 0.98, p <0.001). System frequency responses show distinguishable readouts for iron oxide mNPs with single magnetic domain core diameters of 10 nm and 40 nm, and multi-domain mNPs with a hydrodynamic diameter of 100 nm. Tomographic images show a contrast-to-noise ratio of 23 for 0.5 ml of 12.5 mg Fe/ml mNPs at 1 cm depth. A demonstration involving the injection of mNPs into pork sausage shows the potential for use in biological systems. These results indicate that the proposed mNP imaging approach can potentially be extended to a larger array system with higher-resolution. PMID:24504184

  17. Development of a magnetic nanoparticle susceptibility magnitude imaging array

    NASA Astrophysics Data System (ADS)

    Ficko, Bradley W.; Nadar, Priyanka M.; Hoopes, P. Jack; Diamond, Solomon G.

    2014-02-01

    There are several emerging diagnostic and therapeutic applications of magnetic nanoparticles (mNPs) in medicine. This study examines the potential for developing an mNP imager that meets these emerging clinical needs with a low cost imaging solution that uses arrays of digitally controlled drive coils in a multiple-frequency, continuous-wave operating mode and compensated fluxgate magnetometers. The design approach is described and a mathematical model is developed to support measurement and imaging. A prototype is used to demonstrate active compensation of up to 185 times the primary applied magnetic field, depth sensitivity up to 2.5 cm (p < 0.01), and linearity over five dilutions (R2 > 0.98, p < 0.001). System frequency responses show distinguishable readouts for iron oxide mNPs with single magnetic domain core diameters of 10 and 40 nm, and multi-domain mNPs with a hydrodynamic diameter of 100 nm. Tomographic images show a contrast-to-noise ratio of 23 for 0.5 ml of 12.5 mg Fe ml-1 mNPs at 1 cm depth. A demonstration involving the injection of mNPs into pork sausage shows the potential for use in biological systems. These results indicate that the proposed mNP imaging approach can potentially be extended to a larger array system with higher-resolution.

  18. A superconducting quadrupole magnet array for a heavy ion fusion driver

    SciTech Connect

    Caspi, S.; Bangerter, r.; Chow, K.; Faltens, A.; Gourley, S.; Hinkins, R.; Gupta, R.; Lee, E.; McInturff, A.; Scanlan, R.; Taylor, C.; Wolgast, D.

    2000-06-27

    A multi-channel quadrupole array has been proposed to increase beam intensity and reduce space charge effects in a Heavy Ion Fusion Driver. A single array unit composed of several quadrupole magnets, each with its own beam line, will be placed within a ferromagnetic accelerating core whose cost is directly affected by the array size. A large number of focusing arrays will be needed along the accelerating path. The use of a superconducting quadrupole magnet array will increase the field and reduce overall cost. We report here on the design of a compact 3 x 3 superconducting quadrupole magnet array. The overall array diameter and length including the cryostat is 900 x 700 mm. Each of the 9 quadrupole magnets has a 78 mm warm bore and an operating gradient of 50 T/m over an effective magnetic length of 320 mm.

  19. Correlation of experimental data and three-dimensional finite element modeling of a spinning magnet array

    SciTech Connect

    Lorimer, W.L.; Lieu, D.K. [Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering] [Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering; Hull, J.R.; Mulcahy, T.M.; Rossing, T.D. [Argonne National Lab., IL (United States)] [Argonne National Lab., IL (United States)

    1994-09-01

    Drag forces due to eddy currents induced by the relative motion of a conductor and a magnetic field occur in many practical devices: motors, brakes, magnetic bearings, and magnetically levitated vehicles. Here, a magnet array was spun above an aluminum disk, and the drag torque was measured for various speeds and gap sizes. Drag torques calculated using a three-dimensional finite element program were consistent with measured values. The finite element model was also used to determine the effects of the polarity and position of magnets in the source array. The peak torque was shown to occur when magnets are located at a radius equal to 70% of the disk radius. A magnet array with alternate magnets reversed was shown to produce more than twice the drag of an array comprised of parallel magnets. An approximation for fields under the magnet centers was obtained using a two-dimensional analytical solution.

  20. Magnetic breakdown in an array of overlapping Fermi surfaces

    NASA Astrophysics Data System (ADS)

    Kadigrobov, A. M.; Radi?, D.; Bjeliš, A.

    2015-03-01

    We develop a theoretical framework for a magnetic breakdown in an array of circular two-dimensional bands with a finite overlap of neighboring Fermi surfaces due to the presence of a presumably weak periodic potential, and apply the obtained results to the electron bands in carbon honeycomb structures of doped graphene and intercalated graphite compounds. In contrast to the standard treatment, inaugurated more than fifty years ago by Slutskin and Kadigrobov, with electron semiclassical trajectories encircling significantly overlapping Fermi surfaces, we examine a configuration in which bands are related in a way that the Fermi surfaces only slightly overlap, forming internal band pockets with areas of the size comparable to the area of the quantum magnetic flux for a given external magnetic field. Such band configuration has to be treated quantum mechanically. The calculation leads to the results for magnetic breakdown coefficients comprising an additional large factor with respect to the standard results, proportional to the ratio of the Fermi energy and the cyclotron energy. Also, these coefficients show oscillating dependence on energy, as well as on the wave number of periodic potential. Both mentioned elements enable the adjustment of the preferred wave vector of possible magnetic breakdown induced density wave instability at the highest possible critical temperature.

  1. Magnetic properties of Ni nanowires in self-assembled arrays

    NASA Astrophysics Data System (ADS)

    Zheng, M.; Menon, L.; Zeng, H.; Liu, Y.; Bandyopadhyay, S.; Kirby, R. D.; Sellmyer, D. J.

    2000-11-01

    Magnetic properties of Ni nanowires electrodeposited into self-assembled porous alumina arrays have been investigated. By anodizing aluminum in sulfuric acid and immersing the as-anodized template into phosphoric acid for different lengths of time, we are able to vary the diameters of the subsequently deposited nanowires between 8 and 25 nm. The coercivity measured along wire axis first increases with the wire diameter, reaches a maximum of 950 Oe near a diameter of 18 nm, and then decreases with further increase of wire diameter. The dependence of the magnetization of Ni nanowires is found to follow Bloch's law at low temperature but with the Bloch exponent decreasing from the bulk value and the Bloch constant increasing from the bulk value by an order of magnitude.

  2. Configurational spin reorientation phase transition in magnetic nanowire arrays

    NASA Astrophysics Data System (ADS)

    Tartakovskaya, Elena V.; Pardavi-Horvath, Martha; Vázquez, Manuel

    2010-03-01

    Classical microscopic spin reorientation phase transitions (RPT) are the result of competing magnetocrystalline anisotropies. RPTs can also be observed in discrete macroscopic systems induced by competing shape anisotropies and magnetostatic coupling. Such a configurational RPT was recently observed in series of self-organized hexagonal arrays of 2.5 ?m long, 25-60 nm diameter circular permalloy nanowires grown in anodic alumina matrix. This RPT is a crossover transition from a one-dimensional easy axis "wire" behavior of weakly interacting uniaxial nanowires to a two-dimensional behavior of strongly coupled "wire film" having an easy plane anisotropy. It is shown that RPT takes place due to the competition between the intrinsic dipolar forces in individual wires and the external dipolar field of interacting nanowires in the array. The crossover occurs at a volume ratio of 0.38 for 65 nm periodicity. The experimental results are in agreement with the semi-analytical calculations of the dipolar interaction fields for these arrays of circular ferromagnetic nanowires, and are interpreted in terms of the Landau phase transition theory. The conditions for the crossover and the order of the phase transition are established. Based on the contribution to the magnetic energy from the flower state at the ends of the wires, it is concluded that the observed transition is of the first order.

  3. ELECTROMOTION 2009 3D Analytical Calculation of Forces between

    E-print Network

    Paris-Sud XI, Université de

    ]. For example, wigglers can be build using permanent magnets or electromagnets. Permanent magnet wigglers magnet and a Halbach array and between two Halbach systems Keywords-- Halbach array, Permanent magnet. These results are very interesting to understand the mechanical forces acting on permanent magnets. For those

  4. A Mobile Ferromagnetic Shape Detection Sensor Using a Hall Sensor Array and Magnetic Imaging

    PubMed Central

    Misron, Norhisam; Shin, Ng Wei; Shafie, Suhaidi; Marhaban, Mohd Hamiruce; Mailah, Nashiren Farzilah

    2011-01-01

    This paper presents a Mobile Hall Sensor Array system for the shape detection of ferromagnetic materials that are embedded in walls or floors. The operation of the Mobile Hall Sensor Array system is based on the principle of magnetic flux leakage to describe the shape of the ferromagnetic material. Two permanent magnets are used to generate the magnetic flux flow. The distribution of magnetic flux is perturbed as the ferromagnetic material is brought near the permanent magnets and the changes in magnetic flux distribution are detected by the 1-D array of the Hall sensor array setup. The process for magnetic imaging of the magnetic flux distribution is done by a signal processing unit before it displays the real time images using a netbook. A signal processing application software is developed for the 1-D Hall sensor array signal acquisition and processing to construct a 2-D array matrix. The processed 1-D Hall sensor array signals are later used to construct the magnetic image of ferromagnetic material based on the voltage signal and the magnetic flux distribution. The experimental results illustrate how the shape of specimens such as square, round and triangle shapes is determined through magnetic images based on the voltage signal and magnetic flux distribution of the specimen. In addition, the magnetic images of actual ferromagnetic objects are also illustrated to prove the functionality of Mobile Hall Sensor Array system for actual shape detection. The results prove that the Mobile Hall Sensor Array system is able to perform magnetic imaging in identifying various ferromagnetic materials. PMID:22346653

  5. Magnetic wire trap arrays for biomarker-based molecular detection

    NASA Astrophysics Data System (ADS)

    Vieira, Gregory; Mahajan, Kalpesh; Ruan, Gang; Winter, Jessica; Sooryakumar, R.

    2012-02-01

    Submicrometer-scale magnetic devices built on chip-based platforms have recently been shown to present opportunities for new particle trapping and manipulation technologies. Meanwhile, advances in nanoparticle fabrication allow for the building of custom-made particles with precise control of their size, composition, and other properties such as magnetism, fluorescence, and surface biomarker characteristics. In particular, carefully tailored surface biomarkers facilitate precise binding to targeted molecules, self-actuated construction of hybrid structures, and fluorescence-based detection schemes. Based on these progresses, we present an on-chip detection mechanism for molecules with known surface markers. Hybrid nanostructures consisting of micelle nanoparticles, fluorescent quantum dots, and superparamagnetic iron oxide nanoparticles are used to detect proteins or DNA molecules. The target is detected by the magnetic and fluorescent functionalities of the composite nanostructure, whereas in the absence of the target these signals are not present. Underlying this approach is the simultaneous manipulation via ferromagnetic zigzag nanowire arrays and imaging via quantum dot excitation. This chip-based detection technique could provide a powerful, low cost tool for ultrasensitive molecule detection with ramifications in healthcare diagnostics and small-scale chemical synthesis.

  6. Spin-wave edge modes in finite arrays of dipolarly coupled magnetic nanopillars

    NASA Astrophysics Data System (ADS)

    Lisenkov, Ivan; Tyberkevych, Vasyl; Slavin, Andrei; Bondarenko, Pavel; Ivanov, Boris A.; Bankowski, Elena; Meitzler, Thomas; Nikitov, Sergey

    2014-09-01

    The frequency spectrum of spin-wave edge modes localized near the boundaries of a finite array of dipolarly coupled magnetic nanopillars is calculated theoretically. Two mechanisms of edge mode formation are revealed: inhomogeneity of the internal static magnetic field existing near the array boundaries and time-reversal symmetry breaking of the dipole-dipole interaction. The latter mechanism is analogous to the formation mechanism of a surface Damon-Eschbach mode in continuous in-plane magnetized magnetic films and is responsible for the nonreciprocity of edge modes in finite-width nanopillar arrays. The number of edge modes in nanopillar arrays depends on the spatial profile of the internal static magnetic field near the array boundaries and several edge modes are formed if a substantial field inhomogeneity extends over several rows of nanopillars.

  7. Image tuning techniques for enhancing the performance of pure permanent magnet undulators with small gap/period ratios

    NASA Astrophysics Data System (ADS)

    Tatchyn, R.

    1996-02-01

    The on-axis field of a small-gap undulator constructed out of pure permanent magnet (PM) blocks arranged in an alternating-dipole (i.e., 2 dipoles/period) array can be substantially varied by positioning monolithic permeable plates above and below the undulator jaws. This simple technique, which can be used to control the fundamental photon energy in conventional synchrotron radiation (SR) or Free Electron Laser (FEL) applications requiring sub-octave tuning, can also be shown to suppress magnetic inhomogeneities that can contribute to the undulator's on-axis field errors. If a standard (4 vector rotations/period) Halbach undulator, composed of PM blocks with square cross sections, is rearranged into an alternating-dipole array with the same period, the peak field that can be generated with superimposed image plates can, for a certain range of magnet dimensions, exceed that of the pure-PM Halbach array. This design technique, which can be viewed as intermediate between the "pure-PM" and standard "hybrid/PM" configurations, provides a potentially cost-effective method of enhancing the performance of small-gap, pure-PM insertion devices. In this paper we report on the analysis and recent characterization of pure-PM undulator with superimposed image plates, and discuss possible applications to FEL research.

  8. Magnetic nanoparticle assembly arrays prepared by hierarchical self-assembly on a patterned surface

    NASA Astrophysics Data System (ADS)

    Wen, Tianlong; Zhang, Dainan; Wen, Qiye; Zhang, Huaiwu; Liao, Yulong; Li, Qiang; Yang, Qinghui; Bai, Feiming; Zhong, Zhiyong

    2015-03-01

    Inverted pyramid hole arrays were fabricated by photolithography and used as templates to direct the growth of colloidal nanoparticle assemblies. Cobalt ferrite nanoparticles deposit in the holes to yield high quality pyramid magnetic nanoparticle assembly arrays by carefully controlling the evaporation of the carrier fluid. Magnetic measurements indicate that the pyramid magnetic nanoparticle assembly arrays preferentially magnetize perpendicular to the substrate.Inverted pyramid hole arrays were fabricated by photolithography and used as templates to direct the growth of colloidal nanoparticle assemblies. Cobalt ferrite nanoparticles deposit in the holes to yield high quality pyramid magnetic nanoparticle assembly arrays by carefully controlling the evaporation of the carrier fluid. Magnetic measurements indicate that the pyramid magnetic nanoparticle assembly arrays preferentially magnetize perpendicular to the substrate. Electronic supplementary information (ESI) available: Experimental methods and characterization, a TEM image of cobalt ferrite nanoparticles, SEM images of cobalt ferrite nanoparticle crystals on IPHA formed by fast evaporation and slow pulling out from nanoparticle solution by using a dip coater, a SEM image of a partially filled inverted pyramid hole. See DOI: 10.1039/c4nr07489k

  9. Synthesis, structural order and magnetic behavior of self-assembled εCo nanocrystal arrays

    Microsoft Academic Search

    Victor F. Puntes; Kannan M. Krishnan

    2001-01-01

    The synthesis of magnetic nanoparticles with monodispere size distributions, their self assembly into ordered arrays and their magnetic behavior as a function of structural order (ferrofluids and 2D assemblies) are presented. Magnetic colloids of monodispersed, passivated, cobalt nanocrystals were produced by the rapid pyrolysis of cobalt carbonyl in solution. The size, size distribution (std. dev.<5%) and the shape of the

  10. Fabrication of Magnetically Actuated Polymeric Nanorod Arrays to Mimic Biological Cilia

    Microsoft Academic Search

    A. R. Shields; B. A. Evans; R. L. Carroll; R. Superfine

    2006-01-01

    We report on successful fabrication of free-standing polymer nanorod arrays capable of actuation via externally applied magnetic fields. Our primary motivation is to mimic the ability of epithelial lung cilia to promote microscale fluid transport. Additionally, nanoscale actuator arrays of this nature have a wide variety of possible applications including microfluidics, sensing, and photonics. To fabricate these structures we utilize

  11. Ordered magnetic nanohole and antidot arrays prepared through replication from anodic alumina templates

    NASA Astrophysics Data System (ADS)

    Vázquez, M.; Pirota, K. R.; Navas, D.; Asenjo, A.; Hernández-Vélez, M.; Prieto, P.; Sanz, J. M.

    Highly ordered arrays of Ni nanoholes and Fe 20Ni 80 antidots have been prepared, respectively, by replica/antireplica processing and sputtering techniques using nanoporous alumina membranes as templates. Geometrical characteristics as nanohole/antidot diameter, interpore distance and the overall hexagonal symmetry of arrays are controlled through the original templates. Experimental data on their hysteresis and magnetic domain structure have been taken by vibrating sample magnetometry and magnetic force microscopy, respectively. An analysis of the magnetization process, resulting magnetic anisotropy and magnetic domain structure is summarized considering the influence of those geometry aspects. In particular, the hexagonal symmetry and the density of nanohole/antidots determine the overall magnetic behavior, which is of interest in future high-density magnetic storage systems.

  12. Calibration of a fluxgate magnetometer array and its application in magnetic object localization

    NASA Astrophysics Data System (ADS)

    Pang, Hongfeng; Luo, Shitu; Zhang, Qi; Li, Ji; Chen, Dixiang; Pan, Mengchun; Luo, Feilu

    2013-07-01

    The magnetometer array is effective for magnetic object detection and localization. Calibration is important to improve the accuracy of the magnetometer array. A magnetic sensor array built with four three-axis DM-050 fluxgate magnetometers is designed, which is connected by a cross aluminum frame. In order to improve the accuracy of the magnetometer array, a calibration process is presented. The calibration process includes magnetometer calibration, coordinate transformation and misalignment calibration. The calibration system consists of a magnetic sensor array, a GSM-19T proton magnetometer, a two-dimensional nonmagnetic rotation platform, a 12 V-dc portable power device and two portable computers. After magnetometer calibration, the RMS error has been decreased from an original value of 125.559 nT to a final value of 1.711 nT (a factor of 74). After alignment, the RMS error of misalignment has been decreased from 1322.3 to 6.0 nT (a factor of 220). Then, the calibrated array deployed on the nonmagnetic rotation platform is used for ferromagnetic object localization. Experimental results show that the estimated errors of X, Y and Z axes are -0.049 m, 0.008 m and 0.025 m, respectively. Thus, the magnetometer array is effective for magnetic object detection and localization in three dimensions.

  13. Synthesis and magnetic properties of spinel CoFe 2O 4 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Yuan, J. J.; Zhao, Q.; Xu, Y. S.; Liu, Z. G.; Du, X. B.; Wen, G. H.

    2009-09-01

    Spinel CoFe 2O 4 nanowire arrays were synthesized in nanopores of anodic aluminum oxide (AAO) template using aqueous solution of cobalt and iron nitrates as precursor. The precursor was filled into the nanopores by vacuum impregnation. After heat treatment, it transformed to spinel CoFe 2O 4 nanowires. The structure, morphology and magnetic properties of the sample were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The results indicate that the nanowire arrays are compact. And the individual nanowires have a high aspect ratio, which are about 80 nm in diameter and 10 ?m in length. The nanowires are polycrystalline spinel phase. Magnetic measurements indicate that the nanowire arrays are nearly magnetic isotropic. The reason is briefly discussed. Moreover, the temperature dependence of the coercive force of the nanowire arrays was studied.

  14. Magnet assisted fabrication of microtubule arrays Benjamin M. Hutchins,a

    E-print Network

    Hancock, William O.

    Magnet assisted fabrication of microtubule arrays Benjamin M. Hutchins,a William O. Hancock*b Article on the web 9th May 2006 DOI: 10.1039/b605399h Magnetic fields were used to fashion permanently by mixing 2.3% biotin­tubulin (BTU) with rhodamine-labeled tubulin (1 : 3 rhodamine : unlabeled tubulin, RTU

  15. Approach to fabricating Co nanowire arrays with perpendicular anisotropy: Application of a magnetic field during deposition

    SciTech Connect

    Ge, Shihui; Li, Chao; Ma, Xiao; Li, Wei; Xi, Li; Li, C. X.

    2001-07-01

    Cobalt (Co) nanowire arrays were electrodeposited into the pores of polycarbonate membranes. A magnetic field parallel or perpendicular to the membrane plane was applied during deposition to control the wire growth. X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer were employed to investigate the structure as well as the magnetic properties of the nanowire arrays. The results show that the magnetic field applied during deposition strongly influences the growth of Co nanowires, inducing variations in their crystalline structure and magnetic properties. The sample deposited with the field perpendicular to the membrane plane exhibits a perpendicular magnetic anisotropy with greatly enhanced coercivity and squareness as a result of the preferred growth of Co grains with the c axis perpendicular to the film plane. In contrast, the deposition in a parallel magnetic field forces Co grains to grow with the c axis parallel to the film plane, resulting in in-plane anisotropy. {copyright} 2001 American Institute of Physics.

  16. Ordered arrays of magnetic nanowires investigated by polarized small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Maurer, Thomas; Gautrot, Sébastien; Ott, Frédéric; Chaboussant, Grégory; Zighem, Fatih; Cagnon, Laurent; Fruchart, Olivier

    2014-05-01

    Polarized small-angle neutron scattering (PSANS) experimental results obtained on arrays of ferromagnetic Co nanowires (? ?13 nm) embedded in self-organized alumina (Al2O3) porous matrices are reported. The triangular array of aligned nanowires is investigated as a function of the external magnetic field with a view to determine experimentally the real space magnetization M?(r?) distribution inside the material during the magnetic hysteresis cycle. The observation of field-dependent SANS intensities allows us to characterize the influence of magnetostatic fields. The PSANS experimental data are compared to magnetostatic simulations. These results evidence that PSANS is a technique able to address real-space magnetization distributions in nanostructured magnetic systems. We show that beyond structural information (shape of the objects, two-dimensional organization) already accessible with nonpolarized SANS, using polarized neutrons as the incident beam provides information on the magnetic form factor and stray fields ?0Hd distribution in between nanowires.

  17. Highly Stable and Finely Tuned Magnetic Fields Generated by Permanent Magnet Assemblies

    NASA Astrophysics Data System (ADS)

    Danieli, E.; Perlo, J.; Blümich, B.; Casanova, F.

    2013-05-01

    Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays.

  18. A decoupled control approach for magnetic suspension systems using electromagnets mounted in a planar array

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.

    1993-01-01

    A decoupled control approach for a Large Gap Magnetic Suspension System (LGMSS) is presented. The control approach is developed for an LGMSS which provides five degree-of-freedom control of a cylindrical suspended element that contains a core composed of permanent magnet material. The suspended element is levitated above five electromagnets mounted in a planar array. Numerical results are obtained by using the parameters of the Large Angle Magnetic Suspension Test Fixture (LAMSTF) which is a small scale laboratory model LGMSS.

  19. Tilted microstrip phased arrays with improved electromagnetic decoupling for ultrahigh-field magnetic resonance imaging.

    PubMed

    Pang, Yong; Wu, Bing; Jiang, Xiaohua; Vigneron, Daniel B; Zhang, Xiaoliang

    2014-12-01

    One of the technical challenges in designing a dedicated transceiver radio frequency (RF) array for MR imaging in humans at ultrahigh magnetic fields is how to effectively decouple the resonant elements of the array. In this work, we propose a new approach using tilted microstrip array elements for improving the decoupling performance and potentially parallel imaging capability. To investigate and validate the proposed design technique, an 8-channel volume array with tilted straight-type microstrip elements was designed, capable for human imaging at the ultrahigh field of 7 Tesla. In this volume transceiver array, its electromagnetic decoupling behavior among resonant elements, RF field penetration to biological samples, and parallel imaging performance were studied through bench tests and in vivo MR imaging experiments. In this specific tilted element array design, decoupling among array elements changes with the tilted angle of the elements and the best decoupling can be achieved at certain tilted angle. In vivo human knee MR images were acquired using the tilted volume array at 7 Tesla for method validation. Results of this study demonstrated that the electromagnetic decoupling between array elements and the B1 field strength can be improved by using the tilted element method in microstrip RF coil array designs at the ultrahigh field of 7T. PMID:25526481

  20. Nonlithographic fabrication of 25 nm magnetic nanodot arrays with perpendicular anisotropy over a large area

    SciTech Connect

    Rahman, M. Tofizur; Shams, Nazmun N.; Lai, C.-H. [Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2009-04-01

    A simple method is demonstrated to fabricate 25 nm magnetic nanodot arrays with perpendicular anisotropy over 10 cm{sup 2} coverage area. The nanodot arrays are fabricated by depositing Co/Pt multilayers (MLs) onto the SiO{sub 2} dot arrays formed on a Si wafer. At first, arrays of the SiO{sub 2} dots are fabricated on a Si wafer by anodizing a thin Al film deposited on it. The SiO{sub 2} dots are formed at the base of the anodized alumina (AAO) pores due to the selective oxidation of the Si through the AAO pores during over anodization of the Al film. The average diameter, periodicity, and height of the SiO{sub 2} dots are about 24, 43, and 17 nm, respectively. Then (Co(0.4 nm)/Pt(0.08 nm)){sub 8} MLs with a 3 nm Pt buffer layer is deposited onto the SiO{sub 2} dot arrays by sputtering. The average diameter and periodicity of the Co/Pt nanodot arrays are 25.4 and 43 nm, respectively, with narrow distribution. The nanodot arrays exhibit strong perpendicular anisotropy with a squareness ratio of unity and negative nucleation fields. The coercivity of the nanodot arrays is about one order higher than that of the continuous film, i.e., the same structure deposited on the SiO{sub 2} substrate. The magnetization reversal of the continuous film is governed by domain-wall motion, while the magnetization reversal of the nanodot arrays is dominated by the Stoner-Wohlfarth-like rotation. These results indicate that the fabricated structure can be considered as an isolated nanodot array.

  1. The role of magnetic field in the transition to streaming ablation in wire arrays

    NASA Astrophysics Data System (ADS)

    Martin, M. R.; Seyler, C. E.; Greenly, J. B.

    2010-05-01

    In wire array Z-pinches, the magnetic field configuration and the global field penetration of individual wires play a key role in the ablation plasma dynamics. Knowledge of the magnetic field configuration is necessary to understand the ablation plasma acceleration process near the wires. Two-dimensional resistive magnetohydrodynamics simulations show that a change in the global magnetic field configuration is critical to initiating inward flow of the ablation plasma. Analysis of these simulations show that the initially compressive J ×B force around a wire in its vacuum field configuration undergoes a transition to a configuration in which the Lorentz force can accelerate plasma toward the array axis. This transition is achieved through a low magnetic Reynolds number diffusive flow in which the plasma and the magnetic field are decoupled. The plasma current follows the expanding plasma toward the array axis and, after traveling a critical distance scaling with the array radius divided by the wire number, the global magnetic field threads the wire core, thereby allowing J ×B coronal acceleration into ablation streams.

  2. Least Squares Magnetic-Field Optimization for Portable Nuclear Magnetic Resonance Magnet Design

    SciTech Connect

    Paulsen, Jeffrey L; Franck, John; Demas, Vasiliki; Bouchard, Louis-S.

    2008-03-27

    Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum ina cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cc volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cc volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable"sensitive volumes."

  3. Magnetic wall decoupling method for monopole coil array in ultrahigh field MRI: a feasibility test

    PubMed Central

    Yan, Xinqiang; Zhang, Xiaoliang; Wei, Long

    2014-01-01

    Ultrahigh field (UHF) MR imaging of deeply located target in high dielectric biological samples faces challenges due to the reduced penetration depth at the corresponding high frequencies. Radiative coils, e.g., dipole and monopole coils, have recently been applied for UHF MRI applications to obtain better signal-noise-ratio (SNR) in the area deep inside the human head and body. However, due to the unique structure of radiative coil elements, electromagnetic (EM) coupling between elements in radiative coil arrays cannot be readily addressed by using traditional decoupling methods such as element overlapping and L/C decoupling network. A new decoupling method based on induced current elimination (ICE) or magnetic wall technique has recently been proposed and has demonstrated feasibility in designing microstrip transmission line (MTL) arrays and L/C loop arrays. In this study, an array of two monopole elements decoupled using magnetic wall decoupling technique was designed, constructed and analyzed numerically and experimentally to investigate the feasibility of the decoupling technique in radiative coil array designs for MR imaging at 7 T. An L-shaped capacitive network was employed as the matching circuit and the reflection coefficients (S11) of the monopole element achieved –30 dB or better. Isolation between the two monopole elements was improved from about –10 dB (without decoupling treatment) to better than –30 dB with the ICE/magnetic wall decoupling method. B1 maps and MR images of the phantom were acquired and SNR maps were measured and calculated to evaluate the performance of the ICE/magnetic wall decoupling method. Compared with the monopole elements without decoupling methods, the ICE-decoupled array demonstrated more independent image profiles from each element and had a higher SNR in the peripheral area of the imaging subject. The experimental and simulation results indicate that the ICE/magnetic wall decoupling technique might be a promising solution to reducing the EM coupling of monopole arrays for UHF MRI. PMID:24834419

  4. Arrays

    NSDL National Science Digital Library

    2011-01-01

    This interactive Flash applet helps students develop the concept of equal groups as a foundation for multiplication and division. The applet displays an array of dots, some of which are covered by a card. Student use the visible number of rows and columns to determine the total number of dots. Clicking on the card reveals the full array, and a voice announces the total.

  5. Visible broadband magnetic response from Ag chiral Z-shaped nanohole array

    E-print Network

    Han, Chunrui

    2015-01-01

    We show that broadband magnetic response in visible range can be achieved through an Ag chiral Z-shaped nanohole array. The broadband effect is realized by incorporating multi-scaled inverted SRRs and metal/dielectric nanostrip antenna in one unit cell of only 260 nm square lattice, resulting in multiple excitations of magnetic resonances at different wavelengths. The collective modes show structure dependence and respond separately to LCP and RCP incident light. The Ag Z- and reverse-Z-shaped nanohole arrays have been experimentally realized by shadowing vapor deposition method which exhibit broadband transmission difference, in good agreement with numerical simulations.

  6. Three-dimensional finite element modeling of a magnet array spinning above a conductor

    SciTech Connect

    Lorimer, W.L.; Lieu, D.K. [Univ. of California, Berkeley, CA (United States). Dept. of Mechanical Engineering; Hull, J.R.; Mulcahy, T.M.; Rossing, T.D. [Argonne National Lab., IL (United States)

    1993-12-31

    Drag forces due to eddy currents induced by the relative motion of a conductor and a magnetic field occur in many practical devices: motors, brakes, magnetic bearings, and magnetically levitated vehicles. Recently, finite element codes have included solvers for 3-D eddy current geometries and have the potential to be very useful in the design and analysis of these devices. In this paper, numerical results from three-dimensional modeling of a magnet array spinning above a conductor are compared to experimental results in order to assess the capabilities of these codes.

  7. Exact asymptotic behavior of magnetic stripe domain arrays

    NASA Astrophysics Data System (ADS)

    Johansen, Tom H.; Pan, Alexey V.; Galperin, Yuri M.

    2013-02-01

    The classical problem of magnetic stripe domain behavior in films and plates with uniaxial magnetic anisotropy is addressed. Exact analytical results are derived for the stripe domain widths as a function of applied perpendicular field H, in the regime where the domain period becomes large. The stripe period diverges as (Hc-H)-1/2, where Hc is the critical (infinite period) field, an exact result confirming a previous conjecture. The magnetization approaches saturation as (Hc-H)1/2, a behavior that compares excellently with experimental data obtained for a 4-?m thick ferrite garnet film. The exact analytical solution provides a new basis for precise characterization of uniaxial magnetic films and plates, illustrated by a simple way to measure the domain wall energy. The mathematical approach is applicable for similar analysis of a wide class of systems with competing interactions where a stripe domain phase is formed.

  8. Circular sensor array and nonlinear analysis of homopolar magnetic bearings

    E-print Network

    Wiesenborn, Robert Kyle

    2007-04-25

    Magnetic bearings use variable attractive forces generated by electromagnetic control coils to support rotating shafts with low friction and no material wear while providing variable stiffness and damping. Rotor deflections are stabilized...

  9. Fast magnetic resonance spectroscopic imaging using RF coil arrays

    E-print Network

    Gagoski, Borjan Aleksandar

    2006-01-01

    Conventional Magnetic Resonance Spectroscopic Imaging (MRSI) suffers from both low signal-to-noise (SNR), as well as long acquisition times. The development of high-fidelity gradient coils has opened opportunities for fast ...

  10. Nanoparticle arrays: From magnetic response to coupled plasmon resonances

    NASA Astrophysics Data System (ADS)

    Kravets, V. G.; Schedin, F.; Pisano, G.; Thackray, B.; Thomas, P. A.; Grigorenko, A. N.

    2014-09-01

    We study optical properties of optomagnetic metamaterials consisting of regular arrays of single and double Au nanodots (nanopillars). Using a combination of data from variable angle spectroscopic ellipsometry, transmission, and reflection measurements, we identify localized plasmon resonances of gold nanodots and measure their dependence on dot size and substrate type. We demonstrate that arrays of Au nanopillars can support narrow collective plasmon resonances coupled to in-plane and out-of-plane localized plasmon resonances. The spectral positions of these plasmon modes are extracted from the angular dependence of the transmission and reflection spectra for two beam polarizations. We show that nanoarrays exhibit dramatically different optical response on conductive and nonconductive substrates and study its angular dependence. The optical response of nanoarrays is described well by coupled dipole approximation. The procedure for extracting optical constants of metamaterials based on ellipsometry is discussed and applied to our samples resulting in a calculated negative index of refraction for double-dot arrays at green light.

  11. Equilibrium state of planar arrays of magnetic dipoles in the presence of exchange interaction

    NASA Astrophysics Data System (ADS)

    Shutyi, Anatolij M.; Eliseeva, Svetlana V.; Sementsov, Dmitrij I.

    2015-01-01

    This article investigates the equilibrium states of square-planar arrays of magnetic dipoles. It has been demonstrated that in the presence of an exchange interaction the main equilibrium states are the configurations of dipoles oriented along the system diagonal, along its side, as well as configurations with vortex structures, which may differ by location of the vortex center and, respectively, by magnitude and direction of the magnetic moment of the system. Also the conditions for transitions in the equilibrium configurations, when influenced by a plane field affecting the whole array, or by a normal local field affecting a part of the system dipoles, were considered. The possibility to control magnetic moment of the dipoles system through transitions between different vortex configurations, including a configuration with zero total magnetic moment, has been shown.

  12. Configuration-induced vortex motion in type-II superconducting films with periodic magnetic dot arrays

    NASA Astrophysics Data System (ADS)

    Chen, Q. H.; Shi, D. Q.; Li, W. X.; Zhu, B. Y.; Moshchalkov, V. V.; Dou, S. X.

    2014-06-01

    Using the molecular dynamic method we investigate numerically the current driven vortex motion in a superconducting film with periodic arrays of both ferromagnetic (FM) and anti-parallel ferromagnetic (AFM) dots. The simulation results show that in the absence of thermal fluctuation the vortex motion is dominated by the configurations of the magnetic dot array. This guided vortex motion is only observed at the onset of the depinning of the interstitial vortices. Two guided vortex motion mechanisms are discussed in this work. For the AFM configuration the vortex motion is mainly originated by the existence of magnetic dots with opposite magnetized moments, while for the FM case it is mainly dependent on the degree of the condensed packing of the magnetic dot lattice constant.

  13. High frequency umbilical magnetic probe array for SSX wind tunnel

    NASA Astrophysics Data System (ADS)

    Werth, A. M.; Gray, T.; Brown, M. R.

    2012-10-01

    The Swarthmore Spheromak Experiment (SSX) wind tunnel consists of a high velocity plume of magnetized plasma injected into a copper flux conserver with dimensions L = 1 m and R = 0.08 m (aspect ratio 10:1). The plasma spheromaks in this wind tunnel typically have densities on the order of 1 - 5 x10^15 cm-3 and flow speeds of 50 km/s. In the past, fluctuations and turbulence in the SSX plasma wind tunnel during magnetic reconnection have been examined by means of two high resolution (16 position at 0.46 cm spacing) radial magnetic probes. Results from the radial probes show high frequency magnetic fluctuations at the site of reconnection. Four more probes have been design to help detect magnetic fluctuations and reconnection activity along the axial direction of the wind tunnel. The four new probes have 8 positions at 0.95 cm spacing and have a flexible bellow in vacuum and a quartz jacket. The bellows act as an umbilical giving the probe excellent flexibility and versatility. The flexibility allows the probe to be bent so it lies along the axis of the flux conserver.

  14. Microwave assisted magnetization reversal in cylindrical antidot arrays with in-plane and perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Yumak, Mehmet; Ture, Kerim; Aktas, Gulen; Vega, Victor; Prida, Victor; Garcia, Carlos

    2012-02-01

    Porous anodic alumina is a particularly attractive self-ordered system used as template to fabricate nanostructures. The anodic film contains a self-ordered hexagonal array of parallel pores with tunable pore size and interpore distance, and whose pore locations can be templated. Deposition of magnetic films onto porous alumina leads to the formation of porous magnetic films, whose properties differ significantly from those of unpatterned films. The study of antidot arrays has both technological and fundamental importance. Although porous alumina films are typically synthesized in a planar geometry, in this work we deposited NiFe and Ti/CoCrPt magnetic films with in-plane and out-of-plane anisotropy onto cylindrical-geometry porous anodic alumina substrates to achieve cylindrical antidot arrays. The effect of both, the magnitude of the AC current and the circular magnetic field on the magnetization reversal has been studied for in-plane and perpendicular anisotropies. The level of reduction in the switching field was found to be dependent on the power, the frequency of the microwave pulses and the circular applied magnetic field. Such a reduction is associate with the competition between pumping and damping processes.

  15. Fabrication and magnetic properties of small FePt dot arrays

    NASA Astrophysics Data System (ADS)

    Yan, Z. J.; Takahashi, S.; Kondo, Y.; Ariake, J.; Sakon, T.; Xue, D. S.; Ishio, S.

    2011-05-01

    FePt dot arrays with dot sizes ranging from 100 down to 15 nm were fabricated using sputtering, annealing and patterning techniques. The dot diameter distribution and dot position deviation are greater for smaller dot arrays than for larger dot arrays. The dot arrays produced through a sequence of annealing followed by patterning have a large perpendicular magnetic anisotropy resulting from the highly L10-ordered structure and the perpendicular orientation of the [0 0 1] crystalline axis, whereas samples of annealing after patterning display a magnetic vortex structure. As the dot size reduces from 100 to 29.9 nm, the arrays produced by annealing and then patterning exhibit an increase in the remanent coercivity Hcr from 15.7 to 21 kOe because fewer defects are contained by the smaller dots. This result is explained by nucleation and domain wall propagation mechanisms. For 15.4 nm dot arrays, a model of dot with damaged edge may interpret the decreasing coercivity behaviour.

  16. Role of boundaries in micromagnetic calculations of magnonic spectra of arrays of magnetic nanoelements

    NASA Astrophysics Data System (ADS)

    Dmytriiev, O.; Kruglyak, V. V.; Franchin, M.; Fangohr, H.; Giovannini, L.; Montoncello, F.

    2013-05-01

    We have used micromagnetic simulations performed with open and periodic boundary conditions to study the influence of the presence of array boundaries on the spectra and spatial profiles of collective spin-wave excitations in arrays of magnetic nanoelements. The spectra and spatial profiles of collective spin waves excited in isolated arrays of nanoelements and those forming a part of quasi-infinite arrays are qualitatively different even if the same excitation field is used in the simulations. In particular, the use of periodic boundary conditions suppresses the excitation of nonuniform collective modes by uniform excitation fields. However, the use of nonuniform excitation fields in combination with periodic boundary conditions is shown to enable investigation of the structure of magnonic dispersion curves for quasi-infinite arrays (magnonic crystals) in different directions in the reciprocal space and for different magnonic bands. The results obtained in the latter case show a perfect agreement with those obtained with the dynamical matrix method for infinite arrays of nanoelements of the same geometry and magnetic properties.

  17. Microscopic structure and magnetic behavior of arrays of electrodeposited Ni and Fe nanowires

    SciTech Connect

    Xu, X.; Zangari, G. [Department of Chemical Engineering, University of Virginia, 102 Engineer's Way, Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, 116 Engineer's Way, Charlottesville, Virginia 22904 (United States)

    2005-05-15

    Arrays of Ni and Fe nanowires with length up to 6 {mu}m were fabricated by voltage controlled electrodeposition within track etched polycarbonate membranes with nominal pore diameter 50 nm, using dc or pulsed voltage. Magnetostatic interactions between wires are found to be important in determining magnetic properties and switching processes. Ni arrays switch by quasicoherent rotation when the magnetic field is applied near to the average wire axis, and by curling at large angles. The importance of curling processes increases with wire length, due to the larger demagnetizing field. The properties of Fe wires are dominated by magnetostatic interactions; these arrays switch by curling and no definite easy axis is observed in pulse-plated, amorphous wires.

  18. Localized transfection on arrays of magnetic beads coated with PCR products

    Microsoft Academic Search

    Maria Isabel Santori; Cayetano Gonzalez; Luis Serrano; Mark Isalan

    2005-01-01

    High-throughput gene analysis would benefit from new approaches for delivering DNA or RNA into cells. Here we describe a simple system that allows any molecular biology laboratory to carry out multiple, parallel cell transfections on microscope coverslip arrays. By using magnetically defined positions and PCR product–coated paramagnetic beads, we achieved transfection in a variety of cell lines. Beads may be

  19. Directed Fluid Flow Produced by Arrays of Magnetically Actuated Core-Shell Biomimetic Cilia

    Microsoft Academic Search

    B. L. Fiser; A. R. Shields; B. A. Evans; R. Superfine

    2010-01-01

    We have developed a novel core-shell microstructure that we use to fabricate arrays of flexible, magnetically actuated biomimetic cilia. Our biomimetic cilia mimic the size and beat shape of biological cilia in order to replicate the transport of fluid driven by cilia in many biological systems including the determination of left-right asymmetry in the vertebrate embryonic nodal plate and mucociliary

  20. Defect Related Switching Field Reduction in Small Magnetic Particle Arrays M.J. Donahue

    E-print Network

    Donahue, Michael J.

    . Numerical 3D micromagnetic modeling con#12;rms that the overall reduction of the switching #12;eld, relative, and magnetic MEMS. Hysteresis loop measurements on individual particles of a model system of a 2D array), with the highest measured H sw (max) #25; 50 kA/m (600 Oe). 1 Some of the overall reduction of the average

  1. Magnetic Field Measurements in Wire-Array Z-Pinches using Magneto-Optically Active Waveguides

    SciTech Connect

    Syed, Wasif [School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853 (United States); Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States); Blesener, Isaac; Hammer, David A. [School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 (United States); Laboratory of Plasma Studies, Cornell University, Ithaca, NY 14853 (United States); Lipson, Michal [School of Electrical and Computer Engineering, Cornell University, Ithaca, NY 14853 (United States)

    2009-01-21

    Understanding the magnetic field topology in wire-array Z-pinches as a function of time is of great significance to understanding these high-energy density plasmas especially for their ultimate application to stockpile stewardship and inertial confinement fusion. We are developing techniques to measure magnetic fields as a function of space and time using Faraday rotation of a single longitudinal mode (SLM) laser through a magneto-optically active bulk waveguide (multicomponent terbium borate glass) placed adjacent to, or within, the wire array in 1 MA experiments. We have measured fields >10 T with 100 ns rise times outside of a wire-array for the entire duration of the current pulse and as much as {approx}2 T inside a wire-array for {approx}40 ns from the start of current. This is the first time that such rapidly varying and large fields have been measured using these materials. In a dense Z-pinch, these sensing devices may not survive for long but may provide the magnetic field at the position of the sensor that can be used to corroborate magnetic probes, with which we compare our results.

  2. Miniature Antennas and Arrays Embedded Within Magnetic Photonic Crystals

    Microsoft Academic Search

    Gokhan Mumcu; Kubilay Sertel; John L. Volakis

    2006-01-01

    This letter presents the performance of small antennas embedded within a new class of magnetic photonic crystals (MPCs) constructed from periodic arrangements of homogenous and anisotropic material layers. Earlier studies of these crystals demonstrated that they exhibit slow modes within their propagation bands associated with minimal reflection at the air-crystal interface, drastic slow down of the group velocity and concurrent

  3. Open-loop characteristics of magnetic suspension systems using electromagnets mounted in a planar array

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.; Britcher, Colin P.

    1992-01-01

    The open-loop characteristics of a Large-Gap Magnetic Suspension System (LGMSS) were studied and numerical results are presented. The LGMSS considered provides five-degree-of-freedom control. The suspended element is a cylinder that contains a core composed of permanent magnet material. The magnetic actuators are air core electromagnets mounted in a planar array. Configurations utilizing five, six, seven, and eight electromagnets were investigated and all configurations were found to be controllable from coil currents and observable from suspended element positions. Results indicate that increasing the number of coils has an insignificant effect on mode shapes and frequencies.

  4. Pulse electrodeposition and electrochemical quartz crystal microbalance techniques for high perpendicular magnetic anisotropy cobalt nanowire arrays

    SciTech Connect

    Ursache, Andrei; Goldbach, James T.; Russell, Thomas P.; Tuominen, Mark T. [Department of Physics, University of Massachusetts, 666 N Pleasant St., Hasbrouck Lab, Room 411, Amherst, Massachusetts 01003 (United States); Department of Polymer Science and Engineering, University of Massachusetts, 120 Governors Drive Amherst, Massachusetts 01003 (United States); Department of Physics, University of Massachusetts, 666 N Pleasant St., Hasbrouck Lab, Room 411, Amherst, Massachusetts 01003 (United States)

    2005-05-15

    This research is focused on the development of pulse electrodeposition techniques to fabricate a high-density array of vertically oriented, high-magnetic anisotropy cobalt nanowires using a porous polymer film template. This type of array is a competitive candidate for future perpendicular magnetic media capable of storage densities exceeding 1 Terabit/in.{sup 2} The polymer template, derived from a self-assembling P(S-b-MMA) diblock copolymer film, provides precise control over the nanowire diameter (15 nm) and interwire spacing (24 nm), whereas nanowire length (typically 50 to 1000 nm) is controlled accurately with the aid of real-time electrochemical quartz crystal monitoring. Pulse and pulse-reversed electrodeposition techniques, as compared to dc, are shown to significantly enhance the perpendicular magnetic anisotropy of the magnetic nanowire array and ultimately result in coercivity as large as 2.7 kOe at 300 K. Magnetic and structural characterizations suggest that these properties arise from an improved degree of magnetocrystalline anisotropy (due to c-axis oriented crystal growth and improvements in crystal quality) that strongly supplements the basic shape anisotropy of the nanowires. Low temperature magnetometry is used to investigate exchange bias effects due to the incorporation of CoO antiferromagnetic impurities during the electrodeposition process and subsequent Co oxidation in air.

  5. A smart fully integrated micromachined separator with soft magnetic micro-pillar arrays for cell isolation

    NASA Astrophysics Data System (ADS)

    Dong, Tao; Su, Qianhua; Yang, Zhaochu; Zhang, Yulong; Egeland, Eirik B.; Gu, Dan D.; Calabrese, Paolo; Kapiris, Matteo J.; Karlsen, Frank; Minh, Nhut T.; Wang, K.; Jakobsen, Henrik

    2010-11-01

    A smart fully integrated micromachined separator with soft magnetic micro-pillar arrays has been developed and demonstrated, which can merely employ one independent lab-on-chip to realize cell isolation. The simulation, design, microfabrication and test for the new electromagnetic micro separator were executed. The simulation results of the electromagnetic field in the separator show that special soft magnetic micro-pillar arrays can amplify and redistribute the electromagnetic field generated by the micro-coils. The separator can be equipped with a strong magnetic field to isolate the target cells with a considerably low input current. The micro separator was fabricated by micro-processing technology. An electroplating bath was hired to deposit NiCo/NiFe to fabricate the micro-pillar arrays. An experimental system was set up to verify the function of the micro separator by isolating the lymphocytes, in which the human whole blood mixed with Dynabeads® FlowComp Flexi and monoclonal antibody MHCD2704 was used as the sample. The results show that the electromagnetic micro separator with an extremely low input current can recognize and capture the target lymphocytes with a high efficiency, the separation ratio reaching more than 90% at a lower flow rate. For the electromagnetic micro separator, there is no external magnetizing field required, and there is no extra cooling system because there is less Joule heat generated due to the lower current. The magnetic separator is totally reusable, and it can be used to separate cells or proteins with common antigens.

  6. Asymmetric magnetization reversal process in Co nanohill arrays

    SciTech Connect

    Rosa, W. O.; Martinez, L.; Jaafar, M.; Asenjo, A.; Vazquez, M. [Instituto de Ciencias de Materiales de Madrid, CSIC Sor Juana Ines de la Cruz 3, Cantoblanco, Madrid 28049 (Spain)

    2009-11-15

    Co thin films deposited by sputtering onto nanostructured polymer [poly(methyl methacrylate)] were prepared following replica-antireplica process based on porous alumina membrane. In addition, different capping layers were deposited onto Co nanohills. Morphological and compositional analysis was performed by atomic force microscopy and x-ray photoemission spectroscopy techniques to obtain information about the surface characteristics. The observed asymmetry in the magnetization reversal process at low temperatures is ascribed to the exchange bias generated by the ferromagnetic-antiferromagnetic interface promoted by the presence of Co oxide detected in all the samples. Especially relevant is the case of the Cr capping, where an enhanced magnetic anisotropy in the Co/Cr interface is deduced.

  7. Array combination for parallel imaging in Magnetic Resonance Imaging

    E-print Network

    Spence, Dan Kenrick

    2007-09-17

    and is defined as 00 B? ?= . [2.30] The signal detected in the MR experiment is due to the transverse magnetization, () ( ) ( ) ( ) 0 2 / 0 jt tT xy Mt Mt jMt M ee ? ? ?? =+ = , [2.31] after it has been excited and is returning to equilibrium. Signal... Signal to Noise Ratio FOV Field of View FID Free Induction Decay TR Repetition Time RF Radiofrequency vii TABLE OF CONTENTS Page ABSTRACT...

  8. Evolution of microwave ferromagnetic resonance with magnetic domain structure in FeCoBSi antidot arrays

    NASA Astrophysics Data System (ADS)

    Zhou, Peiheng; Zhang, Nan; Liu, Tao; Xie, Jianliang; Deng, Longjiang

    2014-08-01

    Magnetic domain structure of FeCoBSi antidot array thin films of varying thickness were characterized using surface magneto-optic Kerr effect. Vibrating sample magnetometry and microstrip transmission line measurements helped to associate the microwave magnetic analysis of the antidot arrays with hysteresis studies. The domain structure evolution from quasi-continuous domains to strip domains induced by the competing exchange and dipolar interaction resulted in the change of ferromagnetic resonance from multi-band to single-band. Hence, the mechanisms of multi-resonance are proposed to be related to domain wall motion, natural resonance and spin wave modes. This phenomenon can be used to control the magnetization dynamics in spin wave devices.

  9. Synthesis and magnetic properties of highly arrayed nickel-phosphate nanotubes

    NASA Astrophysics Data System (ADS)

    Lin, Shih-Chin; Chen, San-Yuan; Cheng, Syh-Yuh; Lin, Jen-Chieh

    2005-07-01

    In this study, nanotube arrays of nickel-phosphate have been developed by electroless deposition into sub-micro to nanometer sized pores of the porous alumina templates by hypophosphite electrolytic solution composed of NiSO 4, NaH 2PO 2, NaC 2H 3O 2 and Na 3C 6H 5O 7 at 80-100 °C and pH = 3-6. The dimension of the formed nanotubes has 1 ?m in length, 200-300 nm in diameter and 80-150 nm in thickness of tube walls. Transmission electron microscopy examination of the nanotubes clearly show amorphous hallow structure with a average grain size of ˜5 nm. The hysteresis loops of the nanotube arrays show a coercive field of about 200 Oe under treatment in 95%N 2/5%H 2 atmosphere at 500 °C as the magnetic field was applied along parallel and perpendicular to tube axis. The nanotube arrays also exhibit an anisotropic magnetic property with easier saturation along the perpendicular direction. However, both coercive field and saturation of remanent magnetization of the nanotube arrays become lower while continually increasing heat treatment temperature up to 900 °C.

  10. Magnetic force microscopy investigation of arrays of nickel nanowires and nanotubes

    NASA Astrophysics Data System (ADS)

    Tabasum, M. R.; Zighem, F.; De La Torre Medina, J.; Encinas, A.; Piraux, L.; Nysten, B.

    2014-06-01

    The magnetic properties of arrays of nanowires (NWs) and nanotubes (NTs), 150 nm in diameter, electrodeposited inside nanoporous polycarbonate membranes are investigated. The comparison of the nanoscopic magnetic force microscopy (MFM) imaging and the macroscopic behavior as measured by alternating gradient force magnetometry (AGFM) is made. It is shown that MFM is a complementary technique that provides an understanding of the magnetization reversal characteristics at the microscopic scale of individual nanostructures. The local hysteresis loops have been extracted by MFM measurements. The influence of the shape of such elongated nanostructures on the dipolar coupling and consequently on the squareness of the hysteresis curves is demonstrated. It is shown that the nanowires exhibit stronger magnetic interactions than nanotubes. The non-uniformity of the magnetization states is also revealed by combining the MFM and AGFM measurements.

  11. An Orientation Measurement Method Based on Hall-effect Sensors for Permanent Magnet Spherical Actuators with 3D Magnet Array

    PubMed Central

    Yan, Liang; Zhu, Bo; Jiao, Zongxia; Chen, Chin-Yin; Chen, I-Ming

    2014-01-01

    An orientation measurement method based on Hall-effect sensors is proposed for permanent magnet (PM) spherical actuators with three-dimensional (3D) magnet array. As there is no contact between the measurement system and the rotor, this method could effectively avoid friction torque and additional inertial moment existing in conventional approaches. Curved surface fitting method based on exponential approximation is proposed to formulate the magnetic field distribution in 3D space. The comparison with conventional modeling method shows that it helps to improve the model accuracy. The Hall-effect sensors are distributed around the rotor with PM poles to detect the flux density at different points, and thus the rotor orientation can be computed from the measured results and analytical models. Experiments have been conducted on the developed research prototype of the spherical actuator to validate the accuracy of the analytical equations relating the rotor orientation and the value of magnetic flux density. The experimental results show that the proposed method can measure the rotor orientation precisely, and the measurement accuracy could be improved by the novel 3D magnet array. The study result could be used for real-time motion control of PM spherical actuators. PMID:25342000

  12. Remote Giant Multispectral Plasmonic Shifts of Labile Hinged Nanorod Array via Magnetic Field.

    PubMed

    Geryak, R; Geldmeier, J; Wallace, K; Tsukruk, V V

    2015-04-01

    We report a remotely mediated and fast responsive plasmonic-magnetic nanorod array with extremely large variability in optical appearance (up to 100 nm shifts in scattering maxima) and concurrently for multiple wavelengths in a broad range from UV-vis to near-infrared (at 450, 550, and 670 nm) with an external magnetic field with variable direction. The observed phenomenon demonstrates a rapid, wide-range response controlled via a noninvasive remote stimulus. The remotely controlled system suggested here is a magnetic field-directed assembly of an ordered monolayer array of unipolar oriented magnetic-plasmonic nickel-gold nanorods flexibly hinged to a sticky substrate. The unique geometry of the mobile nanorod array allows for the instant alteration of the surface plasmon polariton modes in the gold segment of the controllably tilting nanorods. This design demonstrates the utility of hybrid bimetallic nanoparticles and gives a novel approach to the design of fast-acting, remotely controlled color-changing nanomaterials for sensing and interfacial transport. PMID:25757064

  13. Crystallographically driven magnetic behaviour of arrays of monocrystalline Co nanowires.

    PubMed

    Ivanov, Yu P; Trabada, D G; Chuvilin, A; Kosel, J; Chubykalo-Fesenko, O; Vázquez, M

    2014-11-28

    Cobalt nanowires, 40 nm in diameter and several micrometers long, have been grown by controlled electrodeposition into ordered anodic alumina templates. The hcp crystal symmetry is tuned by a suitable choice of the electrolyte pH (between 3.5 and 6.0) during growth. Systematic high resolution transmission electron microscopy imaging and analysis of the electron diffraction patterns reveals a dependence of crystal orientation from electrolyte pH. The tailored modification of the crystalline signature results in the reorientation of the magnetocrystalline anisotropy and increasing experimental coercivity and squareness with decreasing polar angle of the 'c' growth axis. Micromagnetic modeling of the demagnetization process and its angular dependence is in agreement with the experiment and allows us to establish the change in the character of the magnetization reversal: from quasi-curling to vortex domain wall propagation modes when the crystal 'c' axis tilts more than 75° in respect to the nanowire axis. PMID:25380279

  14. Crystallographically driven magnetic behaviour of arrays of monocrystalline Co nanowires

    NASA Astrophysics Data System (ADS)

    Ivanov, Yu P.; Trabada, D. G.; Chuvilin, A.; Kosel, J.; Chubykalo-Fesenko, O.; Vázquez, M.

    2014-11-01

    Cobalt nanowires, 40 nm in diameter and several micrometers long, have been grown by controlled electrodeposition into ordered anodic alumina templates. The hcp crystal symmetry is tuned by a suitable choice of the electrolyte pH (between 3.5 and 6.0) during growth. Systematic high resolution transmission electron microscopy imaging and analysis of the electron diffraction patterns reveals a dependence of crystal orientation from electrolyte pH. The tailored modification of the crystalline signature results in the reorientation of the magnetocrystalline anisotropy and increasing experimental coercivity and squareness with decreasing polar angle of the ‘c’ growth axis. Micromagnetic modeling of the demagnetization process and its angular dependence is in agreement with the experiment and allows us to establish the change in the character of the magnetization reversal: from quasi-curling to vortex domain wall propagation modes when the crystal ‘c’ axis tilts more than 75° in respect to the nanowire axis.

  15. Magnetic properties of Ni-Fe nanowire arrays: effect of template material and deposition conditions

    SciTech Connect

    Singleton, John [Los Alamos National Laboratory; Aravamudhan, Shyan [U OF SOUTH FL; Goddard, Paul A [U OF OXFORD; Bhansali, Shekhar [U OF SOUTH FL

    2008-01-01

    The objective of this work is to study the magnetic properties of arrays of Ni-Fe nanowires electrodeposited in different template materials such as porous silicon, polycarbonate and alumina. Magnetic properties were studied as a function of template material, applied magnetic field (parallel and perpendicular) during deposition, wire length, as well as magnetic field orientation during measurement. The results show that application of magnetic field during deposition strongly influences the c-axis preferred orientation growth of Ni-Fe nanowires. The samples with magnetic field perpendicular to template plane during deposition exhibits strong perpendicular anisotropy with greatly enhanced coercivity and squareness ratio, particularly in Ni-Fe nanowires deposited in polycarbonate templates. In case of polycarbonate template, as magnetic field during deposition increases, both coercivity and squareness ratio also increase. The wire length dependence was also measured for polycarbonate templates. As wire length increases, coercivity and squarness ratio decrease, but saturation field increases. Such magnetic behavior (dependence on template material, magnetic field, wire length) can be qualitatively explained by preferential growth phenomena, dipolar interactions among nanowires, and perpendicular shape anisotropy in individual nanowires.

  16. A fully automated in vitro diagnostic system based on magnetic tunnel junction arrays and superparamagnetic particles

    NASA Astrophysics Data System (ADS)

    Lian, Jie; Chen, Si; Qiu, Yuqin; Zhang, Suohui; Shi, Stone; Gao, Yunhua

    2012-04-01

    A fully automated in vitro diagnostic (IVD) system for diagnosing acute myocardial infarction was developed using high sensitivity MTJ array as sensors and nano-magnetic particles as tags. On the chip is an array of 12 × 106 MTJ devices integrated onto a 3 metal layer CMOS circuit. The array is divided into 48 detection areas, therefore 48 different types of bio targets can be analyzed simultaneously if needed. The chip is assembled with a micro-fluidic cartridge which contains all the reagents necessary for completing the assaying process. Integrated with electrical, mechanical and micro-fluidic pumping devices and with the reaction protocol programed in a microprocessor, the system only requires a simple one-step analyte application procedure to operate and yields results of the three major AMI bio-markers (cTnI, MYO, CK-MB) in 15 mins.

  17. Magnetic properties of Co/Pt nanoring arrays deposited on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yoon, Seungha; Ho Lee, Sang; Kwak, Wonyoung; Nam, Chunghee; Bae Kim, Won; Cho, B. K.

    2014-05-01

    Multiple Co/Pt bilayers were deposited on vertically aligned carbon nanotubes on an anodic aluminum oxide template. The structural and the magnetic properties of the nanoring arrays were investigated by varying the number of Co/Pt bilayers in the ranges 3-10 in multilayers with a Ta(3.0 nm)/[Co(1.0 nm)/Pt(1.5 nm)]n/Ta(1.0 nm) structure. The thickness and diameter of the nanorings increased with increasing repeat number. Compared with Co/Pt films, the Co/Pt nanoring arrays showed a larger coercivity. However, the magnetostatic interactions between the nanorings became dominant in the reversal behavior and caused a nonsquare hysteresis loop. Giant magnetoresistance structures consisting of multiple Co/Pt bilayers and a thick Cu spacer exhibited magnetization curve that were in good agreement the summation of the moments of layers with varied bilayer repetition.

  18. Enhanced magnetic response in a gold nanowire pair array through coupling with Bloch surface waves.

    PubMed

    Liu, Hai; Sun, Xiudong; Pei, Yanbo; Yao, Fengfeng; Jiang, Yongyuan

    2011-07-01

    We numerically study the coupling of magnetic plasmon polaritons (MPPs) with Bloch surface waves (BSWs) in a system composed of a one-dimensional gold nanowire pair array lying on a periodic dielectric multilayer. At an appropriate period of the dielectric multilayer, maximum coupling takes place between the MPP and the BSW. It results in two branches of hybridized MPPs with a Rabi-type splitting as large as 125 meV. The maximal magnetic field intensity achieved in the center of nanowire pairs is enhanced greatly and an enhancement factor >1.5 is observed compared with that achieved by a nanowire pair array lying directly on a substrate. This has potential applications in nonlinear optics and near-field enhanced spectroscopy. PMID:21725429

  19. Spin-wave spectra of perpendicularly magnetized circular submicron dot arrays

    NASA Astrophysics Data System (ADS)

    Kakazei, G. N.; Wigen, P. E.; Guslienko, K. Yu.; Novosad, V.; Slavin, A. N.; Golub, V. O.; Lesnik, N. A.; Otani, Y.

    2004-07-01

    Dynamic microwave properties of arrays of circular Ni and Ni81Fe19 dots were studied by X-band ferromagnetic resonance (FMR) technique. All of the dots had the same radius 0.5?m, thickness 50-70nm, and were arranged into rectangular or square array with different interdot separations. In the case of perpendicular magnetization multiple (up to 8) sharp resonance peaks were observed below the main FMR peak, and the relative positions of these peaks were independent of the interdot separations. Quantitative description of the observed multiresonance FMR spectra is given using the dipole-exchange spin wave dispersion equation for a perpendicularly magnetized film where in-plane wave vector is quantized due to the finite dot radius, and the inhomogenetiy of the intradot static demagnetization field in the nonellipsoidal dot is taken into account.

  20. Magnetic and resonance properties of Fe nanowire arrays on oxidised step-bunched silicon templates

    NASA Astrophysics Data System (ADS)

    Polishchuk, D. M.; Tovstolytkin, A. I.; Arora, S. K.; O'Dowd, B. J.; Shvets, I. V.

    2015-03-01

    Room-temperature magnetic properties of planar nanowire arrays of Fe have been studied using comprehensive analysis of FMR and magnetometry data. It has been shown that the Fe NWs are ferromagnetic at room temperature and their magnetic properties are mainly governed by shape anisotropy. Combining parameters derived from the FMR study with experimental data of magnetometry, simulations of hysteresis loops have been performed based on Stoner-Wohlfarth approach. Calculations show that magnetisation reversal of Fe NWs has a coherent-rotation type of localised character. As NW thickness decreases, localisation of the magnetisation reversal mode is found to enhance due to increased inhomogeneity of thinner NWs.

  1. Analysis of magnetic interaction in Ni nanowire array grown using electrodeposition process

    NASA Astrophysics Data System (ADS)

    Rahman, I. Z.; Boboc, A.; Razeeb, K. M.; Rahman, M. A.

    2005-04-01

    Simulation and comparison of magnetic properties were performed on three types of Ni nanowire arrays grown by electrodeposition using commercial nano channel alumina (NCA) templates with nominal pore sizes of 200, 100 and 20 nm. Experimental observations on the structural behaviour of the nanowires grown inside the pores of NCA templates show that the magnetic interaction depends on the effective pore diameter and the interpore distance. A numerical simulation model based on micromagnetic calculations using object-oriented micromagnetic computing framework (OOMMF) has been developed and reported experimental results on coercivity of Ni nanowires generally agreed with the simulated ones.

  2. Biomimetic cilia arrays - fabrication, magnetic actuation, and driven fluid transport phenomena

    NASA Astrophysics Data System (ADS)

    Shields, Adam

    The cilium is one of biology's most basic functional nanostructures, present on nearly every cell and increasingly realized as vital to many aspects of human health. A fundamental reason for the ubiquity of cilia is their ability to effectively interact with fluids at the microscale, where the Reynolds number is low and thus inertia is irrelevant. This ability makes cilia an attractive and popular candidate for an engineered biomimic with potential applications in microfluidics and sensing. In addition, biological ciliated systems are difficult to study for many reasons, and so I demonstrate how a functional biomimetic system can also serve as a model platform for highly controlled studies of biologically relevant, cilia-driven hydrodynamics. Using the template-based microfabrication of a magnetic nanoparticle/polymer composite, I fabricate arrays of magnetically actuated biomimetic cilia at the scale of their biological analogues. I will discuss this fabrication technique and the magnetic actuation of these arrays to mimic the beat of biological cilia. I also report on the nature of the fluid flows driven by the cilia beat, and demonstrate how these cilia arrays can simultaneously generate long-range fluid transport and mixing in distinct fluid flow regimes. Finally, I present these results within the context of canonical hydrodynamics problems and discuss the implications for biological systems, such as the motile cilia recently discovered in the embryonic node.

  3. Dynamic performance of a permanent magnet brushless DC motor powered by a PV array for water pumping

    Microsoft Academic Search

    C. L. Putta Swamy; B. Singh

    1995-01-01

    The dynamic performance of a permanent magnet brushless DC (PMBDC) motor connected to photovoltaic (PV) array through an inverter is analyzed. The mathematical models of PV array, inverter\\/motor and controller are developed. The photovoltaic array is represented by an equivalent circuit whose parameters are computed using experimentally determined current-voltage (I–V) characteristics. The necessary computer algorithm is developed to analyze the

  4. MAGNETIC INDUCTION MAPPING IN TEM OF MICRO AND NANO PATTERNED CO/NI ARRAYS.

    SciTech Connect

    VOLKOV,V.V.; ZHU,Y.; MALAC,M.; LAU,J.W.; SCHOFIELD,M.A.

    2002-08-04

    Understanding magnetic structures and properties of patterned magnetic films at nanometer length-scale is the area of immense technological and fundamental scientific importance. The patterned magnetic films can be used for magnetic sensing . applications, magnetic recording, magnetoelectronics, microactuators and hybrid magneto-superconducting devices. The optimization of film properties is crucially dependent on the understanding of their magnetic properties, which in turn, become sensitive to the specific geometry and, hence, magnetic configurations of a given system when the elements diminish in size. Recent progress in the field of noninterferometric phase retrieval brings the ordinary Fresnel microscopy to a new quantitative level, capable of recovering both the amplitude and phase of the object from the experimental images [1,2], and thus induction mapping of small magnetic elements with known geometry ranging from micro- to few nanometers in size. The key concept behind this approach is the improvement of phase recovery algorithm derived from the transport-of-intensity (TIE) equation with a fast-solution via Fourier transform. A number of quantitative in-situ TEM magnetization experiments can be realized now with the help of magnetic-field calibrated microscope (see, for example [3]). To demonstrate the practical use of the new approach in TEM magnetic imaging with nanoscale resolution we have prepared several films directly on 3mm TEM-grids: (a) square-patterned magnetic films of Co islands with size of 6 pm (Fig. 1), and (b) nano-patterned arrays of Ni-nanodots (Fig.2) with lateral size about 40nm. The Co-films were prepared in UHV system by electron-beam evaporation of Co through an appropriate mask onto 30-nm-thick Si{sub 3}N{sub 4} membrane. The thickness of magnetic elements was approximately 40 nm as determined by EELS. The array of Ni-nanodots on a carbon membrane was prepared by electron-beam TEM-nanolithography followed by oblique angle deposition. Both types of the patterned arrays for Co and Ni films have been characterized by the TEM/ED methods. They were found to have a polycrystalline microstructure with the average crystallite size {approx}10 and 7 nm respectively. The Co films consisted of mixture of cubic and hcp phases. To experimentally check the sensitivity of TIE-recovered phase information to local magnetic configurations a set of in-focus and out-of-focus images was recorded on CCD (llarlk) during the in-situ magnetizing experiments in JEOL3000F microscope at different magnifications using the Gatan Imaging Filter (GIF) as function of applied field (H) and/or specimen tilt angle ({var_phi}) under constant external field. The results of the image processing (Figs.1-2), strongly suggest that TIE-phase retrieval method is a powerful tool suitable for local induction mapping B(x,y) of in-plane magnetization of magnetic elements down to few nanometers scale. The method is fast, robust, insensitive to noise, does not require the holographic equipment, and can be applied to a wide class of objects. The quantitative results can be obtained for films of known or uniform thickness.

  5. Ambient-temperature passive magnetic bearings: Theory and design equations

    SciTech Connect

    Post, R.F.; Ryutov, D.D.

    1997-12-30

    Research has been underway at the Lawrence Livermore National Laboratory to build a theoretical and experimental base for the design of ambient-temperature passive magnetic bearings for a variety of possible applications. in the approach taken the limitations imposed by Earnshaw`s theorem with respect to the stability of passive magnetic bearing systems employing axially symmetric permanent-magnet elements are overcome by employing special combinations of elements, as follows: Levitating and restoring forces are provided by combinations of permanent-magnet-excited elements chosen to provide positive stiffnesses (negative force derivatives) for selected displacements (i.e., those involving translations or angular displacement of the axis of rotation). As dictated by Eamshaw`s theorem, any bearing system thus constructed will be statically unstable for at least one of the remaining possible displacements. Stabilization against this displacement is accomplished by using periodic arrays (`Halbach arrays`) of permanent magnets to induce currents in close-packed inductively loaded circuits, thereby producing negative force derivatives stabilizing the system while in rotation. Disengaging mechanical elements stabilize the system when at rest and when below a low critical speed. The paper discusses theory and equations needed for the design of such systems.

  6. Magnetization reversal and coercivity of Fe3Se4 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Li, D.; Li, S. J.; Zhou, Y. T.; Bai, Y.; Zhu, Y. L.; Ren, W. J.; Long, G.; Zeng, H.; Zhang, Z. D.

    2015-05-01

    The microstructure and magnetic properties of Fe3Se4 nanowire (NW) arrays in anodic aluminum oxide (AAO) porous membrane are studied. Cross-sectional SEM and plane-view TEM images show that the mean wire diameter (dw) and the center-to-center spacing (D) of Fe3Se4 nanowires are about 220 nm and 330 nm, respectively. The field-cooled magnetization dependent on the temperature indicates a Curie temperature around 334 K for the Fe3Se4 nanowires. The coercivities of Fe3Se4 nanowires at 10 K, obtained from the in-plane and out-of-plane hysteresis loops, are as high as 22.4 kOe and 23.3 kOe, which can be understood from the magnetocrystalline anisotropy and the magnetization reversal process.

  7. Magnetic shielding of large high-power-satellite solar arrays using internal currents

    NASA Technical Reports Server (NTRS)

    Parker, L. W.; Oran, W. A.

    1979-01-01

    Present concepts for solar power satellites involve dimensions up to tens of kilometers and operating internal currents up to hundreds of kiloamperes. A question addressed is whether the local magnetic fields generated by these strong currents during normal operation can shield the array against impacts by plasma ions and electrons (and from thruster plasmas) which can cause possible losses such as power leakage and surface erosion. One of several prototype concepts was modeled by a long narrow rectangular panel 2 km wide and 20 km long. The currents flow in a parallel across the narrow dimension (sheet current) and along the edge (wire currents). The wire currents accumulate from zero to 100 kiloamp and are the dominant sources. The magnetic field is approximated analytically. The equations of motion for charged particles in this magnetic field are analyzed. The ion and electron fluxes at points on the surface are represented analytically for monoenergetic distributions and are evaluated.

  8. Skew angle effects in shingled magnetic recording system with double/triple reader head array

    NASA Astrophysics Data System (ADS)

    Elidrissi, Moulay Rachid; Sann Chan, Kheong; Greaves, Simon; Kanai, Yasushi; Muraoka, Hiroaki

    2014-05-01

    Shingled Magnetic Recording (SMR) is a scheme used to extend the life of the current perpendicular magnetic recording technology. SMR enables writing narrow tracks with a wide writer. Currently, SMR employs a single reader and will suffer inter-track interference (ITI) as the tracks become comparable in width to the reader. ITI can be mitigated by using narrower readers; however, narrower readers suffer from increased reader noise. Another approach to combat ITI is to process 2D readback and use ITI cancellation schemes to retrieve the data track. Multiple readbacks can be obtained either with a single reader and multiple revolutions or with a reader array. The former suffers from increased readback latency. In this work, we focus on the latter. When using a reader array, the skew angle poses major challenges. During writing, there is increased adjacent track erasure, and during readback the effective reader pitch varies and there is an increase in the 2D intersymbol interference caused by the rotated reader profile. In this work, we run micromagnetic simulations at different skew angles to train the grain flipping probability model, and then evaluate raw bit channel error rate performance at skew. In particular, we investigate the performance degradation caused by skewing of the 2 or 3 read head array for various read-head geometries.

  9. Application of an array processor to the analysis of magnetic data for the Doublet III tokamak

    SciTech Connect

    Wang, T.S.; Saito, M.T.

    1980-08-01

    Discussed herein is a fast computational technique employing the Floating Point Systems AP-190L array processor to analyze magnetic data for the Doublet III tokamak, a fusion research device. Interpretation of the experimental data requires the repeated solution of a free-boundary nonlinear partial differential equation, which describes the magnetohydrodynamic (MHD) equilibrium of the plasma. For this particular application, we have found that the array processor is only 1.4 and 3.5 times slower than the CDC-7600 and CRAY computers, respectively. The overhead on the host DEC-10 computer was kept to a minimum by chaining the complete Poisson solver and free-boundary algorithm into one single-load module using the vector function chainer (VFC). A simple time-sharing scheme for using the MHD code is also discussed.

  10. Single-domain magnetic pillar array of 35 nm diameter and 65 Gbits/ik2 density for ultrahigh density quantum magnetic storage

    E-print Network

    . These include Co-Cr thin films with vertical grains,`>" barium ferrite powder with a perpendicular c axis,3Single-domain magnetic pillar array of 35 nm diameter and 65 Gbits/ik2 density for ultrahigh density quantum magnetic storage Stephen Y Chou, Mark S. Wei, Peter R. Krauss, and Paul 6. Fischer

  11. Switching modes in easy and hard axis magnetic reversal in a self-assembled antidot array.

    PubMed

    Haering, Felix; Wiedwald, Ulf; Nothelfer, Steffen; Koslowski, Berndt; Ziemann, Paul; Lechner, Lorenz; Wallucks, Andreas; Lebecki, Kristof; Nowak, Ulrich; Gräfe, Joachim; Goering, Eberhard; Schütz, Gisela

    2013-11-22

    We study the reversal mechanisms in a self-assembled, hexagonally ordered Fe antidot array with a period of 200 nm and an antidot diameter of 100 nm which was prepared by polystyrene nanosphere lithography. Direction-dependent information in such a self-assembled sample is obtained by measuring the anisotropic magnetoresistance (AMR) through constrictions processed by focused ion beam milling in nearest neighbor and next nearest neighbor directions. We show that such an originally integral method can be used to investigate the strong in-plane anisotropy introduced by the antidot lattice. The easy and hard axis reversal mechanisms and corresponding AMR signals are modeled by micromagnetic simulations. Additional in-field magnetic force microscopy studies allow the correlation of microscopic switching to features in the integral AMR. We find that the easy axis of magnetization is connected to a distinct periodic magnetic domain pattern, which can be observed during the whole magnetization reversal. While this process is driven by nucleation and propagation of reversed domains, the hard axis reversal is characterized by a (stepwise) rotation of the magnetization via the antidot lattice' easy axes. PMID:24172909

  12. Array of planar Penning traps as a nuclear magnetic resonance molecule for quantum computation

    E-print Network

    G. Ciaramicoli; F. Galve; I. Marzoli; P. Tombesi

    2005-09-16

    An array of planar Penning traps, holding single electrons, can realize an artificial molecule suitable for NMR-like quantum information processing. The effective spin-spin coupling is accomplished by applying a magnetic field gradient, combined to the Coulomb interaction acting between the charged particles. The system lends itself to scalability, since the same substrate can easily accommodate an arbitrary number of traps. Moreover, the coupling strength is tunable and under experimental control. Our theoretical predictions take into account a realistic setting, within the reach of current technology.

  13. Implementation of a decoupled controller for a magnetic suspension system using electromagnets mounted in a planar array

    NASA Technical Reports Server (NTRS)

    Cox, D. E.; Groom, N. J.

    1994-01-01

    An implementation of a decoupled, single-input/single-output control approach for a large angle magnetic suspension test fixture is described. Numerical and experimental results are presented. The experimental system is a laboratory model large gap magnetic suspension system which provides five degree-of-freedom control of a cylindrical suspended element. The suspended element contains a core composed of permanent magnet material and is levitated above five electromagnets mounted in a planar array.

  14. Quantitative imaging of stray fields and magnetization distributions in hard magnetic element arrays

    E-print Network

    Johansen, Tom Henning

    of interaction between the probe and the sample, the different magnetic imaging methods usually either map circu- lar dichroism XMCD 9,10 is able to probe bulk magnetiza- tion. In contrast, different of the Faraday ef- fect. The MOIF sensors can be calibrated with known exter- nal stray fields to achieve

  15. Structure -- Magnetic Property Correlations in TiO 2 Nanotube Arrays

    NASA Astrophysics Data System (ADS)

    Mohammad Hosseinpour, Pegah

    TiO2 nanotube arrays are promising candidates for applications such as photocatalysis and for potential employment in spin-electronic (spintronic) devices. The functionality of TiO2-based nanotubes is highly dependent on their structure (microstructure and crystallographic symmetry) and magnetic properties. Unified understanding of the influence of these factors on the electronic structure of TiO2 is of paramount importance towards engineering these materials. This Dissertation aims at investigating the correlations of the morphology, crystallinity, crystal structure, electronic structure and magnetic properties of TiO2 nanotubes, with potential relevance to their functionality. Self-ordered arrays of amorphous TiO2 nanotubes (pure and Fe-doped with cationic concentration of ~2.1 at%) were synthesized by the electrochemical anodization technique, followed by subjecting them to thermal treatments up to 450 °C to crystallize these nanostructures. A variety of probes---morphological, structural, magnetic and spectroscopic---were used to characterize the properties of these nanostructures as functions of their processing conditions and the dopant content. Structure-functionality relationships in these nanostructures were verified by examining the photodegradation rate of methyl orange (a model water pollutant) in presence of TiO2 nanotubes under UV-Visible light irradiation. Results from this Dissertation research demonstrated that post-synthesis processing conditions---specifically, the nature of the annealing environment, as well as the presence of an external dopant, can alter the crystal structure and local electronic environment in TiO2 nanotubes, with subsequent effects on the magnetic properties of these nanostructures. The fundamental knowledge obtained in this research, on the interrelations of structural-magnetic properties and their potential influence on the functionality of TiO 2-based nanotubes, can be extended to the metal oxide semiconducting systems in general and is anticipated to provide avenues toward novel materials with enhanced functionality that originates from such tailored structural and magnetic characteristics. Despite the success achieved in this Dissertation, there are still open questions to be addressed in order to further enhance the fundamental knowledge of structure---magnetic property correlations in TiO2 nanotubes. In this regard, the concluding section of this Dissertation provides recommendations for additional experiments. Accomplishment of these recommendations is anticipated to provide enhanced insight into the various aspects of property-functionality relationships in TiO2-based nanomaterials, and provides paths to engineer novel multifunctional oxide-based materials for energy-related applications.

  16. A High-Precision, Magnetically Levitated Positioning Stage Toward contactless actuation for industrial manufacturing

    E-print Network

    Maggiore, Manfredi

    magnetic levitation devices utilizing the principle of electromagnetic reluctance to achieve planar microstepper employs air-cored permanent magnet linear synchronous motors (PMLSM) to actuate six DOFs than air cored and the device in [9] uses standard permanent magnets rather than custom-design Halbach

  17. Magnetic behavior of NiCu nanowire arrays: Compositional, geometry and temperature dependence

    SciTech Connect

    Palmero, E. M., E-mail: epalmero@icmm.csic.es; Bran, C.; Real, R. P. del; Vázquez, M. [Institute of Materials Science of Madrid, CSIC, Madrid 28049 (Spain); Magén, C. [Advanced Microscopy Laboratory (LMA), Institute of Nanoscience of Aragón (INA)-ARAID and Department of Condensed Matter Physics, University of Zaragoza, Zaragoza 50018 (Spain)

    2014-07-21

    Arrays of Ni{sub 100?x}Cu{sub x} nanowires ranging in composition 0???x???75, diameter from 35 to 80?nm, and length from 150?nm to 28??m have been fabricated by electrochemical co-deposition of Ni and Cu into self-ordered anodic aluminum oxide membranes. As determined by X-ray diffraction and Transmission Electron Microscopy, the crystalline structure shows fcc cubic symmetry with [111] preferred texture and preferential Ni or Cu lattice depending on the composition. Their magnetic properties such as coercivity and squareness have been determined as a function of composition and geometry in a Vibrating Sample Magnetometer in the temperature range from 10 to 290?K for applied magnetic fields parallel and perpendicular to the nanowires axis. Addition of Cu into the NiCu alloy up to 50% enhances both parallel coercivity and squareness. For the higher Cu content, these properties decrease and the magnetization easy axis becomes oriented perpendicular to the wires. In addition, coercivity and squareness increase by decreasing the diameter of nanowires which is ascribed to the increase of shape anisotropy. The temperature dependent measurements reflect a complex behavior of the magnetic anisotropy as a result of energy contributions with different evolution with temperature.

  18. Precision formed micro magnets: LDRD project summary report

    SciTech Connect

    CHRISTENSON,TODD R.; GARINO,TERRY J.; VENTURINI,EUGENE L.

    2000-02-01

    A microfabrication process is described that provides for the batch realization of miniature rare earth based permanent magnets. Prismatic geometry with features as small as 5 microns, thicknesses up through several hundred microns and with submicron tolerances may be accommodated. The processing is based on a molding technique using deep x-ray lithography as a means to generate high aspect-ratio precision molds from PMMA (poly methyl methacrylate) used as an x-ray photoresist. Subsequent molding of rare-earth permanent magnet (REPM) powder combined with a thermosetting plastic binder may take place directly in the PMMA mold. Further approaches generate an alumina form replicated from the PMMA mold that becomes an intermediate mold for pressing higher density REPM material and allows for higher process temperatures. Maximum energy products of 3--8 MGOe (Mega Gauss Oersted, 1 MGOe = 100/4{pi} kJ/m{sup 3}) are obtained for bonded isotropic forms of REPM with dimensions on the scale of 100 microns and up to 23 MGOe for more dense anisotropic REPM material using higher temperature processing. The utility of miniature precision REPMs is revealed by the demonstration of a miniature multipole brushless DC motor that possesses a pole-anisotropic rotor with dimensions that would otherwise prohibit multipole magnetization using a multipole magnetizing fixture at this scale. Subsequent multipole assembly also leads to miniaturized Halbach arrays, efficient magnetic microactuators, and mechanical spring-like elements which can offset miniaturized mechanical scaling behavior.

  19. Correlations among magnetic, electrical and magneto-transport properties of NiFe nanohole arrays.

    PubMed

    Leitao, D C; Ventura, J; Teixeira, J M; Sousa, C T; Pinto, S; Sousa, J B; Michalik, J M; De Teresa, J M; Vazquez, M; Araujo, J P

    2013-02-13

    In this work, we use anodic aluminum oxide (AAO) templates to build NiFe magnetic nanohole arrays. We perform a thorough study of their magnetic, electrical and magneto-transport properties (including the resistance R(T), and magnetoresistance MR(T)), enabling us to infer the nanohole film morphology, and the evolution from granular to continuous film with increasing thickness. In fact, different physical behaviors were observed to occur in the thickness range of the study (2 nm < t < 100 nm). For t < 10 nm, an insulator-to-metallic crossover was visible in R(T), pointing to a granular film morphology, and thus being consistent with the presence of electron tunneling mechanisms in the magnetoresistance. Then, for 10 nm < t < 50 nm a metallic R(T) allied with a larger anisotropic magnetoresistance suggests the onset of morphological percolation of the granular film. Finally, for t > 50 nm, a metallic R(T) and only anisotropic magnetoresistance behavior were obtained, characteristic of a continuous thin film. Therefore, by combining simple low-cost bottom-up (templates) and top-down (sputtering deposition) techniques, we are able to obtain customized magnetic nanostructures with well-controlled physical properties, showing nanohole diameters smaller than 35 nm. PMID:23315433

  20. Magnetization reversal and dynamics in non-interacting NiFe mesoscopic ring arrays

    NASA Astrophysics Data System (ADS)

    Kaur, M.; Husale, S.; Varandani, D.; Gupta, A.; Senguttuvan, T. D.; Mehta, B. R.; Budhani, R. C.

    2014-04-01

    The dynamics of magnetization (M) reversal and relaxation as a function of temperature (T) are reported in three non-interacting NiFe ring arrays having fixed ring outer diameter and varying widths. Additionally, the dependence of M(H) loop on the angle (?) between magnetic field (H) and the plane of the rings is addressed. The M(H) loops show a double step transition from onion state (OS) to vortex state (VS) at all temperatures (T = 3 to 300 K) and angles (? = 0 to 90°). The critical reversal fields HC1 (OS to VS) and HC2 (VS to OS) show a pronounced dependence on T, ring width, and ?. Estimation of the transverse and vortex domain wall energies reveals that the latter is favored in the OS. The OS is also the remanent state in the smallest rings and decays with the effective energy scale (U0/T) of 50 and 32 meV/K at 10 and 300 K, respectively. The robust in-plane anisotropy of magnetization of ring assemblies is established by scaling the M(H) with ?.

  1. Degradation of Phosphate Ester Hydraulic Fluid in Power Station Turbines Investigated by a Three-Magnet Unilateral Magnet Array

    PubMed Central

    Guo, Pan; He, Wei; García-Naranjo, Juan C.

    2014-01-01

    A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the 1H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different lifetimes were obtained by processing the transverse relaxation curves with a numeric program based on the Inverse Laplace Transformation. The long lifetime components of the transverse relaxation time T2eff and longitudinal relaxation time T1 were chosen to monitor the hydraulic fluid aging. The results demonstrate that an increase of the service time of the turbine oils clearly results in a decrease of T2eff,long and T1,long. This indicates that the T2eff,long and T1,long relaxation times, obtained from the unilateral magnetic resonance measurements, can be applied as indices for degradation of the hydraulic fluid in power station turbines. PMID:24736132

  2. Degradation of phosphate ester hydraulic fluid in power station turbines investigated by a three-magnet unilateral magnet array.

    PubMed

    Guo, Pan; He, Wei; García-Naranjo, Juan C

    2014-01-01

    A three-magnet array unilateral NMR sensor with a homogeneous sensitive spot was employed for assessing aging of the turbine oils used in two different power stations. The Carr-Purcell-Meiboom-Gill (CPMG) sequence and Inversion Recovery-prepared CPMG were employed for measuring the ¹H-NMR transverse and longitudinal relaxation times of turbine oils with different service status. Two signal components with different lifetimes were obtained by processing the transverse relaxation curves with a numeric program based on the Inverse Laplace Transformation. The long lifetime components of the transverse relaxation time T?eff and longitudinal relaxation time T? were chosen to monitor the hydraulic fluid aging. The results demonstrate that an increase of the service time of the turbine oils clearly results in a decrease of T?eff,long and T?,long. This indicates that the T?eff,long and T?,long relaxation times, obtained from the unilateral magnetic resonance measurements, can be applied as indices for degradation of the hydraulic fluid in power station turbines. PMID:24736132

  3. High-efficiency and low-cost permanent magnet guideway consideration for high-Tc superconducting Maglev vehicle practical application

    NASA Astrophysics Data System (ADS)

    Deng, Z.; Wang, J.; Zheng, J.; Jing, H.; Lu, Y.; Ma, G.; Liu, L.; Liu, W.; Zhang, Y.; Wang, S.

    2008-11-01

    In order to improve the cost performance of the present high-Tc superconducting (HTS) Maglev vehicle system for practical application, the multi-pole permanent magnet guideway (PMG) concept was introduced. A well-known double-pole Halbach PMG was chosen as a representative of multi-pole PMGs to compare with traditional monopole PMGs from the point of view of levitation efficiency and cost. Experimental results show that YBCO bulks above the double-pole Halbach PMG can exhibit better load capability and guidance performance as well as dynamics stability at the applied working height between the bulk HTSC and the PMG due to a more reasonable magnetic field distribution at the working range of bulk HTSC. Furthermore, the double-pole PMG configuration can play a more important role in improving guidance performance due to the potential-well field configuration. By comparing with former 'century' PMGs, the double-pole Halbach PMG shows another remarkable advantage in reducing the cost of levitation. As another necessary issue, magnetic field homogeneity and the corresponding magnetic drag force of a double-pole Halbach PMG has been considered by experiment in spite of the above highlights. Synthetically, the multi-pole Halbach PMG design is concluded to be one important choice for future HTS Maglev vehicle applications because of its high efficiency and low cost.

  4. Spacing-dependent dipolar interactions in dendronized magnetic iron oxide nanoparticle 2D arrays and powders.

    PubMed

    Fleutot, Solenne; Nealon, Gareth L; Pauly, Matthias; Pichon, Benoit P; Leuvrey, Cédric; Drillon, Marc; Gallani, Jean-Louis; Guillon, Daniel; Donnio, Bertrand; Begin-Colin, Sylvie

    2013-02-21

    Self-assembly of nanoparticles (NPs) into tailored structures is a promising strategy for the production and design of materials with new functions. In this work, 2D arrays of iron oxide NPs with interparticle distances tuned by grafting fatty acids and dendritic molecules at the NPs surface have been obtained over large areas with high density using the Langmuir-Blodgett technique. The anchoring agent of molecules and the Janus structure of NPs are shown to be key parameters driving the deposition. Finally the influence of interparticle distance on the collective magnetic properties in powders and in monolayers is clearly demonstrated by DC and AC SQUID measurements. The blocking temperature T(B) increases as the interparticle distance decreases, which is consistent with the fact that dipolar interactions are responsible for this increase. Dipolar interactions are found to be stronger for particles assembled in thin films compared to powdered samples and may be described by using the Vogel Fulcher model. PMID:23306456

  5. Size and space controlled hexagonal arrays of superparamagnetic iron oxide nanodots: magnetic studies and application

    PubMed Central

    Ghoshal, Tandra; Maity, Tuhin; Senthamaraikannan, Ramsankar; Shaw, Matthew T.; Carolan, Patrick; Holmes, Justin D.; Roy, Saibal; Morris, Michael A.

    2013-01-01

    Highly dense hexagonally arranged iron oxide nanodots array were fabricated using PS-b-PEO self-assembled patterns. The copolymer molecular weight, composition and choice of annealing solvent/s allows dimensional and structural control of the nanopatterns at large scale. A mechanism is proposed to create scaffolds through degradation and/or modification of cylindrical domains. A methodology based on selective metal ion inclusion and subsequent processing was used to create iron oxide nanodots array. The nanodots have uniform size and shape and their placement mimics the original self-assembled nanopatterns. For the first time these precisely defined and size selective systems of ordered nanodots allow careful investigation of magnetic properties in dimensions from 50?nm to 10?nm, which delineate the nanodots are superparamagnetic, well-isolated and size monodispersed. This diameter/spacing controlled iron oxide nanodots systems were demonstrated as a resistant mask over silicon to fabricate densely packed, identical ordered, high aspect ratio silicon nanopillars and nanowire features. PMID:24072037

  6. Geometrical Design of a Scalable Overlapping Planar Spiral Coil Array to Generate a Homogeneous Magnetic Field

    PubMed Central

    Jow, Uei-Ming; Ghovanloo, Maysam

    2014-01-01

    We present a design methodology for an overlapping hexagonal planar spiral coil (hex-PSC) array, optimized for creation of a homogenous magnetic field for wireless power transmission to randomly moving objects. The modular hex-PSC array has been implemented in the form of three parallel conductive layers, for which an iterative optimization procedure defines the PSC geometries. Since the overlapping hex-PSCs in different layers have different characteristics, the worst case coil-coupling condition should be designed to provide the maximum power transfer efficiency (PTE) in order to minimize the spatial received power fluctuations. In the worst case, the transmitter (Tx) hex-PSC is overlapped by six PSCs and surrounded by six other adjacent PSCs. Using a receiver (Rx) coil, 20 mm in radius, at the coupling distance of 78 mm and maximum lateral misalignment of 49.1 mm (1/?3 of the PSC radius) we can receive power at a PTE of 19.6% from the worst case PSC. Furthermore, we have studied the effects of Rx coil tilting and concluded that the PTE degrades significantly when ? > 60°. Solutions are: 1) activating two adjacent overlapping hex-PSCs simultaneously with out-of-phase excitations to create horizontal magnetic flux and 2) inclusion of a small energy storage element in the Rx module to maintain power in the worst case scenarios. In order to verify the proposed design methodology, we have developed the EnerCage system, which aims to power up biological instruments attached to or implanted in freely behaving small animal subjects’ bodies in long-term electrophysiology experiments within large experimental arenas. PMID:24782576

  7. Organized Silica Microspheres Carrying Ferromagnetic Cobalt Nanoparticles as a Basis for Tip Arrays in Magnetic Force Microscopy

    E-print Network

    Prozorov, Ruslan

    Organized Silica Microspheres Carrying Ferromagnetic Cobalt Nanoparticles as a Basis for Tip Arrays cobalt nanoparticles of size 10 nm well adhered to hard silica microspheres (225-250 nm) were synthesized to the microspherical silica were investigated by XRD, TEM, SEM/EDAX, TGA, DSC, EPR and magnetic susceptibility methods

  8. Fabrication and structural characterization of highly ordered sub-100-nm planar magnetic nanodot arrays over 1 cm2

    E-print Network

    Roshchin, Igor V.

    Fabrication and structural characterization of highly ordered sub-100-nm planar magnetic nanodot; published online 11 October 2006 Porous alumina masks are fabricated by anodization of aluminum films grown ferromagnetic nanodot arrays covering over 1 cm2 were fabricated by electron beam evaporation and subsequent

  9. Endorectal ultrasonography versus phased-array magnetic resonance imaging for preoperative staging of rectal cancer

    PubMed Central

    Halefoglu, Ahmet Mesrur; Yildirim, Sadik; Avlanmis, Omer; Sakiz, Damlanur; Baykan, Adil

    2008-01-01

    AIM: To compare the diagnostic accuracy of pelvic phased-array magnetic resonance imaging (MRI) and endorectal ultrasonography (ERUS) in the preoperative staging of rectal carcinoma. METHODS: Thirty-four patients (15 males, 19 females) with ages ranging between 29 and 75 who have biopsy proven rectal tumor underwent both MRI and ERUS examinations before surgery. All patients were evaluated to determine the diagnostic accuracy of depth of transmural tumor invasion and lymph node metastases. Imaging results were correlated with histopathological findings regarded as the gold standard and both modalities were compared in terms of predicting preoperative local staging of rectal carcinoma. RESULTS: The pathological T stage of the tumors was: pT1 in 1 patient, pT2 in 9 patients, pT3 in 21 patients and pT4 in 3 patients. The pathological N stage of the tumors was: pN0 in 19 patients, pN1 in 9 patients and pN2 in 6 patients. The accuracy of T staging for MRI was 89.70% (27 out of 34). The sensitivity was 79.41% and the specificity was 93.14%. The accuracy of T staging for ERUS was 85.29% (24 out of 34). The sensitivity was 70.59% and the specificity was 90.20%. Detection of lymph node metastases using phased-array MRI gave an accuracy of 74.50% (21 out of 34). The sensitivity and specificity was found to be 61.76% and 80.88%, respectively. By using ERUS in the detection of lymph node metastases, an accuracy of 76.47% (18 out of 34) was obtained. The sensitivity and specificity were found to be 52.94% and 84.31%, respectively. CONCLUSION: ERUS and phased-array MRI are complementary methods in the accurate preoperative staging of rectal cancer. In conclusion, we can state that phased-array MRI was observed to be slightly superior in determining the depth of transmural invasion (T stage) and has same value in detecting lymph node metastases (N stage) as compared to ERUS. PMID:18567078

  10. Nonlinear effects in magnetic garnet films and nonreciprocal optical Bloch oscillations in waveguide arrays

    NASA Astrophysics Data System (ADS)

    Kumar, Pradeep

    This dissertation presents detailed experimental and theoretical investigations of nonlinear and nonreciprocal effects in magnetic garnet films. The dissertation thus comprises two major sections. The first section concentrates on the study of a new class of nonlinear magneto-optic thin film materials possessing strong higher order magnetic susceptibility for nonlinear optical applications. The focus was on enlarging the nonlinear performance of ferrite garnet films by strain generation and compositional gradients in the sputter-deposition growth of these films. Under this project several bismuth-substituted yttrium iron garnet (Bi,Y)3(Fe,Ga)5O12 (acronym as Bi:YIG) films have been sputter-deposited over gadolinium gallium garnet (Gd 3Ga5O12) substrates and characterized for their nonlinear optical response. One of the important findings of this work is that lattice mismatch strain drives the second harmonic (SH) signal in the Bi:YIG films, in agreement with theoretical predictions; whereas micro-strain was found not to correlate significantly with SH signal at the micro-strain levels present in these films. This study also elaborates on the role of the film's constitutive elements and their concentration gradients in nonlinear response of the films. Ultrahigh sensitivity delivered by second harmonic generation provides a new exciting tool for studying magnetized surfaces and buried interfaces, making this work important from both a fundamental and application point of view. The second part of the dissertation addresses an important technological need; namely the development of an on-chip optical isolator for use in photonic integrated circuits. It is based on two related novel effects, nonreciprocal and unidirectional optical Bloch oscillations (BOs), recently proposed and developed by Professor Miguel Levy and myself. This dissertation work has established a comprehensive theoretical background for the implementation of these effects in magneto-optic waveguide arrays. The model systems we developed consist of photonic lattices in the form of one-dimensional waveguide arrays where an optical force is introduced into the array through geometrical design turning the beam sideways. Laterally displaced photons are periodically returned to a central guide by photonic crystal action. The effect leads to a novel oscillatory optical phenomenon that can be magnetically controlled and rendered unidirectional. An on-chip optical isolator was designed based on the unidirectionality of the magneto-opticBloch oscillatory motion. The proposed device delivers an isolation ratio as high as 36 dB that remains above 30 dB in a 0.7 nm wavelength bandwidth, at the telecommunication wavelength 1.55 mum. Slight modifications in isolator design allow one to achieve an even more impressive isolation ratio ~ 55 dB, but at the expense of smaller bandwidth. Moreover, the device allows multifunctionality, such as optical switching with a simultaneous isolation function, well suited for photonic integrated circuits.

  11. Graphoepitaxy of cylinder-forming block copolymers for use as templates to pattern magnetic metal dot arrays.

    PubMed

    Xiao, Shuaigang; Yang, Xiaomin; Edwards, Erik W; La, Young-Hye; Nealey, Paul F

    2005-07-01

    We report a method to fabricate high-quality patterned magnetic dot arrays using block copolymer lithography, metal deposition, and a dry lift-off technique. Long-range order of cylindrical domains oriented perpendicular to the substrate and in hexagonal arrays was induced in the block copolymer films by prepatterning the substrate with topographic features and chemically modifying the surface to exhibit neutral wetting behaviour towards the blocks of the copolymer. The uniformity of the domain size and row spacing of block copolymer templates created in this way was improved compared to those reported in previous studies that used graphoepitaxy of sphere-forming block copolymers. The pattern of block copolymer domains was transferred to a pattern of magnetic metal dots, demonstrating the potential of this technology for the fabrication of patterned magnetic recording media. PMID:21727448

  12. An optimized magnet for magnetic refrigeration

    E-print Network

    Bjørk, R; Smith, A; Christensen, D V; Pryds, N

    2014-01-01

    A magnet designed for use in a magnetic refrigeration device is presented. The magnet is designed by applying two general schemes for improving a magnet design to a concentric Halbach cylinder magnet design and dimensioning and segmenting this design in an optimum way followed by the construction of the actual magnet. The final design generates a peak value of 1.24 T, an average flux density of 0.9 T in a volume of 2 L using only 7.3 L of magnet, and has an average low flux density of 0.08 T also in a 2 L volume. The working point of all the permanent magnet blocks in the design is very close to the maximum energy density. The final design is characterized in terms of a performance parameter, and it is shown that it is one of the best performing magnet designs published for magnetic refrigeration.

  13. Giant magnetoresistance sensors. 1. Internally calibrated readout of scanned magnetic arrays.

    PubMed

    Nordling, John; Millen, Rachel L; Bullen, Heather A; Porter, Marc D; Tondra, Mark; Granger, Michael C

    2008-11-01

    This paper describes efforts aimed at setting the stage for the application of giant magnetoresistance sensor (GMRs) networks as readers for quantification of biolytes selectively captured and then labeled with superparamagnetic particles on a scanned chip-scale array. The novelty and long-range goal of this research draws from the potential development of a card-swipe instrument through which an array of micrometer-sized, magnetically tagged addresses (i.e., a sample stick) can be interrogated in a manner analogous to a credit card reader. This work describes the construction and testing of a first-generation instrument that uses a GMR sensor network to read the response of a "simulated" sample stick. The glass sample stick is composed of 20-nm-thick films of permalloy that have square or rectangular lateral footprints of up to a few hundred micrometers. Experiments were carried out to gain a fundamental understanding of the dependence of the GMR response on the separation between, and planarity of, the scanned sample stick and sensor. Results showed that the complex interplay between these experimentally controllable variables strongly affect the shape and magnitude of the observed signal and, ultimately, the limit of detection. This study also assessed the merits of using on-sample standards as internal references as a facile means to account for small variations in the gap between the sample stick and sensor. These findings were then analyzed to determine various analytical figures of merit (e.g., limit of detection in terms of the amount of magnetizable material on each address) for this readout strategy. An in-depth description of the first-generation test equipment is presented, along with a brief discussion of the potential widespread applicability of the concept. PMID:18826239

  14. Microfluidic sorting and multimodal typing of cancer cells in self-assembled magnetic arrays

    PubMed Central

    Saliba, Antoine-Emmanuel; Saias, Laure; Psychari, Eleni; Minc, Nicolas; Simon, Damien; Bidard, François-Clément; Mathiot, Claire; Pierga, Jean-Yves; Fraisier, Vincent; Salamero, Jean; Saada, Véronique; Farace, Françoise; Vielh, Philippe; Malaquin, Laurent; Viovy, Jean-Louis

    2010-01-01

    We propose a unique method for cell sorting, “Ephesia,” using columns of biofunctionalized superparamagnetic beads self-assembled in a microfluidic channel onto an array of magnetic traps prepared by microcontact printing. It combines the advantages of microfluidic cell sorting, notably the application of a well controlled, flow-activated interaction between cells and beads, and those of immunomagnetic sorting, notably the use of batch-prepared, well characterized antibody-bearing beads. On cell lines mixtures, we demonstrated a capture yield better than 94%, and the possibility to cultivate in situ the captured cells. A second series of experiments involved clinical samples—blood, pleural effusion, and fine needle aspirates— issued from healthy donors and patients with B-cell hematological malignant tumors (leukemia and lymphoma). The immunophenotype and morphology of B-lymphocytes were analyzed directly in the microfluidic chamber, and compared with conventional flow cytometry and visual cytology data, in a blind test. Immunophenotyping results using Ephesia were fully consistent with those obtained by flow cytometry. We obtained in situ high resolution confocal three-dimensional images of the cell nuclei, showing intranuclear details consistent with conventional cytological staining. Ephesia thus provides a powerful approach to cell capture and typing allowing fully automated high resolution and quantitative immunophenotyping and morphological analysis. It requires at least 10 times smaller sample volume and cell numbers than cytometry, potentially increasing the range of indications and the success rate of microbiopsy-based diagnosis, and reducing analysis time and cost. PMID:20679245

  15. Geometry dependence of the annealing effect on the magnetic properties of Fe48Co52 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Su, H. L.; Ji, G. B.; Tang, S. L.; Li, Z.; Gu, B. X.; Du, Y. W.

    2005-04-01

    Highly ordered Fe48Co52 nanowire arrays with various interpore distances and diameters were fabricated by electrochemical deposition. The change of their magnetic properties after annealing has great dependences on the interpore distance and the wire diameter. The model of the prolate ellipsoid chain modified with the magnetostatic interaction is employed to explain this geometry dependence of the annealing effect. After annealing at 550 °C in H2 atmosphere, good hard magnetic properties (at room temperature, coercivity Hc = 3.89 kOe, squareness Mr/Ms = 0.954; at 78 K, Hc = 4.55 kOe, Mr/Ms = 0.954) were obtained in the arrays with a diameter of about 22 nm and an interpore distance of about 50 nm.

  16. Design, fabrication, and calibration of a cryogenic search-coil array for harmonic analysis of quadrupole magnets

    SciTech Connect

    Green, M.I.; Barale, P.J.; Hassenzahl, W.V.; Nelson, D.H.; O'Neill, J.W.; Schafer, R.V.; Taylor, C.E.

    1987-09-01

    A cryogenic search-coil array has been fabricated at LBL for harmonic error analysis of SSC model quadrupoles. It consists of three triplets of coils; the center-coil triplet is 10 cm long, and the end coil triplets are 70 cm long. Design objectives are a high bucking ratio for the dipole and quadrupole signals and utility at cryogenic operating currents (approx.6 kA) with sufficient sensitivity for use at room-temperature currents (approx.10 A). the design and fabrication are described. Individual coils are mechanically measured to +-5 ..mu..m, and their magnetic areas measured to 0.05%. A computer program has been developed to predict the quadrupole and dipole bucking ratios from the mechanical and magnetic measurements. The calibration procedure and accuracy of the array are specified. Results of measurements of SSC model quadrupoles are presented. 1 ref., 4 figs.

  17. Enhanced synchronization in an array of spin torque nano oscillators in the presence of oscillating external magnetic field

    E-print Network

    B. Subash; V. K. Chandrasekar; M. Lakshmanan

    2014-12-23

    We demonstrate that the synchronization of an array of electrically coupled spin torque nano-oscillators (STNO) modelled by Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation can be enhanced appreciably in the presence of a common external microwave magnetic field. The applied microwave magnetic field stabilizes and enhances the regions of synchronization in the parameter space of our analysis, where the oscillators are exhibiting synchronized oscillations thereby emitting improved microwave power. To characterize the synchronized oscillations we have calculated the locking range in the domain of external source frequency.

  18. Towards nonvolatile magnetic crossbar arrays: A three-dimensional-integrated field-coupled domain wall gate with perpendicular anisotropy

    NASA Astrophysics Data System (ADS)

    Breitkreutz, Stephan; Eichwald, Irina; Ziemys, Grazvydas; Hiblot, Gaspard; Csaba, György; Schmitt-Landsiedel, Doris; Becherer, Markus

    2015-05-01

    A novel three-dimensional (3D)-integrated domain wall gate (DWG) providing direct control of the DW propagation in a magnetic nanowire with perpendicular magnetic anisotropy is presented. The pinning of field-driven DWs in a notch is controlled by the fringing fields of a subjacent gate magnet. Depending on the state of the gate magnet, the propagating DW is either pinned in the notch or its movement is supported. Theoretical calculations of controlled DW pinning are shown. We experimentally demonstrate control of the DW motion in magnetic nanowires by other domains in a separated gate layer using magnetic force microscopy. Regarding potential applications, the 3D DWG enables storing and buffering of magnetic domains in order to control the signal flow of 3D-integrated perpendicular nanomagnetic logic. Furthermore, due to the uniformity of input, output, and gate contact, the 3D DWG can act as nonvolatile logic device in order to realize field-driven logic gates and magnetic crossbar arrays.

  19. Large voltage modulation in magnetic field sensors from two-dimensional arrays of Y-Ba-Cu-O nano Josephson junctions

    NASA Astrophysics Data System (ADS)

    Cybart, Shane A.; Cho, E. Y.; Wong, T. J.; Glyantsev, V. N.; Huh, J. U.; Yung, C. S.; Moeckly, B. H.; Beeman, J. W.; Ulin-Avila, E.; Wu, S. M.; Dynes, R. C.

    2014-02-01

    We have fabricated and tested two-dimensional arrays of YBa2Cu3O7-? superconducting quantum interference devices. The arrays contain over 36 000 nano Josephson junctions fabricated from ion irradiation of YBa2Cu3O7-? through narrow slits in a resist-mask that was patterned with electron beam lithography and reactive ion etching. Measurements of current-biased arrays in magnetic field exhibit large voltage modulations as high as 30 mV.

  20. Research on ambient temperature passive magnetic bearings at the Lawrence Livermore National Laboratory

    SciTech Connect

    Post, R.F.; Ryitov, D.D.` Smith, J.R.; Tung, L.S.

    1997-04-01

    Research performed at the Lawrence Livermore National Laboratory on the equilibrium and stability of a new class of ambient-temperature passive bearing systems is described. The basic concepts involved are: (1) Stability of the rotating system is only achieved in the rotating state. That is, disengaging mechanical systems are used to insure stable levitation at rest (when Earnshaw`s theorem applies). (2) Stable levitation by passive magnetic elements can be achieved if the vector sum of the force derivatives of the several elements of the system is net negative (i.e. restoring) for axial, transverse, and tilt-type perturbations from equilibrium. To satisfy the requirements of (2) using only permanent magnet elements we have employed periodic ``Halbach arrays.`` These interact with passive inductive loaded circuits and act as stabilizers, with the primary forces arising from axially symmetric permanent-magnet elements. Stabilizers and other elements needed to create compact passive magnetic bearing systems have been constructed. Novel passive means for stabilizing classes of rotor-dynamic instabilities in such systems have also been investigated.

  1. Off-Axis Electron Holography of Magnetic Nanowires and Chains, Rings, and Planar Arrays of Magnetic Nanoparticles

    E-print Network

    Dunin-Borkowski, Rafal E.

    -dimensional arrays of naturally occurring magnetite crystals in minerals, and single crystalline Co nanowires passed through vacuum (or through a thin region of support film) with respect to a part of the same

  2. Array magnetics modal analysis for the DIII-D tokamak based on localized time-series modelling

    NASA Astrophysics Data System (ADS)

    Olofsson, K. E. J.; Hanson, J. M.; Shiraki, D.; Volpe, F. A.; Humphreys, D. A.; La Haye, R. J.; Lanctot, M. J.; Strait, E. J.; Welander, A. S.; Kolemen, E.; Okabayashi, M.

    2014-09-01

    Time-series analysis of magnetics data in tokamaks is typically done using block-based fast Fourier transform methods. This work presents the development and deployment of a new set of algorithms for magnetic probe array analysis. The method is based on an estimation technique known as stochastic subspace identification (SSI). Compared with the standard coherence approach or the direct singular value decomposition approach, the new technique exhibits several beneficial properties. For example, the SSI method does not require that frequencies are orthogonal with respect to the timeframe used in the analysis. Frequencies are obtained directly as parameters of localized time-series models. The parameters are extracted by solving small-scale eigenvalue problems. Applications include maximum-likelihood regularized eigenmode pattern estimation, detection of neoclassical tearing modes, including locked mode precursors, and automatic clustering of modes, and magnetics-pattern characterization of sawtooth pre- and postcursors, edge harmonic oscillations and fishbones.

  3. Pseudo-one-dimensional Zn-Fe-O Nanostructure Arrays: Controlled Fabrication, Magnetic Properties and Photocatalytic Applications

    NASA Astrophysics Data System (ADS)

    Guo, Xuan

    In the present thesis, several kinds of pseudo-one-dimensional Zn-Fe-O nanostructure arrays with tunable chemical compositions, crystal structures and morphologies are successfully synthesized via a simple wet-chemical ZnO-nanowire-array templating method. Vertically-aligned ZnO nanowire arrays are firstly fabricated on several different substrates and then serve as templates for other nanostructured arrays growth. The ZnO nanowires not only act as morphology-defining skeleton but also contribute chemically to the final composition of the nanostructures. By controlling the reaction time between ZnO and FeCl3 solution, ZnO/ZnFe2O4 nanocable arrays, stoichiometric ZnFe 2O4 nanotube arrays, nonstoichiometric ZnFe2O 4 nanotube arrays, ZnFe2O4/alpha-Fe2O 3 nanotube arrays and alpha-Fe2O3 nanotube arrays can be synthesized in a controlled manner after calcination. Both ZnFe 2O4 and alpha-Fe2O3 nanotube arrays exhibit visible light absorption and their bandgap are estimated to be ˜2.3 eV and ˜1.7 eV, respectively. The detailed structural information of the ZnFe2O4 nanotube arrays are obtained by electron energy loss spectroscopy (EELS). In particular, EELS are carried out for two different series (i.e., temperature and stoichiometric series). The magnetic properties of these samples are found to closely correlate to their structural characteristics. Firstly, with the decrease of the calcination temperature from 600 °C to 400 °C, more Fe3+ ions occupy A sites (tetrahedral sites in spinel structure) rather than their equilibrium B sites (octahedral sites in spinel structure). The deviation from the normal spinel structure leads to the enhancement of superexchange interactions between Fe3+ ions in A and B sites, and thus results in an increase in blocking temperature (T B), magnetic anisotropic constant (K), saturation magnetization (MS, at 3 K and 300 K), coercivity (H C, at 3 K) and a decrease in MS (3K)/MS(300 K) ratios. Secondly, by comparing stoichiometric and nonstoichiometric ZnFe2O4 nanotubes calcinated at the same temperature, we found that the nonstoichiometric nanotubes (Fe:Zn > 2) shows similar ratios of Fe3+ in A and B sites to that of the stoichiometric one. The extra Fe3+ in the crystal also enhances the superexchange interactions of Fe3+, which results in larger T B, K, MS (at 3 K and 300 K) and HC (at 3 K), and smaller MS(3 K)/MS(300 K) ratio. Lastly, alpha-Fe2O 3 nanotubes, as an extreme case of the nonstoichiometric sample, show typical Morin-transition characterization under small external field, and field-induced spin-flop transition at large external field. On the other hand, we found that the visible-light-driven photodegradation activities of ZnO/ZnFe2O4 nanocable arrays are superior to those of the ZnO nanowire arrays and ZnFe2O4 nanotube arrays using RhB as the probe molecules. All the three nanostructures show degradation of RhB molecules under visible light irradiation, but they take different degradation pathways. The degradation of RhB in the presence of ZnO nanowire arrays is attributed to the dye-sensitized mechanism, and the photodegradation activity is the worst. ZnO/ZnFe2O4 nanocable arrays and ZnFe2O4 nanotube arrays have the same degradation mechanism, that is, reactive radicals produced by photogenerated electron-hole pairs in the visible-light-active ZnFe2O4 are responsible for the photodegradation of RhB. However, the nanocable arrays show much higher degradation capability. This is owing to the type II band alignment between ZnO and ZnFe2O4, which greatly promotes the separation of photogenerated electrons and holes in ZnFe2O 4.

  4. Spectral properties of electromotive force induced by periodic magnetization reversal of arrays of coupled magnetic glass-covered microwires

    NASA Astrophysics Data System (ADS)

    Rodionova, V.; Ilyn, M.; Ipatov, M.; Zhukova, V.; Perov, N.; Zhukov, A.

    2012-04-01

    In this paper we present the calculated spectra of signals originating from the magnetization reversal of a system of two identical bistable magnetic moments. We show that in contrast to the spectrum characteristic of magnetization reversal in any common ferromagnetic material, the amplitude of the harmonics in the calculated spectra can change periodically. Also, we present experimental spectra of signals induced by the magnetization reversal of two magnetically coupled glass-covered. Periodic variation of the harmonics amplitude predicted by the calculations was observed in the experimental spectra.

  5. Standing spin-wave mode structure and linewidth in partially disordered hexagonal arrays of perpendicularly magnetized sub-micron Permalloy discs

    SciTech Connect

    Ross, N., E-mail: rossn2282@gmail.com; Kostylev, M., E-mail: mikhail.kostylev@uwa.edu.au [School of Physics, University of Western Australia, Crawley, WA (Australia); Stamps, R. L. [School of Physics, University of Western Australia, Crawley, WA (Australia); SUPA School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2014-09-21

    Standing spin wave mode frequencies and linewidths in partially disordered perpendicular magnetized arrays of sub-micron Permalloy discs are measured using broadband ferromagnetic resonance and compared to analytical results from a single, isolated disc. The measured mode structure qualitatively reproduces the structure expected from the theory. Fitted demagnetizing parameters decrease with increasing array disorder. The frequency difference between the first and second radial modes is found to be higher in the measured array systems than predicted by theory for an isolated disc. The relative frequencies between successive spin wave modes are unaffected by reduction of the long-range ordering of discs in the array. An increase in standing spin wave resonance linewidth at low applied magnetic fields is observed and grows more severe with increased array disorder.

  6. Laminated track design for inductrack maglev systems

    DOEpatents

    Post, Richard F.

    2004-07-06

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  7. Tracking the individual magnetic wires' switchings in ferromagnetic nanowire arrays using the first-order reversal curves (FORC) diagram method

    NASA Astrophysics Data System (ADS)

    Dobrot?, Costin-Ionu?; Stancu, Alexandru

    2015-01-01

    The complex hysteretic properties observed in structured ferromagnetic materials can be revealed with remarkable details in magnetization processes like the first-order reversal curves (FORC) - a characterization technique extensively used in recent years. The really fundamental problem in the analysis of experimental FORC diagrams is related to the possibility to link the hysteretic properties of real physical entities in a unique way with regions from the FORC distributions. Actually, what many scientists are often doing is to use a Preisach-type interpretation of FORC data without a proof for the accuracy of this procedure. In this paper we analyze in detail the relation between the switching events of physical entities given by the Preisach function and the FORC distribution in magnetic nanowire arrays with the aim to show the limits of the conventional interpretation of FORC data. For this type of sample we show how the real switching events are contributing to the experimental diagram. We present in a systematic manner the way in which the switchings of the physical wires are observed multiple times (both as positive or negative contributions). The multiplicity of switching occurrences is not the same for all the wires in the sample, being dependent on the wire intrinsic coercivity and its position in the array. In this manner one can track the switchings contributions of real magnetic wires on the FORC diagram.

  8. Receive array magnetic resonance spectroscopy: Whitened singular value decomposition (WSVD) gives optimal Bayesian solution.

    PubMed

    Rodgers, Christopher T; Robson, Matthew D

    2010-04-01

    Receive array coils play a pivotal role in modern MRI. MR spectroscopy can also benefit from the enhanced signal-to-noise ratio and field of view provided by a receive array. In any experiment using an n-element array, n different complex spectra will be recorded and each spectrum unavoidably contains an undesired noise contribution. Previous algorithms for combining spectra have ignored the fact that the noise detected by different array elements is correlated. We introduce here an algorithm for efficiently, robustly, and automatically combining these n spectra using noise whitening and the singular value decomposition to provide the single combined spectrum that has maximum likelihood in the presence of this correlated noise. Simulations are performed that demonstrate the superiority of this approach to previous methods. Experiments in phantoms and in vivo on the brain, heart, and liver of normal volunteers, at 1.5 T and 3 T, using array coils from eight to 32 elements and with (1)H and (31)P nuclei, validate our approach, which provides signal-to-noise ratio improvements of up to 60% in our tests. The whitening and the singular value decomposition algorithm become most advantageous for large arrays, when the noise is markedly correlated, and when the signal-to-noise ratio is low. PMID:20373389

  9. Performance of a multi-axis ionization chamber array in a 1.5 T magnetic field.

    PubMed

    Smit, K; Kok, J G M; Lagendijk, J J W; Raaymakers, B W

    2014-04-01

    At the UMC Utrecht a prototype MR-linac has been installed. The system consists of an 8 MV Elekta linear accelerator and a 1.5 T Philips MRI system. This paper investigates the performance of the IC PROFILER™, a multi-axis ionization chamber array, in a 1.5 T magnetic field. The influence of the magnetic field on the IC PROFILER™ reproducibility, dose response linearity, pulse rate frequency dependence, power to electronics, panel orientation and ionization chamber shape were investigated. The linearity, reproducibility, pulse rate frequency dependence, panel orientation and ionization chamber shape are unaffected by the magnetic field. When the measurements results are normalized to the centre reference chamber, the measurements can commence unaltered. Orientation of the ionization chambers in the magnetic field is of importance, therefore caution must be taken when comparing or normalizing results from several different axes. IC PROFILER™ dose profiles were compared with film dose profiles obtained simultaneously in the MR-linac. Deviation between the film and the IC PROFILER™ data was caused by the noise in the film, indicating correct performance of the IC PROFILER™ in the transverse 1.5 T magnetic field. PMID:24625540

  10. Performance of a multi-axis ionization chamber array in a 1.5 T magnetic field

    NASA Astrophysics Data System (ADS)

    Smit, K.; Kok, J. G. M.; Lagendijk, J. J. W.; Raaymakers, B. W.

    2014-04-01

    At the UMC Utrecht a prototype MR-linac has been installed. The system consists of an 8 MV Elekta linear accelerator and a 1.5 T Philips MRI system. This paper investigates the performance of the IC PROFILER™, a multi-axis ionization chamber array, in a 1.5 T magnetic field. The influence of the magnetic field on the IC PROFILER™ reproducibility, dose response linearity, pulse rate frequency dependence, power to electronics, panel orientation and ionization chamber shape were investigated. The linearity, reproducibility, pulse rate frequency dependence, panel orientation and ionization chamber shape are unaffected by the magnetic field. When the measurements results are normalized to the centre reference chamber, the measurements can commence unaltered. Orientation of the ionization chambers in the magnetic field is of importance, therefore caution must be taken when comparing or normalizing results from several different axes. IC PROFILER™ dose profiles were compared with film dose profiles obtained simultaneously in the MR-linac. Deviation between the film and the IC PROFILER™ data was caused by the noise in the film, indicating correct performance of the IC PROFILER™ in the transverse 1.5 T magnetic field.

  11. Controlled Assembly of Magnetic Nanoparticles from Magnetotactic Bacteria Using Microelectromagnets Arrays

    Microsoft Academic Search

    Hakho Lee; Alfreda M. Purdon; Vincent Chu; Robert M. Westervelt

    2004-01-01

    Controlled assembly of magnetic nanoparticles was demonstrated by manipulating magnetotactic bacteria in a fluid with microelectromagnets. Magnetotactic bacteria synthesize a chain of magnetic nanoparticles inside their bodies. Microelectromagnets, consisting of multiple layers of lithographically patterned conductors, generate versatile magnetic fields on micrometer length scales, allowing sophisticated control of magnetotactic bacteria inside a microfluidic chamber. A single bacterium was stably trapped

  12. Measuring magnetism in the Milky Way with the Square Kilometre Array

    E-print Network

    Haverkorn, Marijke; Carretti, Ettore; Ferriere, Katia; Frick, Peter; Gaensler, Bryan; Heald, George; Johnston-Hollitt, Melanie; Jones, David; Landecker, Tom; Mao, Sui Ann; Noutsos, Aris; Oppermann, Niels; Reich, Wolfgang; Robishaw, Timothy; Scaife, Anna; Schnitzeler, Dominic; Stepanov, Rodion; Sun, Xiaohui; Taylor, Russ

    2015-01-01

    Magnetic fields in the Milky Way are present on a wide variety of sizes and strengths, influencing many processes in the Galactic ecosystem such as star formation, gas dynamics, jets, and evolution of supernova remnants or pulsar wind nebulae. Observation methods are complex and indirect; the most used of these are a grid of rotation measures of unresolved polarized extragalactic sources, and broadband polarimetry of diffuse emission. Current studies of magnetic fields in the Milky Way reveal a global spiral magnetic field with a significant turbulent component; the limited sample of magnetic field measurements in discrete objects such as supernova remnants and HII regions shows a wide variety in field configurations; a few detections of magnetic fields in Young Stellar Object jets have been published; and the magnetic field structure in the Galactic Center is still under debate. The SKA will unravel the 3D structure and configurations of magnetic fields in the Milky Way on sub-parsec to galaxy scales, includ...

  13. Magnetization Reversal and Magnetic Anisotropy in Ordered CoNiP Nanowire Arrays: Effects of Wire Diameter.

    PubMed

    Van Thiem, Luu; Tu, Le Tuan; Phan, Manh-Huong

    2015-01-01

    Ordered CoNiP nanowires with the same length of 4 µm and varying diameters (d = 100 nm-600 nm) were fabricated by electrodeposition of CoNiP onto polycarbonate templates. X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy confirmed the quality of the fabricated nanowires. Magnetic measurements and theoretical analysis revealed that the magnetization reversal and magnetic anisotropy were significantly influenced by varying of the diameters of the nanowires. There existed a critical wire diameter (dc ? 276 nm), below which the magnetization reversal occurred via a coherent rotation mode, and above which the magnetization reversal occurred via a curling rotation mode. The easy axis of the magnetization tended to change in direction from parallel to perpendicular with respect to the wire axis as the wire diameter exceeded dc ? 276 nm. With increasing wire diameter, the coercive field (Hc) and the remanent to saturation magnetization ratio (Mr/Ms) were also found to rapidly decrease in the range d = 100-400 nm and gradually decrease for d > 400 nm. PMID:25760054

  14. Designed fabrication and characterization of three-dimensionally ordered arrays of core-shell magnetic mesoporous carbon microspheres.

    PubMed

    Yuan, Kaiping; Che, Renchao; Cao, Qi; Sun, Zhenkun; Yue, Qin; Deng, Yonghui

    2015-03-11

    A confined interface coassembly coating strategy based on three-dimensional (3-D) ordered macroporous silica as the nanoreactor was demonstrated for the designed fabrication of novel 3-D ordered arrays of core-shell microspheres consisting of Fe3O4 cores and ordered mesoporous carbon shells. The obtained 3-D ordered arrays of Fe3O4@mesoporous carbon materials possess two sets of periodic structures at both mesoscale and submicrometer scale, high surface area of 326 m(2)/g, and large mesopore size of 19 nm. Microwave absorption test reveals that the obtained materials have excellent microwave absorption performances with maximum reflection loss of up to -57 dB at 8 GHz, and large absorption bandwidth (7.3-13.7 GHz, < -10 dB), due to the combination of the large magnetic loss from iron oxides, the strong dielectric loss from carbonaceous shell, and the strong reflection and scattering of electromagnetic waves of the ordered structures of the mesopores and 3-D arrays of core-shell microspheres. PMID:25647306

  15. Simultaneous isolation and detection of circulating tumor cells with a microfluidic silicon-nanowire-array integrated with magnetic upconversion nanoprobes.

    PubMed

    Wang, Chao; Ye, Min; Cheng, Liang; Li, Rui; Zhu, Wenwen; Shi, Zhen; Fan, Chunhai; He, Jinkang; Liu, Jian; Liu, Zhuang

    2015-06-01

    The development of sensitive and convenient methods for detection, enrichment, and analysis of circulating tumor cells (CTCs), which serve as an importance diagnostic indicator for metastatic progression of cancer, has received tremendous attention in recent years. In this work, a new approach characteristic of simultaneous CTC capture and detection is developed by integrating a microfluidic silicon nanowire (SiNW) array with multifunctional magnetic upconversion nanoparticles (MUNPs). The MUNPs were conjugated with anti-EpCAM antibody, thus capable to specifically recognize tumor cells in the blood samples and pull them down under an external magnetic field. The capture efficiency of CTCs was further improved by the integration with a microfluidic SiNW array. Due to the autofluorescence free nature in upconversion luminescence (UCL) imaging, our approach allows for highly sensitive detection of small numbers of tumor cells, which afterward could be collected for further analysis and re-culturing. We have further demonstrated that this approach can be applied to detect CTCs in clinical blood samples from lung cancer patients, and obtained consistent results by analyzing the UCL signals and the clinical outcomes of lung cancer metastasis. Therefore our approach represents a promising platform in CTC capture and detection with potential clinical utilization in cancer diagnosis and prognosis. PMID:25907039

  16. An improved discrete configuration of a cylinder magnet for portable nuclear magnetic resonance instruments

    NASA Astrophysics Data System (ADS)

    Chen, Jizhong; Xu, Chunyan

    2007-06-01

    The continuous magnetization profile approximated by a discrete source is the main reason for the deteriorating magnetic field homogeneity in Halbach magnet. It is identified by comparing the two-dimensional (2D) field solutions of an ideal cylinder magnet with those of a cylinder magnet constructed from several segment magnets. To improve the magnetic field homogeneity, a cylinder magnet from several crescent-shaped magnets is therefore presented. The programed 2D field solutions of the magnet from the crescent-shaped segments verify that the configuration effectively improves the homogeneity inside the cylinder magnet compared to that of a magnet built from simpler segments. For a small magnet with a required field uniformity and magnitude, the configuration has more advantages than a configuration from typical segments. Hence, the magnet is more appropriate for a portable nuclear magnetic resonance instruments.

  17. Defect Related Switching Field Reduction in Small Magnetic Particle Arrays M.J. Donahue

    E-print Network

    Donahue, Michael J.

    , and compared to the easy axis switching field distribution. Numerical 3D micromagnetic modeling confirms. Hysteresis loop measurements on individual particles of a model system of a 2D array of single domain, sin), with the highest measured Hsw(max) 50 kA/m (600 Oe).1 Some of the overall reduction of the average switching field

  18. Physical realization of magnetic walls using finite-thickness 3D printed arrays

    Microsoft Academic Search

    H. Contopanagos; C. Kyriazidou; W. Merrill; N. G. Alexopoulos

    1999-01-01

    Perfect magnetic conductors (PMC) have been useful in electromagnetics for many years as subsidiary hypothetical surfaces in conjunction with formal dualities between dielectric and magnetic currents and vector potentials. This in turn helped formulating equivalence theorems and solving many scattering problems involving either a single scatterer in a solvable background (aperture in waveguiding structures) or many scatterers in highly symmetrical

  19. Large voltage modulation in magnetic field sensors from two-dimensional arrays of Y-Ba-Cu-O nano Josephson junctions

    SciTech Connect

    Cybart, Shane A., E-mail: scybart@ucsd.edu; Dynes, R. C. [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Cho, E. Y.; Wong, T. J. [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States); Glyantsev, V. N.; Huh, J. U.; Yung, C. S.; Moeckly, B. H. [Superconductor Technologies Inc., Santa Barbara, California 93111 (United States); Beeman, J. W.; Ulin-Avila, E.; Wu, S. M. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    2014-02-10

    We have fabricated and tested two-dimensional arrays of YBa{sub 2}Cu{sub 3}O{sub 7??} superconducting quantum interference devices. The arrays contain over 36?000 nano Josephson junctions fabricated from ion irradiation of YBa{sub 2}Cu{sub 3}O{sub 7??} through narrow slits in a resist-mask that was patterned with electron beam lithography and reactive ion etching. Measurements of current-biased arrays in magnetic field exhibit large voltage modulations as high as 30?mV.

  20. Controlled synthesis and assembly into anisotropic arrays of magnetic cobalt-substituted magnetite nanocubes.

    PubMed

    Yang, Weiwei; Yu, Yongsheng; Wang, Liang; Yang, Chunhui; Li, Haibo

    2015-02-01

    Cubic cobalt-substituted magnetite CoxFe3-xO4 nanocubes (NCs) with uniform composition distributions of Co, Fe and O in the NCs, obtained via solution synthesis, are reported in this paper. Through the control of the reaction conditions, the size of the cubic NCs could be tuned from 35 to 110 nm. It was found that the cubic shape could easily induce the (400) orientation of the NCs on a Si substrate, and applying an external magnetic field in the out-of-plane direction could further enhance the (400) orientation of these NCs on the Si substrate. The highest coercivity of 2.07 kOe could be obtained by assembling the NCs in the external magnetic field. The reported magnetic cobalt-substituted magnetite NCs provide an ideal class of building blocks for studying ferrimagnetic nanoparticle (NP) assemblies with easily controlled magnetic alignment for magnetic tape recording with ever increased areal storage density. PMID:25611252

  1. Planar array of self-assembled GaxFe4-xN nanocrystals in GaN: magnetic anisotropy determined via ferromagnetic resonance.

    PubMed

    Grois, A; Devillers, T; Li, Tian; Bonanni, A

    2014-10-01

    The magnetic anisotropy of a planar array of GaxFe(4 - x)N nanocrystals (NCs) embedded in a GaN host is studied by ferromagnetic resonance. X-ray diffraction and transmission electron microscopy are employed to determine the phase and distribution of the nanocrystals. The magnetic anisotropy is found to be primarily uniaxial with the hard axis normal to the NCs plane and to have a comparably weak in-plane hexagonal symmetry. The origin of the magnetic anisotropy is discussed taking into consideration the morphology of the nanocrystals, the epitaxial relations, strain effects and magnetic coupling between the NCs. PMID:25201242

  2. Cryogenic phased-array for high resolution magnetic resonance imaging (MRI); assessment of clinical and research applications

    NASA Astrophysics Data System (ADS)

    Ip, Flora S.

    Magnetic Resonance (MR) imaging is one of the most powerful tools in diagnostic medicine for soft tissue imaging. Image acquisition techniques and hardware receivers are very important in achieving high contrast and high resolution MR images. An aim of this dissertation is to design single and multi-element room and cryogenic temperature arrays and make assessments of their signal-to-noise ratio (SNR) and SNR gain. In this dissertation, four sets of MR receiver coils are built. They are the receiver-only cryo-coils that are not commercially available. A tuning and matching circuit is attached to each coil. The tuning and matching circuits are simple; however, each device component has to operate at a high magnetic field and cryogenic temperature environment. Remote DC bias of the varactor controls the tuning and matching outside the scanner room. Active detuning of the resonator is done by two p-i-n junction (PIN) diodes. Cooling of the receiver is done by a customized liquid nitrogen cryostat. The first application is to build a 3-Tesla 2x1 horseshoe counter-rotating current (CRC) cryogenic array to image the tibia in a human body. With significant increase in SNR, the surface coil should deliver high contrast and resolution images that can show the trabecular bone and bone marrow structure. This structural image will be used to model the mechanical strength of the bone as well as bone density and chance of fracture. The planar CRC is a unique design of this surface array. The second application is to modify the coil design to 7-Tesla to study the growth of infant rhesus monkey eyes. Fast scan MR images of the infant monkey heads are taken for monitoring shapes of their eyeballs. The monkeys are induced with shortsightedness by eye lenses, and they are scanned periodically to get images of their eyeballs. The field-of-view (FOV) of these images is about five centimeters and the area of interest is two centimeters deep from the surface. Because of these reasons, the MR counter-rotating current coil is sufficient and demonstrated its simplicity over a phased array in this application.

  3. Commensurate states on incommensurate lattices. [for superconducting arrays in magnetic fields

    NASA Technical Reports Server (NTRS)

    Grest, Gary S.; Chaikin, Paul M.; Levine, Dov

    1988-01-01

    A simple one-dimensional model related to flux quantization on superconducting networks or charged particles on a substrate is proposed to investigate whether commensurate states can exist on incommensurate lattices. For both periodic and quasi-crystalline patterns, a set of low-energy states is found which is related to decimation symmetry and periodicity. It is suggested that the present quasi-periodic arrays which possess a decimation operation can be generalized to more-dimensional quasi-crystalline systems.

  4. Cryogenic characterization and testing of magnetically-actuated microshutter arrays for the James Webb Space Telescope

    Microsoft Academic Search

    T. T. King; G. Kletetschka; M. A. Jah; M. A. Beamesderfer; M. J. Li; L. L. Wang; S. H. Moseley; L. M. Sparr; M. D. Jhabvala; A. S. Kutyrev; R. F. Silverberg; D. Rapchun; Y. Zheng; D. S. Schwinger; G. M. Voellmer

    2005-01-01

    Two-dimensional MEMS microshutter arrays (MSA) have been fabricated at the NASA Goddard Space Flight Center (GSFC) for the James Webb Space Telescope (JWST) to enable cryogenic (~35 K) spectrographic astronomy measurements at near-infrared wavelengths. Functioning as a focal plane object selection device, the MSA is a 2D programmable aperture mask with fine resolution, high efficiency and high contrast. The MSA

  5. Cryogenic characterization and testing of magnetically-actuated microshutter arrays for the James Webb Space Telescope

    Microsoft Academic Search

    T T King; G Kletetschka; M A Jah; M A Beamesderfer; M J Li; L L Wang; S H Moseley; L M Sparr; M D Jhabvala; A S Kutyrev; R F Silverberg; D Rapchun; Y Zheng; D S Schwinger; G M Voellmer

    2005-01-01

    Two-dimensional MEMS microshutter arrays (MSA) have been fabricated at the NASA Goddard Space Flight Center (GSFC) for the James Webb Space Telescope (JWST) to enable cryogenic (?35 K) spectrographic astronomy measurements at near-infrared wavelengths. Functioning as a focal plane object selection device, the MSA is a 2D programmable aperture mask with fine resolution, high efficiency and high contrast. The MSA

  6. Eight-Channel Head Array and Control System for Parallel Transmit/Receive Magnetic Resonance Imaging

    E-print Network

    Moody, Katherine

    2014-08-11

    Interest in magnetic resonance imaging (MRI) at high fields strengths (3 Tesla and above) is driven by the associated improvements in signal-to-noise ratio and spectral resolution. In practice, however, technical challenges prevent these benefits...

  7. A 16-Channel Receive Array Insert for Magnetic Resonance Imaging of the Breast at 7T

    E-print Network

    By, Samantha

    2014-04-01

    Breast cancer is the second leading cause of cancer death among females in the United States. Magnetic resonance imaging (MRI) has emerged as a powerful tool for detecting and evaluating the disease, with notable advantages over other modalities...

  8. Reliability of Signal Propagation in Magnetostatically Coupled Arrays of Magnetic Nanoelements

    NASA Astrophysics Data System (ADS)

    van Mourik, Reinier; Gao, Li; Hughes, Brian; Rettner, Charles; Koopmans, Bert; Parkin, Stuart

    2013-03-01

    Nanomagnetic logic (NML) has promise as a low-power, non-volatile, and radiation resistant alternative to CMOS-based computational devices. Lines of magnetostatically coupled magnetic nano-elements (NEs) propagate information, and the intersections between lines form logic gates. We present simulations and experiments exploring the reliability of signal propagation in NML devices composed of lines of nominally rectangular permalloy NEs, typically 90x60 nm^2 in size. An external magnetic field sets the magnetic state of an input bit and also resets each of the NEs' magnetizations along their hard axis direction. As the field is reduced to zero the input state propagates along the line of NEs as they successively relax into one of two equilibrium states. The state of the NEs is probed by (i) a magnetic tunnel junction sensing device integrated with the output NE and (ii) magnetic force microscopy imaging. We conclude that signal propagation is inherently unreliable both through variations in fabrication of the NEs and due to the innate lack of directionality of the flow of information. We demonstrate an alternative clocking method where a domain wall passing underneath an NML device clocks each NE sequentially, thereby increasing the success of signal propagation.

  9. Controlled synthesis and assembly into anisotropic arrays of magnetic cobalt-substituted magnetite nanocubes

    NASA Astrophysics Data System (ADS)

    Yang, Weiwei; Yu, Yongsheng; Wang, Liang; Yang, Chunhui; Li, Haibo

    2015-02-01

    Cubic cobalt-substituted magnetite CoxFe3-xO4 nanocubes (NCs) with uniform composition distributions of Co, Fe and O in the NCs, obtained via solution synthesis, are reported in this paper. Through the control of the reaction conditions, the size of the cubic NCs could be tuned from 35 to 110 nm. It was found that the cubic shape could easily induce the (400) orientation of the NCs on a Si substrate, and applying an external magnetic field in the out-of-plane direction could further enhance the (400) orientation of these NCs on the Si substrate. The highest coercivity of 2.07 kOe could be obtained by assembling the NCs in the external magnetic field. The reported magnetic cobalt-substituted magnetite NCs provide an ideal class of building blocks for studying ferrimagnetic nanoparticle (NP) assemblies with easily controlled magnetic alignment for magnetic tape recording with ever increased areal storage density.Cubic cobalt-substituted magnetite CoxFe3-xO4 nanocubes (NCs) with uniform composition distributions of Co, Fe and O in the NCs, obtained via solution synthesis, are reported in this paper. Through the control of the reaction conditions, the size of the cubic NCs could be tuned from 35 to 110 nm. It was found that the cubic shape could easily induce the (400) orientation of the NCs on a Si substrate, and applying an external magnetic field in the out-of-plane direction could further enhance the (400) orientation of these NCs on the Si substrate. The highest coercivity of 2.07 kOe could be obtained by assembling the NCs in the external magnetic field. The reported magnetic cobalt-substituted magnetite NCs provide an ideal class of building blocks for studying ferrimagnetic nanoparticle (NP) assemblies with easily controlled magnetic alignment for magnetic tape recording with ever increased areal storage density. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr07331b

  10. Force measurements of a magnetic micro actuator proposed for a microvalve array

    NASA Astrophysics Data System (ADS)

    Chang, Pauline J.; Chang, Frank W.; Yuen, Michelle C.; Otillar, Robert; Horsley, David A.

    2014-03-01

    Low-cost, easily-fabricated and power-efficient microvalves are necessary for many microfluidic lab-on-a-chip applications. In this study, we present a simple, low-power, scalable, CMOS-compatible magnetic actuator for microvalve applications composed of a paramagnetic bead as the ball valve over a picoliter reaction well etched into a silicon substrate. The paramagnetic bead, composed of either pure FeSi or magnetite in a SiO2 matrix, is actuated by the local magnetic field gradient generated by a microcoil in an aqueous environment, and the reaction well is situated at the microcoil center. A permanent magnet beneath the microvalve device provides an external magnetic biasing field that magnetizes the bead, enabling bidirectional actuation and reducing the current required to actuate the bead to a level below 10 mA. The vertical and radial magnetic forces exerted on the bead by the microcoil were measured for both pure FeSi and composite beads and agree well with the predictions of 2D axisymmetric finite element method models. Vertical forces were within a range of 13-80 nN, and radial forces were 11-60 nN depending on the bead type. The threshold current required to initiate bead actuation was measured as a function of bead diameter and is found to scale inversely with volume for small beads, as expected based on the magnetic force model. To provide an estimate of the stiction force acting between the bead and the passivation layer on the substrate, repeated actuation trials were used to study the bead throw distance for substrates coated with silicon dioxide, Parylene-C, and photoresist. The stiction observed was lowest for a photoresist-coated substrate, while silicon dioxide and Parylene-C coated substrates exhibited similar levels of stiction.

  11. Experimental investigations on a permanent magnet brushless DC motor fed by PV array for water pumping system

    SciTech Connect

    Putta Swamy, C.L.; Singh, B.; Singh, B.P.; Murthy, S.S. [IIT Delhi, New Delhi (India). Dept. of Electrical Engineering

    1996-12-31

    This paper describes the experimental study carried out on a Permanent Magnet Brushless DC (PMBLDC) Motor drive coupled to a pump load powered by photovoltaic (PV) array for water pumping system. A simple low cost prototype controller has been designed and developed without current and position sensors which reduces drastically the overall cost of the drive system. This controller is used to test the dynamic behavior of the PMBLDC motor drive system. The mathematical model of the system is developed with a view to carrying out a comparison between experimental and simulated response of the drive system. The necessary computer algorithm is developed to analyze the performance under different conditions of varying solar insolation for a pump load. The developed state space equations are simulated to obtain the performance characteristics which are also verified by conducting suitable experiments on the development system.

  12. Global Measurements of the Magnetic Field of the Inner Heliosphere with the Mileura Wide- Field Array in Support of LWS Sentinels

    NASA Astrophysics Data System (ADS)

    Kasper, J. C.; D, O.; Salah, J. E.; Lonsdale, C. J.

    2006-12-01

    The Mileura Wide-Field Array Low Frequency Demonstrator (MWA) is an 80-300 MHz interferometric radio array consisting of 8000 antennas distributed in 16-antenna tiles over several square kilometers in Mileura Station, Western Australia. Selected by the NSF in June 2006, antenna deployment will begin in 2007, and the array is scheduled to become operational within three years. The primary goal of MWA-LFD is to demonstrate the capabilities of a digital array for conducting groundbreaking heliospheric and astrophysical science through wide fields of view, high sensitivity, and multiple beam capabilities. The heliospheric science goals of MWA are to characterize the density, velocity, and magnetic field of the inner heliosphere, from the outer corona to interplanetary space, and to image and localize solar radio bursts. The recently released Sentinels Science and Technology Definition Team report describes the value of supporting observations from ground-based instruments such as the MWA. We will present the MWA and discuss how we will use the array to reconstruct the magnetic connection between the corona and the inner heliosphere, both during quiet times and in the presence of CMEs. In particular, we will demonstrate how observing simultaneously the Faraday rotation of polarized radio emission from hundreds of galaxies within 80 Rs of the Sun will be used to trace the magnetic field topology out to the planned Sentinels orbit. These measurements will provide a global context for the Sentinels observations.

  13. Magnetic exchange coupling in IrMn /NiFe nanostructures: From the continuous film to dot arrays

    NASA Astrophysics Data System (ADS)

    Spizzo, F.; Bonfiglioli, E.; Tamisari, M.; Gerardino, A.; Barucca, G.; Notargiacomo, A.; Chinni, F.; Del Bianco, L.

    2015-02-01

    A comprehensive description of the exchange bias phenomenon in an antiferromagnetic/ferromagnetic IrMn(10 nm)/NiFe(5 nm) continuous film and in arrays of square dots with different sizes (1000, 500, and 300 nm) is presented, which elucidates the temperature dependence of the exchange field Hex and coercivity HC, in conjunction with spatial confinement effects. To achieve this goal, samples prepared by electron beam lithography and lift-off using dc sputtering were subjected to structural investigations by electron microscopy techniques and to magnetic study, through SQUID and magneto-optic magnetometry measurements coupled to micromagnetic calculations. In particular, we have observed that at T =300 K Hex decreases by reducing the size of the dots and it is absent in the smallest ones, whereas the opposite trend is visible at T =10 K (Hex˜1140 Oe in the dots of 300 nm ). The exchange bias mechanism and its thermal evolution have been explained through an exhaustive phenomenological model, which joins spatial confinement effects with other crucial items concerning the pinning antiferromagnetic phase: the magnetothermal stability of the nanograins forming the IrMn layer (mean size ˜10 nm ), assumed as essentially noninteracting from the magnetic point of view; the proven existence of a structurally disordered IrMn region at the interface between the NiFe phase and the bulk of the IrMn layer, with a magnetic glassy nature; and the stabilization of a low-temperature (T <100 K ) frozen collective regime of the IrMn interfacial spins, implying the appearance of a length of magnetic correlation among them.

  14. Magnetic Field Tomography in Nearby Galaxies with the Square Kilometre Array

    E-print Network

    Heald, George; de Blok, W J G; Dettmar, Ralf-Juergen; Fletcher, Andrew; Gaensler, Bryan; Haverkorn, Marijke; Heesen, Volker; Horellou, Cathy; Krause, Marita; Mao, Sui Ann; Oppermann, Niels; Scaife, Anna; Sokoloff, Dmitry; Stil, Jeroen; Tabatabaei, Fatemeh; Takahashi, Keitaro; Taylor, Russ; Williams, Anna

    2015-01-01

    Magnetic fields play an important role in shaping the structure and evolution of the interstellar medium (ISM) of galaxies, but the details of this relationship remain unclear. With SKA1, the 3D structure of galactic magnetic fields and its connection to star formation will be revealed. A highly sensitive probe of the internal structure of the magnetoionized ISM is the partial depolarization of synchrotron radiation from inside the volume. Different configurations of magnetic field and ionized gas within the resolution element of the telescope lead to frequency-dependent changes in the observed degree of polarization. The results of spectro-polarimetric observations are tied to physical structure in the ISM through comparison with detailed modeling, supplemented with the use of new analysis techniques that are being actively developed and studied within the community such as Rotation Measure Synthesis. The SKA will enable this field to come into its own and begin the study of the detailed structure of the mag...

  15. Structural and magnetic characteristics of SrM thin films on Au dot arrays

    NASA Astrophysics Data System (ADS)

    Kaewrawang, A.; Ghasemi, A.; Liu, X.; Morisako, A.

    2009-11-01

    The self-assembled SrM dot array on Au islands has been prepared at various substrate temperatures for underlayer by using DC magnetron sputtering system. C-axis oriented SrM perpendicular to the films can be observed only at substrate temperature for underlayer of room temperature. The intensity of (111) diffraction line for Au and that of (00l) diffraction line for strontium ferrite decreases with increasing substrate temperature for underlayer. The maximum of coercivity and remanent squareness ratio in perpendicular direction are 3.4 kOe and 0.6, respectively, at substrate temperature for underlayer of room temperature.

  16. Controllable step motors and rectifiers of magnetic flux quanta using periodic arrays of asymmetric pinning defects

    NASA Astrophysics Data System (ADS)

    Zhu, B. Y.; Marchesoni, F.; Moshchalkov, V. V.; Nori, Franco

    2003-07-01

    We study the transport of vortices in superconductors with regular arrays of asymmetric pinning wells when applying an alternating electrical current. The asymmetric traps are modelled by the superposition of two interpenetrating square lattices of weak and strong pinning centers with separation smaller than the lattice constant. We show that this system can induce a net rectifying or diode effect for the vortex motion, including collective step-motor-type dynamics, where many vortices move forward a controlled and exact number of pin-lattice spacings at each cycle of the ac driving force. This system exhibits a remarkable net dc response with striking sawtooth-type oscillations. The net dc voltage response Vdc of the ac-driven vortices versus both the half period P and the amplitude FL of the “square wave” ac drive has been detailed in the present work. The influence of the equilibrium thermal noise, the shift between the two pinning sublattices, the degree of translational and orientational disorder, and the size of the simulation system on the Vdc response of the vortex motion at ac drive has also been addressed. Devil staircase and Arnold’s tongue structures are revealed. We also analytically derive all the key features of our numerical results. This system provides a very controllable stepmotor for the control of collective motion. Our results apply mutatis mutandis to arrays of Josephson junctions, colloidal systems with optical traps, Wigner crystals, and any system with repelling movable objects that can be pinned by a lattice of traps.

  17. Magnetic resonance elastography with a phased-array acoustic driver system.

    PubMed

    Mariappan, Yogesh K; Rossman, Phillip J; Glaser, Kevin J; Manduca, Armando; Ehman, Richard L

    2009-03-01

    Dynamic MR elastography (MRE) quantitatively maps the stiffness of tissues by imaging propagating shear waves in the tissue. These waves can be produced from intrinsic motion sources (e.g., due to cardiac motion), from external motion sources that produce motion directly at depth in tissue (e.g., amplitude-modulated focused ultrasound), and from external actuators that produce motion at the tissue surface that propagates into the tissue. With external actuator setups, typically only a single transducer is used to create the shear waves, which in some applications might have limitations due to shadowing and attenuation of the waves. To address these limitations, a phased-array acoustic driver system capable of applying independently controlled waveforms to each channel was developed and tested. It was found that the system produced much more uniform illumination of the object, improving the quality of the elastogram. It was also found that the accuracy of the stiffness value of any arbitrary region of interest could be improved by obtaining maximal shear wave illumination with the phased array capability of the system. PMID:19132758

  18. Taking a hard line with biotemplating: cobalt-doped magnetite magnetic nanoparticle arrays.

    PubMed

    Bird, Scott M; Galloway, Johanna M; Rawlings, Andrea E; Bramble, Jonathan P; Staniland, Sarah S

    2015-04-01

    Rapid advancements made in technology, and the drive towards miniaturisation, means that we require reliable, sustainable and cost effective methods of manufacturing a wide range of nanomaterials. In this bioinspired study, we take advantage of millions of years of evolution, and adapt a biomineralisation protein for surface patterning of biotemplated magnetic nanoparticles (MNPs). We employ soft-lithographic micro-contact printing to pattern a recombinant version of the biomineralisation protein Mms6 (derived from the magnetotactic bacterium Magnetospirillum magneticum AMB-1). The Mms6 attaches to gold surfaces via a cysteine residue introduced into the N-terminal region. The surface bound protein biotemplates highly uniform MNPs of magnetite onto patterned surfaces during an aqueous mineralisation reaction (with a mean diameter of 90 ± 15 nm). The simple addition of 6% cobalt to the mineralisation reaction maintains the uniformity in grain size (with a mean diameter of 84 ± 14 nm), and results in the production of MNPs with a much higher coercivity (increased from ?156 Oe to ?377 Oe). Biotemplating magnetic nanoparticles on patterned surfaces could form a novel, environmentally friendly route for the production of bit-patterned media, potentially the next generation of ultra-high density magnetic data storage devices. This is a simple method to fine-tune the magnetic hardness of the surface biotemplated MNPs, and could easily be adapted to biotemplate a wide range of different nanomaterials on surfaces to create a range of biologically templated devices. PMID:25825205

  19. Stability considerations for magnetic suspension systems using electromagnets mounted in a planar array

    NASA Technical Reports Server (NTRS)

    Groom, Nelson J.; Britcher, Colin P.

    1991-01-01

    Mathematical models of a 5, 6, 7, and 8 coil large gap magnetic suspension system (MSDS) are presented. Some of the topics covered include: force and torque equations, reduction of state-space form, natural modes, origins of modes, effect of rotation in azimuth (yaw), future work, and n-coil ring conclusions.

  20. Tracking electron pathways with magnetic field: Aperiodic Aharonov-Bohm oscillations in coherent transport through a periodic array of quantum dots

    NASA Astrophysics Data System (ADS)

    Petrosyan, L. S.; Shahbazyan, T. V.

    2015-01-01

    We study resonant tunneling through a periodic square array of quantum dots sandwiched between modulation-doped quantum wells. If a magnetic field is applied parallel to the quantum dot plane, the tunneling current exhibits a highly complex Aharonov-Bohm oscillation pattern due to the interference of multiple pathways traversed by a tunneling electron. Individual pathways associated with conductance beats can be enumerated by sweeping the magnetic field at various tilt angles. Remarkably, Aharonov-Bohm oscillations are aperiodic unless the magnetic field slope relative to the quantum dot lattice axes is a rational number.

  1. Vortex pinning vs superconducting wire network: origin of periodic oscillations induced by applied magnetic fields in superconducting films with arrays of nanomagnets

    NASA Astrophysics Data System (ADS)

    Gomez, A.; del Valle, J.; Gonzalez, E. M.; Chiliotte, C. E.; Carreira, S. J.; Bekeris, V.; Prieto, J. L.; Schuller, Ivan K.; Vicent, J. L.

    2014-06-01

    Hybrid magnetic arrays embedded in superconducting films are ideal systems to study the competition between different physical (such as the coherence length) and structural length scales such as are available in artificially produced structures. This interplay leads to oscillation in many magnetically dependent superconducting properties such as the critical currents, resistivity and magnetization. These effects are generally analyzed using two distinct models based on vortex pinning or wire network. In this work, we show that for magnetic dot arrays, as opposed to antidot (i.e. holes) arrays, vortex pinning is the main mechanism for field induced oscillations in resistance R(H), critical current Ic(H), magnetization M(H) and ac-susceptibility ? ac(H) in a broad temperature range. Due to the coherence length divergence at Tc, a crossover to wire network behaviour is experimentally found. While pinning occurs in a wide temperature range up to Tc, wire network behaviour is only present in a very narrow temperature window close to Tc. In this temperature interval, contributions from both mechanisms are operational but can be experimentally distinguished.

  2. The MAIN Shirt: a textile-integrated magnetic induction sensor array.

    PubMed

    Teichmann, Daniel; Kuhn, Andreas; Leonhardt, Steffen; Walter, Marian

    2014-01-01

    A system is presented for long-term monitoring of respiration and pulse. It comprises four non-contact sensors based on magnetic eddy current induction that are textile-integrated into a shirt. The sensors are technically characterized by laboratory experiments that investigate the sensitivity and measuring depth, as well as the mutual interaction between adjacent pairs of sensors. The ability of the device to monitor respiration and pulse is demonstrated by measurements in healthy volunteers. The proposed system (called the MAIN (magnetic induction) Shirt) does not need electrodes or any other skin contact. It is wearable, unobtrusive and can easily be integrated into an individual's daily routine. Therefore, the system appears to be a suitable option for long-term monitoring in a domestic environment or any other unsupervised telemonitoring scenario. PMID:24412900

  3. The MAIN Shirt: A Textile-Integrated Magnetic Induction Sensor Array

    PubMed Central

    Teichmann, Daniel; Kuhn, Andreas; Leonhardt, Steffen; Walter, Marian

    2014-01-01

    A system is presented for long-term monitoring of respiration and pulse. It comprises four non-contact sensors based on magnetic eddy current induction that are textile-integrated into a shirt. The sensors are technically characterized by laboratory experiments that investigate the sensitivity and measuring depth, as well as the mutual interaction between adjacent pairs of sensors. The ability of the device to monitor respiration and pulse is demonstrated by measurements in healthy volunteers. The proposed system (called the MAIN (magnetic induction) Shirt) does not need electrodes or any other skin contact. It is wearable, unobtrusive and can easily be integrated into an individual's daily routine. Therefore, the system appears to be a suitable option for long-term monitoring in a domestic environment or any other unsupervised telemonitoring scenario. PMID:24412900

  4. Measurements of magnetic field fluctuations using an array of Hall detectors on the TEXTOR tokamak

    NASA Astrophysics Data System (ADS)

    Duran, I.; Stöckel, J.; Mank, G.; Finken, K. H.; Fuchs, G.; Oost, G. Van

    2002-10-01

    Hall detectors have been used to measure the magnetic field together with its' fluctuations in the boundary of a tokamak. The results show, that the measurements which have been performed so far, mainly by use of coils together with subsequent integration, either on-line or later by computer, can be substituted by Hall probe measurements giving the desired value of B directly. Because the integration of the coil signal becomes more and more difficult with long pulses, Hall detectors may give advantages in future fusion devices. We implemented a stack of nine Hall detectors mounted on three planes on a rod in such a way, that the three components of the magnetic field can be measured. To avoid capacitive and charge pickup from the plasma, the probes are electrically shielded. The damping due to skin effect within this shield has been taken into account. The probes have been calibrated using a known magnetic field of a straight wire driven with a LC bank. This field has been precisely measured with a Rogowski coil. The dependence of the Hall coefficient on the frequency has been measured and the pickup in the feeds due to ? has been withdrawn from the results. We demonstrate the method with measurements on the TEXTOR tokamak, where we could clearly detect the small stray fields associated with magnetohydrodynamic (MHD) fluctuations. On TEXTOR we have been able to detect the MHD activity preceding discharge disruptions as well as the precursors of the so called sawteeth. The results are compared to those of other diagnostics on TEXTOR as, e.g., magnetic loops and electron cyclotron emission, and they do well compare.

  5. Seismo-magnetic multi-point ULF studies before the 2009 L'Aquila earthquake using the South European GeoMagnetic Array

    NASA Astrophysics Data System (ADS)

    Prattes, G.; Schwingenschuh, K.; Eichelberger, H.; Besser, B.; Magnes, W.; Stachel, M.; Vellante, M.; Villante, U.; Nenovski, P.

    2010-05-01

    A strong earthquake (Ml=5.8, Mw=6.3) hit L'Aquila (Central Italy, Abruzzo region, LT=UT+1) on April 6, 2009, 01:32 UT, causing more than 300 deaths. We present a seismo-magnetic analysis of local ULF measurements for the time period one year before the main stroke. As part of the South European GeoMagnetic Array (SEGMA) the evaluated station L'Aquila in closest distance to the epicentre of the main seismic event is ~ 6 km. We consider three further SEGMA stations: Castello Tesino, Ranchio (both Italy) and Nagycenk (Hungary) for comparison and the Kp geomagnetic index to distinguish local- , global- and geomagnetic effects. Further local seismic activities are respected. The instrumentation consists of fluxgate magnetometers with a sampling frequency of 1 Hz. Concerning signal processing the standardized polarization method was applied based on the ratio between the vertical and horizontal power spectral density. A frequency band from 10-100 mHz focused on 10-15 mHz was used during the nighttime period from 22.00 - 02.00 UT. The polarization analysis was introduced and applied for previous seismic events by Hayakawa et al., GRL, 23, 241, 1996.; Molchanov et al., GRL, 19, 1495, 1992.; Prattes et al., NHESS, 2008. A sophisticated method was performed by Ida, et al, NHESS, 2008. With these calculations we expect clearer precursor signatures and they could contribute to EQ forecast. The results are explained using a simple source magnetic dipole model near the EQ focus. The results obtained are explained by the attenuation in the electrical conductive lithosphere.

  6. Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak

    SciTech Connect

    Duran, Ivan; Hronova, Olena; Stoeckel, Jan [Association EURATOM/IPP.CR, Institute of Plasma Physics AS CR, v. v. i., Za Slovankou 3, 182 00 Praha 8 (Czech Republic); Sentkerestiova, Jana [Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University, Brehova 7, 115 19 Praha 1 (Czech Republic); Havlicek, Josef [Association EURATOM/IPP.CR, Institute of Plasma Physics AS CR, v. v. i., Za Slovankou 3, 182 00 Praha 8 (Czech Republic); Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Praha 2 (Czech Republic)

    2008-10-15

    We have performed the first tests of 'integrated' Hall sensors (IHSs) in a tokamak in-vessel environment. IHS combines the sensing element together with the complex electronic circuitry on a single small chip. The on-chip integrated circuits provide stabilization of the supply voltage, output amplification, noise suppression, and elimination of temperature dependencies. Eight IHSs of A1322LUA type produced by Allegro MicroSystems, Inc. were mounted on a stainless steel ring symmetrically encircling the CASTOR plasmas in poloidal direction 10 mm outside the limiter radius. IHSs were oriented such that they measure the horizontal and vertical magnetic fields. We found out that these sensors qualify for in-vessel use of small to middle sized fusion devices where the radiation is not an issue and the temperature below 150 deg. C can be guaranteed. The main advantages over the traditional pickup coils are the smaller size and more straightforward interpretation of output without the need of rather cumbersome integration and drift removal procedure associated with the use of inductive loops. We successfully exploited the sensors for determination of vertical plasma displacement on CASTOR. This new diagnostic helped us to shed more light into long term observed discrepancy on CASTOR between vertical plasma displacement as deduced by standard magnetic and by nonmagnetic diagnostics (Langmuir probes, bolometers)

  7. Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamaka)

    NASA Astrophysics Data System (ADS)

    Duran, Ivan; Hronová, Olena; Stöckel, Jan; Sentkerestiová, Jana; Havlicek, Josef

    2008-10-01

    We have performed the first tests of "integrated" Hall sensors (IHSs) in a tokamak in-vessel environment. IHS combines the sensing element together with the complex electronic circuitry on a single small chip. The on-chip integrated circuits provide stabilization of the supply voltage, output amplification, noise suppression, and elimination of temperature dependencies. Eight IHSs of A1322LUA type produced by Allegro MicroSystems, Inc. were mounted on a stainless steel ring symmetrically encircling the CASTOR plasmas in poloidal direction 10 mm outside the limiter radius. IHSs were oriented such that they measure the horizontal and vertical magnetic fields. We found out that these sensors qualify for in-vessel use of small to middle sized fusion devices where the radiation is not an issue and the temperature below 150 °C can be guaranteed. The main advantages over the traditional pickup coils are the smaller size and more straightforward interpretation of output without the need of rather cumbersome integration and drift removal procedure associated with the use of inductive loops. We successfully exploited the sensors for determination of vertical plasma displacement on CASTOR. This new diagnostic helped us to shed more light into long term observed discrepancy on CASTOR between vertical plasma displacement as deduced by standard magnetic and by nonmagnetic diagnostics (Langmuir probes, bolometers).

  8. Magnetic measurements using array of integrated Hall sensors on the CASTOR tokamak

    NASA Astrophysics Data System (ADS)

    ?uran, Ivan; Hronová, Olena; Stöckel, Jan; Sentkerestiová, Jana; Havlicek, Josef

    2008-10-01

    We have performed the first tests of ``integrated'' Hall sensors (IHSs) in a tokamak in-vessel environment. IHS combines the sensing element together with the complex electronic circuitry on a single small chip. The on-chip integrated circuits provide stabilization of the supply voltage, output amplification, noise suppression, and elimination of temperature dependencies. Eight IHSs of A1322LUA type produced by Allegro MicroSystems, Inc. were mounted on a stainless steel ring symmetrically encircling the CASTOR plasmas in poloidal direction 10 mm outside the limiter radius. IHSs were oriented such that they measure the horizontal and vertical magnetic fields. We found out that these sensors qualify for in-vessel use of small to middle sized fusion devices where the radiation is not an issue and the temperature below 150 °C can be guaranteed. The main advantages over the traditional pickup coils are the smaller size and more straightforward interpretation of output without the need of rather cumbersome integration and drift removal procedure associated with the use of inductive loops. We successfully exploited the sensors for determination of vertical plasma displacement on CASTOR. This new diagnostic helped us to shed more light into long term observed discrepancy on CASTOR between vertical plasma displacement as deduced by standard magnetic and by nonmagnetic diagnostics (Langmuir probes, bolometers).

  9. Anomalies in vortex lattice dynamics driven by induced ac currents in superconducting films with magnetic arrays of two-fold symmetry

    NASA Astrophysics Data System (ADS)

    Moreno, A. J.; Chiliotte, C. E.; Pasquini, G.; Bekeris, V.; Gomez, A.; del Valle, J.; Gonzalez, E. M.; Prieto, J. L.; Vicent, J. L.

    2015-01-01

    We study the dynamics of the vortex lattice driven by ac induced currents in the critical state regime, for T > 0.70 TC. The samples are superconducting films grown on top of two-fold symmetry array of magnetic dots. In these heterostructures, the induced ac currents flow parallel to the short and to the long side of the pinning array in different areas of the samples simultaneously. This behavior produces remarkable effects in the vortex lattice dynamics. First of all, periodic features are observed in the ac susceptibility versus applied magnetic field measurements which are related to matching effects between the vortex lattices and the magnetic array. However, the vortex lattice reconfiguration observed in magnetotransport experiments is absent. Some of these features are revealed as maxima instead of being minima, indicating higher mobility at certain matching fields. Competing unstable vortex configurations could lead to increase vortex mobility precluding the reconfiguration transition. At high temperatures, where the matching effects show up, the magnetic permeability of the dots is the mechanism that governs the JC(T) behavior. Moreover, the temperature dependence of the pinning force FP(T) shows a temperature crossover related to an unexpected enhancement in vortex mobility. Vortex–vortex interaction and the interplay between trapped and interstitial vortices are a hint to explain these phenomena.

  10. Coronal temperature, density, and magnetic field maps of a solar acitve region using the Owens Valley Solar Array

    NASA Technical Reports Server (NTRS)

    Gary, Dale E.; Hurford, G. J.

    1994-01-01

    We present the first results of solar active region observations with the recently completed five-element Owens Valley Solar Array. On 1991 October 24, maps of Active Region AR 6891 were obtained at 22 frequencies from 1.2-7.0 GHz to provide brightness temperature spectra at each point. This is the first time that both high spatial and frequency-resolution brightness temperature spectra have been available over such a broad radio-frequency range. We find that over most of the region the spectra fall into one of the two well-defined categories: thermal free-free or thermal gyroresonance. In these cases, we use the spectra to deduce the spatial variation of physical parameters-electron temperature, column emission measure (intergral n(sup 2)(sub e) dl), and the coronal magnetic field strength-in and around the active region. Over a limited area of the region, the spectra resemble neither of the simple types, and alternative interpretations are required. The possibilties include the presence of fine structure that is unresolved at low frequencies; the presence of a small number of nonthermal electrons; or the presence of overlying, cooler 10(exp 6) K material which at low frequencies absorbs the hot (3 x 10(exp 6) K) thermal emission generated below.

  11. Magnetic behavior of as-deposited and annealed CoFe and CoFeCu nanowire arrays by ac-pulse electrodeposition

    NASA Astrophysics Data System (ADS)

    Ramazani, A.; Almasi-Kashi, M.; Golafshan, E.; Arefpour, M.

    2014-09-01

    CoFe and CoFeCu self-organized alloy nanowires were grown into anodic aluminum oxide template by potentiostatic mode of ac-pulse electrodeposition technique and subsequently annealed at 580 °C. The influence of bath composition, off-time between pulses and annealing treatment on the Cu content, microstructure and magnetic properties of CoFeCu nanowire arrays have been discussed. Increasing the off-time between pulses decreased the coercivity and saturation magnetization of the CoFeCu nanowires due to substitution of Co and Fe with Cu atoms which resulted in electroless process. Coercivity and squareness of the annealed samples increased due to improvement of samples crystallinity. Magnetic measurements showed high perpendicular magnetic anisotropy of the nanowires with easy axis parallel to nanowires axis. X-ray diffraction results indicated that annealed CoFeCu nanowires were polycrystalline with two distinct CoFe and Cu phases.

  12. Submillimeter Array Observations of Magnetic Fields in G240.31+0.07: An Hourglass in a Massive Cluster-forming Core

    NASA Astrophysics Data System (ADS)

    Qiu, Keping; Zhang, Qizhou; Menten, Karl M.; Liu, Hauyu B.; Tang, Ya-Wen; Girart, Josep M.

    2014-10-01

    We report the first detection of an hourglass magnetic field aligned with a well-defined outflow rotation system in a high-mass, star-forming region. The observations were performed with the Submillimeter Array toward G240.31+0.07, which harbors a massive, flattened, and fragmenting molecular cloud core and a wide-angle bipolar outflow. The polarized dust emission at 0.88 mm reveals a clear hourglass-shaped magnetic field aligned within 20° of the outflow axis. Maps of high-density tracing spectral lines, e.g., H13CO+ (4-3), show that the core is rotating about its minor axis, which is also aligned with the magnetic field axis. Therefore, both the magnetic field and kinematic properties observed in this region are surprisingly consistent with the theoretical predictions of the classic paradigm of isolated low-mass star formation. The strength of the magnetic field in the plane of sky is estimated to be ~1.1 mG, resulting in a mass-to-magnetic flux ratio of 1.4 times the critical value and a turbulent-to-ordered magnetic energy ratio of 0.4. We also find that the specific angular momentum almost linearly decreases from r ~ 0.6 pc to 0.03 pc scales, which is most likely attributed to magnetic braking.

  13. Nonuniform radiation damage in permanent magnet quadrupoles

    SciTech Connect

    Danly, C. R.; Merrill, F. E.; Barlow, D.; Mariam, F. G. [Los Alamos National Laboratory, Los Alamos, New Mexico 87544 (United States)

    2014-08-15

    We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL’s pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components.

  14. Nonuniform radiation damage in permanent magnet quadrupoles.

    PubMed

    Danly, C R; Merrill, F E; Barlow, D; Mariam, F G

    2014-08-01

    We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL's pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components. PMID:25173260

  15. Nonuniform radiation damage in permanent magnet quadrupoles

    NASA Astrophysics Data System (ADS)

    Danly, C. R.; Merrill, F. E.; Barlow, D.; Mariam, F. G.

    2014-08-01

    We present data that indicate nonuniform magnetization loss due to radiation damage in neodymium-iron-boron Halbach-style permanent magnet quadrupoles. The proton radiography (pRad) facility at Los Alamos uses permanent-magnet quadrupoles for magnifying lenses, and a system recently commissioned at GSI-Darmsdadt uses permanent magnets for its primary lenses. Large fluences of spallation neutrons can be produced in close proximity to these magnets when the proton beam is, intentionally or unintentionally, directed into the tungsten beam collimators; imaging experiments at LANL's pRad have shown image degradation with these magnetic lenses at proton beam doses lower than those expected to cause damage through radiation-induced reduction of the quadrupole strength alone. We have observed preferential degradation in portions of the permanent magnet quadrupole where the field intensity is highest, resulting in increased high-order multipole components.

  16. Magnetic resonance tomography using elongated transmitter and in-loop receiver arrays for time-efficient 2-D imaging of subsurface aquifer structures

    NASA Astrophysics Data System (ADS)

    Jiang, C.; Müller-Petke, M.; Lin, J.; Yaramanci, U.

    2015-02-01

    Surface nuclear magnetic resonance (surface-NMR) is a promising technique for exploring shallow subsurface aquifer structures. Surface-NMR can be applied in environments that are characterized as a 1-D layered Earth. The technique utilizes a single loop and is referred to as magnetic resonance sounding. The technique referred to as magnetic resonance tomography (MRT) allows complex 2-D aquifer structures to be explored. Currently, MRT requires multiple loops and a roll along measurement scheme, which causes long survey time. We propose a loop layout using an elongated transmitter and an in-loop receiver arrays (ETRA) to conduct a 2-D survey with just one measurement. We present a comprehensive comparison between the new layout and the common approaches based on sensitivity and resolution analyses and show synthetic and field data. The results show that ETRA generates subsurface images at sufficient resolution with significantly lower survey times than other loop layouts.

  17. Array of Hall Effect Sensors for Linear Positioning of a Magnet Independently of Its Strength Variation. A Case Study: Monitoring Milk Yield during Milking in Goats

    PubMed Central

    García-Diego, Fernando-Juan; Sánchez-Quinche, Angel; Merello, Paloma; Beltrán, Pedro; Peris, Cristófol

    2013-01-01

    In this study we propose an electronic system for linear positioning of a magnet independent of its modulus, which could vary because of aging, different fabrication process, etc. The system comprises a linear array of 24 Hall Effect sensors of proportional response. The data from all sensors are subject to a pretreatment (normalization) by row (position) making them independent on the temporary variation of its magnetic field strength. We analyze the particular case of the individual flow in milking of goats. The multiple regression analysis allowed us to calibrate the electronic system with a percentage of explanation R2 = 99.96%. In our case, the uncertainty in the linear position of the magnet is 0.51 mm that represents 0.019 L of goat milk. The test in farm compared the results obtained by direct reading of the volume with those obtained by the proposed electronic calibrated system, achieving a percentage of explanation of 99.05%. PMID:23793020

  18. Supramolecular control of the magnetic anisotropy in two-dimensional high-spin Fe arrays at a metal interface

    Microsoft Academic Search

    Pietro Gambardella; Sebastian Stepanow; Alexandre Dmitriev; Jan Honolka; Frank M. F. de Groot; Magalí Lingenfelder; Subhra Sen Gupta; D. D. Sarma; Peter Bencok; Stefan Stanescu; Sylvain Clair; Stéphane Pons; Nian Lin; Ari P. Seitsonen; Harald Brune; Johannes V. Barth; Klaus Kern

    2009-01-01

    Magnetic atoms at surfaces are a rich model system for solid-state magnetic bits exhibiting either classical or quantum behaviour. Individual atoms, however, are difficult to arrange in regular patterns. Moreover, their magnetic properties are dominated by interaction with the substrate, which, as in the case of Kondo systems, often leads to a decrease or quench of their local magnetic moment.

  19. The reliability of the seismo-magnetic method derived from ULF/ELF observations by the South European Geomagnetic Array (SEGMA)

    NASA Astrophysics Data System (ADS)

    Schwingenschuh, Konrad; Prattes, Gustav; Eichelberger, Hans Ulrich; Magnes, Werner; Berghofer, Gerhard; Aydogar, Özer; Besser, Bruno P.; Boudjada, Mohammed; Stangl, Günter; Zhang, Tie Long; Wolbang, Daniel; Vellante, Massimo; Villante, Umberto; Rozhnoi, Alexander; Solovieva, Maria; Nenovski, Petko; Veztergom, Victor; Szendr?i, Judith

    2013-04-01

    In the frame of the South European GeoMagnetic Array (SEGMA) project magnetic field variations are studied in the frequency range from several milli-Hz to several Hz. The fluxgate and induction coil magnetometers are located in Italy, Bulgaria and Hungary. The scientific objectives comprises field-line resonances, space weather phenomena and seismo-magnetic (SM) studies. In our present study on the reliability of the seismo-magnetic method we emphasize on the influence of external non-seismic sources on the quality of seismo-magnetic studies. External magnetic sources include lightning, power lines, railway and traffic as well as geomagnetic variations of magnetospheric origin. We observe anomalies of the ratio of the vertical to horizontal magnetic field component in the ultra/extreme-low-frequency (ULF/ELF) frequency range up to several Hz [2]. These signals can be produced in the lithosphere near a seismic active region and are interpreted as earthquake precursors. In order to differentiate geomagnetic from seismo-magnetic fluctuations, we use mainly observations around midnight because the night time geomagnetic fluctuations are much smaller than during day time. The SEGMA network provides the unique opportunity to use multipoint observations, which are also useful to distinguish local from global phenomena. In order to get undisturbed magnetic field observations, the stations are located outside populated areas [2]. The electrical conductivity of the soil in the vicinity of magnetometers on the terrestrial surface is a further source for interferences. This type of disturbances caused by induced electrical currents can be minimized either by a careful selection of the magnetometer site ans/or by the measurement of the conductivity profile in the vicinity of the instrument site. In the frame of the investigation of the April 6, 2009 L'Aquila earthquake magneto-telluric methods have been used to measure the conductivity profile near the epicenter of the earthquake and thus correct the observed magnetic field fluctuations [1]. A further interference source which can reduce the sensitivity of the seismo-magnetic methods (SM) is the mechanical vibration of the magnetometer sensors. We present a SM reliability number taking into account all above mentioned interference sources. The SM number can be used to improve the sensitivity of the seismo-magnetic method. References [1] G. Prattes, et al.: Ultra Low Frequency (ULF) European multi station magnetic field analysis before and during the 2009 earthquake at L'Aquila regarding regional geotechnical information, Nat. Hazards Earth Syst. Sci., 11, 1959-1968, 2011 [2] K. Schwingenschuh, et al.: 'Clean' observations of magnetic field fluctuations on planetary surfaces, Aerospace EMC, 2012 Proceedings ESA Workshop on 21-23 May 2012, 4 p., 2012.

  20. Novel magnetite-silica nanocomposite (Fe3O4-SBA-15) particles for DNA binding and gene delivery aided by a magnet array.

    PubMed

    Yiu, Humphrey H P; McBain, Stuart C; Lethbridge, Zoe A D; Lees, Martin R; Palona, Iryna; Olariu, Cristina I; Dobson, Jon

    2011-04-01

    Novel magnetite-silica nanocomposite particles were prepared using SBA-15 nanoporous silica as template. Magnetite nanoparticles were impregnated into the nanopore array of the silica template through thermal decomposition of iron(III) acetylacetonate, Fe(AcAc)3 at 200 degrees C. These composite particles were characterized using TEM, XRD and SQUID magnetometry. The TEM images showed that the size of composite particles was around 500 nm and the particles retained the nanoporous array of SBA-15. The formation of magnetite nanoparticles was confirmed by the powder XRD study. These composite particles also exhibited ferrimagnetic properties. By coating with short chain polyethyleneimine (PEI), these particles are capable of binding DNA molecules for gene delivery and transfection. With an external magnetic field, the transfection efficiency was shown to have an increase of around 15%. The results indicated that these composite nanoparticles may be further developed as a new tool for nanomagnetic gene transfection. PMID:21776740

  1. Determination of radial location of rotating magnetic islands by use of poloidal soft x-ray detector arrays in the STOR-M tokamak

    SciTech Connect

    Dreval, M. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada); IPP NSC Kharkov Institute of Physics and Technology, Kharkiv (Ukraine); Xiao, C.; Elgriw, S.; Trembach, D.; Hirose, A. [Plasma Physics Laboratory, University of Saskatchewan, Saskatoon, SK S7N 5E2 (Canada); Wolfe, S. [Plasmionique, Brossard, Quebec, J4X 2S3 (Canada)

    2011-05-15

    A technique is presented for determining the radial location of the rotating magnetic islands in the STOR-M tokamak by use of soft x-ray (SXR) detector arrays. The location is determined by examining the difference in the integrated SXR emission intensities through two adjacent lines of sight. A model for calculating dependence of the line integrated SXR emission intensity on the radius, the mode numbers and the magnetic island geometry, has been developed. The SXR difference signal shows phase inversion when the impact parameter of the line of sight sweeps across the magnetic islands. Experimentally, the difference SXR signals significantly reduce noise and suppress the influence of background plasma fluctuations through common mode rejection when a dominant mode exists in the STOR-M tokamak. The radial locations of the m= 2 magnetic islands have been determined under several experimental conditions in the STOR-M discharges. With the decrease in the tokamak discharge current and thus the increase of the safety factor at the edge, the radial location of the m= 2 magnetic islands has been found to move radially inward.

  2. 2452 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 39, NO. 11, NOVEMBER 2011 Permanent-Magnet Helicon Discharge Array

    E-print Network

    Chen, Francis F.

    entail large and heavy electromagnets and their dc power supplies. Annular permanent magnets can produce2452 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 39, NO. 11, NOVEMBER 2011 Permanent-Magnet Helicon ionization efficiency, but they require a dc magnetic field, which normally would be an electromagnet large

  3. Quantitative Study of Liver Magnetic Resonance Spectroscopy Quality at 3T Using Body and Phased Array Coils with Physical Analysis and Clinical Evaluation

    PubMed Central

    Xu, Li; Gu, Shiyong; Feng, Qianjin; Liang, Changhong; Xin, Sherman Xuegang

    2015-01-01

    This study aims to investigate the quality difference of short echo time (TE) breathhold 1H magnetic resonance spectroscopy (MRS) of the liver at 3.0T using the body and phased array coils, respectively. In total, 20 pairs of single-voxel proton spectra of the liver were acquired at 3.0T using the phased array and body coils as receivers. Consecutive stacks of breathhold spectra were acquired using the point resolved spectroscopy (PRESS) technique at a short TE of 30 ms and a repetition time (TR) of 1500 ms. The first spectroscopy sequence was “copied” for the second acquisition to ensure identical voxel positioning. The MRS prescan adjustments of shimming and water suppression, signal-to noise ratio (SNR), and major liver quantitative information were compared between paired spectra. Theoretical calculation of the SNR and homogeneity of the region of interest (ROI, 2 cm×2 cm×2 cm) using different coils loaded with 3D liver electromagnetic model of real human body was implemented in the theoretical analysis. The theoretical analysis showed that, inside the ROI, the SNR of the phase array coil was 2.8387 times larger than that of body coil and the homogeneity of the phase array coil and body coil was 80.10% and 93.86%, respectively. The experimental results showed excellent correlations between the paired data (all r > 0.86). Compared with the body coil group, the phased array group had slightly worse shimming effect and better SNR (all P values < .01). The discrepancy of the line width because of the different coils was approximately 0.8 Hz (0.00625 ppm). No significant differences of the major liver quantitative information of Cho/Lip2 height, Cho/Lip2 area, and lipid content were observed (all P values >0.05). The theoretical analysis and clinical experiment showed that the phased array coil was superior to the body coil with respect to 3.0T breathhold hepatic proton MRS. PMID:25881016

  4. Dynamic templating: A new pathway for the assembly of large-area arrays of plasmonic, magnetic and semiconductor nanomaterials

    NASA Astrophysics Data System (ADS)

    Farzinpour, Pouyan

    Substrate-based nanostructures are of great importance due to their applications in microelectronic devices, chemical sensors, catalysis and photovoltaics. This dissertation describes a novel fabrication technique for the formation of periodic arrays of substrate-based nanoparticles. The prescribed route, referred to as dynamic templating, requires modest levels of instrumentation consisting of a sputter coater, micrometer-scale shadow masks and a tube furnace. The route has broad applicability, having already produced periodic arrays of gold, silver, copper, platinum, nickel, cobalt, germanium and Au--Ag alloys on substrates as diverse as silicon, sapphire, silicon--carbide, and glass. The newly devised method offers large-area, high-throughput capabilities for the fabrication of periodic arrays of sub-micrometer and nanometer-scale structures and overcomes a significant technological barrier to the widespread use of substrate-based templated assembly by eliminating the need for periodic templates having nanoscale features. Because this technique only requires modest levels of instrumentation, researchers are now able to fabricate periodic arrays of nanostructures that would otherwise require advanced fabrication facilities.

  5. Magnetic Forces Simulation of Bulk HTS over Permanent Magnetic Railway with Numerical Method

    NASA Astrophysics Data System (ADS)

    Lu, Yiyun; Zhuang, Shujun

    2012-10-01

    Magnetic levitation forces of bulk high temperature superconductor (HTS) above two types permanent magnet railway (PMR) is simulated using finite element method (FEM). The models are formulated by H-formulation and resolving codes is developed using Finite Element Program Generator (FEPG). The E- J power law is used to describe the electrical field vs. current density nonlinear characteristic of HTS. The applied magnetic fields induced by the PMR are calculated by the standard analysis method with the equivalent surface current model. By the method, the calculation formulation of magnetic fields generated by Halbach PMR and symmetrical PMR is derived respectively. The simulation results show that the finite element dynamic mesh rebuilding problem of HTS magnetic levitation transportation system comprised of bulk HTS and PMR can be easily avoided by the methods.

  6. OH MASER SOURCES IN W49N: PROBING MAGNETIC FIELD AND DIFFERENTIAL ANISOTROPIC SCATTERING WITH ZEEMAN PAIRS USING THE VERY LONG BASELINE ARRAY

    SciTech Connect

    Deshpande, Avinash A. [Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Goss, W. M. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Mendoza-Torres, J. E., E-mail: desh@rri.res.in, E-mail: mgoss@aoc.nrao.edu, E-mail: mend@inaoep.mx [Instituto Nacional de Astrofísica Optica y Electrónica, Tonantzintla, Puebla 72840 (Mexico)

    2013-09-20

    Our analysis of a Very Long Baseline Array 12 hr synthesis observation of the OH masers in the well-known star-forming region W49N has yielded valuable data that enable us to probe distributions of magnetic fields in both the maser columns and the intervening interstellar medium (ISM). The data, consisting of detailed high angular resolution images (with beam width ?20 mas) of several dozen OH maser sources, or spots, at 1612, 1665, and 1667 MHz, reveal anisotropic scatter broadening with typical sizes of a few tens of milliarcseconds and axial ratios between 1.5 and 3. Such anisotropies have been reported previously by Desai et al. and have been interpreted as being induced by the local magnetic field parallel to the Galactic plane. However, we find (1) apparent angular sizes of, on average, a factor of about 2.5 less than those reported by Desai et al., indicating significantly less scattering than inferred previously, and (2) a significant deviation in the average orientation of the scatter-broadened images (by ?10°) from that implied by the magnetic field in the Galactic plane. More intriguingly, for a few Zeeman pairs in our set, significant differences (up to 6?) are apparent in the scatter-broadened images for the two hands of circular polarization, even when the apparent velocity separation is less than 0.1 km s{sup –1}. This may possibly be the first example of a Faraday rotation contribution to the diffractive effects in the ISM. Using the Zeeman pairs, we also study the distribution of the magnetic field in the W49N complex, finding no significant trend in the spatial structure function. In this paper, we present the details of our observations and analysis leading to these findings, discuss implications of our results for the intervening anisotropic magneto-ionic medium, and suggest possible implications for the structure of magnetic fields within this star-forming region.

  7. OH Maser Sources in W49N: Probing Magnetic Field and Differential Anisotropic Scattering with Zeeman Pairs Using the Very Long Baseline Array

    NASA Astrophysics Data System (ADS)

    Deshpande, Avinash A.; Goss, W. M.; Mendoza-Torres, J. E.

    2013-09-01

    Our analysis of a Very Long Baseline Array 12 hr synthesis observation of the OH masers in the well-known star-forming region W49N has yielded valuable data that enable us to probe distributions of magnetic fields in both the maser columns and the intervening interstellar medium (ISM). The data, consisting of detailed high angular resolution images (with beam width ~20 mas) of several dozen OH maser sources, or spots, at 1612, 1665, and 1667 MHz, reveal anisotropic scatter broadening with typical sizes of a few tens of milliarcseconds and axial ratios between 1.5 and 3. Such anisotropies have been reported previously by Desai et al. and have been interpreted as being induced by the local magnetic field parallel to the Galactic plane. However, we find (1) apparent angular sizes of, on average, a factor of about 2.5 less than those reported by Desai et al., indicating significantly less scattering than inferred previously, and (2) a significant deviation in the average orientation of the scatter-broadened images (by ~10°) from that implied by the magnetic field in the Galactic plane. More intriguingly, for a few Zeeman pairs in our set, significant differences (up to 6?) are apparent in the scatter-broadened images for the two hands of circular polarization, even when the apparent velocity separation is less than 0.1 km s-1. This may possibly be the first example of a Faraday rotation contribution to the diffractive effects in the ISM. Using the Zeeman pairs, we also study the distribution of the magnetic field in the W49N complex, finding no significant trend in the spatial structure function. In this paper, we present the details of our observations and analysis leading to these findings, discuss implications of our results for the intervening anisotropic magneto-ionic medium, and suggest possible implications for the structure of magnetic fields within this star-forming region.

  8. An improved permanent magnet quadrupole design with larger good field region for high intensity proton linacs

    NASA Astrophysics Data System (ADS)

    Mathew, Jose V.; Rao, S. V. L. S.; Krishnagopal, S.; Singh, P.

    2013-11-01

    The Low Energy High Intensity Proton Accelerator (LEHIPA), being developed at the Bhabha Atomic Research Centre (BARC) will produce a 20 MeV, 30 mA, continuous wave (CW) proton beam. At these low velocities, space-charge forces dominate, and could lead to larger beam sizes and beam halos. Hence in the design of the focusing lattice of the LEHIPA drift tube linac (DTL) using permanent magnet quadrupoles (PMQs), a larger good field region is preferred. Here we study, using the two dimensional (2D) and three dimensional (3D) simulation codes PANDIRA and RADIA, four different types of cylindrical PMQ designs: 16-segment trapezoidal Halbach configuration, bullet-nosed geometry and 8- and 16-segment rectangular geometries. The trapezoidal Halbach geometry is used in a variety of accelerators since it provides very high field gradients in small bores, while the bullet-nosed geometry, which is a combination of the trapezoidal and rectangular designs, is used in some DTLs. This study shows that a larger good field region is possible in the 16-segment rectangular design as compared to the Halbach and bullet-nosed designs, making it more attractive for high-intensity proton linacs. An improvement in good-field region by ˜16% over the Halbach design is obtained in the optimized 16-segment rectangular design, although the field gradient is lower by ˜20%. Tolerance studies show that the rectangular segment PMQ design is substantially less sensitive to the easy axis orientation errors and hence will be a better choice for DTLs.

  9. An historical review of seismometer array development

    Microsoft Academic Search

    E. W. Carpenter

    1965-01-01

    The development of seismometer arrays in the context of nuclear detection is briefly outlined. The original array concept was for ten seismometers distributed in an area of a few square kilometers, but technological progress with magnetic tape recording and subsequent processing led to the construction of crossed linear arrays with dimensions of a few tens of kilometers. The linear arrays,

  10. Simultaneous B1 + homogenization and specific absorption rate hotspot suppression using a magnetic resonance phased array transmit coil.

    PubMed

    Van den Berg, Cornelis A T; van den Bergen, Bob; Van de Kamer, Jeroen B; Raaymakers, Bas W; Kroeze, Hugo; Bartels, Lambertus W; Lagendijk, Jan J W

    2007-03-01

    In high-field MRI severe problems with respect to B(1) (+) uniformity and specific absorption rate (SAR) deposition pose a great challenge to whole-body imaging. In this study the potential of a phased array transmit coil is investigated to simultaneously reduce B(1) (+) nonuniformity and SAR deposition. This was tested by performing electromagnetic simulations of a phased array TEM coil operating at 128 MHz loaded with two different homogeneous elliptical phantoms and four dielectric patient models. It was shown that the wave interference of a circularly polarized RF field with an ellipse and a pelvis produces largely identical B(1) (+) and electric field patterns. Especially for obese patients, this results in large B(1) (+) nonuniformity and global areas with elevated SAR deposition. It is demonstrated that a phased array transmit coil can reduce these phenomena. The technique was especially successful in suppressing SAR hotspots with a decrease up to 50%. The application of optimized settings for an ellipse to the patient models leads to comparable results as obtained with the patient-specific optimizations. This suggests that generic phase/amplitude port settings are possible, requiring no preinformation about patient-specific RF fields. Such a scheme would, due to its simultaneous B(1) (+) homogenization and extra SAR margin, have many benefits for whole-body imaging at 3 T. PMID:17326185

  11. Magnetic nanohole superlattices

    DOEpatents

    Liu, Feng

    2013-05-14

    A magnetic material is disclosed including a two-dimensional array of carbon atoms and a two-dimensional array of nanoholes patterned in the two-dimensional array of carbon atoms. The magnetic material has long-range magnetic ordering at a temperature below a critical temperature Tc.

  12. Syntheses and structure characterizations of multi- dimensional cyanide-bridged lanthanide-transition metal arrays: Studies on their magnetic properties

    NASA Astrophysics Data System (ADS)

    Du, Bin

    2000-11-01

    Novel cyanide bridged lanthanide-transition metal arrays were prepared. Two-dimensional [K(DMF)7Ln[M(CN)4]2] ? (Ln = Eu, Yb; M = Ni, Pt) are made of puckered sheets and interstitial K2[M(CN)4]. Three-dimensional [(NH4)(DMF) 4Yb[Pt(CN)4]2]? consists of parallel columns bundled through hydrogen bonds and is the first example in which Ln(III) is coordinated to four [M(CN)4]2- groups. Monohydrate complexes form either a zigzag chain or ``stairway-like'' structure. The latter resembles previously reported ``diamond-like'' structure, but with its trans-bridging [Pt(CN)4] 2- perpendicular to the ``diamonds''. Oligomeric (H 2O)n(DMF)(12-n)Ln2[M(CN) 4]3 is formed if there is multiple ligating water. [(H2O)2(DMF)8Ln2[M(CN)4] 3]? (Ln = Dy, Yb) were obtained from solid state H 2O-DMF ligand exchange reactions, with the retention of basic structures of parent compounds. Structural isomers were obtained for one-dimensional arrays containing [Ni(CN)4]2-. An improved synthetic route for these complexes reduces reaction time from 2 weeks to 30 minutes. Type B isomers are the thermodynamically stable ones whereas Type A isomers are the kinetically favored ones. Ln(III) does not affect the formation of structural isomers. Assembly mechanisms were proposed for all array complexes based on two complex ion-pairs [(DMF)6Ln[M(CN)4] 2]- and [(DMF)7Ln[M(CN)4

  13. Use of a SQUID array to detect T-cells with magnetic nanoparticles in determining transplant rejection

    NASA Astrophysics Data System (ADS)

    Flynn, Edward R.; Bryant, H. C.; Bergemann, Christian; Larson, Richard S.; Lovato, Debbie; Sergatskov, Dmitri A.

    2007-04-01

    Acute rejection in organ transplant is signaled by the proliferation of T-cells that target and kill the donor cells requiring painful biopsies to detect rejection onset. An alternative non-invasive technique is proposed using a multi-channel superconducting quantum interference device (SQUID) magnetometer to detect T-cell lymphocytes in the transplanted organ labeled with magnetic nanoparticles conjugated to antibodies specifically attached to lymphocytic ligand receptors. After a magnetic field pulse, the T-cells produce a decaying magnetic signal with a characteristic time of the order of a second. The extreme sensitivity of this technique, 10 5 cells, can provide early warning of impending transplant rejection and monitor immune-suppressive chemotherapy.

  14. Array Games

    NSDL National Science Digital Library

    Mrs. Watts

    2007-10-05

    Arrays are very important in Computer Programming. An array is a way to store similar items in computer memory. The items may be numbers, words, pictures, or even sounds. Many games use an array because it is an easy way to keep track of the objects used to play the game. The Arrow Game uses an array to store arrow ...

  15. Fabrication and magnetic properties of La-X (X = Co, Ni, and Fe) nanotube arrays prepared by electrodeposition methods

    NASA Astrophysics Data System (ADS)

    Chen, J. Y.; Shi, D. W.; Ahmad, N.; Liu, D. P.; Zhou, W. P.; Han, X. F.

    2013-08-01

    Well-ordered La-X (X = Co, Ni and Fe) nanotubes, with the average diameter of ˜200 nm, wall thicknesses of ˜40 nm, have been fabricated into anodized aluminum oxide template by potentiostatic electrodeposition method. Various composition of La-X nanotubes were obtained by tuning the applied deposition potential. Magnetization measurements reveal that doped La could enhance the coercivity (Hc) of La-X nanotubes and their easy axis is perpendicular to the nanotube axis. There is a transition from the curling to transverse mode with increase of angle. Temperature dependent magnetization indicates the existence of superparamagnetic nanoparticles and that the surface effect results in the increase of saturation magnetization (Ms) at low temperature. Abnormal behavior of temperature dependent Hc may result from thermal excitation, magnetoelastic anisotropy, as well as oxide layer of nanotube inner surface induced coupling. These one-dimensional rare-earth transition metal nanostructures could have potential applications in novel spintronics device, ultra-small magnetic media, drug delivery, or other nanodevice.

  16. Influence of Y-doped induced defects on the optical and magnetic properties of ZnO nanorod arrays prepared by low-temperature hydrothermal process

    PubMed Central

    2012-01-01

    One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E2(H) mode intensity and increase of E1(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods. PMID:22768847

  17. Radio-frequency spectroscopy of a linear array of Bose-Einstein condensates in a magnetic lattice

    NASA Astrophysics Data System (ADS)

    Surendran, P.; Jose, S.; Wang, Y.; Herrera, I.; Hu, H.; Liu, X.; Whitlock, S.; McLean, R.; Sidorov, A.; Hannaford, P.

    2015-02-01

    We report site-resolved radio-frequency spectroscopy measurements of Bose-Einstein condensates of 87Rb atoms in about 100 sites of a one-dimensional (1D) 10-? m -period magnetic lattice produced by a grooved magnetic film plus bias fields. Site-to-site variations of the trap bottom, atom temperature, condensate fraction, and chemical potential indicate that the magnetic lattice is remarkably uniform, with variations in the trap bottoms of only ±0.4 mG. At the lowest trap frequencies (radial and axial frequencies of 1.5 kHz and 260 Hz, respectively), temperatures down to 0.16 ? K are achieved in the magnetic lattice, and at the smallest trap depths (50 kHz) condensate fractions up to 80% are observed. With increasing radial trap frequency (up to 20 kHz, or aspect ratio up to ˜80 ) large condensate fractions persist, and the highly elongated clouds approach the quasi-1D Bose gas regime. The temperature estimated from analysis of the spectra is found to increase by a factor of about 5, which may be due to suppression of rethermalizing collisions in the quasi-1D Bose gas. Measurements for different holding times in the lattice indicate a decay of the atom number with a half-life of about 0.9 s due to three-body losses and the appearance of a high-temperature (˜1.5 ? K ) component which is attributed to atoms that have acquired energy through collisions with energetic three-body decay products.

  18. Method and apparatus for control of a magnetic structure

    DOEpatents

    Challenger, Michael P. (Bothell, WA); Valla, Arthur S. (Bothell, WA)

    1996-06-18

    A method and apparatus for independently adjusting the spacing between opposing magnet arrays in charged particle based light sources. Adjustment mechanisms between each of the magnet arrays and the supporting structure allow the gap between the two magnet arrays to be independently adjusted. In addition, spherical bearings in the linkages to the magnet arrays permit the transverse angular orientation of the magnet arrays to also be adjusted. The opposing magnet arrays can be supported above the ground by the structural support.

  19. Amazing Arrays

    NSDL National Science Digital Library

    Format Edit

    2012-04-18

    This is a hands-on lesson for introducing and practicing building arrays to create models that represent the distributive property of multiplication, and then using those arrays to draw models of the equations they represent.

  20. Nanocylinder arrays

    DOEpatents

    Tuominen, Mark; Schotter, Joerg; Thurn-Albrecht, Thomas; Russell, Thomas P.

    2007-03-13

    Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

  1. Nanocylinder arrays

    DOEpatents

    Tuominen, Mark (Shutesbury, MA); Schotter, Joerg (Bielefeld, DE); Thurn-Albrecht, Thomas (Freiburg, DE); Russell, Thomas P. (Amherst, MA)

    2009-08-11

    Pathways to rapid and reliable fabrication of nanocylinder arrays are provided. Simple methods are described for the production of well-ordered arrays of nanopores, nanowires, and other materials. This is accomplished by orienting copolymer films and removing a component from the film to produce nanopores, that in turn, can be filled with materials to produce the arrays. The resulting arrays can be used to produce nanoscale media, devices, and systems.

  2. Magnetism

    NSDL National Science Digital Library

    University Corporation for Atmospheric Research Windows to the Universe team

    2007-12-12

    This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

  3. Crustal thickness and Vp/Vs estimates near the Brunswick magnetic anomaly using receiver functions from the SESAME array

    NASA Astrophysics Data System (ADS)

    Parker, E. H.; Hawman, R. B.; Fischer, K. M.; Wagner, L. S.

    2012-12-01

    The Southeastern Suture of the Appalachian Margin Experiment (SESAME) is designed to investigate lithospheric dynamics associated with the Paleozoic collision between the Suwanee terrane and Laurentia as well as subsequent Mesozoic rifting and passive margin formation. So far, we have deployed 63 broadband instruments along two N-S trending profiles across Georgia and northern Florida. A third NW-trending profile consisting of 19 stations extends across accreted terranes of the southern Appalachians from Augusta, GA to eastern TN. The N-S profiles are intended to provide constraints on variations in crustal structure across the Brunswick magnetic anomaly (BMA), a prominent magnetic low coinciding with south-dipping crustal-scale seismic reflectors evident on COCORP profiles in south Georgia. The seismic reflectivity is likely a consequence of suturing, but the BMA has been interpreted as an edge effect related to collision as well as an effect of mafic magmatism south of the suture zone. H-k stacking using 10 teleseismic receiver functions from station W27, located ~50-km north of the suture on the western N-S profile, suggests a crustal thickness (H) of 42-44 km and average crustal Vp/Vs (k) of 1.73-1.80. These estimates are in agreement with previous well-constrained stacking results from USNSN station GOGA, located ~70-km to the northeast, that suggest a crustal thickness of 41-43 km and average Vp/Vs 1.72-1.76. The proposed suture zone itself lies beneath sediments of the Atlantic Coastal Plain, and receiver functions from stations in this region appear to be strongly affected by high-amplitude reverberations within the sedimentary column. Therefore, preliminary H-k stacking results from stations directly over the BMA may be unreliable. However, receiver functions from station W23 near the Inner Piedmont-Coastal Plain boundary (near the north, up-dip end of the suture zone) display variations in Ps delay time and amplitude with event back-azimuth. Receiver functions from the S-azimuth (South American trench) display a relatively weak Ps conversion at ~4 seconds, while receiver functions from the NW-azimuth (Aleutian trench) show a more complex signal with an arrival at ~4 s followed by a higher-amplitude arrival at ~6 seconds. This may be indicative of compositional heterogeneity across the suture, anisotropy within the crust or mantle, or complexity at the crust-mantle interface related to collision of the Suwanee terrane. Forthcoming data from additional stations will provide improved constraints on crustal structure across the BMA.

  4. Magnetic and dielectric properties of one-dimensional array of S = 1/2 linear trimer system Na2Cu3Ge4O12

    NASA Astrophysics Data System (ADS)

    Yasui, Yukio; Kawamura, Yuji; Kobayashi, Yoshiaki; Sato, Masatoshi

    2014-05-01

    Magnetic susceptibility ?, specific heat C, capacitance Cp, and 23Na-NMR measurements have been carried out on polycrystalline samples of quantum spin linear trimer system Na2Cu3Ge4O12, which has the one-dimensional array of Cu3O8 trimers formed of edge-sharing three CuO4 square planes. The exchange interactions between the Cu2+ (S = 1/2) spins have been determined by analyzing ?-T and C-T curves. By employing the isolated S = 1/2 Heisenberg trimer model above 70 K, the nearest-neighbor exchange couplings J1 and the second-neighbor one J2 in trimer have been evaluated to J1/kB = 30 ± 20 K (antiferromagnetic) and J2/kB = 340 ± 20 K. At low temperature region, two spins of the edge in the Cu3O8 trimers form a nonmagnetic singlet by strong antiferromagnetic interaction J2, and the spin left in the center of the Cu3O8 trimer forms one-dimensional chains by the exchange interaction J3 between the trimers. By employing the S = 1/2 uniform Heisenberg chain model below 70 K, we have evaluated to J3/kB = 18 ± 1 K. The mechanism of multiferroic behavior at Tc = 2 K is discussed.

  5. Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging

    PubMed Central

    El-Ghussein, Fadi; Mastanduno, Michael A.; Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.

    2013-01-01

    Abstract. A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans. PMID:23979460

  6. Hybrid photomultiplier tube and photodiode parallel detection array for wideband optical spectroscopy of the breast guided by magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    El-Ghussein, Fadi; Mastanduno, Michael A.; Jiang, Shudong; Pogue, Brian W.; Paulsen, Keith D.

    2014-01-01

    A new optical parallel detection system of hybrid frequency and continuous-wave domains was developed to improve the data quality and accuracy in recovery of all breast optical properties. This new system was deployed in a previously existing system for magnetic resonance imaging (MRI)-guided spectroscopy, and allows incorporation of additional near-infrared wavelengths beyond 850 nm, with interlaced channels of photomultiplier tubes (PMTs) and silicon photodiodes (PDs). The acquisition time for obtaining frequency-domain data at six wavelengths (660, 735, 785, 808, 826, and 849 nm) and continuous-wave data at three wavelengths (903, 912, and 948 nm) is 12 min. The dynamic ranges of the detected signal are 105 and 106 for PMT and PD detectors, respectively. Compared to the previous detection system, the SNR ratio of frequency-domain detection was improved by nearly 103 through the addition of an RF amplifier and the utilization of programmable gain. The current system is being utilized in a clinical trial imaging suspected breast cancer tumors as detected by contrast MRI scans.

  7. Interference mode-locking of 2D magnetized colloids driven by dc and ac forces in periodic pinning arrays

    NASA Astrophysics Data System (ADS)

    Song, K. N.; Wang, H. L.; Ren, J.; Cao, Y. G.

    2015-01-01

    Using the Langevin simulation, we investigate the interference mode-locking of two-dimensional (2D) magnetized colloids on a substrate with periodic pinning centers. The colloidal particles are prepared initially in a 2D crystalline state and then driven simultaneously by direct-current (dc) and alternating-current (ac) forces. In the presence of a superimposed ac force, we find pronounced mode-locking steps in the characteristics of the averaged velocity versus dc force within a certain range of amplitude and frequency of the ac force. The mode-locking steps are attributed to an interference effect between the ac force and the modulation generated by the coherent motion of colloidal particles in a weak pinning potential. The step width ?fdc is found to oscillate in a Bessel function-like form with the amplitude of the ac force, in good agreement with previous results of vortex lattices. But, we find that ?fdc changes in an inverted parabola form with the frequency of the ac force and the substrate pinning strength as well as the interaction strength between colloidal particles. The averaged velocity at the step vstep is shown to increase linearly with the frequency of the ac force and the interaction strength between colloidal particles. The obtained results are helpful for fractionation of mesoscopic particles.

  8. Magnetism

    NSDL National Science Digital Library

    This radio broadcast discusses the history of magnetism from the time of its discovery by an apocryphal Greek sheperd until the late 16th century and the work of William Gilbert. There is also discussion of who pioneered the study of magnetism, what theories they constructed from its curious abilities, and how the power of the magnet was brought out of the realm of magic and into the service of science. The broadcast concludes with a discussion of why magnetism is still mysterious and how the modern search for the single magnetic pole, or magnetic monopole, could provide a fundamental unit of magnetism, essential for ultimate explanation. The broadcast is 41 minutes and 45 seconds in length.

  9. Prostate Cancer: Added Value of Subtraction Dynamic Imaging in 3T Magnetic Resonance Imaging with a Phased-array Body Coil

    PubMed Central

    Chung, Jae-Joon; Hong, Soon Won; Chung, Byung Ha; Kim, Joo Hee; Kim, Ki Whang

    2008-01-01

    Purpose To determine the added value of dynamic subtraction magnetic resonance (MR) imaging for the localization of prostate cancer. Materials and Methods We examined 21 consecutive patients who underwent MR imaging in 3T unit with a phased-array body coil and then had radical prostatectomy. After T2-weighted fast spin-echo imaging, we performed a contrast-enhanced dynamic 3D gradient-echo imaging consisting of pre-contrast, 2 successive early-phased (first imaging was started just after the appearance of contrast material in the aortic bifurcation followed by second imaging 35 seconds after the initiation of first imaging) and one 5-minute delayed post-contrast series. Subtraction of pre-contrast images from corresponding post-contrast images of each phase was performed on the console. Results On ROC analysis, the overall accuracy (Az value) of dynamic imaging combined with subtraction imaging was higher than T2-weighted imaging (p = 0.001) or conventional dynamic imaging alone (p = 0.074) for localization of cancer foci regardless of their zonal locations. Among pathologically verified 81 lesions, the mean volume of detected lesions with the subtraction images (n = 49, 0.69 cm3) was smaller than with T2-weighted images (n = 14, 1.05 cm3) or conventional dynamic images (n = 43, 0.71 cm3). Conclusion For localization of small prostate cancer, additional subtraction for the dynamic imaging could be superior to both T2-weighted imaging and un-subtracted dynamic imaging. PMID:18972597

  10. DNA Arrays

    NSDL National Science Digital Library

    This animation from Cold Spring Harbor Laboratory's Dolan DNA Learning Center presents DNA arrays. The animation contains information on Pat Brown's discovery and the purpose of DNA arrays to study gene expression as well as its role in the development of pharmacogenomic treatment for diseases such as cancer.

  11. Magnetization reversal in exchange biased IrMn/Fe ring arrays Yu-feng Hou, Qing-feng Zhan, and Kannan M. Krishnana

    E-print Network

    Krishnan, Kannan M.

    Mn/Fe lithographic structures. The magnetic anisotropy geometry of the exchange biased ring is revealed by fitting- served in magnetic ring structures,15 but the detailed mecha- nism of magnetic reversal is not well dependent magneto-optical Kerr effect MOKE magnetometry, magnetic force micros- copy MFM , and micromagnetic

  12. Magnetism

    NSDL National Science Digital Library

    David Stern

    This overview of magnetism provides a brief history prior to 1600 and continues with the work of William Gilbert, Hans Christian Oersted, and Andre-Marie Ampere in describing and exploring the magnetosphere and learning the role that electric current plays in producing magnetism. Magnetic field lines are then discussed, citing the work of Michael Faraday. The work of James Clerk Maxwell and Heinrich Hertz is mentioned in a discussion of the relationship of light waves and radio waves as part of the electromagnetic spectrum.

  13. Impulse arrays

    NASA Astrophysics Data System (ADS)

    Temes, C. L.

    1991-05-01

    This report considers impulse radar signals in terms of their propagation from an array of elements. The far-field electric vector is proportional to the derivative of the current in an infinitesimal dipole representing each element. Although not physically realizable, this model is used as an approximation to illustrate some array properties peculiar to impulse, or ultra-wideband (UWB), excitations. Thus, for example, a 1-ns rounded baseband pulse with a cosine-squared shape theoretically propagates as a single sinusoidal cycle centered at L-band (1 GHz) with 100 percent bandwidth. The far field from an array of elements is considered as a function of angle.

  14. Enthalpy arrays

    NASA Astrophysics Data System (ADS)

    Torres, Francisco E.; Kuhn, Peter; de Bruyker, Dirk; Bell, Alan G.; Wolkin, Michal V.; Peeters, Eric; Williamson, James R.; Anderson, Gregory B.; Schmitz, Gregory P.; Recht, Michael I.; Schweizer, Sandra; Scott, Lincoln G.; Ho, Jackson H.; Elrod, Scott A.; Schultz, Peter G.; Lerner, Richard A.; Bruce, Richard H.

    2004-06-01

    We report the fabrication of enthalpy arrays and their use to detect molecular interactions, including protein-ligand binding, enzymatic turnover, and mitochondrial respiration. Enthalpy arrays provide a universal assay methodology with no need for specific assay development such as fluorescent labeling or immobilization of reagents, which can adversely affect the interaction. Microscale technology enables the fabrication of 96-detector enthalpy arrays on large substrates. The reduction in scale results in large decreases in both the sample quantity and the measurement time compared with conventional microcalorimetry. We demonstrate the utility of the enthalpy arrays by showing measurements for two protein-ligand binding interactions (RNase A + cytidine 2'-monophosphate and streptavidin + biotin), phosphorylation of glucose by hexokinase, and respiration of mitochondria in the presence of 2,4-dinitrophenol uncoupler.

  15. Adaptive arrays

    Microsoft Academic Search

    S. Applebaum

    1976-01-01

    A method for adaptively optimizing the signal-to-noise ratio of an array antenna is presented. Optimum element weights are derived for a prescribed environment and a given signal direction. The derivation is extended to the optimization of a \\

  16. Revisiting the Curie balance concept:Toward simple high field magnetic measurements

    NASA Astrophysics Data System (ADS)

    Rochette, P.; Vadeboin, F.

    2003-04-01

    A combination of standard electronic balance and movable permanent magnet field source (Halbach cylinder: HC) is demonstrated using two HCs of 0.3 and 1 T fields. These HCs produce strong vertical gradients of high stability and homogeneity, adequate for a robust calibration of mass deviation versus magnetization. Combining the two field values and assuming saturation, high field susceptibility and saturation magnetization are obtained with high sensitivity (about 3 10-7 SI and 0.1 A/m, corresponding to a 0.1 mg balance sensitivity) and high speed. This set-up opens the possibility for systematic high field parameters determination on standard samples. Implementation using a variable field up to 2 T is possible. Moreover anisotropy measurement of high field induced magnetization is directly available using a rotating HC.

  17. Magnetic Cusp Configuration of the SPL Plasma Generator

    SciTech Connect

    Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kuechler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier [CERN, 385 Route de Meyrin, 1211 Geneva (Switzerland)

    2011-09-26

    The Superconducting Proton Linac (SPL) is a novel linear accelerator concept currently studied at CERN. As part of this study, a new Cs-free, RF-driven external antenna H{sup -} plasma generator has been developed to withstand an average thermal load of 6 kW. The magnetic configuration of the new plasma generator includes a dodecapole cusp field and a filter field separating the plasma heating and H{sup -} production regions. Ferrites surrounding the RF antenna serve in enhancing the coupling of the RF to the plasma. Due to the space requirements of the plasma chamber cooling circuit, the cusp magnets are pushed outwards compared to Linac4 and the cusp field strength in the plasma region is reduced by 40% when N-S magnetized magnets are used. The cusp field strength and plasma confinement can be improved by replacing the N-S magnets with offset Halbach elements of which each consists of three magnetic sub-elements with different magnetization direction. A design challenge is the dissipation of RF power induced by eddy currents in the cusp and filter magnets which may lead to overheating and demagnetization. In view of this, a copper magnet cage has been developed that shields the cusp magnets from the radiation of the RF antenna.

  18. A simple, small and low cost permanent magnet design to produce homogeneous magnetic fields.

    PubMed

    Manz, B; Benecke, M; Volke, F

    2008-05-01

    A new portable, pocket-size NMR probe based on a novel permanent magnet arrangement is presented. It is based on a Halbach-type magnet design which mimics the field of a spherical dipole by using cylindrical bar and ring magnets. The magnet system is made up of only three individual magnets, and most field calculations and optimisations can be performed analytically. A prototype system has been built using a set of small, off the shelf commercially available permanent magnets. Proton linewidths of 50 ppm FWHM could be achieved at a field strength of 1T. Calculations show that with custom-sized permanent magnets, linewidths of less than 1 ppm can be achieved over sample volumes of up to 1 mm3, which would in theory enable chemical shift resolved proton spectroscopy on mass-limited samples. But even with the achieved linewidth of 50 ppm, this can be a useful portable sensor for small amounts of liquid samples with restricted molecular mobility, like gels, polymers or high viscosity liquids. PMID:18314366

  19. A simple, small and low cost permanent magnet design to produce homogeneous magnetic fields

    NASA Astrophysics Data System (ADS)

    Manz, B.; Benecke, M.; Volke, F.

    2008-05-01

    A new portable, pocket-size NMR probe based on a novel permanent magnet arrangement is presented. It is based on a Halbach-type magnet design which mimics the field of a spherical dipole by using cylindrical bar and ring magnets. The magnet system is made up of only three individual magnets, and most field calculations and optimisations can be performed analytically. A prototype system has been built using a set of small, off the shelf commercially available permanent magnets. Proton linewidths of 50 ppm FWHM could be achieved at a field strength of 1 T. Calculations show that with custom-sized permanent magnets, linewidths of less than 1 ppm can be achieved over sample volumes of up to 1 mm 3, which would in theory enable chemical shift resolved proton spectroscopy on mass-limited samples. But even with the achieved linewidth of 50 ppm, this can be a useful portable sensor for small amounts of liquid samples with restricted molecular mobility, like gels, polymers or high viscosity liquids.

  20. Sonar Arrays and Array Processing

    NASA Astrophysics Data System (ADS)

    Baggeroer, A. B.

    2005-04-01

    Arrays of hydrophones have been part of Navy sonar systems for over fifty years now. They are used both passively and actively and now are quite sophisticated. These arrays were used in fixed configuration such as the SOSUS system and towed arrays deployed from surface ships and submarines. One can assert that these arrays were a key factor in winning the cold war. Similarly, medical ultrasonics have used many of the techniques initially developed for sonar systems save four orders of magnitude in frequency. The major area where modern sonars differ involves the use of adaptive array processing whereby one usually needs to localize a weak signal in the presence of strong interference in a nonstationary environment. Most of the recent literature concerns advancing these techniques especially making them more robust to environmental uncertainties including calibration and properties of the ocean. This presentation will give an overview of the state of the art in sonar and hopefully establish a few points of relevance with nondestructive testing.

  1. Electromagnetically Clean Solar Arrays

    NASA Technical Reports Server (NTRS)

    Stem, Theodore G.; Kenniston, Anthony E.

    2008-01-01

    The term 'electromagnetically clean solar array' ('EMCSA') refers to a panel that contains a planar array of solar photovoltaic cells and that, in comparison with a functionally equivalent solar-array panel of a type heretofore used on spacecraft, (1) exhibits less electromagnetic interferences to and from other nearby electrical and electronic equipment and (2) can be manufactured at lower cost. The reduction of electromagnetic interferences is effected through a combination of (1) electrically conductive, electrically grounded shielding and (2) reduction of areas of current loops (in order to reduce magnetic moments). The reduction of cost is effected by designing the array to be fabricated as a more nearly unitary structure, using fewer components and fewer process steps. Although EMCSAs were conceived primarily for use on spacecraft they are also potentially advantageous for terrestrial applications in which there are requirements to limit electromagnetic interference. In a conventional solar panel of the type meant to be supplanted by an EMCSA panel, the wiring is normally located on the back side, separated from the cells, thereby giving rise to current loops having significant areas and, consequently, significant magnetic moments. Current-loop geometries are chosen in an effort to balance opposing magnetic moments to limit far-0field magnetic interactions, but the relatively large distances separating current loops makes full cancellation of magnetic fields problematic. The panel is assembled from bare photovoltaic cells by means of multiple sensitive process steps that contribute significantly to cost, especially if electomagnetic cleanliness is desired. The steps include applying a cover glass and electrical-interconnect-cell (CIC) sub-assemble, connecting the CIC subassemblies into strings of series-connected cells, laying down and adhesively bonding the strings onto a panel structure that has been made in a separate multi-step process, and mounting the wiring on the back of the panel. Each step increases the potential for occurrence of latent defects, loss of process control, and attrition of components. An EMCSA panel includes an integral cover made from a transparent material. The silicone cover supplants the individual cover glasses on the cells and serves as an additional unitary structural support that offers the advantage, relative to glass, of the robust, forgiving nature of the silcone material. The cover contains pockets that hold the solar cells in place during the lamination process. The cover is coated with indium tin oxide to make its surface electrically conductive, so that it serves as a contiguous, electrically grounded shield over the entire panel surface. The cells are mounted in proximity to metallic printed wiring. The painted-wiring layer comprises metal-film traces on a sheet of Kapton (or equivalent) polyimide. The traces include contact pads on one side of the sheet for interconnecting the cells. Return leads are on the opposite side of the sheet, positioned to form the return currents substantially as mirror images of, and in proximity to, the cell sheet currents, thereby minimizing magnetic moments. The printed-wiring arrangement mimics the back-wiring arrangement of conventional solar arrays, but the current-loop areas and the resulting magnetic moments are much smaller because the return-current paths are much closer to the solar-cell sheet currents. The contact pads are prepared with solder fo electrical and mechanical bonding to the cells. The pocketed cover/shield, the solar cells, the printed-wiring layer, an electrical bonding agent, a mechanical-bonding agent, a composite structural front-side face sheet, an aluminum honeycomb core, and a composite back-side face sheet are all assembled, then contact pads are soldered to the cells and the agents are cured in a single lamination process.

  2. dc and high frequency magnetic properties of nanopatterned CoFe2O4 arrays fabricated using sol-gel precursors

    E-print Network

    Chandrasekhar, Venkat

    fabricated on insulating oxidized silicon substrates and on epitaxial thin films of ferroelectric BiFeO3. We-dimensional magnetic structures of elemental magnets like cobalt,1,2 nickel,3,4 alloys like permalloy,5,6 and metal-oxides of ferromagnetic oxides having Curie temperatures above room temperature have potential for applications in memory

  3. Development of a field free line magnet for projection MPI

    NASA Astrophysics Data System (ADS)

    Konkle, Justin; Goodwill, Patrick; Conolly, Steven

    2011-03-01

    The field free line (FFL) magnet has the potential to greatly increase signal to noise ratio (SNR) or to decrease scan time for magnetic particle imaging (MPI). The use of an FFL will decrease scan time by reducing image dimensionality from a 3D image to a projection image. Alternatively, in comparison to a 3D scan of equal scan time, an FFL scanner will increase SNR through more signal averages. An FFL magnet would enable projection imaging as is used in projection x-ray and is common in angiography. The Philips and Lubeck groups have pioneered the design of field free line magnets for MPI and have shown that they can achieve power efficiency similar to that of a field free point, the standard in MPI. Current FFL magnet designs have not been optimized for characteristics such as gradient efficiency and gradient magnitude homogeneity. This work shows a 2.25 T/m Halbach quadrupole permanent magnet design that produces a homogeneous magnetic field along the field free line. Along the FFL, we experimentally measured a field maximum of 2mT within the imaging field of view (FOV), and we experimentally measured that the gradient perpendicular to the FFL deviates by a maximum of 3.4%. In future work, we plan to produce an x-space MPI image using the FFL magnet. We also plan to improve upon this design using optimization techniques.

  4. Design of a permanent magnet with a mechanical sweep suitable for variable-temperature continuous-wave and pulsed EPR spectroscopy.

    PubMed

    Bauer, C; Raich, H; Jeschke, G; Blümler, P

    2009-06-01

    A magnetic system is introduced which consists of three nested rings of permanent magnets of a Halbach dipolar layout and is capable for EPR spectroscopy. Two of the rings can be rotated independently to adjust the magnetic flux in the center and even allow for mechanical field sweeps. The presented prototype achieves a magnetic flux range of 0.0282-0.3013T with a minimal sweep of 0.15mT and homogeneity of about 10(-3). First applications with CW and pulsed Mims ENDOR as well as ESEEM experiments on a sample of a glycine single crystal doped with 1% copper nitrate demonstrate that flux range, sweep accuracy and homogeneity of this prototype is sufficient for EPR experiments on most solid samples. Together with a recently improved design magnets can be build which could serve as compact and easily transportable replacement of standard electromagnets with negligible consumption of power or coolants. PMID:19299174

  5. Design of a permanent magnet with a mechanical sweep suitable for variable-temperature continuous-wave and pulsed EPR spectroscopy

    NASA Astrophysics Data System (ADS)

    Bauer, C.; Raich, H.; Jeschke, G.; Blümler, P.

    2009-06-01

    A magnetic system is introduced which consists of three nested rings of permanent magnets of a Halbach dipolar layout and is capable for EPR spectroscopy. Two of the rings can be rotated independently to adjust the magnetic flux in the center and even allow for mechanical field sweeps. The presented prototype achieves a magnetic flux range of 0.0282-0.3013 T with a minimal sweep of 0.15 mT and homogeneity of about 10 -3. First applications with CW and pulsed Mims ENDOR as well as ESEEM experiments on a sample of a glycine single crystal doped with 1% copper nitrate demonstrate that flux range, sweep accuracy and homogeneity of this prototype is sufficient for EPR experiments on most solid samples. Together with a recently improved design magnets can be build which could serve as compact and easily transportable replacement of standard electromagnets with negligible consumption of power or coolants.

  6. Magnetic anisotropy of cobalt nanoparticle 2D arrays grown on corrugated MnF2(1 1 0) and CaF2(1 1 0) surfaces

    NASA Astrophysics Data System (ADS)

    Baranov, D. A.; Krichevtsov, B. B.; Gastev, S. V.; Banschikov, A. G.; Fedorov, V. V.; Koshmak, K. V.; Suturin, S. M.; Sokolov, N. S.

    2013-02-01

    Cobalt nanoparticle 2D arrays with different effective thicknesses of cobalt layer (2 nm < deff < 10 nm) were grown by molecular beam epitaxy on CaF2(1 1 0)/Si(0 0 1) and MnF2(1 1 0)/CaF2(1 1 0)/Si(0 0 1) substrates with corrugated morphology of the surface. Surface morphology analysis showed that for effective thickness of cobalt layer deff = 5 nm the lateral dimensions of cobalt islands are about 5-10 nm and the distances between the islands differs in a half along and across the grooves. In both types of the heterostructures the shape of hysteresis loops measured by LMOKE depend on orientation of in-plane magnetic field relative to the direction of the grooves. The azimuthal dependence of coercive field Hc in Co/CaF2(1 1 0)/Si(0 0 1) structures corresponds to Stoner-Wohlfarth model's predictions, which takes into account the anisotropy of individual particles. In contrast to that, in Co/MnF2(1 1 0)/CaF2(1 1 0)/Si(0 0 1) structures these dependences are analogous to those predicted by the model based on account of magnetic-dipole interaction between particles which are placed in chains (chain-of-spheres-model). Possible explanations of the difference in magnetic anisotropy are suggested.

  7. Coupling Between Waveguide-Fed Slot Arrays

    NASA Technical Reports Server (NTRS)

    Rengarajan, Sembiam

    2011-01-01

    Coupling between two waveguide-fed planar slot arrays has been investigated using full-wave analysis. The analysis employs the method-of-moments solution to the pertinent coupled integral equations for the aperture electric field of all slots. In order to compute coupling between two arrays, the input port of the first array is excited with a TE(sub 10) mode wave while the second one is match-terminated. After solving the moment method matrix equations, the aperture fields of all slots are obtained and thereby the TE(sub 10) mode wave received at the input port of the second array is determined. Coupling between two arrays is the ratio of the wave amplitude arriving in the second array port to the incident wave amplitude at the first array port. The coupling mechanism has been studied as a function of spacing between arrays in different directions, e.g. the electric field plane, the magnetic field plane, and the diagonal plane. Computed coupling values are presented for different array geometries. This work is novel since it provides a good understanding of coupling between waveguide-fed slot arrays as a function of spacing and orientation for different aperture distributions and array architectures. This serves as a useful tool for antenna design engineers and system engineers.

  8. Size-Tuned ZnO Nanocrucible Arrays for Magnetic Nanodot Synthesis via Atomic Layer Deposition-Assisted Block Polymer Lithography.

    PubMed

    Lin, Chun-Hao; Polisetty, Srinivas; O'Brien, Liam; Baruth, Andrew; Hillmyer, Marc A; Leighton, Chris; Gladfelter, Wayne L

    2015-02-24

    Low-temperature atomic layer deposition of conformal ZnO on a self-assembled block polymer lithographic template comprising well-ordered, vertically aligned cylindrical pores within a poly(styrene) (PS) matrix was used to produce nanocrucible templates with pore diameters tunable via ZnO thickness. Starting from a PS template with a hexagonal array of 30 nm diameter pores on a 45 nm pitch, the ZnO thickness was progressively increased to narrow the pore diameter to as low as 14 nm. Upon removal of the PS by heat treatment in air at 500 °C to form an array of size-tunable ZnO nanocrucibles, permalloy (Ni80Fe20) was evaporated at normal incidence, filling the pores and creating an overlayer. Argon ion beam milling was then used to etch back the overlayer (a Damascene-type process), leaving a well-ordered array of isolated ZnO nanocrucibles filled with permalloy nanodots. Microscopy and temperature-dependent magnetometry verified the diameter reduction with increasing ZnO thickness. The largest diameter (30 nm) dots exhibit a ferromagnetic multidomain/vortex state at 300 K, with relatively weakly temperature-dependent coercivity. Reducing the diameter leads to a crossover to a single-domain state and eventually superparamagnetism at sufficiently high temperature, in quantitative agreement with expectations. We argue that this approach could render this form of block polymer lithography compatible with high-temperature processing (as required for technologically important high perpendicular anisotropy ordered alloys, for instance), in addition to enabling separation-dependent studies to probe interdot magnetostatic interactions. PMID:25603043

  9. Ultrawide Bandwidth 2 $\\\\,\\\\times\\\\,$2 Microstrip Patch Array Antenna Using Electromagnetic BandGap Structure (EBG)

    Microsoft Academic Search

    Dalia Nashaat; Hala A. Elsadek; Esmat A. Abdallah; Magdy F. Iskander; Hadia M. Elhenawy

    2011-01-01

    Four types of EBG structures are proposed and used in the design of a patch antenna array to improve the bandwidth, gain and reduce the overall array size. The four ground plane designs for the 2 2 microstrip patch antenna array (MPAA) are; spiral artificial magnetic conductor (SAMC) ground plane, an SAMC embedded with a large spiral artificial magnetic conductor

  10. caArray - Array Data Management System

    Cancer.gov

    Skip to Page Content Build 2.5.3_RC1 | Node: NCICB Welcome to caArray Browse Login Register About caArray What is caArray? Release Notes User Guide Global Quick Links National Cancer Institute (NCI) NCI Center for Biomedical Informatics and Information

  11. Nanotube Array

    NASA Astrophysics Data System (ADS)

    Hazra, A.; Dutta, K.; Bhowmik, B.; Manjuladevi, V.; Gupta, R. K.; Chattopadhyay, P. P.; Bhattacharyya, P.

    2014-09-01

    A TiO2 nanotube array was grown electrochemically by using single and mixed electrolyte/s with 20 V constant potential at room temperature. Anodization was carried out for 120 min using five different electrolytes, e.g., H3PO4, NH4F, HF, NH4F with H3PO4 and HF with H3PO4. Structural characterizations of the grown titania nanotubes were conducted by using x-ray diffraction and field emission scanning electron microscopy. Optical properties of the grown nanotubes were investigated through photoluminescence (PL) spectroscopy. In the case of the 4 M H3PO4 electrolyte, no perceptible growth of nanotubes was observed. The individual electrolytes of 0.3 M NH4F and 1 M HF resulted into the formation of the wall-connected nanotubes. In contrast, the mixed electrolytes comprising the strong (NH4F, HF) and weak (H3PO4) electrolytes have been found to be efficient for the growth of wall-separated titania nanotubes. The results of the PL spectroscopy have demonstrated that the free-standing nanotubes offer low PL intensity compared to its connected counterpart owing to the lower carrier recombination rate of free-standing nanotubes.

  12. High resolution magnetic resonance imaging of the anterior visual pathway in patients with optic neuropathies using fast spin echo and phased array local coils.

    PubMed Central

    Gass, A; Barker, G J; MacManus, D; Sanders, M; Riordan-Eva, P; Tofts, P S; Thorpe, J; McDonald, W I; Moseley, I F; Miller, D H

    1995-01-01

    High resolution MRI of the anterior visual pathways was evaluated using frequency selective fat suppressed fast spin echo (FSE) sequences in conjunction with phased array local coils in patients with optic neuropathies. Fifteen normal controls and 57 patients were examined. Coronal T2 weighted fat suppressed FSE images were obtained in 11 minutes with an in plane resolution of 0.39 x 0.39 mm. The optic nerve and its sheath containing CSF were clearly differentiated. Central retinal vessels were often visible. In demyelinating optic neuritis and in anterior ischaemic optic neuropathy high signal within the nerve was readily delineated. Meningiomas and gliomas involving the optic nerve were precisely visualised both in the orbit and intracranially. Extrinsic compression of the optic nerves was readily visualised in carotid artery ectasia and dysthyroid eye disease. Enlarged subarachnoid spaces around the optic nerves were demonstrated in benign intracranial hypertension. High resolution MRI of the anterior visual pathway represents an advance in the diagnosis and management of patients presenting with optic neuropathy. Images PMID:7745403

  13. Development of a monolithic ferrite memory array

    NASA Technical Reports Server (NTRS)

    Heckler, C. H., Jr.; Bhiwandker, N. C.

    1972-01-01

    The results of the development and testing of ferrite monolithic memory arrays are presented. This development required the synthesis of ferrite materials having special magnetic and physical characteristics and the development of special processes; (1) for making flexible sheets (laminae) of the ferrite composition, (2) for embedding conductors in ferrite, and (3) bonding ferrite laminae together to form a monolithic structure. Major problems encountered in each of these areas and their solutions are discussed. Twenty-two full-size arrays were fabricated and fired during the development of these processes. The majority of these arrays were tested for their memory characteristics as well as for their physical characteristics and the results are presented. The arrays produced during this program meet the essential goals and demonstrate the feasibility of fabricating monolithic ferrite memory arrays by the processes developed.

  14. The NASA Inductrack Model Rocket Launcher at the Lawrence Livermore National Laboratory

    NASA Technical Reports Server (NTRS)

    Tung, L. S.; Post, R. F.; Cook, E.; Martinez-Frias, J.

    2000-01-01

    The Inductrack magnetic levitation system, developed at the Lawrence Livermore National Laboratory, is being studied for its possible use for launching rockets. Under NASA sponsorship, a small model system is being constructed at the Laboratory to pursue key technical aspects of this proposed application. The Inductrack is a passive magnetic levitation system employing special arrays of high-field permanent magnets (Halbach arrays) on the levitating carrier, moving above a "track" consisting of a close-packed array of shorted coils with which are interleaved with special drive coils. Halbach arrays produce a strong spatially periodic magnetic field on the front surface of the arrays, while canceling the field on their back surface. Relative motion between the Halbach arrays and the track coils induces currents in those coils. These currents levitate the carrier cart by interacting with the horizontal component of the magnetic field. Pulsed currents in the drive coils, synchronized with the motion of the carrier, interact with the vertical component of the magnetic field to provide acceleration forces. Motional stability, including resistance to both vertical and lateral aerodynamic forces, is provided by having Halbach arrays that interact with both the upper and the lower sides of the track coils. In its completed form the model system that is under construction will have a track approximately 100 meters in length along which the carrier cart will be propelled up to peak speeds of Mach 0.4 to 0.5 before being decelerated. Preliminary studies of the parameters of a full-scale system have also been made. These studies address the problems of scale-up, including means to simplify the track construction and to reduce the cost of the pulsed-power systems needed for propulsion.

  15. Design of 3x3 focusing array for heavy ion driver. Final report on CRADA

    SciTech Connect

    Martovetsky, N N

    2005-03-30

    This memo presents a design of a 3 x 3 quadrupole array for HIF. It contains 3 D magnetic field computations of the array build with racetrack coils with and without different shields. It is shown that it is possible to have a low error magnetic field in the cells and shield the stray fields to acceptable levels. The array design seems to be a practical solution to any size array for future multi-beam heavy ion fusion drivers.

  16. Magnetic multipole redirector of moving plasmas

    DOEpatents

    Crow, James T. (Albuquerque, NM); Mowrer, Gary R. (Cedar Crest, NM)

    1999-01-01

    A method and apparatus for redirecting moving plasma streams using a multiple array of magnetic field generators (e.g., permanent magnets or current bearing wires). Alternate rows of the array have opposite magnetic field directions. A fine wire mesh may be employed to focus as well as redirect the plasma.

  17. Integrated infrared array technology

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.; Mccreight, C. R.

    1986-01-01

    An overview of integrated infrared (IR) array technology is presented. Although the array pixel formats are smaller, and the readout noise of IR arrays is larger, than the corresponding values achieved with optical charge-coupled-device silicon technology, substantial progress is being made in IR technology. Both existing IR arrays and those being developed are described. Examples of astronomical images are given which illustrate the potential of integrated IR arrays for scientific investigations.

  18. RESEARCH PAPER Theoretical analysis of a new, efficient microfluidic magnetic bead

    E-print Network

    magnetic bead separation. It com- bines an external array of mm-sized permanent magnets with magnetization simulation of an experimentally realistic system geometry. The array of permanent magnets pro- vides long-range magnetic forces that attract the beads to the channel bottom, while the soft magnetic elements provide

  19. 7-T magnetic resonance imaging of the inner ear's anatomy by using dual four-element radiofrequency coil arrays and the VIBE sequence

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Nam; Heo, Phil; Kim, Young-Bo; Han, Gyu-Cheol

    2015-02-01

    An ultra-high-field magnetic resonance (MR) scanner and a specially-optimized radiofrequency (RF) coil and sequence protocol are required to obtain high-resolution images of the inner ear that can noninvasively confirm pathologic diagnoses. In phantom studies, the MR signal distribution of the gradient echo MR images generated by using a customized RF coil was compared with that of a commercial volume coil. The MR signal intensity of the customized RF coil decreases rapidly from near the RF coil plane toward the exterior of the phantom. However, the signal sensitivity of this coil is superior on both sides of the phantom, corresponding to the petrous pyramid. In in-vivo 7-T MR imaging, a customized RF coil and a volumetric-interpolated breath-hold examination imaging sequence are employed for visualization of the inner ear's structure. The entire membranous portion of the cochlear and the three semicircular canals, including the ductus reunions, oval window, and round window with associated nervous tissue, were clearly depicted with sufficient spatial coverage for adequate inspection of the surrounding anatomy. Developments from a new perspective to inner ear imaging using the 7-T modality could lead to further improved image sensitivity and, thus, enable ultra-structural MR imaging.

  20. Magnetic bead based immuno-detection of Listeria monocytogenes and Listeria ivanovii from infant formula and leafy green vegetables using the Bio-Plex suspension array system.

    PubMed

    Day, J B; Basavanna, U

    2015-04-01

    Listeriosis, a disease contracted via the consumption of foods contaminated with pathogenic Listeria species, can produce severe symptoms and high mortality in susceptible people and animals. The development of molecular methods and immuno-based techniques for detection of pathogenic Listeria in foods has been challenging due to the presence of assay inhibiting food components. In this study, we utilize a macrophage cell culture system for the isolation and enrichment of Listeria monocytogenes and Listeria ivanovii from infant formula and leafy green vegetables for subsequent identification using the Luminex xMAP technique. Macrophage monolayers were exposed to infant formula, lettuce and celery contaminated with L. monocytogenes or L. ivanovii. Magnetic microspheres conjugated to Listeria specific antibody were used to capture Listeria from infected macrophages and then analyzed using the Bio-Plex 200 analyzer. As few as 10 CFU/mL or g of L. monocytogenes was detected in all foods tested. The detection limit for L. ivanovii was 10 CFU/mL in infant formula and 100 CFU/g in leafy greens. Microsphere bound Listeria obtained from infected macrophage lysates could also be isolated on selective media for subsequent confirmatory identification. This method presumptively identifies L. monocytogenes and L. ivanovii from infant formula, lettuce and celery in less than 28 h with confirmatory identifications completed in less than 48 h. PMID:25475329

  1. Microwave transmission measurements through wire array photonic crystals

    NASA Astrophysics Data System (ADS)

    Dewar, Graeme; Souther, Nathan; Johnson, Michael

    2008-08-01

    We have measured the microwave transmission between 12 and 18 GHz through wire arrays formed into two dimensional square lattices. One array made of copper wire 0.14 mm in radius consisted of five rows by 21 columns having a lattice constant of 5.2 mm. This array exhibited a pass band above 15 GHz, in good agreement with the calculated plasma frequency found from an expression for the permittivity derived in the long wavelength limit. A second array was made with Nichrome wire of radius 18 ?m and lattice constant 1.1 mm. This array was filled with dielectric loaded with powdered magnetite. A sample of this metamaterial 5.8 mm thick and with no externally applied magnetic field exhibited a pass band above 17 GHz. Implications for creating metamaterials with a negative index of refraction from wire arrays embedded in a magnetic host are discussed.

  2. Parallel arrays of Josephson junctions for submillimeter local oscillators

    NASA Technical Reports Server (NTRS)

    Pance, Aleksandar; Wengler, Michael J.

    1992-01-01

    In this paper we discuss the influence of the DC biasing circuit on operation of parallel biased quasioptical Josephson junction oscillator arrays. Because of nonuniform distribution of the DC biasing current along the length of the bias lines, there is a nonuniform distribution of magnetic flux in superconducting loops connecting every two junctions of the array. These DC self-field effects determine the state of the array. We present analysis and time-domain numerical simulations of these states for four biasing configurations. We find conditions for the in-phase states with maximum power output. We compare arrays with small and large inductances and determine the low inductance limit for nearly-in-phase array operation. We show how arrays can be steered in H-plane using the externally applied DC magnetic field.

  3. Exploring Functional Connectivity Networks with Multichannel Brain Array Coils

    E-print Network

    Anteraper, Sheeba Arnold

    The use of multichannel array head coils in functional and structural magnetic resonance imaging (MRI) provides increased signal-to-noise ratio (SNR), higher sensitivity, and parallel imaging capabilities. However, their ...

  4. A 4kb memory array for MRAM development

    E-print Network

    Qazi, Masood

    2007-01-01

    The circuits for a A 4kb array of Magnetic Tunnel Junctions (MTJs) have been designed and fabricated in a 0:18¹m CMOS process with three levels of metal. Support circuitry for addressing, reading, writing, and test mode ...

  5. Magnetic pinning of flux lattice in superconducting-nanomagnet hybrids

    Microsoft Academic Search

    D. Perez de Lara; B. G. Ng; R. K. Dumas; E. M. Gonzalez; Kai Liu; C. A. Ross; Ivan K. Schuller; J. L. Vicent

    2011-01-01

    Strong superconducting pinning effects are observed from magnetic landscapes produced by arrays of circular rings with varying magnetic remanent states. The collective and the background pinning of superconducting Nb films is strongly enhanced by the stray magnetic field produced by an array of circular Ni rings magnetized to form “onion” (bidomain) states. On the other hand, when the same rings

  6. Impedance boundary conditions for regular dense arrays of dipole scatterers

    Microsoft Academic Search

    Sergei A. Tretyakov; Ari J. Viitanen; Stanislav I. Maslovski; Ilpo E. Saarela

    2003-01-01

    A simple analytical boundary condition to model the electromagnetic properties of planar arrays of dipole particles is developed for the normal plane-wave incidence. The impedance condition connects the averaged tangential electric and magnetic fields in the grid plane. The results for the reflection coefficient are compared with numerical simulations of reflection from arrays of small conducting strips. The model can

  7. A Case for Redundant Arrays of Hybrid Disks (RAHD)

    Microsoft Academic Search

    Frank Wang; Na Helian; Sining Wu; Yike Guo; Derek Deng; Vineet Khare; C. Liao; M. Rashidi; Andy Parker

    2008-01-01

    Hybrid Hard Disk Drive was originally concepted by Samsung, which incorporates a Flash memory in a magnetic disk. The combined ultra-high-density benefits of magnetic storage and the low-power and fast read access of NAND technology inspires us to construct Redundant Arrays of Hybrid Disks (RAHD) to offer a possible alternative to today's Redundant Arrays of Independent Disks (RAIDs) and\\/or Massive

  8. Array to Multiply

    NSDL National Science Digital Library

    2013-01-28

    In this lesson, students will understand the concept of arrays and will be able to create/draw an array for multiplication sentences. Engaging center game is used to help student with concrete visual representation of multiplication sentences.

  9. Nuclear magnetic resonance gyroscope

    Microsoft Academic Search

    F. A. Karwacki; J. Griffin

    1985-01-01

    A nuclear magnetic resonance gyroscope which derives angular rotation from the phases of precessing nuclear moments utilizes a single-resonance cel situated in the center of a uniform dc magnetic field. The field is generated by current flow through a circular array of coils between parallel plates. It also utilizes a pump and readout beam and associated electronics for signal processing

  10. Investigation of magnetic field manipulated electrons produced from laser-driven ultrafast x-ray sources using x-ray emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Lee, Changju; Davidson, R. Andrew; Guo, Ting

    2015-03-01

    We used x-ray emission spectroscopy to study energetic electrons (10–100?keV) generated at the laser focus of an intense ultrafast laser interacting with a primary thin film tape target. The electrons penetrated the tape and reached a secondary target of thin metal foils as the probe. The trajectories of these electrons were manipulated with an external magnetic field generated from a home-made Halbach magnet. The interaction of these energetic electrons with the probe produced characteristic x-rays, which were used to infer the flux and temperature of the electrons emitted from the laser focus at the primary tape target. A potential application using these energetic electrons is discussed.

  11. Phased-array radars

    Microsoft Academic Search

    Eli Brookner

    1985-01-01

    The operating principles, technology, and applications of phased-array radars are reviewed and illustrated with diagrams and photographs. Consideration is given to the antenna elements, circuitry for time delays, phase shifters, pulse coding and compression, and hybrid radars combining phased arrays with lenses to alter the beam characteristics. The capabilities and typical hardware of phased arrays are shown using the US

  12. caArray - Browse

    Cancer.gov

    Skip to Page Content Build 2.5.3_RC1 | Node: NCICB Welcome to caArray Browse Login Register About caArray What is caArray? Release Notes User Guide Global Quick Links National Cancer Institute (NCI) NCI Center for Biomedical Informatics and Information

  13. The Square Kilometre Array

    NASA Astrophysics Data System (ADS)

    Taylor, A. R.

    2008-07-01

    The SKA is a global project to plan and construct the next-generation international radio telescope operating at metre to cm wavelengths. More than 50 institutes in 19 countries are involved in its development. The SKA will be an interferometric array with a collecting area of up to one million square metres and maximum baseline of at least 3000 km. The SKA reference design includes field-of-view expansion technology that will allow instantaneous imaging of up to several tens of degrees. The SKA is being designed to address fundamental questions in cosmology, physics and astronomy. The key science goals range from the epoch or re-ionization, dark energy, the formation and evolution of galaxies and large-scale structure, the origin and evolution of cosmic magnetism, strong-field tests of gravity and gravity wave detection, the cradle of life, and the search for extraterrestrial intelligence. The sensitivity, field-of-view and angular resolution of the SKA will make possible a program to create a multi-epoch data base of wide-angle relative astrometry to a few ?as precision for ~10,000,000 radio sources with S > 10 ?Jy.

  14. IMPROVEMENT OF SYNCHRONOUS AND ASYNCHRONOUS MOTOR DRIVE SYSTEMS SUPPLIED BY PHOTOVOLTAIC ARRAYS WITH FREQUENCY CONTROL

    Microsoft Academic Search

    Laid Zarour; Rachid Chenni; Abdelhalim Borni; Aissa Bouzid

    2008-01-01

    The dynamic performances of a permanent magnet synchronous motor (PMSM) and an asynchronous motor (ASM) con- nected to a photovoltaic (PV) array through an inverter are analyzed. The mathematical models of PV array, inverter\\/motor and controller are developed. The photovoltaic array is represented by an equivalent circuit whose parameters are computed using experimentally determined current-voltage (I ¡V ) characteristics. The

  15. Use of Faraday probing to estimate current distribution in wire array z pinches

    Microsoft Academic Search

    S. N. Bland; D. J. Ampleford; S. C. Bott; A. Guite; G. N. Hall; S. M. Hardy; S. V. Lebedev; P. Shardlow; A. Harvey-Thompson; F. Suzuki; K. H. Kwek

    2006-01-01

    In order to understand the formation and dynamics of plasma in wire array z-pinch experiments, measurements of the distribution of current throughout the array are required. We present details of two Faraday probing diagnostics aimed at exploring the magnetic fields and hence distribution of current in an array. An imaging Faraday system utilizes a short laser pulse to make estimates

  16. Optimized Superconducting Quadrupole Arrays for Multiple Beam Transport

    SciTech Connect

    Meinke, Rainer, B.; Goodzeit, Carl, L.; Ball, Millicent, J.

    2005-09-20

    This research project advanced the development of reliable, cost-effective arrays of superconducting quadrupole magnets for use in multi-beam inertial fusion accelerators. The field in each array cell must be identical and meet stringent requirements for field quality and strength. An optimized compact array design using flat double-layer pancake coils was developed. Analytical studies of edge termination methods showed that it is feasible to meet the requirements for field uniformity in all cells and elimination of stray external field in several ways: active methods that involve placement of field compensating coils on the periphery of the array or a passive method that involves use of iron shielding.

  17. Microshutter Arrays for James Webb Space Telescope

    NASA Technical Reports Server (NTRS)

    Li, Mary J.; Acuna, Nadine; Beamesderfer, Michael; Ewin, Audrey; Fettig, Rainer; Franz, Dave; Hess, Larry; Hu, Ron; Kelly, Dan; King, Todd

    2004-01-01

    Two-dimensional MEMS microshutter arrays are being developed at NASA Goddard Space Flight Center for use in the near-infrared region on the James Webb Space Telescope (JWST). The microshutter arrays are designed for the selective transmission of light with high efficiency and high contrast. The JWST environment requires cryogenic operation at 35K. Microshutter arrays are fabricated out of silicon-oxide-insulated (SOI) silicon wafers. Arrays are close-packed silicon nitride membranes with a pixel size of 100x200 p. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. The mechanical shutter arrays are fabricated using MEMS technologies. The processing includes a multi- layer metal deposition and patterning of shutter electrodes and magnetic pads, reactive ion etching (NE) of the front side to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, followed by a deep RIE (DRIE) back-etch down to the nitride shutter membrane to form W e s and relieve shutters from the silicon substrate. An additional metal deposition and patterning is used to form back electrodes. Shutters are actuated using a magnetic force and latched using an electrostatic force. . . . KEYWORDS: microshutter, MEMS, RIE, DRIE, micro-optics, near inbred, space telescope

  18. Programmable Aperture with MEMS Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Moseley, Samuel; Li, Mary; Kutyrev, Alexander; Kletetschka, Gunther; Fettig, Rainer

    2011-01-01

    A microshutter array (MSA) has been developed for use as an aperture array for multi-object selections in James Webb Space Telescope (JWST) technology. Light shields, molybdenum nitride (MoN) coating on shutters, and aluminum/aluminum oxide coatings on interior walls are put on each shutter for light leak prevention, and to enhance optical contrast. Individual shutters are patterned with a torsion flexure that permits shutters to open 90 deg. with a minimized mechanical stress concentration. The shutters are actuated magnetically, latched, and addressed electrostatically. Also, micromechanical features are tailored onto individual shutters to prevent stiction. An individual shutter consists of a torsion hinge, a shutter blade, a front electrode that is coated on the shutter blade, a backside electrode that is coated on the interior walls, and a magnetic cobalt-iron coating. The magnetic coating is patterned into stripes on microshutters so that shutters can respond to an external magnetic field for the magnetic actuation. A set of column electrodes is placed on top of shutters, and a set of row electrodes on sidewalls is underneath the shutters so that they can be electrostatically latched open. A linear permanent magnet is aligned with the shutter rows and is positioned above a flipped upside-down array, and sweeps across the array in a direction parallel to shutter columns. As the magnet sweeps across the array, sequential rows of shutters are rotated from their natural horizontal orientation to a vertical open position, where they approach vertical electrodes on the sidewalls. When the electrodes are biased with a sufficient electrostatic force to overcome the mechanical restoring force of torsion bars, shutters remain latched to vertical electrodes in their open state. When the bias is removed, or is insufficient, the shutters return to their horizontal, closed positions. To release a shutter, both the electrode on the shutter and the one on the back wall where the shutter sits are grounded. The shutters with one or both ungrounded electrodes are held open. Sub-micron bumps underneath light shields and silicon ribs on back walls are the two features to prevent stiction. These features ensure that the microshutter array functions properly in mechanical motions. The MSA technology can be used primarily in multi-object imaging and spectroscopy, photomask generation, light switches, and in the stepper equipment used to make integrated circuits and MEMS (microelectromechanical systems) devices.

  19. Superconducting Bolometer Array Architectures

    NASA Technical Reports Server (NTRS)

    Benford, Dominic; Chervenak, Jay; Irwin, Kent; Moseley, S. Harvey; Shafer, Rick; Staguhn, Johannes; Wollack, Ed; Oegerle, William (Technical Monitor)

    2002-01-01

    The next generation of far-infrared and submillimeter instruments require large arrays of detectors containing thousands of elements. These arrays will necessarily be multiplexed, and superconducting bolometer arrays are the most promising present prospect for these detectors. We discuss our current research into superconducting bolometer array technologies, which has recently resulted in the first multiplexed detections of submillimeter light and the first multiplexed astronomical observations. Prototype arrays containing 512 pixels are in production using the Pop-Up Detector (PUD) architecture, which can be extended easily to 1000 pixel arrays. Planar arrays of close-packed bolometers are being developed for the GBT (Green Bank Telescope) and for future space missions. For certain applications, such as a slewed far-infrared sky survey, feedhorncoupling of a large sparsely-filled array of bolometers is desirable, and is being developed using photolithographic feedhorn arrays. Individual detectors have achieved a Noise Equivalent Power (NEP) of -10(exp 17) W/square root of Hz at 300mK, but several orders of magnitude improvement are required and can be reached with existing technology. The testing of such ultralow-background detectors will prove difficult, as this requires optical loading of below IfW. Antenna-coupled bolometer designs have advantages for large format array designs at low powers due to their mode selectivity.

  20. Giant Magnetoimpedance Current Sensor With Array-Structure Double Probes

    Microsoft Academic Search

    Bing Han; Tao Zhang; Ke Zhang; Bin Yao; Xinglong Yue; Dongyan Huang; Huan Ren; Xinyan Tang

    2008-01-01

    We have designed a novel giant magnetoimpedance (GMI) noncontact current sensor with array structure double probes. Unlike previously reported sensors, our sensor's probes consist of many pieces of commercial amorphous ribbons, which are parallel to each other, equidistant, and connected in series, and a permanent magnet provides a bias magnetic field. The double-probe output shows the best sensitivity and linearity

  1. Electronic Switch Arrays for Managing Microbattery Arrays

    NASA Technical Reports Server (NTRS)

    Mojarradi, Mohammad; Alahmad, Mahmoud; Sukumar, Vinesh; Zghoul, Fadi; Buck, Kevin; Hess, Herbert; Li, Harry; Cox, David

    2008-01-01

    Integrated circuits have been invented for managing the charging and discharging of such advanced miniature energy-storage devices as planar arrays of microscopic energy-storage elements [typically, microscopic electrochemical cells (microbatteries) or microcapacitors]. The architecture of these circuits enables implementation of the following energy-management options: dynamic configuration of the elements of an array into a series or parallel combination of banks (subarrarys), each array comprising a series of parallel combination of elements; direct addressing of individual banks for charging/or discharging; and, disconnection of defective elements and corresponding reconfiguration of the rest of the array to utilize the remaining functional elements to obtain the desited voltage and current performance. An integrated circuit according to the invention consists partly of a planar array of field-effect transistors that function as switches for routing electric power among the energy-storage elements, the power source, and the load. To connect the energy-storage elements to the power source for charging, a specific subset of switches is closed; to connect the energy-storage elements to the load for discharging, a different specific set of switches is closed. Also included in the integrated circuit is circuitry for monitoring and controlling charging and discharging. The control and monitoring circuitry, the switching transistors, and interconnecting metal lines are laid out on the integrated-circuit chip in a pattern that registers with the array of energy-storage elements. There is a design option to either (1) fabricate the energy-storage elements in the corresponding locations on, and as an integral part of, this integrated circuit; or (2) following a flip-chip approach, fabricate the array of energy-storage elements on a separate integrated-circuit chip and then align and bond the two chips together.

  2. Sorting white blood cells in microfabricated arrays

    NASA Astrophysics Data System (ADS)

    Castelino, Judith Andrea Rose

    Fractionating white cells in microfabricated arrays presents the potential for detecting cells with abnormal adhesive or deformation properties. A possible application is separating nucleated fetal red blood cells from maternal blood. Since fetal cells are nucleated, it is possible to extract genetic information about the fetus from them. Separating fetal cells from maternal blood would provide a low cost noninvasive prenatal diagnosis for genetic defects, which is not currently available. We present results showing that fetal cells penetrate further into our microfabricated arrays than adult cells, and that it is possible to enrich the fetal cell fraction using the arrays. We discuss modifications to the array which would result in further enrichment. Fetal cells are less adhesive and more deformable than adult white cells. To determine which properties limit penetration, we compared the penetration of granulocytes and lymphocytes in arrays with different etch depths, constriction size, constriction frequency, and with different amounts of metabolic activity. The penetration of lymphocytes and granulocytes into constrained and unconstrained arrays differed qualitatively. In constrained arrays, the cells were activated by repeated shearing, and the number of cells stuck as a function of distance fell superexponentially. In unconstrained arrays the number of cells stuck fell slower than an exponential. We attribute this result to different subpopulations of cells with different sticking parameters. We determined that penetration in unconstrained arrays was limited by metabolic processes, and that when metabolic activity was reduced penetration was limited by deformability. Fetal cells also contain a different form of hemoglobin with a higher oxygen affinity than adult hemoglobin. Deoxygenated cells are paramagnetic and are attracted to high magnetic field gradients. We describe a device which can separate cells using 10 ?m magnetic wires to deflect the paramagnetic cells. We present preliminary results from a test system that separates paramagnetic beads from latex beads. The separation is limited by our ability to produce the high field gradients which are necessary to separate cells according to their hemoglobin content, and we present estimates of the magnetic gradients we achieved.

  3. Testing Microshutter Arrays Using Commercial FPGA Hardware

    NASA Technical Reports Server (NTRS)

    Rapchun, David

    2008-01-01

    NASA is developing micro-shutter arrays for the Near Infrared Spectrometer (NIRSpec) instrument on the James Webb Space Telescope (JWST). These micro-shutter arrays allow NIRspec to do Multi Object Spectroscopy, a key part of the mission. Each array consists of 62414 individual 100 x 200 micron shutters. These shutters are magnetically opened and held electrostatically. Individual shutters are then programmatically closed using a simple row/column addressing technique. A common approach to provide these data/clock patterns is to use a Field Programmable Gate Array (FPGA). Such devices require complex VHSIC Hardware Description Language (VHDL) programming and custom electronic hardware. Due to JWST's rapid schedule on the development of the micro-shutters, rapid changes were required to the FPGA code to facilitate new approaches being discovered to optimize the array performance. Such rapid changes simply could not be made using conventional VHDL programming. Subsequently, National Instruments introduced an FPGA product that could be programmed through a Labview interface. Because Labview programming is considerably easier than VHDL programming, this method was adopted and brought success. The software/hardware allowed the rapid change the FPGA code and timely results of new micro-shutter array performance data. As a result, numerous labor hours and money to the project were conserved.

  4. Carbon nanotube nanoelectrode arrays

    DOEpatents

    Ren, Zhifeng (Newton, MA); Lin, Yuehe (Richland, WA); Yantasee, Wassana (Richland, WA); Liu, Guodong (Fargo, ND); Lu, Fang (Burlingame, CA); Tu, Yi (Camarillo, CA)

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  5. Detector arrays in spectroscopy

    NASA Astrophysics Data System (ADS)

    Birkinshaw, K.

    Spatially dispersed spectra of ions, electrons or photons are traditionally measured by scanning the spectra across a narrow slit behind which is a detector. However, the efficiency increase offered by arrays of detectors is so large that their development is increasingly demanding the attention of spectrometer manufacturers. One-dimensional arrays of independent detectors (discrete electrode arrays) offer the highest data accumulation rate as detection can occur simultaneously at many sites, but a high resolution array of this type requires much associated electronics and this has limited the size and the market of such devices. The design and performance issues relating to discrete electrode arrays are discussed and a new high resolution array with all electronics integrated on a single silicon chip developed at Aberystwyth is described. A familiarity with silicon technology is not required by the reader. It is shown that integration brings not only advantages of scale but also of performance.

  6. Two-dimensional tunable magnetic photonic crystals

    Microsoft Academic Search

    Chul-Sik Kee; Jae-Eun Kim; Hae Yong Park; H. Lim

    2000-01-01

    We have calculated the photonic band structure for a cubic block of magnetically saturated ferrite material having a triangular array of circular holes that is under the influence of an external static magnetic field Hex=Hexz applied in the hole direction. In this two-dimensional magnetic photonic crystal, the saturated magnetism can affect the transverse electric (TE) mode whose electric field lies

  7. Nonreciprocal Effects in Magnetic Photonic Crystals

    Microsoft Academic Search

    Alex Figotin; Ilya Vitebskiy

    2006-01-01

    Magnetic photonic crystals are periodic arrays of lossless materials, at least one of which being magnetically polarized. Magnetization, either spontaneous or induced, is associated with nonreciprocal effects, such as Faraday rotation. In addition, magnetic photonic crystals of certain configuration can also display strong spectral asymmetry, implying that electromagnetic waves propagate in one direction much faster or slower than in the

  8. Nondestructive testing and crack evaluation of ferromagnetic material by using the linearly integrated hall sensor array

    Microsoft Academic Search

    Jinyi Lee; Jiseong Hwang; Jongwoo Jun; Seho Choi

    2008-01-01

    Magnetic flux leakage testing (MFLT), which measures the distribution of a magnetic field on a magnetized specimen by using\\u000a a magnetic sensor such as a Hall sensor, is an effective nondestructive testing (NDT) method for detecting surface cracks\\u000a on magnetized ferromagnetic materials. A scan-type magnetic camera, based on the principle of MFLT, uses an inclined Hall\\u000a sensor array on a

  9. Algorithms for Sorting Arrays

    NSDL National Science Digital Library

    Mrs. Watts

    2007-09-26

    It is often necessary to have elements of an array sorted into ascending or descending order. There are several approaches or algorithms available for sorting unordered arrays. Choosing an appropriate algorithm may depend upon the situation, however, some well-known algorithms are just more efficient than others. Exercise 1 To move an element in an array, an algorithm must make sure that each element being moved is inserted into an empty location or it will overwrite the current element. Therefore, to swap two items in an array, one of the items must be moved to an empty location ...

  10. Electrically reconfigurable logic array

    NASA Technical Reports Server (NTRS)

    Agarwal, R. K.

    1982-01-01

    To compose the complicated systems using algorithmically specialized logic circuits or processors, one solution is to perform relational computations such as union, division and intersection directly on hardware. These relations can be pipelined efficiently on a network of processors having an array configuration. These processors can be designed and implemented with a few simple cells. In order to determine the state-of-the-art in Electrically Reconfigurable Logic Array (ERLA), a survey of the available programmable logic array (PLA) and the logic circuit elements used in such arrays was conducted. Based on this survey some recommendations are made for ERLA devices.

  11. Modifying Wire Array Z-pinch Ablation Structure and Implosion Dynamics Using Coiled Arrays

    NASA Astrophysics Data System (ADS)

    Hall, Gareth N.; Bland, Simon N.; Lebedev, Sergey V.; Chittenden, Jeremy P.; Palmer, James B. A.; Suzuki-Vidal, Francisco A.; Swadling, George F.; Niasse, Nicolas; Knapp, P. F.; Blesener, I. C.; McBride, R. D.; Chalenski, D. A.; Bell, K. S.; Greenly, J. B.; Blanchard, T.; Wilhelm, H.; Hammer, D. A.; Kusse, B. R.; Bott, Simon C.

    2009-01-01

    Coiled arrays, a cylindrical array in which each wire is formed into a helix, suppress the modulation of ablation at the fundamental wavelength. Outside the vicinity of the wire cores, ablation flow from coiled arrays is modulated at the coil wavelength and has a 2-stream structure in the r,? plane. Within the vicinity of the helical wires, ablation is concentrated at positions with the greatest azimuthal displacement and plasma is axially transported from these positions such that the streams become aligned with sections of the coil furthest from the array axis. The GORGON MHD code accurately reproduces this observed ablation structure, which can be understood in terms of J×B forces that result from the interaction of the global magnetic field with a helical current path as well as additional current paths suggested by the simulations. With this ability to control where ablation streamers occur, large wavelength coils were constructed such that the breaks that form in the wires had sufficient axial separation to prevent perturbations in the implosion sheath from merging. This produces a new mode of implosion in which the global instability can be controlled and perturbations correlated between all wires in an array. For large wavelength 8-wire coiled arrays, this produced a dramatic increase in x-ray power, equalling that of a 32-wire straight array. These experiments were carried out on the MAGPIE generator (1 MA, 240 ns) at Imperial College, and the COBRA generator (1 MA, 100 ns) at Cornell University.

  12. Modifying Wire Array Z-pinch Ablation Structure and Implosion Dynamics Using Coiled Arrays

    SciTech Connect

    Hall, Gareth N.; Bland, Simon N.; Lebedev, Sergey V.; Chittenden, Jeremy P.; Palmer, James B. A.; Suzuki-Vidal, Francisco A.; Swadling, George F.; Niasse, Nicolas [Blackett Laboratory, Imperial College, London, SW7 2BW (United Kingdom); Knapp, P. F.; Blesener, I. C.; McBride, R. D.; Chalenski, D. A.; Bell, K. S.; Greenly, J. B.; Blanchard, T.; Wilhelm, H.; Hammer, D. A.; Kusse, B. R. [Laboratory of Plasma Studies, Cornell University, Ithaca, US (United States); Bott, Simon C. [University of California, San Diego, US (United States)

    2009-01-21

    Coiled arrays, a cylindrical array in which each wire is formed into a helix, suppress the modulation of ablation at the fundamental wavelength. Outside the vicinity of the wire cores, ablation flow from coiled arrays is modulated at the coil wavelength and has a 2-stream structure in the r,{theta} plane. Within the vicinity of the helical wires, ablation is concentrated at positions with the greatest azimuthal displacement and plasma is axially transported from these positions such that the streams become aligned with sections of the coil furthest from the array axis. The GORGON MHD code accurately reproduces this observed ablation structure, which can be understood in terms of JxB forces that result from the interaction of the global magnetic field with a helical current path as well as additional current paths suggested by the simulations. With this ability to control where ablation streamers occur, large wavelength coils were constructed such that the breaks that form in the wires had sufficient axial separation to prevent perturbations in the implosion sheath from merging. This produces a new mode of implosion in which the global instability can be controlled and perturbations correlated between all wires in an array. For large wavelength 8-wire coiled arrays, this produced a dramatic increase in x-ray power, equalling that of a 32-wire straight array. These experiments were carried out on the MAGPIE generator (1 MA, 240 ns) at Imperial College, and the COBRA generator (1 MA, 100 ns) at Cornell University.

  13. Versatile microfluidic droplets array for bioanalysis.

    PubMed

    Hu, Shan-Wen; Xu, Bi-Yi; Ye, Wei-Ke; Xia, Xing-Hua; Chen, Hong-Yuan; Xu, Jing-Juan

    2015-01-14

    We propose a novel method to obtain versatile droplets arrays on a regional hydrophilic chip that is fabricated by PDMS soft lithography and regional plasma treatment. It enables rapid liquid dispensation and droplets array formation just making the chip surface in contact with solution. By combining this chip with a special Christmas Tree structure, the droplets array with concentrations in gradient is generated. It possesses the greatly improved performance of convenience and versatility in bioscreening and biosensing. For example, high throughput condition screening of toxic tests of CdSe quantum dots on HL-60 cells are conducted and cell death rates are successfully counted quickly and efficiently. Furthermore, a rapid biosensing approach for cancer biomarkers carcinoma embryonic antigen (CEA) is developed via magnetic beads (MBs)-based sandwich immunoassay methods. PMID:25525675

  14. A Compact, Modular Superconducting Bolometer Array Package

    NASA Technical Reports Server (NTRS)

    Benford, Dominic J.

    2008-01-01

    We have designed a detector package to house a superconducting bolometer array, SQUID multiplexers, bias and integration circuitry, optical filtering, electrical connectors, and thermal/mechanical interfaces. This package has been used successfully in the GISMO 2mm camera, a 128-pixel camera operating at a base temperature of 270mK. Operation at lower temperatures is allowed by providing direct heat sinking to the SQUIDS and bias resistors, which generate the bulk of the dissipation in the package. Standard electrical connectors provide reliable contact while enabling quick installation and removal of the package. Careful design has gone into the compensation for differing thermal expansions, the need for heat sinking of the bolometer array, and the placement of magnetic shielding in critical areas. In this presentation, we detail the design and performance of this detector package and describe its scalability to 1280- pixel arrays in the near future.

  15. 2210 IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 Synthesis, Structural Order and Magnetic Behavior of

    E-print Network

    Krishnan, Kannan M.

    2210 IEEE TRANSACTIONS ON MAGNETICS, VOL. 37, NO. 4, JULY 2001 Synthesis, Structural Order into ordered arrays and their magnetic behavior as a function of structural order (ferrofluids and 2D and Magnetic Behavior of Self-Assembled "-Co Nanocrystal Arrays Victor F. Puntes and Kannan M. Krishnan

  16. Optical phased array technology

    Microsoft Academic Search

    PAUL F. MCMANAMON; TERRY A. DORSCHNER; DAVID L. CORKUM; LARRY J. FRIEDMAN; DOUGLAS S. HOBBS; MICHAEL HOLZ; SERGEY LIBERMAN; HUY Q. NGUYEN; DANIEL P. RESLER; RICHARD C. SHARP; EDWARD A. WATSON

    1996-01-01

    Optical phased arrays represent an enabling new technology that makes possible simple affordable, lightweight, optical sensors offering very precise stabilization, random-access pointing programmable multiple simultaneous beams, a dynamic focus\\/defocus capability, and moderate to excellent optical power handling capability. These new arrays steer or otherwise operate on an already formed beam. A phase profile is imposed on an optical beam as

  17. Adaptive array control

    Microsoft Academic Search

    L. R. Burgess; A. E. Zeger; J. R. Binkley

    1975-01-01

    Radar targets such as slow, low flying aircraft and moving ground vehicles may be detected by employing an adaptively controlled antenna array with an AMTI radar set, conformally mounted in a high performance jet aircraft. Clutter cancellation is achieved through moving the active subaperture of the phased array to the rear of the aircraft with the transmission and reception of

  18. Array for detecting microbes

    DOEpatents

    Andersen, Gary L.; DeSantis, Todd D.

    2014-07-08

    The present embodiments relate to an array system for detecting and identifying biomolecules and organisms. More specifically, the present embodiments relate to an array system comprising a microarray configured to simultaneously detect a plurality of organisms in a sample at a high confidence level.

  19. The Relationship of Magnetic Stiffness Between Single and Multiple YBCO Superconductors over Permanent Magnet Guideway

    NASA Astrophysics Data System (ADS)

    Lu, Yiyun; Lu, Bingjuan; Wang, Suyu

    2011-09-01

    For YBCO bulk levitating over a permanent magnet guideway (PMG), the magnetic stiffness is connected directly with the pinning properties of the measured sample. An experimental setup has been built to investigate the vertical and lateral magnetic stiffness of five high-temperature superconducting (HTS) bulk arrays over a PMG by two methods: the additive method, i.e., calculating the summation of the measured magnetic stiffness values of each HTS bulk in the array; the direct method, i.e., measuring directly the magnetic stiffness of the HTS bulk array. From the experimental results, it is found that the resultant magnetic stiffness of the HTS bulk array composing of multiple YBCO bulk is related with the magnetic stiffness of each individual single bulk, but the additive method does not predict the magnetic stiffness of the array very well because of the interaction between adjacent HTS bulk. The resultant magnetic stiffness of the HTS bulk array is less than the summation magnetic stiffness of each single HTS bulk. One numerical method is used to calculate the magnetic stiffness for comparing with experimental results. The results may be helpful to the design and optimization of the superconducting magnetic levitation system.

  20. Magnetic neurosurgery.

    PubMed

    Howard, M A; Grady, M S; Ritter, R C; Gillies, G T; Broaddus, W C; Dacey, R G

    1996-01-01

    Because of the complex shape of many brain structures, the ideal brain probe would be highly flexible and give the neurosurgeon the ability to independently and precisely control movement of the probe tip. A magnetic surgery system has been developed that implements this concept. Flexible brain probes with small permanent magnetic tips are placed on the brain surface through a small burr hole and then magnetically manipulated within the brain. Drive forces are produced by an array of six superconducting magnets suspended within a cryostatic helmet. They produce a maximum force of 3 times the threshold needed to move the probe through the parenchymal tissues at its normal speed of 1 mm/s. Computer-controlled magnetic impulses precisely direct the probe movement in any direction desired with movement accuracy of 0.47 mm in phantom gels. Probe position is monitored 3 times per second with orthogonally oriented microchannel plate X-ray systems, X-ray dose from a 3-hour simulated procedure is comparable to that of a chest X-ray. In vivo and in vitro feasibility studies have been carried out in dog and pig brains. Preclinical trials are planned for clinical applications including implantation of flexible brachytherapy threads. PMID:8938941

  1. Results from a prototype permanent magnet dipole-quadrupole hybrid for the PEP-II B-factory

    SciTech Connect

    Sullivan, M.; Bowden, G.; Ecklund, S. [and others

    1997-06-01

    We describe the construction of a prototype hybrid permanent magnet dipole and quadrupole. The magnet consists of two concentric rings of Sm{sub 2}Co{sub 17} magnetic material 5 cm in length. The outer ring is made of 16 uniformly magnetized blocks assembled as a Halbach dipole and the inner ring has 32 blocks oriented in a similar fashion so as to generate a quadrupole field. The resultant superimposed field is an offset quadrupole field which allows us to center the field on the high-energy beam in the interaction region of the PEP-II B-factory. The dipole blocks are glued to the inside surface of an outer support collar and the quadrupole blocks are held in a fixture that allows radial adjustment of the blocks prior to potting the entire assembly with epoxy. An extensive computer model of the magnet has been made and from this model we developed a tuning algorithm that allowed us to greatly reduce the n=3 17 harmonics of the magnet.

  2. Multibeam Phased Array Antennas

    NASA Technical Reports Server (NTRS)

    Popovic, Zoya; Romisch, Stefania; Rondineau, Sebastien

    2004-01-01

    In this study, a new architecture for Ka-band multi-beam arrays was developed and demonstrated experimentally. The goal of the investigation was to demonstrate a new architecture that has the potential of reducing the cost as compared to standard expensive phased array technology. The goals of this specific part of the project, as stated in the yearly statement of work in the original proposal are: 1. Investigate bounds on performance of multi-beam lens arrays in terms of beamwidths, volume (size), isolation between beams, number of simultaneous beams, etc. 2. Design a small-scale array to demonstrate the principle. The array will be designed for operation around 3OGHz (Ka-band), with two 10-degree beamwidth beams. 3. Investigate most appropriate way to accomplish fine-tuning of the beam pointing within 5 degrees around the main beam pointing angle.

  3. Micromachined electrode array

    DOEpatents

    Okandan, Murat (Edgewood, NM); Wessendorf, Kurt O. (Albuquerque, NM)

    2007-12-11

    An electrode array is disclosed which has applications for neural stimulation and sensing. The electrode array, in certain embodiments, can include a plurality of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. In other embodiments of the electrode array, the electrodes can be fixed to the substrate. The electrode array can be formed from a combination of bulk and surface micromachining, and can include electrode tips having an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis.

  4. Microfabricated ion trap array

    DOEpatents

    Blain, Matthew G. (Albuquerque, NM); Fleming, James G. (Albuquerque, NM)

    2006-12-26

    A microfabricated ion trap array, comprising a plurality of ion traps having an inner radius of order one micron, can be fabricated using surface micromachining techniques and materials known to the integrated circuits manufacturing and microelectromechanical systems industries. Micromachining methods enable batch fabrication, reduced manufacturing costs, dimensional and positional precision, and monolithic integration of massive arrays of ion traps with microscale ion generation and detection devices. Massive arraying enables the microscale ion traps to retain the resolution, sensitivity, and mass range advantages necessary for high chemical selectivity. The reduced electrode voltage enables integration of the microfabricated ion trap array with on-chip circuit-based rf operation and detection electronics (i.e., cell phone electronics). Therefore, the full performance advantages of the microfabricated ion trap array can be realized in truly field portable, handheld microanalysis systems.

  5. High density pixel array

    NASA Technical Reports Server (NTRS)

    Wiener-Avnear, Eliezer (Inventor); McFall, James Earl (Inventor)

    2004-01-01

    A pixel array device is fabricated by a laser micro-milling method under strict process control conditions. The device has an array of pixels bonded together with an adhesive filling the grooves between adjacent pixels. The array is fabricated by moving a substrate relative to a laser beam of predetermined intensity at a controlled, constant velocity along a predetermined path defining a set of grooves between adjacent pixels so that a predetermined laser flux per unit area is applied to the material, and repeating the movement for a plurality of passes of the laser beam until the grooves are ablated to a desired depth. The substrate is of an ultrasonic transducer material in one example for fabrication of a 2D ultrasonic phase array transducer. A substrate of phosphor material is used to fabricate an X-ray focal plane array detector.

  6. Developing an Inflatable Solar Array

    NASA Technical Reports Server (NTRS)

    Malone, Patrick K.; Jankowski, Francis J.; Williams, Geoffery T.; Vendura, George J., Jr.

    1992-01-01

    Viewgraphs describing the development of an inflatable solar array as part of the Inflatable Torus Solar Array Technology (ITSAT) program are presented. Program phases, overall and subsystem designs, and array deployment are addressed.

  7. Magnetoplasmon excitations in quantum dot arrays

    Microsoft Academic Search

    B. P van Zyl; E. Zaremba

    2000-01-01

    Motivated by the far-infrared transmission experiments of Demel et al., we have investigated the magnetoplasmon excitations in an array of quantum dots within the Thomas–Fermi–Dirac–von Weizsäcker (TFDW) approximation. Detailed calculations of the magnetic dispersion and power absorption from a uniform radiation field unambiguously demonstrates that the noncircular symmetry of the individual dots is responsible for the anticrossing behaviour observed in

  8. SERS based immuno-microwell arrays for multiplexed detection of foodborne pathogenic bacteria

    NASA Astrophysics Data System (ADS)

    Sun, Jian; Hankus, Mikella E.; Cullum, Brian M.

    2009-05-01

    A novel surface enhanced Raman scattering (SERS)-based immuno-microwell array has been developed for multiplexed detection of foodborne pathogenic bacteria. The immuno-microwell array was prepared by immobilizing the optical addressable immunomagnetic beads (IMB) into the microwell array on one end of a fiber optic bundle. The IMBs, magnetic beads coated with specific antibody to specific bacteria, were used for immunomagnetic separation (IMS) of corresponding bacteria. The magnetic separation by the homemade magnetic separation system was evaluated in terms of the influences of several important parameters including the beads concentration, the sample volume and the separation time. IMS separation efficiency of the model bacteria E.coli O157:H7 was 63% in 3 minutes. The microwell array was fabricated on hydrofluoric acid etched end of a fiber optic bundle containing 30,000 fiber elements. After being coated with silver, the microwell array was used as a uniform SERS substrate with the relative standard deviation of the SERS enhancement across the microwell array < 2% and the enhancement factor as high as 2.18 x 107. The antibody modified microwell array was prepared for bacteria immobilization into the microwell array, which was characterized by a sandwich immunoassay. To demonstrate the potential of multiplexed SERS detection with the immuno-microwell array, the SERS spectra of different Raman dye labeled magnetic beads as well as mixtures were measured on the mircrowell array. In bead mixture, different beads were identified by the characteristic SERS bands of the corresponding Raman label.

  9. Assembly of ordered microsphere arrays: Platforms for microarrays

    NASA Astrophysics Data System (ADS)

    Xu, Wanling

    Microarrays are powerful tools in gene expression assessment, protein profiling, and protein function screening, as well as cell and tissue analysis. With thousands of small array spots assembled in an ordered array, these small devices makes it possible to screen for multiple targets in a fast, parallel, high-throughput manner. The well-developed technology of DNA microarrays, also called DNA chips, has proved successful in all kinds of biological experiments, including the human genome-sequencing project. The development of protein arrays has lagged behind that of DNA arrays mainly because of the greater complexity of proteins. Some parts of the microarray technology can be transplanted into the realm of protein arrays, while others cannot. The challenges from the complexity of protein targets demand more robust and powerful devices. Traditional planar arrays, in which proteins bind directly to a planar surface, have a drawback in that some proteins will be denatured or cluster together after immobilization. Microsphere-based microarrays represent a more advanced strategy. The functional proteins are first attached to microspheres; these microspheres are then immobilized in arrays on a planar surface. In this dissertation, two approaches to assembling arrays of microspheres will be discussed. The hydrodynamic approach uses surface micromachining and Deep Reactive Ion Etching techniques to form an array of channels through a silicon wafer. By drawing fluid containing the microspheres through the channels they become trapped in the channels and thereby immobilized. In the magnetic approach, permalloy films are deposited on a silicon substrate and subsequently patterned to form magnetic attachment sites. An external magnetic field is then applied and the magnetic microspheres then assemble on these sites. Both devices are able to immobilize microspheres in an ordered array, as opposed to coarsely grouping them in array spots. The assembled arrays are robust in that they ensure a resolution rate of almost 100%. In addition, different patterns of array spots with various spacings and diameters can be fabricated to satisfy different requirements. Moreover, the devices are easy to clean and reuse, and the experimental set-ups are relatively simple and portable. All these features make them good platforms for all kinds of microarrays.

  10. Compound semiconductor SPAD arrays

    NASA Astrophysics Data System (ADS)

    Harmon, Eric S.; Naydenkov, Mikhail; Hyland, James T.

    2013-06-01

    Single photon avalanche diodes (SPADs) are revolutionizing ultra-sensitive photodetection applications, providing single photon sensitivity, high quantum efficiency and low dark noise at or near room temperature. When aggregated into arrays, these devices have demonstrated the ability to operate as photon number resolving detectors with wide dynamic range, or as single-photon imaging detectors. SPAD array performance has reached a point where replacing vacuum tube based MCP and PMT photodetectors for most applications is inevitable. Compound semiconductor SPAD arrays offer the unique proposition to tailor performance to match application specific wavelength, speed and radiation hardness requirements. We present a theoretical framework describing performance limits to compound semiconductor SPAD arrays and our latest experimental results detailing the performance of GaAs SPAD arrays. These devices achieve nanosecond rise and fall times, excellent photon number resolving capability, and low dark count rates. Single photon number resolving is demonstrated with 4% single photon detection efficiency at room temperature with dark count rates below 7 Mcps/mm2. Compound semiconductor SPAD arrays have the opportunity to provide orders of magnitude improvement in dark count rate and radiation hardness over silicon SPAD arrays, as well as the ability to detect wavelengths where silicon is blind.

  11. Space Station solar array

    NASA Technical Reports Server (NTRS)

    Forestieri, A. F.

    1984-01-01

    Space station solar array configurations and power system technologies were compared. Planar silicon arrays offer low technology risk but high weight and drag area. Concentrator arrays of silicon or gallium arsenide (preferred) promise lower cost and drag area but increase technology risk. Planar and power tower require fewer control moment gyros (CMG's). Delta is more rigid but requires more CMG's. Flexible body effects are not significant. All configurations can be assembled. Power tower is preferred for proximity operations. All configurations require 6 to 8 launches. Manned operations after two to three. All configurations can accommodate all candidate electrical power systems options.

  12. Nonuniformly spaced array imaging

    NASA Astrophysics Data System (ADS)

    Li, Hsueh-Jyh; Huang, Gen-Tay; Yen, Shih-Liang

    1993-03-01

    In this paper an image reconstruction algorithm for a randomly spaced array imaging is developed. Based on the fact that the sampled bistatic Fourier space data can occupy almost the same region as that of a rotating object imaging if the angular coverage is suitably defined, the range-Doppler reconstruction method developed in the rotating object imaging can be applied to the uniformly spaced circular array imaging case. When the array elements are randomly spaced, three more steps, a range alignment, a phase compensation, and an interpolation, are required to preprocess the measured signals. Experimental and numerical results have shown the effectiveness of the proposed algorithm.

  13. Far-infrared excitations in rectangular antidot arrays

    Microsoft Academic Search

    M. Hochgräfe; B. P. van Zyl; Ch. Heyn; D. Heitmann; E. Zaremba

    2001-01-01

    We have investigated far-infrared excitations in rectangular arrays of antidots in modulation-doped AlxGa1-xAs-GaAs heterostructures. In the rectangular antidot lattice the degeneracy of modes of a square array is lifted and a rich spectrum of higher-frequency modes is excited, particularly at small magnetic fields. These modes are sensitive to the direction of linear polarized radiation. Our experimental results are compared with

  14. MEMS Microshutter Arrays for James Webb Space Telescope

    NASA Technical Reports Server (NTRS)

    Li, Mary J.; Beamesderfer, Michael; Babu, Sachi; Bajikar, Sateesh; Ewin, Audrey; Franz, Dave; Hess, Larry; Hu, Ron; Jhabvala, Murzy; Kelly, Dan; King, Todd; Kletetschkar, Gunther; Kutyrev, Alexander; Lynch, Barney; Moseley, Harvey; Mott, Brent; Oh, Lance; Rapchum, Dave; Ray, Chris; Sappington, Carol; Silverberg, Robert; Smith, Wayne; Snodgrass, Steve; Steptoe-Jackson, Rosalind; Valeriano

    2006-01-01

    MEMS microshutter arrays are being developed at NASA Goddard Space Flight Center for use as an aperture array for a Near-Infrared Spectrometer (NirSpec). The instruments will be carried on the James Webb Space Telescope (JWST), the next generation of space telescope after Hubble Space Telescope retires. The microshutter arrays are designed for the selective transmission of light with high efficiency and high contrast, Arrays are close-packed silicon nitride membranes with a pixel size of 100x200 microns. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. Light shields are made on to each shutter for light leak prevention so to enhance optical contrast, Shutters are actuated magnetically, latched and addressed electrostatically. The shutter arrays are fabricated using MEMS technologies.

  15. Intelligent field emission arrays

    E-print Network

    Hong, Ching-yin, 1973-

    2003-01-01

    Field emission arrays (FEAs) have been studied extensively as potential electron sources for a number of vacuum microelectronic device applications. For most applications, temporal current stability and spatial current ...

  16. Phased array acoustic antenna

    SciTech Connect

    Balser, M.; Ambler, F. E.

    1985-12-17

    A system for remote measurement of wind velocity in the atmosphere, operating from ground level. An array of acoustic transducer elements which provide for transmitting a beam of acoustic energy along a path and receiving such transmitted energy as scattered by wind in the path. The system includes signal transmitting means for driving the arrays, and signal receiving means, with a switching system for connecting the elements of the array to the transmitting means and to the receiving means, for operation as a monostatic system. Phase control for the transmitted signals comprising phase shifters and switches for selectively connecting driving signals to the elements of the array for driving selected elements at different phases to produce first, second and third beams in sequence at three different predetermined angles from a single antenna.

  17. CLAES focal plane array

    NASA Astrophysics Data System (ADS)

    Roche, A. E.; Sterritt, L. W.; Kumer, J. B.; Callary, P. C.; Nielsen, R. L.

    The Cryogenic Limb Array Etalon Spectrometer for the NASA Upper Atmospheric Research Satellite uses solid-state focal plane arrays to detect emission from the earth's atmosphere over the IR wavelength range 3.5 to 13 microns. This paper discusses the design of the focal plane detector assembly and compares calculated performance with measurements. Measurements were made of focal plane noise and responsivity as functions of frequency (2 to 500 Hz) and temperature (12 to 19 K), pixel-to-pixel and across-array crosstalk, and linearity over a dynamic range of 100,000. The measurements demonstrate that the arrays satisfy the science requirements, and that, in general, there is reasonable agreement between the measurements and the analytical model.

  18. Flexible retinal electrode array

    DOEpatents

    Okandan, Murat (Albuquerque, NM); Wessendorf, Kurt O. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

    2006-10-24

    An electrode array which has applications for neural stimulation and sensing. The electrode array can include a large number of electrodes each of which is flexibly attached to a common substrate using a plurality of springs to allow the electrodes to move independently. The electrode array can be formed from a combination of bulk and surface micromachining, with electrode tips that can include an electroplated metal (e.g. platinum, iridium, gold or titanium) or a metal oxide (e.g. iridium oxide) for biocompatibility. The electrode array can be used to form a part of a neural prosthesis, and is particularly well adapted for use in an implantable retinal prosthesis where the electrodes can be tailored to provide a uniform gentle contact pressure with optional sensing of this contact pressure at one or more of the electrodes.

  19. Cherenkov Telescope Array Technologies

    NASA Astrophysics Data System (ADS)

    Vandenbroucke, Justin

    2014-08-01

    The Cherenkov Telescope Array (CTA) will feature innovative technologies to achieve an order of magnitude greater sensitivity than the current generation of ground-based imaging atmospheric Cherenkov telescope (IACT) arrays. Several telescope designs of various sizes are currently in the prototyping stage. In addition to the traditional single-mirror Davies-Cotton design used for IACTs to date, a dual-mirror Schwarzschild-Couder design is being prototyped for both the small (4 m diameter) and medium (9.5 m diameter) telescopes. The dual-mirror designs feature compact focal planes that enable Cherenkov photon detection with innovative photo-detectors including silicon photomultipliers. The prototype telescopes are also testing several designs for readout electronics to capture the fast 10 ns) Cherenkov light pulses from hundreds of thousands of channels across the array. Finally, the CTA prototype telescopes are testing technologies for telescope mounts and mirrors that meet the unique needs of a large array of IACTs.

  20. Expandable LED array interconnect

    DOEpatents

    Yuan, Thomas Cheng-Hsin; Keller, Bernd

    2011-03-01

    A light emitting device that can function as an array element in an expandable array of such devices. The light emitting device comprises a substrate that has a top surface and a plurality of edges. Input and output terminals are mounted to the top surface of the substrate. Both terminals comprise a plurality of contact pads disposed proximate to the edges of the substrate, allowing for easy access to both terminals from multiple edges of the substrate. A lighting element is mounted to the top surface of the substrate. The lighting element is connected between the input and output terminals. The contact pads provide multiple access points to the terminals which allow for greater flexibility in design when the devices are used as array elements in an expandable array.

  1. OncoArray Network

    Cancer.gov

    The overall goal of the OncoArray Network is to gain new insight into the genetic architecture and mechanisms underlying breast, ovarian, prostate, colorectal, and lung cancers. The Network's major aim is to discover new cancer susceptibility variants.

  2. Protein Functionalized Nanodiamond Arrays

    PubMed Central

    2010-01-01

    Various nanoscale elements are currently being explored for bio-applications, such as in bio-images, bio-detection, and bio-sensors. Among them, nanodiamonds possess remarkable features such as low bio-cytotoxicity, good optical property in fluorescent and Raman spectra, and good photostability for bio-applications. In this work, we devise techniques to position functionalized nanodiamonds on self-assembled monolayer (SAMs) arrays adsorbed on silicon and ITO substrates surface using electron beam lithography techniques. The nanodiamond arrays were functionalized with lysozyme to target a certain biomolecule or protein specifically. The optical properties of the nanodiamond-protein complex arrays were characterized by a high throughput confocal microscope. The synthesized nanodiamond-lysozyme complex arrays were found to still retain their functionality in interacting with E. coli. PMID:20672037

  3. Parametric array calibration 

    E-print Network

    Wan, Shuang

    2011-01-01

    The subject of this thesis is the development of parametric methods for the calibration of array shape errors. Two physical scenarios are considered, the online calibration (self-calibration) using far-field sources and ...

  4. Random array grid collimator

    DOEpatents

    Fenimore, E.E.

    1980-08-22

    A hexagonally shaped quasi-random no-two-holes touching grid collimator. The quasi-random array grid collimator eliminates contamination from small angle off-axis rays by using a no-two-holes-touching pattern which simultaneously provides for a self-supporting array increasng throughput by elimination of a substrate. The presentation invention also provides maximum throughput using hexagonally shaped holes in a hexagonal lattice pattern for diffraction limited applications. Mosaicking is also disclosed for reducing fabrication effort.

  5. Adaptive processing array systems

    NASA Astrophysics Data System (ADS)

    Gabriel, William F.

    1992-01-01

    Adaptive array systems have undergone enormous growth and progress in the past two decades. Because this multidiscipline technology area is both complex and mathematics intensive, it often appears alien (and perhaps impractical) to the nonspecialist. To help bridge those gaps, this tutorial paper is limited to just three principal topic areas: sidelobe cancellers, fully adaptive arrays, and superresolution techniques. In each case, background material is included for perspective and clarity, and carefully selected references are provided. Recent developments are discussed briefly where appropriate.

  6. Magnetic interactions in nanostructured films

    Microsoft Academic Search

    Lan Gao

    2004-01-01

    Magnetic interactions in nanostructured films are important topics for understanding micromagnetism. They play significant roles in recording media and magnetic random access memory (MRAM). Due to measurement sensitivity limitations, arrays of hundreds of elements must be fabricated to obtain a high enough signal-to-noise ratio. The results are often clouded by statistical variations such as dot shape, size, and spacing. Thus,

  7. Full light absorption in single arrays of spherical nanoparticles

    E-print Network

    Ra'di, Y; Kosulnikov, S U; Omelyanovich, M M; Morits, D; Osipov, A V; Simovski, C R; Tretyakov, S A

    2015-01-01

    In this paper we show that arrays of core-shell nanoparticles function as effective thin absorbers of light. In contrast to known metamaterial absorbers, the introduced absorbers are formed by single planar arrays of spherical inclusions and enable full absorption of light incident on either or both sides of the array. We demonstrate possibilities for realizing different kinds of symmetric absorbers, including resonant, ultra-broadband, angularly selective, and all-angle absorbers. The physical principle behind these designs is explained considering balanced electric and magnetic responses of unit cells. Photovoltaic devices and thermal emitters are the two most important potential applications of the proposed designs.

  8. Design of a dual sensor probe array for internal field measurement in Versatile Experiment Spherical Torus.

    PubMed

    Jeong-hun, Yang; Chung, Kyoung-Jae; An, YoungHwa; Jung, Bong Ki; Jo, Jong Gab; Hwang, Y S

    2012-10-01

    A dual sensor probe array is designed and constructed for internal magnetic field measurement at Versatile Experiment Spherical Torus (VEST) at the Seoul National University. Simultaneous use of Hall sensors and chip inductors allows cross-calibration among the measurements and compensation for each other's weaknesses while their small sizes are expected to cause only mild plasma perturbations. Calibration of the dual sensor probe array, using a Helmholtz coil, shows good sensitivity for the magnetic field measurement of the VEST. Prior to Ohmic start-up, the magnetic field structure inside the vacuum chamber is measured by using the calibrated probe array. The dual sensor probe array is expected to be useful in analyzing the temporal magnetic field structure change during the magnetic reconnection and in reconstruction of the current profile during the discharge of the VEST device. PMID:23126895

  9. Carbon nanotube array actuators

    NASA Astrophysics Data System (ADS)

    Geier, S.; Mahrholz, T.; Wierach, P.; Sinapius, M.

    2013-09-01

    Experimental investigations of highly vertically aligned carbon nanotubes (CNTs), also known as CNT-arrays, are the main focus of this paper. The free strain as result of an active material behavior is analyzed via a novel experimental setup. Previous test experiences of papers made of randomly oriented CNTs, also called Bucky-papers, reveal comparably low free strain. The anisotropy of aligned CNTs promises better performance. Via synthesis techniques like chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD), highly aligned arrays of multi-walled carbon nanotubes (MWCNTs) are synthesized. Two different types of CNT-arrays are analyzed, morphologically first, and optically tested for their active characteristics afterwards. One type of the analyzed arrays features tube lengths of 750-2000 ?m with a large variety of diameters between 20 and 50 nm and a wave-like CNT-shape. The second type features a maximum, almost uniform, length of 12 ?m and a constant diameter of 50 nm. Different CNT-lengths and array types are tested due to their active behavior. As result of the presented tests, it is reported that the quality of orientation is the most decisive property for excellent active behavior. Due to their alignment, CNT-arrays feature the opportunity to clarify the actuation mechanism of architectures made of CNTs.

  10. Inducing the LCP-Array

    E-print Network

    Fischer, Johannes

    2011-01-01

    We show how to modify the linear-time construction algorithm for suffix arrays based on induced sorting (Nong et al., DCC'09) such that it computes the array of longest common prefixes (LCP-array) as well. Practical tests show that this outperforms recent LCP-array construction algorithms (Gog and Ohlebusch, ALENEX'11).

  11. Fabrication and characterization of nanostructured magnetic particles for applications in data storage

    E-print Network

    Farhoud, Maya S. (Maya Sami)

    2001-01-01

    Arrays of nanostructured magnetic particles ('nanomagnets') have potential applications in ultra-high-density data storage devices and dynamic magnetic memories, and are model systems for the study of magnetic phenomena ...

  12. Sampled Longest Common Prefix Array

    E-print Network

    Sirén, Jouni

    2010-01-01

    When augmented with the longest common prefix (LCP) array and some other structures, the suffix array can solve many string processing problems in optimal time and space. A compressed representation of the LCP array is also one of the main building blocks in many compressed suffix tree proposals. In this paper, we describe a new compressed LCP representation: the sampled LCP array. We show that when used with a compressed suffix array (CSA), the sampled LCP array often offers better time/space trade-offs than the existing alternatives. We also show how to construct the compressed representations of the LCP array directly from a CSA.

  13. All-weather vehicle classification using magnetometer arrays

    NASA Astrophysics Data System (ADS)

    Casalegno, James W.

    2002-08-01

    Arrays of vector magnetometers employing matched field processing have demonstrated the ability to accurately detect, track, and characterize the magnetic signature of vehicles traveling within range of the sensor field, regardless of weather conditions. This processing works on all types of vehicles, including passenger cars, light trucks, tractor-trailers, tanks, armored personnel carriers, etc. Consistency among the magnetic dipole estimates from similar vehicles has led to investigations of the ability to classify using magnetic information obtained from this process. Preliminary results suggest that separation of the permanent and induced portions of a vehicle's magnetic moment can provide the basis for an accurate, all-weather vehicle classifier.

  14. Incipient magnetic rotation? A magnetic dipole band in 104Cd

    E-print Network

    D. G. Jenkins; R. Wadsworth; J. A. Cameron; M. P. Carpenter; C. J. Chiara; R. M. Clark M. Devlin; P. Fallon; D. B. Fossan; I. M. Hibbert; R. V. F. Janssens; V. P. Janzen; R. Kruecken; D. R. LaFosse; G. J. Lane; T. Lauritsen; I. Y. Lee; A. O. Macchiavelli; C. M. Parry; D. G. Sarsantities; J. M. Sears; D. Seweryniak; J. F. Smith; K. Starosta; D. Ward; I. Wiedenhoever; A. N. Wilson; J. N. Wilson; S. Frauendorf

    2000-07-05

    High spin states of the nucleus 104Cd have been studied using the Gammapshere array. The level scheme for 104Cd has been revised and evidence for a structure consisting of magnetic dipole transitions is presented. Shell model calculations, published previously, are invoked to support an interpretation of this structure as an incpient case of magnetic rotation where the transversal magnetic dipole moment is not strong enough to break the signature symmetry.

  15. Composite arrays of superconducting microstrip line resonators

    NASA Astrophysics Data System (ADS)

    Mohebbi, H. R.; Benningshof, O. W. B.; Taminiau, I. A. J.; Miao, G. X.; Cory, D. G.

    2014-03-01

    A novel design of an array of half-wave superconductive microstrip resonators is described. The resonator is intended to be useful for electron spin resonance studies of thin film samples at cryogenic temperatures. It achieves a high quality factor, has a small mode-volume, and creates a uniform magnetic field in a plane above the resonator. The device is made of thin film Niobium on sapphire wafer and is tested with a static magnetic field. Variation of Q-factor versus the magnetic field's strength at different temperatures is reported and is in a good agreement with simulation when the loss due to the vortices is included. Also, the power-dependence response of the resonator is shown in experiments and is verified by capturing the nonlinearity associated with the surface impedance of the superconducting film into the circuit model of the device.

  16. Composite arrays of superconducting microstrip line resonators

    SciTech Connect

    Mohebbi, H. R., E-mail: hmohebbi@uwaterloo.ca; Miao, G. X. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Department of Electrical and Computer Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Benningshof, O. W. B. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Taminiau, I. A. J. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Cory, D. G. [Institute for Quantum Computing, Waterloo, Ontario N2L 3G1 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2L 2Y5 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

    2014-03-07

    A novel design of an array of half-wave superconductive microstrip resonators is described. The resonator is intended to be useful for electron spin resonance studies of thin film samples at cryogenic temperatures. It achieves a high quality factor, has a small mode-volume, and creates a uniform magnetic field in a plane above the resonator. The device is made of thin film Niobium on sapphire wafer and is tested with a static magnetic field. Variation of Q-factor versus the magnetic field's strength at different temperatures is reported and is in a good agreement with simulation when the loss due to the vortices is included. Also, the power-dependence response of the resonator is shown in experiments and is verified by capturing the nonlinearity associated with the surface impedance of the superconducting film into the circuit model of the device.

  17. Stability of discrete breathers in magnetic metamaterials

    E-print Network

    Pelinovsky, Dmitry

    Stability of discrete breathers in magnetic metamaterials Dmitry Pelinovsky1 and Vassilis Rothos2 1 describing magnetic metamaterials which consist of periodic arrays of split- ring resonators [4, 7]: ¨qn + V criterion to the multi-site breathers in magnetic metamaterials. 2 Formalism In what follows, we shall use

  18. Magnetic Domain-Wall Racetrack Memory

    Microsoft Academic Search

    Stuart S. P. Parkin; Masamitsu Hayashi; Luc Thomas

    2008-01-01

    Recent developments in the controlled movement of domain walls in magnetic nanowires by short pulses of spin-polarized current give promise of a nonvolatile memory device with the high performance and reliability of conventional solid-state memory but at the low cost of conventional magnetic disk drive storage. The racetrack memory described in this review comprises an array of magnetic nanowires arranged

  19. Solar array flight experiment

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Emerging satellite designs require increasing amounts of electrical power to operate spacecraft instruments and to provide environments suitable for human habitation. In the past, electrical power was generated by covering rigid honeycomb panels with solar cells. This technology results in unacceptable weight and volume penalties when large amounts of power are required. To fill the need for large-area, lightweight solar arrays, a fabrication technique in which solar cells are attached to a copper printed circuit laminated to a plastic sheet was developed. The result is a flexible solar array with one-tenth the stowed volume and one-third the weight of comparably sized rigid arrays. An automated welding process developed to attack the cells to the printed circuit guarantees repeatable welds that are more tolerant of severe environments than conventional soldered connections. To demonstrate the flight readiness of this technology, the Solar Array Flight Experiment (SAFE) was developed and flown on the space shuttle Discovery in September 1984. The tests showed the modes and frequencies of the array to be very close to preflight predictions. Structural damping, however, was higher than anticipated. Electrical performance of the active solar panel was also tested. The flight performance and postflight data evaluation are described.

  20. Microelectronic electroporation array

    NASA Astrophysics Data System (ADS)

    Johnson, Lee J.; Shaffer, Kara J.; Skeath, Perry; Perkins, Frank K.; Pancrazio, Joseph; Scribner, Dean

    2004-06-01

    Gene Array technology has allowed for the study of gene binding by creating thousands of potential binding sites on a single device. A limitation of the current technology is that the effects of the gene and the gene-derived proteins cannot be studied in situ the same way, thousand site cell arrays are not readily available. We propose a new device structure to study the effects of gene modification on cells. This new array technology uses electroporation to target specific areas within a cell culture for transfection of genes. Electroporation arrays will allow high throughput analysis of gene effects on a given cell's response to a stress or a genes ability to restore normal cell function in disease modeling cells. Fluorescent imaging of dye labeled indicator molecules or cell viability will provide results indicating the most effective genes. The electroporation array consists of a microelectronic circuit, ancillary electronics, protecting electrode surface for cell culturing and a perfusion system for gene or drug delivery. The advantages of the current device are that there are 3200 sites for electroporation, all or any subsets of the electrodes can be activated. The cells are held in place by the electrode material. This technology could also be applied to high throughput screening of cell impermeant drugs.

  1. Adaptive multibeam antenna array

    NASA Astrophysics Data System (ADS)

    Novikov, V. I.

    1984-01-01

    An adaptive multibeam antenna array is considered which will enhance the advantages of a plain one. By providing simultaneous reception of signals from different directions and their sequential processing. The optimization of the array control for maximum interference suppression in the radiation pattern is emphasized. The optimum control is sought with respect to the signal-to-interference power ratio as a genaralized criterion. Sampled useful signals and transmission coefficients are found to be complex-conjugate quantities, assuming compatible formation of beams, so that synphasal equiamplitude addition of signals from all array element is attainable by unique settings of the weight factors. Calculations are simplified by letting the useful signal power in the 1-th beam be approximately equal to the k-th weight factor, before optimizing the weight vector for maximum signal-to-interference ratio. A narrowband interference described by power P and vector V of signal distribution over the array is considered as an example, to demonstrate the algorithm of synthesis. The algorithm, using the Butler matrix, was executed experimentally on a computer for a linear equidistant antenna array of 32 elements with compatible formation of beams.

  2. Magnetic ratchet for biotechnological applications

    NASA Astrophysics Data System (ADS)

    Auge, A.; Weddemann, A.; Wittbracht, F.; Hütten, A.

    2009-05-01

    Transport and separation of magnetic beads are important in "lab on a chip" environments for biotechnological applications. One possible solution for this is the on-off ratchet concept. An asymmetric magnetic potential and Brownian motion of magnetic beads are required for such a ratchet. The asymmetric magnetic potential is achieved by combining an external magnetic field with a spatially periodic array of conducting lines. In this work finite element method simulations are carried out to design this asymmetric potential and to evaluate transport rates. Furthermore, experiments are carried out so as to compare to the simulation results.

  3. BIG KARL and COSY: Examples for high performance magnet design taught by {open_quotes}Papa Klaus{close_quotes}

    SciTech Connect

    Bechtstedt, U.; Hacker, U.; Maier, R.; Martin, S. [Institut fuer Kernphysik, Juelich (Germany); Berg, G.P.A. [Indiana Univ. Cyclotron Facility, Bloomington, IN (United States); Hardt, A. [Fachhochschule Aachen Juelich (Germany); Huerlimann, W. [Power Consulting Ltd., Baden (Switzerland); Meissburger, J. [Institut fuer angewandte Mathematik, Juelich (Germany); Roemer, J.G.M. [Leybold-Heraeus GmbH, Koeln (Germany)] [and others

    1995-02-01

    The past decades have seen a tremendous development in nuclear, middle, and high energy physics. This advance was in a great part promoted by the availability of newer and more powerful instruments. Over time, these instruments grew in size as well as in sophistication and precision. Nearly all these devices had one fundamental thing in common - magnetic fields produced with currents and iron. The precision demanded by the new experiments and machines did bring the magnet technology to new frontiers requiring the utmost in the accuracy of magnetic fields. The complex properties of the iron challenged innumerable physicists in the attempt to force the magnetic fields into the desired shape. Experience and analytical insight were the pillars for coping with those problems and only few mastered the skills and were in addition able to communicate their intricate knowledge. It was a fortuitous situation that the authors got to know Klaus Halbach who belonged to those few and who shared his knowledge contributing thus largely to the successful completion of two large instruments that were built at the Forschungszentrum Juelich, KFA, for nuclear and middle energy physics. In one case the efforts went to the large spectrometer named BIG KARL whose design phase started in the early 70`s. In the second case the work started in the early 80`s with the task to build a high precision 2.5 GeV proton accelerator for cooled stored and extracted beams known as COSY-Juelich.

  4. Periodic nanowire array at the crystal interface.

    PubMed

    Nakamura, Atsutomo; Mizoguchi, Teruyasu; Matsunaga, Katsuyuki; Yamamoto, Takahisa; Shibata, Naoya; Ikuhara, Yuichi

    2013-07-23

    A dislocation in a crystalline material has dangling bonds at its core and a strong strain field in its vicinity. Consequently, the dislocation attracts solute atoms and forms a so-called Cottrell atmosphere along the dislocation. A crystalline dislocation can be used as a template to produce nanowires by selectively doping foreign atoms along the dislocation. However, control of the configuration, spacing, and density of the formed periodic nanowire array has heretofore been extremely difficult. Here we show a method for fabricating ordered, electrically conductive nanowire arrays using periodic dislocations at crystal interfaces. As a demonstration, we fabricated arrays of titanium nanowires arranged at intervals of either 13 or 90 nm and then confirmed by scanning probe microscopy that they exhibit electrical conductivity inside an insulating aluminum oxide. Significantly, we were able to precisely control nanowire periodicity by the choice of crystal orientation and/or crystal planes at the crystal interface. This simple method for the fabrication of periodic nanowire arrays of highly controlled density should be widely applicable to electrical, magnetic, and optical devices. PMID:23876048

  5. Supersymetric laser arrays

    E-print Network

    El-Ganainy, Ramy; Khajavikhan, Mercedeh; Christodoulides, Demetrios

    2015-01-01

    We introduce the concept of supersymmetric laser arrays that consists of a main optical lattice and its superpartner structure, and we investigate the onset of their lasing oscillations. Due to the coupling of the two constituent lattices, their degenerate optical modes form doublets, while the extra mode associated with unbroken supersymmetry forms a singlet state. Singlet lasing can be achieved for a wide range of design parameters either by introducing stronger loss in the partner lattice or by pumping only the main array. Our findings suggest the possibility of building single-mode, high-power laser arrays and are also important for understanding light transport dynamics in multimode Parity-Time symmetric photonic structures.

  6. Coaxial phased array antenna

    NASA Technical Reports Server (NTRS)

    Ellis, H., Jr. (inventor)

    1980-01-01

    A coaxial antenna array for communicating circularly polarized electromagnetic radiation is disclosed. A pair of open ended antenna cavities is coaxially constructed and operates by excitation of linear radiation elements arranged within each of the cavities. A pair of crossed dipole radiation devices is centered within the inner cavity and operated by means of a phase shifting network circuit to transmit as well as receive circularly polarized radiation. Four monopole radiation devices are symmetrically arranged to operate in the outer cavity in phase quadrature by means of the phase shifting network circuit to both transmit and receive circularly polarized electromagnetic radiation. Combined operation of the two antenna cavities with a 180 deg phase differential between the fields related to the two antenna cavities provides a broad beam, relatively wide frequency bandwidth communication capability. Particular embodiments disclosed feature a generally square cavity array as well as a circular cavity array.

  7. Photovoltaic array reliability optimization

    NASA Technical Reports Server (NTRS)

    Ross, R. G., Jr.

    1982-01-01

    An overview of the photovoltaic array reliability problem is presented, and a high reliability/minimum cost approach to this problem is presented. Design areas covered are cell failure, interconnect fatigue, and electrical insulation breakdown, and three solution strategies are discussed. The first involves controlling component failures in the solar cell (cell cracking, cell interconnects) and at the module level (must be statistically treated). Second, a fault tolerant circuit is designed which reduces array degradation, improves module yield losses, and controls hot-spot heating. Third, cost optimum module replacement strategies are also effective in reducing array degradation. This can be achieved by minimizing the life-cycle energy cost of the photovoltaic system. The integration of these solutions is aimed at reducing the 0.01% failure rate.

  8. Levitated Duct Fan (LDF) Aircraft Auxiliary Generator

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; Emerson, Dawn C.; Gallo, Christopher A.; Thompson, William K.

    2011-01-01

    This generator concept includes a novel stator and rotor architecture made from composite material with blades attached to the outer rotating shell of a ducted fan drum rotor, a non-contact support system between the stator and rotor using magnetic fields to provide levitation, and an integrated electromagnetic generation system. The magnetic suspension between the rotor and the stator suspends and supports the rotor within the stator housing using permanent magnets attached to the outer circumference of the drum rotor and passive levitation coils in the stator shell. The magnets are arranged in a Halbach array configuration.

  9. Optimization of a 3x3 focusing array for heavy ion drivers

    SciTech Connect

    Martovetsky, N N; Meinke, R B

    2005-08-08

    A heavy ion driver for inertial fusion will accelerate an array of beams through common induction cores and then direct the beams onto the DT target. An array of quadrupole focusing magnets is used to prevent beam expansion from space charge forces. In the array, the magnet fields from the coils embracing the beams are coupled, which reduces the cost of superconductor and increases the focusing power. The challenges in designing such an array are meeting the strict requirements for the quadrupole field inside the beam pipes and preventing stray fields outside. We report our optimization effort on designing such an array and show that 3 x 3 or larger arrays are feasible and practical to build with flat racetrack coils.

  10. Solar array subsystems study

    NASA Technical Reports Server (NTRS)

    Richardson, P. W.; Miller, F. Q.; Badgley, M. B.

    1980-01-01

    The effects on life cycle costs of a number of technology areas are examined for a LEO, 500 kW solar array. A baseline system conceptual design is developed and the life cycle costs estimated in detail. The baseline system requirements and design technologies are then varied and their relationships to life cycle costs quantified. For example, the thermal characteristics of the baseline design are determined by the array materials and masses. The thermal characteristics in turn determine configuration, performance and hence life cycle cost.

  11. Wire Array Photovoltaics

    NASA Astrophysics Data System (ADS)

    Turner-Evans, Dan

    Over the past five years, the cost of solar panels has dropped drastically and, in concert, the number of installed modules has risen exponentially. However, solar electricity is still more than twice as expensive as electricity from a natural gas plant. Fortunately, wire array solar cells have emerged as a promising technology for further lowering the cost of solar. Si wire array solar cells are formed with a unique, low cost growth method and use 100 times less material than conventional Si cells. The wires can be embedded in a transparent, flexible polymer to create a free-standing array that can be rolled up for easy installation in a variety of form factors. Furthermore, by incorporating multijunctions into the wire morphology, higher efficiencies can be achieved while taking advantage of the unique defect relaxation pathways afforded by the 3D wire geometry. The work in this thesis shepherded Si wires from undoped arrays to flexible, functional large area devices and laid the groundwork for multijunction wire array cells. Fabrication techniques were developed to turn intrinsic Si wires into full p-n junctions and the wires were passivated with a-Si:H and a-SiNx:H. Single wire devices yielded open circuit voltages of 600 mV and efficiencies of 9%. The arrays were then embedded in a polymer and contacted with a transparent, flexible, Ni nanoparticle and Ag nanowire top contact. The contact connected >99% of the wires in parallel and yielded flexible, substrate free solar cells featuring hundreds of thousands of wires. Building on the success of the Si wire arrays, GaP was epitaxially grown on the material to create heterostructures for photoelectrochemistry. These cells were limited by low absorption in the GaP due to its indirect bandgap, and poor current collection due to a diffusion length of only 80 nm. However, GaAsP on SiGe offers a superior combination of materials, and wire architectures based on these semiconductors were investigated for multijunction arrays. These devices offer potential efficiencies of 34%, as demonstrated through an analytical model and optoelectronic simulations. SiGe and Ge wires were fabricated via chemical-vapor deposition and reactive ion etching. GaAs was then grown on these substrates at the National Renewable Energy Lab and yielded ns lifetime components, as required for achieving high efficiency devices.

  12. Automated array assembly

    NASA Technical Reports Server (NTRS)

    Williams, B. F.

    1976-01-01

    Manufacturing techniques are evaluated using expenses based on experience and studying basic cost factors for each step to evaluate expenses from a first-principles point of view. A formal cost accounting procedure is developed which is used throughout the study for cost comparisons. The first test of this procedure is a comparison of its predicted costs for array module manufacturing with costs from a study which is based on experience factors. A manufacturing cost estimate for array modules of $10/W is based on present-day manufacturing techniques, expenses, and materials costs.

  13. Array signal processing

    SciTech Connect

    Haykin, S.; Justice, J.H.; Owsley, N.L.; Yen, J.L.; Kak, A.C.

    1985-01-01

    This is the first book to be devoted completely to array signal processing, a subject that has become increasingly important in recent years. The book consists of six chapters. Chapter 1, which is introductory, reviews some basic concepts in wave propagation. The remaining five chapters deal with the theory and applications of array signal processing in (a) exploration seismology, (b) passive sonar, (c) radar, (d) radio astronomy, and (e) tomographic imaging. The various chapters of the book are self-contained. The book is written by a team of five active researchers, who are specialists in the individual fields covered by the pertinent chapters.

  14. Flux avalanches in superconducting films with periodic arrays of holes.

    SciTech Connect

    Vlasko-Vlasov, V.; Welp, U.; Metlushko, V.; Crabtree, G. W.; Materials Science Division; Inst. of Solid State Physics RAS

    2000-01-01

    The magnetic flux dynamics in Nb films with periodic hole arrays is studied magneto-optically. Flux motion in the shape of microavalanches along {l_brace}100{r_brace} and {l_brace}110{r_brace} directions of the hole lattice is observed. At lower temperatures anisotropic large scale thermo-magnetic avalanches dominate flux entry and exit. At T-T{sub c} critical-state-like field patterns periodically appear at fractions of the matching field.

  15. Superconducting bulk magnets for magnetic levitation systems

    NASA Astrophysics Data System (ADS)

    Fujimoto, H.; Kamijo, H.

    2000-06-01

    The major applications of high-temperature superconductors have mostly been confined to products in the form of wires and thin films. However, recent developments show that rare-earth REBa 2Cu 3O 7- x and light rare-earth LREBa 2Cu 3O 7- x superconductors prepared by melt processes have a high critical-current density at 77 K and high magnetic fields. These superconductors will promote the application of bulk high-temperature superconductors in high magnetic fields; the superconducting bulk magnet for the Maglev train is one possible application. We investigated the possibility of using bulk magnets in the Maglev system, and examined flux-trapping characteristics of multi-superconducting bulks arranged in array.

  16. Science with the Square Kilometre Array

    NASA Technical Reports Server (NTRS)

    Lazio, Joseph; Huynh, Minh

    2010-01-01

    The Square Kilometre Array (SKA) is the centimeter- and meter-wavelength telescope for the 21st Century. Its Key Science Projects are (a) The end of the Dark Ages, involving searches for an H i signature and the first metalrich systems; (b) Testing theories of gravitation using an array of pulsars to search for gravitational waves and relativistic binaries to probe the strong-field regime; (c) Observations of H i to a redshift z 2 from which to study the evolution of galaxies and dark energy. (d) Astrobiology including planetary formation within protoplanetary disks; and (c) The origin and evolution of cosmic magnetism, both within the Galaxy and in intergalactic space. The SKA will operate over the wavelength range of at least 1.2 cm to 4 m (70 MHz to 25 GHz), providing milliarcsecond resolution at the shortest wavelengths.

  17. Automated inspection of surface breaking cracks using GMR sensor arrays

    SciTech Connect

    Pelkner, Matthias; Reimund, Verena; Erthner, Thomas; Panke, Nicolai; Kreutzbruck, Marc [BAM Federal Institute for Material Research and Testing, Unter den Eichen 87, 12205 Berlin (Germany)

    2014-02-18

    We present a prototype for automated magnetic stray field testing of ferromagnetic roller bearings. For this purpose NDE-adapted GMR sensor arrays (giant magneto resistance) are used for the detection of surface breaking cracks. The sensors are miniaturized down to the lower ?m-regime to achieve adequate spatial resolution. In doing so, sensor arrays with up to 48 elements are used to inspect the bearing surface within a few seconds only. In contrast to magnetic particle inspection (MPI), where the global magnetization requires a further inspection step and succeeding demagnetization, the presented prototype only locally magnetize the surface area in the vicinity of the GMR Sensors. For the local magnetization, the applied sub-surface magnetic field was simulated and proofed for detecting flaws with a depth of a few 10 ?m. By multiplexing the sensor array with an adapted read out electronics we quasi simultaneously detect the normal field component of about 100?m above the surface. The detection of artificial notches with a depth of 40 ?m and more could be resolved with a SNR better than 20 dB. The presented testing facility is fast and provides a step towards automated testing of safety relevant steel components.

  18. Multi-array borehole resistivity and induced polarization method with mathematical inversion of redundant data

    DOEpatents

    Ward, Stanley H. (Salt Lake City, UT)

    1989-01-01

    Multiple arrays of electric or magnetic transmitters and receivers are used in a borehole geophysical procedure to obtain a multiplicity of redundant data suitable for processing into a resistivity or induced polarization model of a subsurface region of the earth.

  19. Ferromagnetic resonance response of electron-beam patterned arrays of ferromagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Jung, Sukkoo; Watkins, Byron; Feller, Jeffrey; Ketterson, John; Chandrasekhar, Venkat

    2001-03-01

    We report on the fabrication and the dynamic magnetic properties of periodic permalloy dot arrays. Electron-beam lithography and e-gun evaporation have been used to make the arrays with the aspect ratio of 2 (dot diameter : 40 nm, height : 80 nm) and periods of 100 - 200 nm. The magnetic properties of the arrays and their interactions have been investigated by ferromagnetic resonance (FMR), magnetic force microscopy (MFM), and SQUID magnetometry. The measured FMR data show that the position and magnitude of resonant absorption peaks strongly depend on the angle between magnetic field and the lattice structure. The results of dot arrays with various kinds of structural parameters will be presented. Supported by Army Research Office, DAAD19-99-1-0334/P001

  20. Wave modes of collective vortex gyration in dipolar-coupled-dot-array magnonic crystals

    PubMed Central

    Han, Dong-Soo; Vogel, Andreas; Jung, Hyunsung; Lee, Ki-Suk; Weigand, Markus; Stoll, Hermann; Schütz, Gisela; Fischer, Peter; Meier, Guido; Kim, Sang-Koog

    2013-01-01

    Lattice vibration modes are collective excitations in periodic arrays of atoms or molecules. These modes determine novel transport properties in solid crystals. Analogously, in periodical arrangements of magnetic vortex-state disks, collective vortex motions have been predicted. Here, we experimentally observe wave modes of collective vortex gyration in one-dimensional (1D) periodic arrays of magnetic disks using time-resolved scanning transmission x-ray microscopy. The observed modes are interpreted based on micromagnetic simulation and numerical calculation of coupled Thiele equations. Dispersion of the modes is found to be strongly affected by both vortex polarization and chirality ordering, as revealed by the explicit analytical form of 1D infinite arrays. A thorough understanding thereof is fundamental both for lattice vibrations and vortex dynamics, which we demonstrate for 1D magnonic crystals. Such magnetic disk arrays with vortex-state ordering, referred to as magnetic metastructure, offer potential implementation into information processing devices. PMID:23877284

  1. Dynamics of conical wire array Z-pinch implosions

    NASA Astrophysics Data System (ADS)

    Ampleford, D. J.; Lebedev, S. V.; Bland, S. N.; Bott, S. C.; Chittenden, J. P.; Jennings, C. A.; Kantsyrev, V. L.; Safronova, A. S.; Ivanov, V. V.; Fedin, D. A.; Laca, P. J.; Yilmaz, M. F.; Nalajala, V.; Shrestha, I.; Williamson, K.; Osborne, G.; Haboub, A.; Ciardi, A.

    2007-10-01

    A modification of the wire array Z pinch, the conical wire array, has applications to the understanding of wire array implosions and potentially to pulse shaping relevant to inertial confinement fusion. Results are presented from imploding conical wire array experiments performed on university scale 1 MA generators—the MAGPIE generator (1 MA, 240 ns) at Imperial College London [I. H. Mitchell et al., Rev. Sci Instrum. 67, 1533 (1996)] and the Nevada Terawatt Facility's Zebra generator (1 MA, 100 ns) at the University of Nevada, Reno [B. Bauer et al., in Dense Z-Pinches, edited by N. Pereira, J. Davis, and P. Pulsifer (AIP, New York, 1997), Vol. 409, p. 153]. This paper will discuss the implosion dynamics of conical wire arrays. Data indicate that mass ablation from the wires in this complex system can be reproduced with a rocket model with fixed ablation velocity. Modulations in the ablated plasma are present, the wavelength of which is invariant to a threefold variation in magnetic field strength. The axial variation in the array leads to a zippered precursor column formation. An initial implosion of a magnetic bubble near the cathode is followed by the implosion zippering upwards. Spectroscopic data demonstrating a variation of plasma parameters (e.g., electron temperature) along the Z-pinch axis is discussed, and experimental data are compared to magnetohydrodynamic simulations.

  2. Resonant Reflection From Dipole Arrays Located Very Near To Conducting Planes

    Microsoft Academic Search

    P. A. Belov; S. A. Tretyakov

    2002-01-01

    Plane-wave reflection from regular arrays of small particles positioned very near to an ideally conducting plane is theoretically studied. It is found that extremely thin (in wavelength) coverings with resonant properties can be realized if the array particles are small dipole antennas loaded by bulk inductances. This offers a possibility to realize an artificial magnetic conductor as a thin covering

  3. Partially reflecting sheet arrays

    Microsoft Academic Search

    G. V. Trentini

    1956-01-01

    Multiple reflections of electromagnetic waves between two planes are studied, and the increase in directivity that results by placing a partially reflecting sheet in front of an antenna with a reflecting screen is investigated at a wavelength of 3.2 cm. The construction and performance of various models of such arrays is discussed. Thus, for example, a \\

  4. Dynamically reconfigurable microphone arrays

    Microsoft Academic Search

    E. Martinson; B. Fransen

    2011-01-01

    ? Abstract—Robotic sound localization has traditionally been restricted to either on-robot microphone arrays or embedded microphones in aware environments, each of which have limitations due to their static configurations. This work overcomes the static configuration problems by using visual localization to track multiple wireless microphones in the environment with enough accuracy to combine their auditory streams in a traditional localization

  5. Omnidirectional coded loudspeaker arrays

    Microsoft Academic Search

    S. El-Khamy; O. Abdel-Alim

    1983-01-01

    The feeding of loudspeaker arrays by special sequences, or codes, with the purpose of obtaining isotropic radiation intensity patterns is considered in this paper. In particular, new codes of the Huffman codes type, which are generated by combination of Barker codes, are considered. This type of feeding is shown to result in almost isotropic patterns which are superior to those

  6. Automated array assembly

    NASA Technical Reports Server (NTRS)

    Daiello, R. V.

    1977-01-01

    A general technology assessment and manufacturing cost analysis was presented. A near-term (1982) factory design is described, and the results of an experimental production study for the large-scale production of flat-panel silicon and solar-cell arrays are detailed.

  7. TRMM Solar Array Panels

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This final report presents conclusions/recommendations concerning the TRMM Solar Array; deliverable list and schedule summary; waivers and deviations; as-shipped performance data, including flight panel verification matrix, panel output detail, shadow test summary, humidity test summary, reverse bias test panel; and finally, quality assurance summary.

  8. Arrays for space applications

    NASA Technical Reports Server (NTRS)

    Schuman, Harvey K.; Antonik, Paul; Malagisi, Carmen

    1989-01-01

    Concepts that were studied for application in space based radar (SBR) systems are presented. These antenna systems were for low earth orbit and require large fields of view (FOV). The systems included both space-fed and corporate-fed arrays.

  9. Antenna array research

    NASA Technical Reports Server (NTRS)

    Tai, C.

    1973-01-01

    Antenna array research on electromagnetic field problems in inhomogeneous media is presented along with characteristics of the Eaton lens. Comparisons are given of the radiation pattern and directivity of small Luneburg lens with a homogeneous lens. References and figure captions on radiation patterns are included.

  10. Cherenkov Telescope Array (CTA)

    NASA Astrophysics Data System (ADS)

    Barres de Almeida, U.; de Gouveia Dal Pino, E. M.

    2014-10-01

    Gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation ground-based gamma-ray observatory. CTA will consist of two arrays for full sky coverage and will be operated as an open observatory. It will provide a deep insight into the high-energy universe.

  11. Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization

    DOEpatents

    Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)

    2000-12-19

    In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

  12. Electromagnetic unidirectionality and frozen modes in magnetic photonic crystals

    Microsoft Academic Search

    Alex Figotin; Ilya Vitebskiy

    2006-01-01

    Magnetic photonic crystals are periodic arrays of lossless materials, at least one of which being magnetically polarized. Magnetization, either spontaneous or induced, is associated with nonreciprocal effects, such as Faraday rotation. Magnetic photonic crystals of certain configuration can also display strong spectral asymmetry, implying that light propagates in one direction much faster or slower than in the opposite direction. This

  13. PLASMA DIAGNOSTIC AND PERFORMANCE OF A PERMANENT MAGNET HALL THRUSTER

    E-print Network

    Boyer, Edmond

    . The idea of using an array of permanent magnets, instead of an electromagnet, to produce a radial magneticPLASMA DIAGNOSTIC AND PERFORMANCE OF A PERMANENT MAGNET HALL THRUSTER José Leonardo Ferreira, João of the Permanent Magnet Hall Thruster (PMHT) developed at the Plasma laboratory of the University of Brasilia

  14. A superconducting quadrupole array for transport of multiple high current beams

    SciTech Connect

    Faltens, A.; Shuman, D.

    1999-11-01

    We present a conceptual design of a superconducting quadrupole magnet array for the side-by-side transport of multiple high current particle beams in induction linear accelerators. The magnetic design uses a modified cosine 20 current distribution inside a square cell boundary. Each interior magnet's neighbors serve as the return flux paths and the poles are placed as close as possible to each other to facilitate this. No iron is present in the basic 2-D magnetic design; it will work at any current level without correction windings. Special 1/8th quadrupoles are used along the transverse periphery of the array to contain and channel flux back into the array, making every channel look as part of an infinite array. This design provides a fixed dimension array boundary equal to the quadrupole radius that can be used for arrays of any number of quadrupole channels, at any field level. More importantly, the design provides magnetic field separation between the array and the induction cores which may be surrounding it. Flux linkage between these two components can seriously affect the operation of both of them.

  15. Angular dependence of the coercivity in arrays of ferromagnetic nanowires

    NASA Astrophysics Data System (ADS)

    Holanda, J.; Silva, D. B. O.; Padrón-Hernández, E.

    2015-03-01

    We present a new magnetic model for polycrystalline nanowires arrays in porous anodic aluminum oxide. The principal consideration here is the crystalline structure and the morphology of the wires and them the dipolar interactions between the crystals into the wire. Other aspect here is the direct calculation of the dipolar energy for the interaction of one wire with the others in the array. The free energy density was formulated for polycrystalline nanowires arrays in order to determinate the anisotropy effective field. It was using the microstructure study by scanning and transmission electron microscopy for the estimation of the real structure of the wires. After the structural analysis we used the angular dependences for the coercivity field and for the remnant magnetization to determine the properties of the wires. All analysis were made by the theory treatment proposed by Stoner and Wohlfarth.

  16. Mutual coupling effects in antenna arrays, volume 1

    NASA Technical Reports Server (NTRS)

    Collin, R. E.

    1986-01-01

    Mutual coupling between rectangular apertures in a finite antenna array, in an infinite ground plane, is analyzed using the vector potential approach. The method of moments is used to solve the equations that result from setting the tangential magnetic fields across each aperture equal. The approximation uses a set of vector potential model functions to solve for equivalent magnetic currents. A computer program was written to carry out this analysis and the resulting currents were used to determine the co- and cross-polarized far zone radiation patterns. Numerical results for various arrays using several modes in the approximation are presented. Results for one and two aperture arrays are compared against published data to check on the agreement of this model with previous work. Computer derived results are also compared against experimental results to test the accuracy of the model. These tests of the accuracy of the program showed that it yields valid data.

  17. Large scale two-dimensional arrays of magnesium diboride superconducting quantum interference devices

    SciTech Connect

    Cybart, Shane A., E-mail: scybart@ucsd.edu; Dynes, R. C. [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States); Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Wong, T. J.; Cho, E. Y. [Department of Physics, University of California San Diego, La Jolla, California 92093 (United States); Beeman, J. W. [Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Yung, C. S.; Moeckly, B. H. [Superconductor Technologies Inc., Santa Barbara, California 93111 (United States)

    2014-05-05

    Magnetic field sensors based on two-dimensional arrays of superconducting quantum interference devices were constructed from magnesium diboride thin films. Each array contained over 30?000 Josephson junctions fabricated by ion damage of 30?nm weak links through an implant mask defined by nano-lithography. Current-biased devices exhibited very large voltage modulation as a function of magnetic field, with amplitudes as high as 8?mV.

  18. Plasma-wave coupling and propagation using phased waveguide arrays

    Microsoft Academic Search

    S. Bernabel; W. M. Hooke; R. W. Motley; F. J. Paoloni; M. A. Heald; M. Brambilla

    1977-01-01

    A study of the coupling and propagation of electron plasma waves excited by waveguide arrays is presented. The waves are generated in a low-temperature linear plasma column in a homogeneous magnetic field. As predicted from a theoretical model, efficient coupling to plasma waves can be obtained under appropriate conditions. These studies are of relevance to plasma heating in that the

  19. Topological quantization and degeneracy in Josephson-junction arrays

    Microsoft Academic Search

    M. Y. Choi; J. Choi

    2001-01-01

    We consider the conductivity quantization in two-dimensional arrays of mesoscopic Josephson junctions, and examine the associated degeneracy in various regimes of the system. The filling factor of the system may be controlled by the gate voltage as well as the magnetic field, and its appropriate value for quantization is obtained by employing the Jain hierarchy scheme both in the charge

  20. Application of field emitter arrays to microwave power amplifiers

    Microsoft Academic Search

    David R. Whaley; Bartley M. Gannon; Carl R. Smith; Carter M. Armstrong; Capp A. Spindt

    2000-01-01

    This paper describes the operation of a field emitter array (FEA) as the electron source of a traveling-wave tube (TWT) amplifier. Issues of beam control and focus at high current density and low magnetic field are addressed as well as issues relating to the inherent high emittance of the FEA beam and cathode protection from ion bombardment. Large signal, nonlinear

  1. Magnetic force microscopy measurements in external magnetic fields-comparison between coated probes and an iron filled carbon nanotube probe

    Microsoft Academic Search

    F. Wolny; T. Mühl; U. Weissker; A. Leonhardt; U. Wolff; D. Givord; B. Büchner

    2010-01-01

    We performed magnetic force microscopy (MFM) measurements in external magnetic fields parallel to the sample plane to qualitatively study their effect on the magnetization of different kinds of MFM probes. As a test structure we used an array of rectangular ferromagnetic thin film elements aligned with the external magnetic field direction. MFM images were taken while the field was increased

  2. Spatially resolved single photon detection with a quantum sensor array

    PubMed Central

    Zagoskin, A. M.; Wilson, R. D.; Everitt, M.; Savel'ev, S.; Gulevich, D. R.; Allen, J.; Dubrovich, V. K.; Il'ichev, E.

    2013-01-01

    We propose a method of resolving a spatially coherent signal, which contains on average just a single photon, against the background of local noise at the same frequency. The method is based on detecting the signal simultaneously in several points more than a wavelength apart through the entangling interaction of the incoming photon with the quantum metamaterial sensor array. The interaction produces the spatially correlated quantum state of the sensor array, characterised by a collective observable (e.g., total magnetic moment), which is read out using a quantum nondemolition measurement. We show that the effects of local noise (e.g., fluctuations affecting the elements of the array) are suppressed relative to the signal from the spatially coherent field of the incoming photon as , where N is the number of array elements. The realisation of this approach in the microwave range would be especially useful and is within the reach of current experimental techniques. PMID:24322568

  3. Focusing magnets for HIF based on racetracks

    Microsoft Academic Search

    Nicolai N. Martovetsky; Robert R. Manahan

    2001-01-01

    Heavy ion fusion (HIF) is considered a promising path to a practical fusion reactor. A driver for a HIF reactor will require a large number of quadrupole arrays to focus heavy ion beams. A conceptual design, and trade off studies of the quadrupole array based on racetracks are presented. A comparison with a conventional shell magnet is given and advantages

  4. Carbon nanotube array based sensor

    DOEpatents

    Lee, Christopher L.; Noy, Aleksandr; Swierkowski, Stephan P.; Fisher, Karl A.; Woods, Bruce W.

    2005-09-20

    A sensor system comprising a first electrode with an array of carbon nanotubes and a second electrode. The first electrode with an array of carbon nanotubes and the second electrode are positioned to produce an air gap between the first electrode with an array of carbon nanotubes and the second electrode. A measuring device is provided for sensing changes in electrical capacitance between the first electrode with an array of carbon nanotubes and the second electrode.

  5. suffix arrays * 11 1 100013

    E-print Network

    Zong, Chengqing

    -rile.hu,xia.s.wang}@nokia.com Abstract: In this paper a novel fast translation algorithm based on the data structure of suffix arrays arrays A New Approach to Fast Translation Method Based on Suffix Arrays Hu Rile1,2 , Zong Chengqing1 is proposed to solve the translation service problem in restricted domains for specific tasks with limited

  6. Adaptive coherent optical receiver array

    Microsoft Academic Search

    L. B. Mercer

    1990-01-01

    A linear four element adaptive heterodyne optical receiver array employing semiconductor lasers is described. The array adaptively adjusts the phase of each subaperture IF signal to correct for wavefront tilt and distortion and nonuniform optical and RF path delays across the array by phase-locking each channel to a reference channel.

  7. Antenna arrays with frequency compensation

    NASA Astrophysics Data System (ADS)

    Chaplin, A. F.; Koval', B. V.

    1988-02-01

    It is shown that the principle of least ordered sequences can be used to design linear nonequidistant arrays with suppression of additional diffraction peaks of the radiation pattern. This provides for a uniform sidelobe level and a stable directive gain in a wide frequency range. The range and directivity properties of such arrays are analyzed, and an efficient method of array synthesis is proposed.

  8. Tutorial: Performance and reliability in redundant disk arrays

    NASA Technical Reports Server (NTRS)

    Gibson, Garth A.

    1993-01-01

    A disk array is a collection of physically small magnetic disks that is packaged as a single unit but operates in parallel. Disk arrays capitalize on the availability of small-diameter disks from a price-competitive market to provide the cost, volume, and capacity of current disk systems but many times their performance. Unfortunately, relative to current disk systems, the larger number of components in disk arrays leads to higher rates of failure. To tolerate failures, redundant disk arrays devote a fraction of their capacity to an encoding of their information. This redundant information enables the contents of a failed disk to be recovered from the contents of non-failed disks. The simplest and least expensive encoding for this redundancy, known as N+1 parity is highlighted. In addition to compensating for the higher failure rates of disk arrays, redundancy allows highly reliable secondary storage systems to be built much more cost-effectively than is now achieved in conventional duplicated disks. Disk arrays that combine redundancy with the parallelism of many small-diameter disks are often called Redundant Arrays of Inexpensive Disks (RAID). This combination promises improvements to both the performance and the reliability of secondary storage. For example, IBM's premier disk product, the IBM 3390, is compared to a redundant disk array constructed of 84 IBM 0661 3 1/2-inch disks. The redundant disk array has comparable or superior values for each of the metrics given and appears likely to cost less. In the first section of this tutorial, I explain how disk arrays exploit the emergence of high performance, small magnetic disks to provide cost-effective disk parallelism that combats the access and transfer gap problems. The flexibility of disk-array configurations benefits manufacturer and consumer alike. In contrast, I describe in this tutorial's second half how parallelism, achieved through increasing numbers of components, causes overall failure rates to rise. Redundant disk arrays overcome this threat to data reliability by ensuring that data remains available during and after component failures.

  9. Thickness dependence of the levitation performance of double-layer high-temperature superconductor bulks above a magnetic rail

    NASA Astrophysics Data System (ADS)

    Sun, R. X.; Zheng, J.; Liao, X. L.; Che, T.; Gou, Y. F.; He, D. B.; Deng, Z. G.

    2014-10-01

    A double-layer high-temperature superconductor (HTSC) arrangement was proposed and proved to be able to bring improvements to both levitation force and guidance force compared with present single-layer HTSC arrangement. To fully exploit the applied magnetic field by a magnetic rail, the thickness dependence of a double-layer HTSC arrangement on the levitation performance was further investigated in the paper. In this study, the lower-layer bulk was polished step by step to different thicknesses, and the upper-layer bulk with constant thickness was directly superimposed on the lower-layer one. The levitation force and the force relaxation of the double-layer HTSC arrangement were measured above a Halbach magnetic rail. Experimental result shows that a bigger levitation force and a less levitation force decay could be achieved by optimizing the thickness of the lower-layer bulk HTSC. This thickness optimization method could be applied together with former reported double-layer HTSC arrangement method with aligned growth sector boundaries pattern. This series of study on the optimized combination method do bring a significant improvement on the levitation performance of present HTS maglev systems.

  10. Unified heliostat array project

    SciTech Connect

    Not Available

    1980-06-01

    A set of diagrams and outlines describes a project to develop a unified heliostat array on an inclined structure. Project progress and performance is diagrammed. The proposed site is Barstow, California, and the soil properties, seismic zone, wind, temperature range, ice and snow for the area are given. For 1, 10, and 25 MWt unified heliostat arrays, aspect ratios are given for various plan views and elevations. Designs are sketched for three existing inclined structures. The relative advantages and disadvantages of concrete, steel, and timber are briefly outlined. Several design factors are presented, and the basic design concepts and some construction details are given. Possible changes in steel tonnage in the design, and cost estimates are presented. (LEW)

  11. Microreactor Array Device

    PubMed Central

    Wiktor, Peter; Brunner, Al; Kahn, Peter; Qiu, Ji; Magee, Mitch; Bian, Xiaofang; Karthikeyan, Kailash; LaBaer, Joshua

    2015-01-01

    We report a device to fill an array of small chemical reaction chambers (microreactors) with reagent and then seal them using pressurized viscous liquid acting through a flexible membrane. The device enables multiple, independent chemical reactions involving free floating intermediate molecules without interference from neighboring reactions or external environments. The device is validated by protein expressed in situ directly from DNA in a microarray of ~10,000 spots with no diffusion during three hours incubation. Using the device to probe for an autoantibody cancer biomarker in blood serum sample gave five times higher signal to background ratio compared to standard protein microarray expressed on a flat microscope slide. Physical design principles to effectively fill the array of microreactors with reagent and experimental results of alternate methods for sealing the microreactors are presented. PMID:25736721

  12. Microreactor Array Device

    NASA Astrophysics Data System (ADS)

    Wiktor, Peter; Brunner, Al; Kahn, Peter; Qiu, Ji; Magee, Mitch; Bian, Xiaofang; Karthikeyan, Kailash; Labaer, Joshua

    2015-03-01

    We report a device to fill an array of small chemical reaction chambers (microreactors) with reagent and then seal them using pressurized viscous liquid acting through a flexible membrane. The device enables multiple, independent chemical reactions involving free floating intermediate molecules without interference from neighboring reactions or external environments. The device is validated by protein expressed in situ directly from DNA in a microarray of ~10,000 spots with no diffusion during three hours incubation. Using the device to probe for an autoantibody cancer biomarker in blood serum sample gave five times higher signal to background ratio compared to standard protein microarray expressed on a flat microscope slide. Physical design principles to effectively fill the array of microreactors with reagent and experimental results of alternate methods for sealing the microreactors are presented.

  13. Microreactor array device.

    PubMed

    Wiktor, Peter; Brunner, Al; Kahn, Peter; Qiu, Ji; Magee, Mitch; Bian, Xiaofang; Karthikeyan, Kailash; LaBaer, Joshua

    2015-01-01

    We report a device to fill an array of small chemical reaction chambers (microreactors) with reagent and then seal them using pressurized viscous liquid acting through a flexible membrane. The device enables multiple, independent chemical reactions involving free floating intermediate molecules without interference from neighboring reactions or external environments. The device is validated by protein expressed in situ directly from DNA in a microarray of ~10,000 spots with no diffusion during three hours incubation. Using the device to probe for an autoantibody cancer biomarker in blood serum sample gave five times higher signal to background ratio compared to standard protein microarray expressed on a flat microscope slide. Physical design principles to effectively fill the array of microreactors with reagent and experimental results of alternate methods for sealing the microreactors are presented. PMID:25736721

  14. Dynamics of Nucleosome Arrays

    NASA Astrophysics Data System (ADS)

    Poirier, Michael

    2007-03-01

    DNA sites wrapped into chromatin are sterically occluded from proteins that must bind for processes such as RNA transcription and DNA repair. However, the role of chromatin compaction in biological function is poorly understood. To understand the biological functions of chromatin compaction, we constructed nucleosome arrays that are built with a tandem repeat of high affinity nucleosome positioning sequences, which contain probes for DNA accessibility and chromatin structure. I will describe our results that use restriction enzyme digestion and fluorescence resonance energy transfer to determine the probability for DNA site exposure within compacted nucleosome arrays and the time scale for changes in chromatin compaction. I will then discuss how these results help explain how proteins gain access to DNA sites buried within chromatin.

  15. Array Transposition in SSD

    NASA Technical Reports Server (NTRS)

    Bailey, David H.; Kutler, Paul (Technical Monitor)

    1989-01-01

    One obstacle to running very large two- and three-dimensional codes on the Cray X-MP and Y-MP systems is to efficiently perform array transpositions using SSD storage. This article discusses how such transpositions can be performed by means of algorithms that feature exclusively unit stride, long vector transfers between main memory and SSD, and which only require a single pass through the data (provided sufficient main memory buffers are available).

  16. Array Transposition in SSD

    NASA Technical Reports Server (NTRS)

    Bailey, David H.; Kutler, Paul (Technical Monitor)

    1998-01-01

    One obstacle to running very large two- and three-dimensional codes on the Cray X-MP and Y-MP systems is to efficiently perform array transpositions using SSD storage. This article discusses how such transpositions can be performed by means of algorithms that feature exclusively unit stride, long vector transfers between main memory and SSD, and which only require a single pass through the data (provided sufficient main memory buffers are available).

  17. The CHARA optical array

    NASA Technical Reports Server (NTRS)

    Mcalister, Harold A.

    1992-01-01

    The Center for High Angular Resolution Astronomy (CHARA) was established in the College of Arts and Sciences at Georgia State University in 1984 with the goals of designing, constructing, and then operating a facility for very high spatial resolution astronomy. The interest in such a facility grew out of the participants' decade of activity in speckle interferometry. Although speckle interferometry continues to provide important astrophysical measurements of a variety of objects, many pressing problems require resolution far beyond that which can be expected from single aperture telescopes. In early 1986, CHARA received a grant from the National Science Foundation which has permitted a detailed exploration of the feasibility of constructing a facility which will provide a hundred-fold increase in angular resolution over what is possible by speckle interferometry at the largest existing telescopes. The design concept for the CHARA Array was developed initially with the contractural collaboration of United Technologies Optical Systems, Inc., in West Palm Beach, Florida, an arrangement that expired in August 1987. In late November 1987, the Georgia Tech Research Institute joined with CHARA to continue and complete the design concept study. Very high-resolution imaging at optical wavelengths is clearly coming of age in astronomy. The CHARA Array and other related projects will be important and necessary milestones along the way toward the development of a major national facility for high-resolution imaging--a true optical counterpart to the Very Large Array. Ground-based arrays and their scientific output will lead to high resolution facilities in space and, ultimately, on the Moon.

  18. The Murchison Widefield Array

    E-print Network

    Mitchell, Daniel A; Ord, Stephen M; Bernardi, Gianni; Wayth, Randall B; Edgar, Richard G; Clark, Michael A; Dal, Kevin; Pfister, Hanspeter; Gleadow, Stewart J; Arcus, W; Briggs, F H; Benkevitch, L; Bowman, J D; Bunton, J D; Burns, S; Cappallo, R J; Corey, B E; de Oliveira-Costa, A; Desouza, L; Doeleman, S S; Derome, M F; Emrich, D; Glossop, M; Goeke, R; Krishna, M R Gopala; Hazelton, B; Herne, D E; Hewitt, J N; Kamini, P A; Kaplan, D L; Kasper, J C; Kincaid, B B; Kocz, J; Kowald, E; Kratzenberg, E; Kumar, D; Lonsdale, C J; Lynch, M J; Madhavi, S; Matejek, M; McWhirter, S R; Morales, M F; Morgan, E; Oberoi, D; Pathikulangara, J; Prabu, T; Rogers, A; Salah, J E; Sault, R J; Shankar, N Udaya; Srivani, K S; Stevens, J; Tingay, S J; Vaccarella, A; Waterson, M; Webster, R L; Whitney, A R; Williams, A; Williams, C

    2010-01-01

    It is shown that the excellent Murchison Radio-astronomy Observatory site allows the Murchison Widefield Array to employ a simple RFI blanking scheme and still calibrate visibilities and form images in the FM radio band. The techniques described are running autonomously in our calibration and imaging software, which is currently being used to process an FM-band survey of the entire southern sky.

  19. Phased array antenna control

    NASA Technical Reports Server (NTRS)

    Doland, G. D. (inventor)

    1978-01-01

    Several new and useful improvements in steering and control of phased array antennas having a small number of elements, typically on the order of 5 to 17 elements are provided. Among the improvements are increasing the number of beam steering positions, reducing the possibility of phase transients in signals received or transmitted with the antennas, and increasing control and testing capacity with respect to the antennas.

  20. Fluorescence Based Sensor Arrays

    Microsoft Academic Search

    Roberto Paolesse; Donato Monti; Francesca Dini; Corrado Di Natale

    \\u000a Fluorescence-based cross reactive sensor arrays have experienced significant development in the last decade because of the\\u000a advantages that they can offer with respect to other transduction mechanisms, in terms of the usual performance parameters\\u000a such as sensitivity, selectivity and so on. From this point of view, a great impulse to this development has been due to the\\u000a realization of novel

  1. Photovoltaic cell array

    NASA Technical Reports Server (NTRS)

    Eliason, J. T. (inventor)

    1976-01-01

    A photovoltaic cell array consisting of parallel columns of silicon filaments is described. Each fiber is doped to produce an inner region of one polarity type and an outer region of an opposite polarity type to thereby form a continuous radial semi conductor junction. Spaced rows of electrical contacts alternately connect to the inner and outer regions to provide a plurality of electrical outputs which may be combined in parallel or in series.

  2. Solid state neutron detector array

    DOEpatents

    Seidel, John G. (Pittsburgh, PA); Ruddy, Frank H. (Monroeville, PA); Brandt, Charles D. (Mount Lebanon, PA); Dulloo, Abdul R. (Pittsburgh, PA); Lott, Randy G. (Pittsburgh, PA); Sirianni, Ernest (Monroeville, PA); Wilson, Randall O. (Greensburg, PA)

    1999-01-01

    A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors.

  3. Solid state neutron detector array

    DOEpatents

    Seidel, J.G.; Ruddy, F.H.; Brandt, C.D.; Dulloo, A.R.; Lott, R.G.; Sirianni, E.; Wilson, R.O.

    1999-08-17

    A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors. 7 figs.

  4. Spaceborne Processor Array

    NASA Technical Reports Server (NTRS)

    Chow, Edward T.; Schatzel, Donald V.; Whitaker, William D.; Sterling, Thomas

    2008-01-01

    A Spaceborne Processor Array in Multifunctional Structure (SPAMS) can lower the total mass of the electronic and structural overhead of spacecraft, resulting in reduced launch costs, while increasing the science return through dynamic onboard computing. SPAMS integrates the multifunctional structure (MFS) and the Gilgamesh Memory, Intelligence, and Network Device (MIND) multi-core in-memory computer architecture into a single-system super-architecture. This transforms every inch of a spacecraft into a sharable, interconnected, smart computing element to increase computing performance while simultaneously reducing mass. The MIND in-memory architecture provides a foundation for high-performance, low-power, and fault-tolerant computing. The MIND chip has an internal structure that includes memory, processing, and communication functionality. The Gilgamesh is a scalable system comprising multiple MIND chips interconnected to operate as a single, tightly coupled, parallel computer. The array of MIND components shares a global, virtual name space for program variables and tasks that are allocated at run time to the distributed physical memory and processing resources. Individual processor- memory nodes can be activated or powered down at run time to provide active power management and to configure around faults. A SPAMS system is comprised of a distributed Gilgamesh array built into MFS, interfaces into instrument and communication subsystems, a mass storage interface, and a radiation-hardened flight computer.

  5. Hexagonal Mirror Array

    NASA Technical Reports Server (NTRS)

    1999-01-01

    NASA's Space Optics Manufacturing Technology Center has been working to expand our view of the universe via sophisticated new telescopes. The Optics Center's goal is to develop low-cost, advanced space optics technologies for the NASA program in the 21st century, including the long-term goal of imaging Earth-like planets in distant solar systems. A segmented array of mirrors was designed by the Space Optics Manufacturing Technology Center for solar the concentrator test stand at the Marshall Space Flight Center (MSFC) for powering solar thermal propulsion engines. Each hexagon mirror has a spherical surface to approximate a parabolic concentrator when combined into the entire 18-foot diameter array. The aluminum mirrors were polished with a diamond turning machine, that creates a glass-like reflective finish on metal. The precision fabrication machinery at the Space Optics Manufacturing Technology Center at MSFC can polish specialized optical elements to a world class quality of smoothness. This image shows optics physicist, Vince Huegele, examining one of the 144-segment hexagonal mirrors of the 18-foot diameter array at the MSFC solar concentrator test stand.

  6. Hexagonal Mirror Array

    NASA Technical Reports Server (NTRS)

    1999-01-01

    NASA's Space Optics Manufacturing Technology Center has been working to expand our view of the universe via sophisticated new telescopes. The Optics Center's goal is to develop low-cost, advanced space optics technologies for the NASA program in the 21st century, including the long-term goal of imaging Earth-like planets in distant solar systems. A segmented array of mirrors was designed by the Space Optics Manufacturing Technology Center for the solar concentrator test stand at the Marshall Space Flight Center (MSFC) for powering solar thermal propulsion engines. Each hexagon mirror has a spherical surface to approximate a parabolic concentrator when combined into the entire 18-foot diameter array. The aluminum mirrors were polished with a diamond turning machine that creates a glass-like reflective finish on metal. The precision fabrication machinery at the Space Optics Manufacturing Technology Center at MSFC can polish specialized optical elements to a world class quality of smoothness. This image shows optics physicist, Vince Huegele, examining one of the 144-segment hexagonal mirrors of the 18-foot diameter array at the MSFC solar concentrator test stand.

  7. Mir Cooperative Solar Array

    NASA Technical Reports Server (NTRS)

    Skor, Mike; Hoffman, Dave J.

    1997-01-01

    The Mir Cooperative Solar Array (MCSA), produced jointly by the United States and Russia, was deployed on the Mir Russian space station on May 25, 1996. The MCSA is a photovoltaic electrical power system that can generate up to 6 kW. The power from the MCSA is needed to extend Mir's lifetime and to support experiments conducted there by visiting U.S. astronauts. The MCSA was brought to Mir via the Space Shuttle Atlantis on the STS-74 mission, launched November 12, 1995. This cooperative venture combined the best technology of both countries: the United States provided high-efficiency, lightweight photovoltaic panel modules, whereas Russia provided the array structure and deployment mechanism. Technology developed in the Space Station Freedom Program, and now being used in the International Space Station, was used to develop MCSA's photovoltaic panel. Performance data obtained from MCSA operation on Mir will help engineers better understand the performance of the photovoltaic panel modules in orbit. This information will be used to more accurately predict the performance of the International Space Station solar arrays. Managed by the NASA Lewis Research Center for NASA's International Space Station Program Office in Houston, Texas, the MCSA Project was completed on time and under budget despite a very aggressive schedule.

  8. DSN Array Simulator

    NASA Technical Reports Server (NTRS)

    Tikidjian, Raffi; Mackey, Ryan

    2008-01-01

    The DSN Array Simulator (wherein 'DSN' signifies NASA's Deep Space Network) is an updated version of software previously denoted the DSN Receive Array Technology Assessment Simulation. This software (see figure) is used for computational modeling of a proposed DSN facility comprising user-defined arrays of antennas and transmitting and receiving equipment for microwave communication with spacecraft on interplanetary missions. The simulation includes variations in spacecraft tracked and communication demand changes for up to several decades of future operation. Such modeling is performed to estimate facility performance, evaluate requirements that govern facility design, and evaluate proposed improvements in hardware and/or software. The updated version of this software affords enhanced capability for characterizing facility performance against user-defined mission sets. The software includes a Monte Carlo simulation component that enables rapid generation of key mission-set metrics (e.g., numbers of links, data rates, and date volumes), and statistical distributions thereof as functions of time. The updated version also offers expanded capability for mixed-asset network modeling--for example, for running scenarios that involve user-definable mixtures of antennas having different diameters (in contradistinction to a fixed number of antennas having the same fixed diameter). The improved version also affords greater simulation fidelity, sufficient for validation by comparison with actual DSN operations and analytically predictable performance metrics.

  9. Weld quality evaluation using a high temperature SQUID array

    SciTech Connect

    Clark, D. D. (David D.); Espy, M. A. (Michelle A.); Kraus, Robert H., Jr.; Matlachov, A. N. (Andrei N.); Lamb, J. S. (Jessica S.)

    2002-01-01

    This paper presents preliminary data for evaluating weld quality using high temperature SQUIDS. The SQUIDS are integrated into an instrument known as the SQUID Array Microscope, or SAMi. The array consists of ll SQUIDs evenly distributed over an 8.25 mm baseline. Welds are detected using SAMi by using an on board coil to induce eddy currents in a conducting sample and measuring the resulting magnetic fields. The concept is that the induced magnetic fields will differ in parts of varying weld quality. The data presented here was collected from three stainless steel parts using SAMi. Each part was either solid, included a good weld, or included a bad weld. The induced magnetic field's magnitude and phase relative to the induction signal were measured. For each sample considered, both the magnitude and phase data were measurably different than the other two samples. These results indicate that it is possible to use SAMi to evaluate weld quality.

  10. Passive microfluidic array card and reader

    Microsoft Academic Search

    Lawrence Christopher Dugan; Matthew A. Coleman

    2011-01-01

    A microfluidic array card and reader system for analyzing a sample. The microfluidic array card includes a sample loading section for loading the sample onto the microfluidic array card, a multiplicity of array windows, and a transport section or sections for transporting the sample from the sample loading section to the array windows. The microfluidic array card reader includes a

  11. Modeling high gradient magnetic separation from biological fluids.

    SciTech Connect

    Bockenfeld, D.; Chen, H.; Rempfer, D.; Kaminski, M. D.; Rosengart, A. J.; Chemical Engineering; Illinois Inst. of Tech.; Univ. of Chicago, Pritzker School of Medicine

    2006-01-01

    A proposed portable magnetic separator consists of an array of biocompatible capillary tubing and magnetizable wires immersed in an externally applied homogeneous magnetic field. While subject to the homogeneous magnetic field, the wires create high magnetic field gradients, which aid in the collection of blood-borne magnetic nanospheres from blood flow. In this study, a 3-D numerical model was created using COMSOL Multiphysics 3.2 software to determine the configuration of the wire-tubing array from two possible configurations, one being an array with rows alternating between wires and tubing, and the other being an array where wire and tubing alternate in two directions. The results demonstrated that the second configuration would actually capture more of the magnetic spheres. Experimental data obtained by our group support this numerical result.

  12. The Expanded Owens Valley Solar Array (EOVSA)

    NASA Astrophysics Data System (ADS)

    Gary, Dale E.; Hurford, Gordon J.; Nita, Gelu M.; White, Stephen M.; McTiernan, James; Fleishman, Gregory D.

    2014-06-01

    The Expanded Owens Valley Solar Array (EOVSA) near Big Pine, CA is undergoing commissioning as a solar-dedicated microwave imaging array operating in the frequency range 2.5-18 GHz. The solar science to be addressed focuses on the 3D structure of the solar corona (magnetic field, temperature and density), and on the particle acceleration, transport and heating in solar flares. The project will support the scientific community by providing open data access and software tools for analysis and modeling of the data, to exploit synergies with on-going solar research in other wavelengths. The array consists of a total of 15 antennas, including the two 27-m antennas with He-cooled receivers for sensitive calibration, and thirteen 2.1-m antennas that each view the entire disk of the Sun. The system includes a completely new control system, broadband signal transmission, and high-speed digital signal processing, using new technology developed for the Frequency Agile Solar Radiotelescope (FASR). We present an overview of the instrument, the current status of commissioning activities, and some initial observations to assess performance.This research is supported by NSF grants AST-1312802, and NASA grants NNX11AB49G and NNX10AF27G to New Jersey Institute of Technology.

  13. Fabrication of Microshutter Arrays for James Webb Space Telescope

    NASA Technical Reports Server (NTRS)

    Li, Mary J.; Zheng, Yun; Hess, Larry; Hu, Ron; Kelly, Dan; Lynch, Barney; Oh, Lance; Ray, Chris; Smith, Wayne; Babu, Sachi

    2004-01-01

    Two-dimensional MEMS microshutter arrays are being developed at NASA Goddard Space Flight Center for use in the near-infrared region on the Next Generation Space Telescope (NGST). The microshutter arrays are designed for the selective transmission of light with high efficiency and high contrast. The NGST environment requires cryogenic operation at 45K. Microshutter arrays are fabricated out of silicon-oxide-insulated (SOI) silicon wafers. Arrays are close-packed silicon nitride membranes with a pixel size of 100x100 microns. Individual shutters are patterned with a torsion flexure permitting shutters to open 90 degrees with a minimized mechanical stress concentration. The mechanical shutter arrays are fabricated using MEMS technologies. The processing includes a multi-layer metal deposition and patterning of shutter electrodes and magnetic pads, reactive ion etching (RE) of the front side to form shutters out of the nitride membrane, an anisotropic back-etch for wafer thinning, followed by a deep RIE (DRIE) back-etch down to the nitride shutter membrane to form frames and relieve shutters from the silicon substrate. An additional metal deposition and patterning is used to form back electrodes. Shutters are actuated using a magnetic force and latched using an electrostatic force.

  14. Abstract--This paper presents the design of an array composed of 5 5 digital electromagnetic actuators which each

    E-print Network

    Paris-Sud XI, Université de

    of a previous study and secondly, the array is designed by taking into account the magnetic and electromagnetic while considering the magnetic and electromagnetic interactions between the elementary actuators. II. ELEMENTARY DIGITAL ACTUATOR A. Principle The elementary actuator is composed of five Permanent Magnets (PMs

  15. Studies of the Dynamics of Ablation Stream development in Wire Arrays on COBRA

    NASA Astrophysics Data System (ADS)

    Greenly, John; Martin, Matthew; Seyler, Charles

    2007-11-01

    Wire-array simulations with the 3D GORGON code (see adjoining poster by Martin et al.) show a characteristic evolution in the development of streams of ablated material ejected from the wires toward the array axis. In simulations of aluminum arrays, the fundamental behavior occurs in two steps. The first is the development of coronal plasma that is trapped around the wire core in closed ``local'' magnetic flux. This coronal plasma, together with the closed flux, is then accelerated inward after a certain ``dwell'' time, leaving behind a radially distributed current density with entirely open ``global'' magnetic field lines, producing smooth, distributed acceleration of ablated plasma inward from the wire core until the onset of the final implosion. Interpretation of these dynamics in terms of simple physical modeling will be discussed, and experimental evidence of these phenomena from imaging and magnetic field diagnostics on arrays on the COBRA facility at Cornell will be presented.

  16. Target localization techniques for vehicle-based electromagnetic induction array applications

    NASA Astrophysics Data System (ADS)

    Miller, Jonathan S.; Schultz, Gregory M.; Shubitidze, Fridon; Marble, Jay A.

    2010-04-01

    State-of-the-art electromagnetic induction (EMI) arrays provide significant capability enhancement to landmine, unexploded ordnance (UXO), and buried explosives detection applications. Arrays that are easily configured for integration with a variety of mobile platforms offer improved safety and efficiency to personnel conducting detection operations including site remediation, explosive ordnance disposal, and humanitarian demining missions. We present results from an evaluation of two vehicle-based frequency domain EMI arrays. Our research includes implementation of a simple circuit model to estimate target location from sensor measurements of the scattered vertical magnetic field component. Specifically, we characterize any conductive or magnetic target using a set of parameters that describe the eddy current and magnetic polarizations induced about a set of orthogonal axes. Parameter estimations are based on the fundamental resonance mode of a series inductance and resistance circuit. This technique can be adapted to a variety of EMI array configurations, and thus offers target localization capabilities to a number of applications.

  17. Magnetism and Magnetic Properties

    NSDL National Science Digital Library

    Roberta Schneck

    2011-10-13

    Students will identify properties of magnetism and begin to develop understanding of their practical applications. Students will also begin to develop understanding of the essential nature of Earth's magnetic fields.

  18. The kilopixel array pathfinder project (KAPPa), a 16-pixel integrated heterodyne focal plane array: characterization of the single pixel prototype

    NASA Astrophysics Data System (ADS)

    Wheeler, Caleb H.; Groppi, Christopher E.; Mani, Hamdi; McGarey, Patrick; Kuenzi, Linda; Weinreb, Sander; Russell, Damon S.; Kooi, Jacob W.; Lichtenberger, Arthur W.; Walker, Christopher K.; Kulesa, Craig

    2014-07-01

    We report on the laboratory testing of KAPPa, a 16-pixel proof-of-concept array to enable the creation THz imaging spectrometer with ~1000 pixels. Creating an array an order of magnitude larger than the existing state of the art of 64 pixels requires a simple and robust design as well as improvements to mixer selection, testing, and assembly. Our testing employs a single pixel test bench where a novel 2D array architecture is tested. The minimum size of the footprint is dictated by the diameter of the drilled feedhorn aperture. In the adjoining detector block, a 6mm × 6mm footprint houses the SIS mixer, LNA, matching and bias networks, and permanent magnet. We present an initial characterization of the single pixel prototype using a computer controlled test bench to determine Y-factors for a parameter space of LO power, LO frequency, IF bandwidth, magnet field strength, and SIS bias voltage. To reduce the need to replace poorly preforming pixels that are already mounted in a large format array, we show techniques to improve SIS mixer selection prior to mounting in the detector block. The 2D integrated 16-pixel array design has been evolved as we investigate the properties of the single pixel prototype. Carful design of the prototype has allowed for rapid translation of single pixel design improvements to be easily incorporated into the 16-pixel model.

  19. Diode laser array

    NASA Technical Reports Server (NTRS)

    Carlson, Nils W. (Inventor); Evans, Gary A. (Inventor); Kaiser, Charlie J. (Inventor)

    1990-01-01

    A diode laser array comprises a substrate of a semiconductor material having first and second opposed surfaces. On the first surface is a plurality of spaced gain sections and a separate distributed Bragg reflector passive waveguide at each end of each gain section and optically connecting the gain sections. Each gain section includes a cavity therein wherein charge carriers are generated and recombine to generate light which is confined in the cavity. Also, the cavity, which is preferably a quantum well cavity, provides both a high differential gain and potentially large depth of loss modulation. Each waveguide has a wavelength which is preferably formed by an extension of the cavity of the gain sections and a grating. The grating has a period which provides a selective feedback of light into the gain sections to supporting lasing, which allows some of the light to be emitted from the waveguide normal to the surface of the substrate and which allows optical coupling of the gain sections. Also, the grating period provides an operating wavelength which is on the short wavelength side of the gain period of the gain sections required for laser oscillation. An RF pulse is applied so as to maximize the magnitude of the loss modulation and the differential gain in the gain sections. The array is operated by applying a DC bias to all the gain sections at a level just below the threshold of the gain sections to only one of the gain sections which raises the bias in all of the gain sections to a level that causes all of the gain sections to oscillate. Thus, a small bias can turn the array on and off.

  20. Phased array ghost elimination

    PubMed Central

    Kellman, Peter; McVeigh, Elliot R.

    2007-01-01

    Parallel imaging may be applied to cancel ghosts caused by a variety of distortion mechanisms, including distortions such as off-resonance or local flow, which are space variant. Phased array combining coefficients may be calculated that null ghost artifacts at known locations based on a constrained optimization, which optimizes SNR subject to the nulling constraint. The resultant phased array ghost elimination (PAGE) technique is similar to the method known as sensitivity encoding (SENSE) used for accelerated imaging; however, in this formulation is applied to full field-of-view (FOV) images. The phased array method for ghost elimination may result in greater flexibility in designing acquisition strategies. For example, in multi-shot EPI applications ghosts are typically mitigated by the use of an interleaved phase encode acquisition order. An alternative strategy is to use a sequential, non-interleaved phase encode order and cancel the resultant ghosts using PAGE parallel imaging. Cancellation of ghosts by means of phased array processing makes sequential, non-interleaved phase encode acquisition order practical, and permits a reduction in repetition time, TR, by eliminating the need for echo-shifting. Sequential, non-interleaved phase encode order has benefits of reduced distortion due to off-resonance, in-plane flow and EPI delay misalignment. Furthermore, the use of EPI with PAGE has inherent fat-water separation and has been used to provide off-resonance correction using a technique referred to as lipid elimination with an echo-shifting N/2-ghost acquisition (LEENA), and may further generalized using the multi-point Dixon method. Other applications of PAGE include cancelling ghosts which arise due to amplitude or phase variation during the approach to steady state. Parallel imaging requires estimates of the complex coil sensitivities. In vivo estimates may be derived by temporally varying the phase encode ordering to obtain a full k-space dataset in a scheme similar to the autocalibrating TSENSE method. This scheme is a generalization of the UNFOLD method used for removing aliasing in undersampled acquisitions. The more general scheme may be used to modulate each EPI ghost image to a separate temporal frequency as described in this paper. PMID:16705636

  1. Optimum FIR array filters

    NASA Astrophysics Data System (ADS)

    Williamson, Darrell; Musumeci, Phillip C.; Teo, Kok Lay

    1988-08-01

    An optimum finite impulse response (FIR) filter bank is derived that recovers a desired signal from an array of sensors in the presence of random sensor noise and one or more coherent interfering noise sources. The required filter order is determined by the relative delays between the signal and coherent noise at each sensor, and is independent of the time duration of either the signal or coherent noise. Usually, the presence of only three sensors is sufficient to be able to eliminate the effect of coherent noise sources provided the filter order M is sufficiently large.

  2. A ‘global fit’ method for analysis of angular precession measurements at large Ge ? arrays

    Microsoft Academic Search

    L. Weissman; M. Hass; N. Benczer-Koller; C. Broude; G. Kumbartzki

    1998-01-01

    The recent availability of large ?-ray arrays has opened new domains in experiments for measurements of magnetic moments. The study of oblate structures in heavy nuclei as well as of superdeformed bands are good examples of the new nuclear regions that have become amenable to the transient field magnetic moment measurements. These measurements are very difficult to perform even with

  3. 3D MHD simulations of radial wire arrays

    NASA Astrophysics Data System (ADS)

    Jennings, C.; Ampleford, D.; Ciardi, A.; Chittenden, J.; Bland, S.; Niasse, N.

    2008-04-01

    We present 3D resistive MHD simulations evaluating multi-MA radial wire arrays as a potential compact, high intensity source for inertial confinement fusion and laboratory astrophysics. A radial wire array consists of wires running radially outwards from a central electrode, and was first investigated at the 1 MA level on the MAGPIE generator at Imperial College. Originally used as a method of producing magnetic tower laboratory jets relevant to astrophysics[1], they have also shown potential as a high power x-ray source. Able to produce x-ray pulses with a rise time and peak power comparable to cylindrical wire arrays, radial arrays occupy a smaller volume and may consequently be able to access higher power densities. We discuss simulation results reproducing radial array experiments performed on the MAGPIE facility as a means of benchmarking our model. This model is then used to evaluate radial wire arrays in the multi-MA regime for planned experiments on the Saturn generator of Sandia National Laboratories. [1] A. Ciardi et al, Phys. Plasmas 14, 056501 (2007)

  4. STRUCTURE AND MAGNETIC FIELDS IN THE PRECESSING JET SYSTEM SS 433. III. EVOLUTION OF THE INTRINSIC BRIGHTNESS OF THE JETS FROM A DEEP MULTI-EPOCH VERY LARGE ARRAY CAMPAIGN

    SciTech Connect

    Bell, Michael R.; Roberts, David H.; Wardle, John F. C., E-mail: mrbell@mpa-garching.mpg.de, E-mail: roberts@brandeis.edu, E-mail: wardle@brandeis.edu [Department of Physics, MS-057, Brandeis University, 415 South Street, Waltham, MA 02453 (United States)

    2011-08-01

    We present a sequence of five deep observations of SS 433 made over the summer of 2007 using the Very Large Array in the A configuration at 5 and 8 GHz. In this paper, we study the brightness profiles of the jets and their time evolution. We also examine the spectral index distribution in the source. We find (as previously reported from the analysis of a single earlier image) that the profiles of the east and west jets are remarkably similar if projection and Doppler beaming are taken into account. The sequence of five images allows us to disentangle the evolution of brightness of individual pieces of jet from the variations of jet power originating at the core. We find that the brightness of each piece of the jet fades as an exponential function of age (or distance from the core), e{sup -}{tau}/{tau}{sup '}, where {tau} is the age at emission and {tau}' = 55.9 {+-} 1.7 days. This evolutionary model describes both the east and west jets equally well. There is also significant variation (by a factor of at least five) in jet power with birth epoch, with the east and west jets varying in synchrony. The lack of deceleration between the scale of the optical Balmer line emission (10{sup 15} cm) and that of the radio emission (10{sup 17} cm) requires that the jet material is much denser than its surroundings. We find that the density ratio must exceed 300:1.

  5. Electrode array for neural stimulation

    DOEpatents

    Wessendorf, Kurt O. (Albuquerque, NM); Okandan, Murat (Edgewood, NM); Stein, David J. (Albuquerque, NM); Yang, Pin (Albuquerque, NM); Cesarano, III, Joseph (Albuquerque, NM); Dellinger, Jennifer (Albuquerque, NM)

    2011-08-16

    An electrode array for neural stimulation is disclosed which has particular applications for use in a retinal prosthesis. The electrode array can be formed as a hermetically-sealed two-part ceramic package which includes an electronic circuit such as a demultiplexer circuit encapsulated therein. A relatively large number (up to 1000 or more) of individually-addressable electrodes are provided on a curved surface of a ceramic base portion the electrode array, while a much smaller number of electrical connections are provided on a ceramic lid of the electrode array. The base and lid can be attached using a metal-to-metal seal formed by laser brazing. Electrical connections to the electrode array can be provided by a flexible ribbon cable which can also be used to secure the electrode array in place.

  6. Electrodynamic Arrays Having Nanomaterial Electrodes

    NASA Technical Reports Server (NTRS)

    Trigwell, Steven (Inventor); Biris, Alexandru S. (Inventor); Calle, Carlos I. (Inventor)

    2013-01-01

    An electrodynamic array of conductive nanomaterial electrodes and a method of making such an electrodynamic array. In one embodiment, a liquid solution containing nanomaterials is deposited as an array of conductive electrodes on a substrate, including rigid or flexible substrates such as fabrics, and opaque or transparent substrates. The nanomaterial electrodes may also be grown in situ. The nanomaterials may include carbon nanomaterials, other organic or inorganic nanomaterials or mixtures.

  7. A mask programmable DSP array

    Microsoft Academic Search

    R. D. Albon; G. E. Floyd; J. E. Coles

    1989-01-01

    A 125000-gate 1.4-?m CMOS DSP (digital signal processor) array, which offers single-chip solutions for functions such as convolution and fast Fourier transforms, is described. High performance is obtained using full-custom RAM and multipliers, and the required system function is achieved by configuring a conventional gate array. Examples of possible applications include two standard products already designed using the DSP array.

  8. Solid state image sensing arrays

    NASA Technical Reports Server (NTRS)

    Sadasiv, G.

    1972-01-01

    The fabrication of a photodiode transistor image sensor array in silicon, and tests on individual elements of the array are described along with design for a scanning system for an image sensor array. The spectral response of p-n junctions was used as a technique for studying the optical-absorption edge in silicon. Heterojunction structures of Sb2S3- Si were fabricated and a system for measuring C-V curves on MOS structures was built.

  9. Active membrane phased array radar

    NASA Technical Reports Server (NTRS)

    Moussessian, Alina; Del Castillo, Linda; Huang, John; Sadowy, Greg; Hoffman, James; Smith, Phil; Hatake, Toshiro; Derksen, Chuck; Lopez, Bernardo; Caro, Ed

    2005-01-01

    We have developed the first membrane-based active phased array in L-band (1.26GHz). The array uses membrane compatible Transmit/Receive (T/R) modules (membrane T/R) for each antenna element. We use phase shifters within each T/R module for electronic beam steering. We will discuss the T/R module design and integration with the membrane, We will also present transmit and receive beam-steering results for the array.

  10. Finite size effect on spread of resonance frequencies in arrays of coupled vortices

    SciTech Connect

    Vogel, Andreas; Drews, André; Im, Mi-Young; Fischer, Peter; Meier, Guido

    2011-01-25

    Dynamical properties of magnetic vortices in arrays of magnetostatically coupled ferromagnetic disks are studied by means of a broadband ferromagnetic-resonance (FMR) setup. Magnetic force microscopy and magnetic transmission soft X-ray microscopy are used to image the core polarizations and the chiralities which are both found to be randomly distributed. The resonance frequency of vortex-core motion strongly depends on the magnetostatic coupling between the disks. The parameter describing the relative broadening of the absorption peak observed in the FMR transmission spectra for a given normalized center-to-center distance between the elements is shown to depend on the size of the array.

  11. The Askaryan radio array

    NASA Astrophysics Data System (ADS)

    Meures, Thomas; ARA Collaboration

    2013-05-01

    The Askar'yan Radio Array (ARA), a neutrino detector to be situated at the South Pole next to the IceCube detector, will be sensitive to ultrahigh-energy cosmic neutrinos above 0.1 EeV and will have the greatest sensitivity within the favored energy range from 0.1 EeV up to 10 EeV. Neutrinos of this energy are guaranteed by current observations of the GZK-cutoff by the HiRes and Pierre Auger Observatories. The detection method is based on Cherenkov emission by a neutrino induced cascade in the ice, coherent at radio wavelengths, which was predicted by Askar'yan in 1962 and verified in beam tests at SLAC in 2006. The detector is planned to consist of 37 stations with 16 antennas each, deployed at depths of up to 200 m under the ice surface. During the last two polar seasons (2010 - 2011, 2011 - 2012), a prototype station and a first detector station were successfully deployed and are taking data. These data have been and are currently being analyzed to study the ambient noise background and the radio frequency properties of the South Pole ice sheet. A worldwide collaboration is working on the planning, construction and data analysis of the detector array. This article will give a short report on the status of the ARA detector and show recent results from the recorded data.

  12. Analog pixel array detectors.

    PubMed

    Ercan, A; Tate, M W; Gruner, S M

    2006-03-01

    X-ray pixel array detectors (PADs) are generally thought of as either digital photon counters (DPADs) or X-ray analog-integrating pixel array detectors (APADs). Experiences with APADs, which are especially well suited for X-ray imaging experiments where transient or high instantaneous flux events must be recorded, are reported. The design, characterization and experimental applications of several APAD designs developed at Cornell University are discussed. The simplest design is a ;flash' architecture, wherein successive integrated X-ray images, as short as several hundred nanoseconds in duration, are stored in the detector chips for later off-chip digitization. Radiography experiments using a prototype flash APAD are summarized. Another design has been implemented that combines flash capability with the ability to continuously stream X-ray images at slower (e.g. milliseconds) rates. Progress is described towards radiation-hardened APADs that can be tiled to cover a large area. A mixed-mode PAD, design by combining many of the attractive features of both APADs and DPADs, is also described. PMID:16495611

  13. The Cherenkov Telescope Array

    NASA Astrophysics Data System (ADS)

    Jeffrey, Grube; Consortium, CTA

    2013-01-01

    The last few years have seen stunning results both from ground-based gamma-ray astronomy from H.E.S.S., MAGIC, and VERITAS as the imaging atmospheric Cherenkov technique has matured, and from space since the 2008 launch of the Fermi Gamma-ray Space Telescope. The Cherenkov Telescope Array (CTA) is a global collaboration formed to develop a next-generation ground-based array of imaging atmospheric Cherenkov telescopes with a significant advance in capabilities over current ground- and space-based telescopes. In particular, CTA aims to have a factor of 10 improvement in sensitivity in the core energy range of 100 GeV to some 10's TeV, a threshold energy well below 100 GeV, a factor of 3-5 improvement in angular resolution, and an effective area of at least several square kilometers for energies above 10 TeV. This talk will highlight some of the science drivers that motivate CTA, and discuss the status of the observatory’s development.

  14. A magnetic tunnel to shelter hyperpolarized fluids

    NASA Astrophysics Data System (ADS)

    Milani, Jonas; Vuichoud, Basile; Bornet, Aurélien; Miéville, Pascal; Mottier, Roger; Jannin, Sami; Bodenhausen, Geoffrey

    2015-02-01

    To shield solutions carrying hyperpolarized nuclear magnetization from rapid relaxation during transfer through low fields, the transfer duct can be threaded through an array of permanent magnets. The advantages are illustrated for solutions containing hyperpolarized 1H and 13C nuclei in a variety of molecules.

  15. A magnetic tunnel to shelter hyperpolarized fluids.

    PubMed

    Milani, Jonas; Vuichoud, Basile; Bornet, Aurélien; Miéville, Pascal; Mottier, Roger; Jannin, Sami; Bodenhausen, Geoffrey

    2015-02-01

    To shield solutions carrying hyperpolarized nuclear magnetization from rapid relaxation during transfer through low fields, the transfer duct can be threaded through an array of permanent magnets. The advantages are illustrated for solutions containing hyperpolarized (1)H and (13)C nuclei in a variety of molecules. PMID:25725861

  16. Studying the Magnetic Universe with the EVLA

    Microsoft Academic Search

    A. J. Beasley

    2000-01-01

    Magnetic fields are thought to be important in virtually all astrophysical contexts, but they are difficult to observe. Radio observations offer some of the few direct probes of the strength, structure, and topology of magnetic fields, including synchrotron emission, Zeeman splitting, and Faraday rotation. The Expanded Very Large Array (EVLA) will be an extremely sensitive instrument for measuring the distribution

  17. Nanoelectrode array for electrochemical analysis

    DOEpatents

    Yelton, William G. (Sandia Park, NM); Siegal, Michael P. (Albuquerque, NM)

    2009-12-01

    A nanoelectrode array comprises a plurality of nanoelectrodes wherein the geometric dimensions of the electrode controls the electrochemical response, and the current density is independent of time. By combining a massive array of nanoelectrodes in parallel, the current signal can be amplified while still retaining the beneficial geometric advantages of nanoelectrodes. Such nanoelectrode arrays can be used in a sensor system for rapid, non-contaminating field analysis. For example, an array of suitably functionalized nanoelectrodes can be incorporated into a small, integrated sensor system that can identify many species rapidly and simultaneously under field conditions in high-resistivity water, without the need for chemical addition to increase conductivity.

  18. Long Wavelength Array Station Architecture

    E-print Network

    Ellingson, Steven W.

    .1 Antenna (ANT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2 Array 4.3 Beamforming Unit (BFU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4 Monitoring & Control System (MCS) 20 6.1 Data Recorders

  19. Integrated residential photovoltaic array development

    NASA Technical Reports Server (NTRS)

    Shepard, N. F., Jr.

    1981-01-01

    An advanced, universally-mountable, integrated residential photovoltaic array concept was defined based upon an in-depth formulation and evaluation of three candidate approaches which were synthesized from existing or proposed residential array concepts. The impact of module circuitry and process sequence is considered and technology gaps and performance drivers associated with residential photovoltaic array concepts are identified. The actual learning experience gained from the comparison of the problem areas of the hexagonal shingle design with the rectangular module design led to what is considered an advanced array concept. Building the laboratory mockup provided actual experience and the opportunity to uncover additional technology gaps.

  20. Micrometeorite exposure of solar arrays

    NASA Astrophysics Data System (ADS)

    Weishaupt, U.; Kuczera, H.; Rott, M.

    1986-11-01

    Permanent losses of a part of the available power on solar arrays of ESA satellites, possibly caused by micrometeoroid or space debris impacts were studied in hypervelocity impact simulations at a plasma accelerator using ECS and Olympus solar panel structures. Results confirm that significant damage of the solar arrays can be caused by small hypervelocity particles. Using a solar array simulator connected to the test sample, penetration phenomena and arc triggering effects were investigated within the efficiency range of the accelerator. Temporary or permanent short circuits between the solar cells and the panel structure may lead to a loss of solar array power and additional damage may be created if arcing occurs.