Sample records for high field optical-pumping

  1. Thin film detection of High Energy Materials: Optical Pumping Approach

    CERN Document Server

    Barthwal, Sachin


    We present our work on High Energy Material detection based on thin film of Lithium using the phenomenon of Optical Pumping. The Li atoms present in the thin film are optically pumped to one of the ground hyperfine energy levels so that they can no more absorb light from the resonant light source. Now in presence of a RF signal, which quantifies the ambient magnetic field, this polarized atomic system is again randomized thus making it reabsorb the resonant light. This gives a quantified measurement of the magnetic field surrounding the thin film detector. This is then mapped to the presence of magnetic HEM and hence the HEM are detected. Our approach in this regard starts with verifying the stability of Lithium atoms in various solvents so as to get a suitable liquid medium to form a thin film. In this regard, various UV-visible characterization spectra are presented to finally approach a stable system for the detection. We have worked on around 10 polar and non- polar solvents to see the stability criteria....

  2. Study of spin-exchange optically pumped 3He cells with high polarisation and long lifetimes (United States)

    Parnell, S. R.; Babcock, E.; Nünighoff, K.; Skoda, M. W. A.; Boag, S.; Masalovich, S.; Chen, W. C.; Georgii, R.; Wild, J. M.; Frost, C. D.


    We present a detailed investigation into 3He neutron spin filter cells polarised by spin exchange optical pumping (SEOP). We include measurements of the absolute 3He polarisation using neutron transmission and characterisation of both the X-factor and 3He relaxation times ( T1) for a number of cells. For one cell we calculated a maximum 3He polarisation of 79% with a T1 of 633 h. The measured X-factor of this cell, X=0.17±0.01, is low. For all cells polarisations of >71% are observed. In addition we present 3He relaxation data for a new design of magneto-static cavity with a field of high homogeneity ΔB/B0≈3.5×10-4 cm-1. This compact device provides a magnetic field in an orientation suitable for in situ optical pumping that minimises the field inhomogeneity contribution to the T1 to 930 h in a 1 bar cell, the longest reported on beam thus far. The results suggest that high 3He polarisation with long relaxation times can now be routinely obtained with SEOP, enabling time independent incident beam polarisation to be easily implemented across many different neutron scattering instruments.

  3. High Power Optically Pumped Semiconductor Lasers for Sodium Guidestar Applications (United States)

    Hackett, Shawn


    Optically pumped semiconductor lasers (OPSLs) are shown to provide a much more compact and less expensive source for illumination of the sodium layer of the mesosphere for use as a sodium laser guidestar via single and two photon excitation schemes. This represents a revolution in laser guidestar technology as the cost, size, and power requirements for a laser guidestar system are shown to have been decreased by an order of magnitude with guidestar performance shown to be similar to previous sources. Sodium laser guidestar sources for broadband simultaneous illumination of multiple lines are developed and simulated. Simulations are then compared to actual returns for multi-line sodium laser guidestars. The simultaneous multi-line laser guidestar is shown to be superior to the single line laser guidestar for equal output powers both via modeling and via on sky returns performed at Starfire Optical Range (SOR) with a combination of a legacy narrowband laser guidestars and a broadband OPSL guidestar. The multi-line OPSL guidestars are shown to provide the first continuous wave source for use as a polychromatic laser guidestar (PLGS) to correct for tip and tilt aberrations. Different methods for utilization of the PLGS are simulated and compared showing that the OPSL sources developed are suitable for use as a CW PLGS to correct for tip and tilt with current generation telescopes and adaptive optics systems. Wave optics and Bloch equation simulations are then developed and performed to determine the utility and optimal setup for LGS and PLGS systems which prove OPSL's utility as the next generation of sodium laser guidestars.

  4. Optical pumping and xenon NMR

    Energy Technology Data Exchange (ETDEWEB)

    Raftery, M. Daniel [Univ. of California, Berkeley, CA (United States)


    Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping 129Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the 131Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

  5. Optical pumping and xenon NMR

    Energy Technology Data Exchange (ETDEWEB)

    Raftery, M.D.


    Nuclear Magnetic Resonance (NMR) spectroscopy of xenon has become an important tool for investigating a wide variety of materials, especially those with high surface area. The sensitivity of its chemical shift to environment, and its chemical inertness and adsorption properties make xenon a particularly useful NMR probe. This work discusses the application of optical pumping to enhance the sensitivity of xenon NMR experiments, thereby allowing them to be used in the study of systems with lower surface area. A novel method of optically-pumping [sup 129]Xe in low magnetic field below an NMR spectrometer and subsequent transfer of the gas to high magnetic field is described. NMR studies of the highly polarized gas adsorbed onto powdered samples with low to moderate surface areas are now possible. For instance, NMR studies of optically-pumped xenon adsorbed onto polyacrylic acid show that xenon has a large interaction with the surface. By modeling the low temperature data in terms of a sticking probability and the gas phase xenon-xenon interaction, the diffusion coefficient for xenon at the surface of the polymer is determined. The sensitivity enhancement afforded by optical pumping also allows the NMR observation of xenon thin films frozen onto the inner surfaces of different sample cells. The geometry of the thin films results in interesting line shapes that are due to the bulk magnetic susceptibility of xenon. Experiments are also described that combine optical pumping with optical detection for high sensitivity in low magnetic field to observe the quadrupoler evolution of 131 Xe spins at the surface of the pumping cells. In cells with macroscopic asymmetry, a residual quadrupolar interaction causes a splitting in the [sup 131]Xe NMR frequencies in bare Pyrex glass cells and cells with added hydrogen.

  6. Study of spin-exchange optically pumped {sup 3}He cells with high polarisation and long lifetimes

    Energy Technology Data Exchange (ETDEWEB)

    Parnell, S.R. [Academic Unit of Radiology, University of Sheffield, Sheffield S10 2JF (United Kingdom); ISIS Neutron and Muon Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)], E-mail:; Babcock, E. [Insitut Laue-Langevin, 6, rue J. Horowitz, F-38042 Grenoble Cedex 9 (France); Nuenighoff, K. [Institut fuer Festkoerperforschung, Forschungszentrum Juelich, 52425 Juelich (Germany); Skoda, M.W.A.; Boag, S. [ISIS Neutron and Muon Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Masalovich, S. [Neutronenforschungsquelle Heinz Maier-Leibnitz, Technische Universitaet Muenchen, Lichtenbergstr, 1, 85747 Garching (Germany); Chen, W.C. [National Institute of Standards and Technology (NIST), Gaithersburg, MD 20899 (United States); Georgii, R. [Neutronenforschungsquelle Heinz Maier-Leibnitz, Technische Universitaet Muenchen, Lichtenbergstr, 1, 85747 Garching (Germany); Wild, J.M. [Academic Unit of Radiology, University of Sheffield, Sheffield S10 2JF (United Kingdom); Frost, C.D. [ISIS Neutron and Muon Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)


    We present a detailed investigation into {sup 3}He neutron spin filter cells polarised by spin exchange optical pumping (SEOP). We include measurements of the absolute {sup 3}He polarisation using neutron transmission and characterisation of both the X-factor and {sup 3}He relaxation times (T{sub 1}) for a number of cells. For one cell we calculated a maximum {sup 3}He polarisation of 79% with a T{sub 1} of 633 h. The measured X-factor of this cell, X=0.17{+-}0.01, is low. For all cells polarisations of >71% are observed. In addition we present {sup 3}He relaxation data for a new design of magneto-static cavity with a field of high homogeneity {delta}B/B{sub 0}{approx}3.5x10{sup -4}cm{sup -1}. This compact device provides a magnetic field in an orientation suitable for in situ optical pumping that minimises the field inhomogeneity contribution to the T{sub 1} to 930 h in a 1 bar cell, the longest reported on beam thus far. The results suggest that high {sup 3}He polarisation with long relaxation times can now be routinely obtained with SEOP, enabling time independent incident beam polarisation to be easily implemented across many different neutron scattering instruments.

  7. Low-threshold optically pumped lasing in highly strained germanium nanowires. (United States)

    Bao, Shuyu; Kim, Daeik; Onwukaeme, Chibuzo; Gupta, Shashank; Saraswat, Krishna; Lee, Kwang Hong; Kim, Yeji; Min, Dabin; Jung, Yongduck; Qiu, Haodong; Wang, Hong; Fitzgerald, Eugene A; Tan, Chuan Seng; Nam, Donguk


    The integration of efficient, miniaturized group IV lasers into CMOS architecture holds the key to the realization of fully functional photonic-integrated circuits. Despite several years of progress, however, all group IV lasers reported to date exhibit impractically high thresholds owing to their unfavourable bandstructures. Highly strained germanium with its fundamentally altered bandstructure has emerged as a potential low-threshold gain medium, but there has yet to be a successful demonstration of lasing from this seemingly promising material system. Here we demonstrate a low-threshold, compact group IV laser that employs a germanium nanowire under a 1.6% uniaxial tensile strain as the gain medium. The amplified material gain in strained germanium can sufficiently overcome optical losses at 83 K, thus allowing the observation of multimode lasing with an optical pumping threshold density of ~3.0 kW cm-2. Our demonstration opens new possibilities for group IV lasers for photonic-integrated circuits.

  8. Optically pumped polarized ion sources

    Energy Technology Data Exchange (ETDEWEB)

    Zelenski, A.N.


    Polarization transfer collisions between protons, atomic hydrogen, or deuterium and optically pumped alkali-metal vapour are implemented in the high current optically pumped polarized ion source (OPPIS) and the laser driven source (LDS) of nuclear polarized atoms for target applications. The OPPIS technique overcomes the limitations on intensity of the conventional atomic beam source technique and meets the requirements of the new generation of polarization experiments at multi-GeV accelerators and colliders. 17 refs., 3 figs.

  9. High-sensitivity operation of single-beam optically pumped magnetometer in a kHz frequency range (United States)

    Savukov, I.; Kim, Y. J.; Shah, V.; Boshier, M. G.


    Optically pumped magnetometers (OPM) can be used in various applications, from magnetoencephalography to magnetic resonance imaging and nuclear quadrupole resonance (NQR). OPMs provide high sensitivity and have the significant advantage of non-cryogenic operation. To date, many magnetometers have been demonstrated with sensitivity close to 1 fT, but most devices are not commercialized. Most recently, QuSpin developed a model of OPM that is low cost, high sensitivity, and convenient for users, which operates in a single-beam configuration. Here we developed a theory of single-beam (or parallel two-beam) magnetometers and showed that it is possible to achieve good sensitivity beyond their usual frequency range by tuning the magnetic field. Experimentally we have tested and optimized a QuSpin OPM for operation in the frequency range from DC to 1.7 kHz, and found that the performance was only slightly inferior despite the expected decrease due to deviation from the spin-exchange relaxation-free regime.

  10. Highly efficient oscillator for an optically pumped 192-μm far-infrared laser (United States)

    Liu, Chuang; Qu, Yanchen; Zhao, Weijiang; Zhang, Ruiliang


    We demonstrate an efficient CH3F oscillator based on an anti-reflection coated Ge dichroic beam splitter. When pumped by the 10R32 line of a CO2 laser (10.17 μm), 0.81-mJ far-infrared laser is obtained with the wavelength of 192 μm. The energy conversion efficiency of 0.16 % is the highest for an optically pumped 192-μm laser system to our knowledge. The beam quality factor of Mx2 and My2 is 1.53 and 1.57, respectively. Further, this oscillator can be extended to optically pumped far-infrared lasers with various wavelengths.

  11. Optically pumped atoms

    CERN Document Server

    Happer, William; Walker, Thad


    Covering the most important knowledge on optical pumping of atoms, this ready reference is backed by numerous examples of modelling computation for optical pumped systems. The authors show for the first time that modern scientific computing software makes it practical to analyze the full, multilevel system of optically pumped atoms. To make the discussion less abstract, the authors have illustrated key points with sections of MATLAB codes. To make most effective use of contemporary mathematical software, it is especially useful to analyze optical pumping situations in the Liouville spa

  12. High-efficiency optical pumping of nuclear polarization in a GaAs quantum well (United States)

    Mocek, R. W.; Korenev, V. L.; Bayer, M.; Kotur, M.; Dzhioev, R. I.; Tolmachev, D. O.; Cascio, G.; Kavokin, K. V.; Suter, D.


    The dynamic polarization of nuclear spins by photoexcited electrons is studied in a high quality GaAs/AlGaAs quantum well. We find a surprisingly high efficiency of the spin transfer from the electrons to the nuclei as reflected by a maximum nuclear field of 0.9 T in a tilted external magnetic field of 1 T strength only. This high efficiency is due to a low leakage of spin out of the polarized nuclear system, because mechanisms of spin relaxation other than the hyperfine interaction are strongly suppressed, leading to a long nuclear relaxation time of up to 1000 s. A key ingredient to that end is the low impurity concentration inside the heterostructure, while the electrostatic potential from charged impurities in the surrounding barriers becomes screened through illumination by which the spin relaxation time is increased compared to keeping the system in the dark. This finding indicates a strategy for obtaining high nuclear spin polarization as required for long-lasting carrier spin coherence.

  13. Method for optical pumping of thin laser media at high average power (United States)

    Zapata, Luis E [Livermore, CA; Beach, Raymond J [Livermore, CA; Honea, Eric C [Sunol, CA; Payne, Stephen A [Castro Valley, CA


    A thin, planar laser material is bonded to a light guide of an index-matched material forming a composite disk. Diode array or other pump light is introduced into the composite disk through the edges of the disk. Pump light trapped within the composite disk depletes as it multi-passes the laser medium before reaching an opposing edge of the disk. The resulting compound optical structure efficiently delivers concentrated pump light and to a laser medium of minimum thickness. The external face of the laser medium is used for cooling. A high performance cooler attached to the external face of the laser medium rejects heat. Laser beam extraction is parallel to the heat flux to minimize optical distortions.

  14. Reliable Optical Pump Architecture for Highly Coherent Lasers Used in Space Metrology Applications (United States)

    Erlig, Herman; Qiu, Yueming; Poberezhskiy, Ilya Y.; Meras, Patrick L.; Chang, Daniel H.; Wu, Yen-Hung


    The design and initial demonstration of a laser pump module (LPM) incorporating single-mode, grating-stabilized 808-nm diode lasers and a low-loss, high-port-count optical combiner are completed. The purpose of the developed LPM is to reliably pump an Nd:YAG crystal in the laser head (LH), which serves as the optical metrology source for SIMLite mission. Using the narrow-linewidth, single-mode laser diodes enables placement of the pump power near Nd adsorption peak, which enhances pumping efficiency. Grating stabilization allows for stable pump spectra as diode operating temperature and bias current change. The low-loss, high-port-count optical combiner enables efficient combining of tens of pumps. Overall, the module supports 5+ years of continuous operation at 2 W of pump power with reliability approaching 100 percent. The LPM consists of a laser diode farm (LDF) and a pump beam combiner (PBC). An array of 807- to 808-nm fiber-pigtailed laser diodes makes up the LDF. A Bragg grating in each 5- m core single-mode (SM) fiber pigtail acts to stabilize the lasing spectra over a range of diode operating conditions. These commercially available single-mode laser diodes can deliver up to 150 mW of optical power. The outputs from the multiple pumps in the LDF are routed to the PBC, which is a 37-input by 1-output all-fiber device. The input ports consist of 5- m core SM fiber, while the output port consists of 105- m core, 0.15 NA (numerical aperture) multi-mode (MM) fiber. The combiner is fabricated by fusing the 37 input fibers while simultaneously tapering the fused region. At the completion of this process, the MM fiber is spliced to the end of the adiabatic taper, and, for protection, the combiner is sheathed by a capillary tube. A compact and robust metal housing was designed and fabricated to protect the PBC during space deployment.

  15. Simplified approach for quantitative calculations of optical pumping (United States)

    Atoneche, Fred; Kastberg, Anders


    We present a simple and pedagogical method for quickly calculating optical pumping processes based on linearised population rate equations. The method can easily be implemented on mathematical software run on modest personal computers, and can be generalised to any number of concrete situations. We also show that the method is still simple with realistic experimental complications taken into account, such as high level degeneracy, impure light polarisation, and an added external magnetic field. The method and the associated mathematical toolbox should be of value in advanced physics teaching, and can also facilitate the preparation of research tasks.

  16. Integrating a High Resolution Optically Pumped Magnetometer with a Multi-Rotor UAV towards 3-D Magnetic Gradiometry (United States)

    Braun, A.; Walter, C. A.; Parvar, K.


    The current platforms for collecting magnetic data include dense coverage, but low resolution traditional airborne surveys, and high resolution, but low coverage terrestrial surveys. Both platforms leave a critical observation gap between the ground surface and approximately 100m above ground elevation, which can be navigated efficiently by new technologies, such as Unmanned Aerial Vehicles (UAVs). Specifically, multi rotor UAV platforms provide the ability to sense the magnetic field in a full 3-D tensor, which increases the quality of data collected over other current platform types. Payload requirements and target requirements must be balanced to fully exploit the 3-D magnetic tensor. This study outlines the integration of a GEM Systems Cesium Vapour UAV Magnetometer, a Lightware SF-11 Laser Altimeter and a uBlox EVK-7P GPS module with a DJI s900 Multi Rotor UAV. The Cesium Magnetometer is suspended beneath the UAV platform by a cable of varying length. A set of surveys was carried out to optimize the sensor orientation, sensor cable length beneath the UAV and data collection methods of the GEM Systems Cesium Vapour UAV Magnetometer when mounted on the DJI s900. The target for these surveys is a 12 inch steam pipeline located approximately 2 feet below the ground surface. A systematic variation of cable length, sensor orientation and inclination was conducted. The data collected from the UAV magnetometer was compared to a terrestrial survey conducted with the GEM GST-19 Proton Procession Magnetometer at the same elevation, which also served a reference station. This allowed for a cross examination between the UAV system and a proven industry standard for magnetic field data collection. The surveys resulted in optimizing the above parameters based on minimizing instrument error and ensuring reliable data acquisition. The results demonstrate that optimizing the UAV magnetometer survey can yield to industry standard measurements.

  17. Spontaneous emission effects in optically pumped x-ray FEL

    Energy Technology Data Exchange (ETDEWEB)

    Smetanin, I.V.; Grigor`ev, S.V. [P.N. Lebedev Physics Institute, Moscow (Russian Federation)


    An effect of spontaneous emission in both quantum and classical regimes of the optically pumped X-ray free electron laser (FEL) in investigated. The quantum properties of an FEL are determined by the ratio of the separation {h_bar} between the absorption and emission lines (i.e. the quanta emitted) and their effective width {Delta}{epsilon} {eta}={h_bar}/{Delta}{epsilon}. In the conventional classical regime {eta} {much_lt} 1 an electron emits and absorbes a great number of shortwavelength photons over the interaction region, the gain in FEL being the result of these competitive processes. In the quantum limit {eta} {much_gt} 1 the emission and absorption lines are completely separated and thus the FEL becomes a two-level quantum oscillator with a completely inverted active medium. Spontaneous emission causes the electron to leave the range of energies where resonant interaction with the laser field occurs, thus effectively reducing the number of particles that take part in generating the induced X-ray signal. This effect is found to be crucial for lasing in optically pumped X-ray FEL. The characteristic relaxation times are calculated for both classical and quantum FEL regimes. It is shown that spontaneous emission results in FEL electron beam threshold current, which is of rather high value. An optimal range of pumping laser intensities is determined.

  18. Microfabricated optically pumped magnetometer arrays for biomedical imaging (United States)

    Perry, A. R.; Sheng, D.; Krzyzewski, S. P.; Geller, S.; Knappe, S.


    Optically-pumped magnetometers have demonstrated magnetic field measurements as precise as the best superconducting quantum interference device magnetometers. Our group develops miniature alkali atom-based magnetic sensors using microfabrication technology. Our sensors do not require cryogenic cooling, and can be positioned very close to the sample, making these sensors an attractive option for development in the medical community. We will present our latest chip-scale optically-pumped gradiometer developed for array applications to image magnetic fields from the brain noninvasively. These developments should lead to improved spatial resolution, and potentially sensitive measurements in unshielded environments.

  19. Observation of Ultrafast Magnon Dynamics in Antiferromagnetic Nickel Oxide by Optical Pump-Probe and Terahertz Time-Domain Spectroscopies (United States)

    Kohmoto, T.; Moriyasu, T.; Wakabayashi, S.; Jinn, H.; Takahara, M.; Kakita, K.


    We have studied the ultrafast magnon dynamics in an antiferromagnetic 3d-transition-metal monoxide, nickel oxide (NiO), using optical pump-probe spectroscopy and terahertz time-domain spectroscopy (THz-TDS). THz damped magnon oscillations were observed in the Faraday rotation signal and in the transmitted THz electric field via optical pump-probe spectroscopy and THz-TDS, respectively. The magnon signals were observed in both the optical pump-probe spectroscopy and THz-TDS experiments, which shows that both Raman- and infrared-active modes are included in the NiO magnon modes. The magnon relaxation rate observed using THz-TDS was found to be almost constant up to the Néel temperature T N (= 523 K) and to increase abruptly near that temperature. This shows that temperature-independent spin-spin relaxation dominates up to T N . In our experiment, softening of the magnon frequency near T N was clearly observed. This result shows that the optical pump-probe spectroscopy and THz-TDS have high frequency resolution and a high signal to noise ratio in the THz region. We discuss the observed temperature dependence of the magnon frequencies using three different molecular field theories. The experimental results suggest that the biquadratic contribution of the exchange interaction plays an important role in the temperature dependence of the sublattice magnetization and the magnon frequency in cubic antiferromagnetic oxides.

  20. Observation of Ultrafast Magnon Dynamics in Antiferromagnetic Nickel Oxide by Optical Pump-Probe and Terahertz Time-Domain Spectroscopies (United States)

    Kohmoto, T.; Moriyasu, T.; Wakabayashi, S.; Jinn, H.; Takahara, M.; Kakita, K.


    We have studied the ultrafast magnon dynamics in an antiferromagnetic 3d-transition-metal monoxide, nickel oxide (NiO), using optical pump-probe spectroscopy and terahertz time-domain spectroscopy (THz-TDS). THz damped magnon oscillations were observed in the Faraday rotation signal and in the transmitted THz electric field via optical pump-probe spectroscopy and THz-TDS, respectively. The magnon signals were observed in both the optical pump-probe spectroscopy and THz-TDS experiments, which shows that both Raman- and infrared-active modes are included in the NiO magnon modes. The magnon relaxation rate observed using THz-TDS was found to be almost constant up to the Néel temperature T N (= 523 K) and to increase abruptly near that temperature. This shows that temperature-independent spin-spin relaxation dominates up to T N . In our experiment, softening of the magnon frequency near T N was clearly observed. This result shows that the optical pump-probe spectroscopy and THz-TDS have high frequency resolution and a high signal to noise ratio in the THz region. We discuss the observed temperature dependence of the magnon frequencies using three different molecular field theories. The experimental results suggest that the biquadratic contribution of the exchange interaction plays an important role in the temperature dependence of the sublattice magnetization and the magnon frequency in cubic antiferromagnetic oxides.

  1. Ultra-sensitive Magnetic Microscopy with an Optically Pumped Magnetometer (United States)

    Kim, Young Jin; Savukov, Igor


    Optically pumped magnetometers (OPMs) based on lasers and alkali-metal vapor cells are currently the most sensitive non-cryogenic magnetic field sensors. Many applications in neuroscience and other fields require high-resolution, high-sensitivity magnetic microscopic measurements. In order to meet this demand we combined a cm-size spin-exchange relaxation-free (SERF) OPM and flux guides (FGs) to realize an ultra-sensitive FG-OPM magnetic microscope. The FGs serve to transmit the target magnetic flux to the OPM thus improving both the resolution and sensitivity to small magnetic objects. We investigated the performance of the FG-OPM device using experimental and numerical methods, and demonstrated that an optimized device can achieve a unique combination of high resolution (80 μm) and high sensitivity (8.1 pT/). In addition, we also performed numerical calculations of the magnetic field distribution in the FGs to estimate the magnetic noise originating from the domain fluctuations in the material of the FGs. We anticipate many applications of the FG-OPM device such as the detection of micro-biological magnetic fields; the detection of magnetic nano-particles; and non-destructive testing. From our theoretical estimate, an FG-OPM could detect the magnetic field of a single neuron, which would be an important milestone in neuroscience.

  2. Grating THz laser with optical pumping (United States)

    Khoury, Jed; Haji-saeed, Bahareh; Woods, Charles; Kierstead, John


    In this paper, we present a design for a widely tunable solid-state optically and electrically pumped THz laser based on the Smith-Purcell free-electron laser. In the free-electron laser, an energetic electron beam pumps a metallic grating to generate surface plasmons. Our solid-state optically pumped design consists of a thin layer of dielectic, such as SiNx, sandwiched between a corrugated structure and a thin metal or semiconductor layer. The lower layer is for current streaming, and replaces the electron beam in the original design. The upper layer consists of one micro-grating for coupling the electromagnetic field in, another for coupling out, and a nano-grating for coupling with the current in the lower layer for electromagnetic field generation. The surface plasmon waves generated from the upper layer by an external electromagnetic field, and the lower layer by the applied current, are coupled. Emission enhancement occurs when the plasmonic waves in both layers are resonantly coupled.

  3. An Optically Pumped Magnetometer Working in the Light-Shift Dispersed Mz Mode. (United States)

    Schultze, Volkmar; Schillig, Bastian; IJsselsteijn, Rob; Scholtes, Theo; Woetzel, Stefan; Stolz, Ronny


    We present an optically pumped magnetometer working in a new operational mode-the light-shift dispersed Mz (LSD-Mz) mode. It is realized combining various features; (1) high power off-resonant optical pumping; (2) Mz configuration, where pumping light and magnetic field of interest are oriented parallel to each other; (3) use of small alkali metal vapor cells of identical properties in integrated array structures, where two such cells are pumped by circularly polarized light of opposite helicity; and (4) subtraction of the Mz signals of these two cells. The LSD-Mz magnetometer's performance depends on the inherent and very complex interplay of input parameters. In order to find the configuration of optimal magnetometer resolution, a sensitivity analysis of the input parameters by means of Latin Hypercube Sampling was carried out. The resulting datasets of the multi-dimensional parameter space exploration were assessed by a subsequent physically reasonable interpretation. Finally, the best shot-noise limited magnetic field resolution was determined within that parameter space. As the result, using two 50 mm3 integrated vapor cells a magnetic field resolution below 10 fT/√Hz at Earth's magnetic field strength is possible.

  4. An Optically Pumped Magnetometer Working in the Light-Shift Dispersed Mz Mode

    Directory of Open Access Journals (Sweden)

    Volkmar Schultze


    Full Text Available We present an optically pumped magnetometer working in a new operational mode—the light-shift dispersed Mz (LSD-Mz mode. It is realized combining various features; (1 high power off-resonant optical pumping; (2 Mz configuration, where pumping light and magnetic field of interest are oriented parallel to each other; (3 use of small alkali metal vapor cells of identical properties in integrated array structures, where two such cells are pumped by circularly polarized light of opposite helicity; and (4 subtraction of the Mz signals of these two cells. The LSD-Mz magnetometer’s performance depends on the inherent and very complex interplay of input parameters. In order to find the configuration of optimal magnetometer resolution, a sensitivity analysis of the input parameters by means of Latin Hypercube Sampling was carried out. The resulting datasets of the multi-dimensional parameter space exploration were assessed by a subsequent physically reasonable interpretation. Finally, the best shot-noise limited magnetic field resolution was determined within that parameter space. As the result, using two 50 mm3 integrated vapor cells a magnetic field resolution below 10 fT/√Hz at Earth’s magnetic field strength is possible.

  5. Optically-pumped dilute nitride spin-VCSEL. (United States)

    Schires, Kevin; Al Seyab, Rihab; Hurtado, Antonio; Korpijärvi, Ville-Markus; Guina, Mircea; Henning, Ian D; Adams, Michael J


    We report the first room temperature optical spin-injection of a dilute nitride 1300 nm vertical-cavity surface-emitting laser (VCSEL) under continuous-wave optical pumping. We also present a novel experimental protocol for the investigation of optical spin-injection with a fiber setup. The experimental results indicate that the VCSEL polarization can be controlled by the pump polarization, and the measured behavior is in excellent agreement with theoretical predictions using the spin flip model. The ability to control the polarization of a long-wavelength VCSEL at room temperature emitting at the wavelength of 1.3 µm opens up a new exciting research avenue for novel uses in disparate fields of technology ranging from spintronics to optical telecommunication networks.

  6. Hybrid optical pumping of K and Rb atoms in a paraffin coated vapor cell (United States)

    Li, Wenhao; Peng, Xiang; Budker, Dmitry; Wickenbrock, Arne; Pang, Bo; Zhang, Rui; Guo, Hong


    Dynamic hybrid optical pumping effects with a radio-frequency-field-driven nonlinear magneto-optical rotation (RF NMOR) scheme are studied in a dual-species paraffin coated vapor cell. By pumping K atoms and probing $^{87}$Rb atoms, we achieve an intrinsic magnetic resonance linewidth of 3 Hz and the observed resonance is immune to power broadening and light-shift effects. Such operation scheme shows favorable prospects for atomic magnetometry applications.

  7. 1300 nm optically pumped quantum dot spin vertical external-cavity surface-emitting laser

    Energy Technology Data Exchange (ETDEWEB)

    Alharthi, S. S., E-mail:; Henning, I. D.; Adams, M. J. [School of Computer Science and Electronic Engineering, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Orchard, J. [Department of Physics and Astronomy, University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Clarke, E. [EPSRC National Centre for III-V Technologies, University of Sheffield, Mappin Street, S1 3JD Sheffield (United Kingdom)


    We report a room temperature optically pumped Quantum Dot-based Spin-Vertical-External-Cavity Surface-Emitting laser (QD Spin-VECSEL) operating at the telecom wavelength of 1.3 μm. The active medium was composed of 5 × 3 QD layers; each threefold group was positioned at an antinode of the standing wave of the optical field. Circularly polarized lasing in the QD-VECSEL under Continuous-Wave optical pumping has been realized with a threshold pump power of 11 mW. We further demonstrate at room temperature control of the QD-VECSEL output polarization ellipticity via the pump polarization.

  8. Davisson-Germer Prize Talk¯Spin Relaxation in Optical Pumping (United States)

    Happer, William


    This talk will review the role of spin relaxation in optically pumped gaseous systems. Such systems have turned out to have important applications in many areas -- most recently in the production of hyperpolarized He-3 and Xe-129 gases for magnetic resonance imaging of human lungs. Systems of practical interest always have very slowly relaxing spins that permit large quantities (liter-atmospheres at room temperature) of spins to be polarized to many tens of percent and stored for hours. Some of the spin-relaxation physics is reasonably well understood, for example: the optical pumping itself, the trapping of resonant radiation and its control by quenching gases, the establishment of a spin temperature by spin-exchange collisions or by the optical pumping, the transfer of angular momentum between spin systems in spin-exchange collisions, the slowing down of electronic spin relaxation because of the angular momentum stored in the nuclear spins, gas-phase relaxation due to sudden binary collisions or three-body collisions where molecules are formed, wall interactions, and interactions with inhomogeneous magnetic fields. There are also some important relaxation mechanisms that are still not well understood. The analysis of relaxation in these systems provides many instructive, real-world applications of angular momentum algebra and density matrices.

  9. Superluminescence from an optically pumped molecular tunneling junction by injection of plasmon induced hot electrons

    Directory of Open Access Journals (Sweden)

    Kai Braun


    Full Text Available Here, we demonstrate a bias-driven superluminescent point light-source based on an optically pumped molecular junction (gold substrate/self-assembled molecular monolayer/gold tip of a scanning tunneling microscope, operating at ambient conditions and providing almost three orders of magnitude higher electron-to-photon conversion efficiency than electroluminescence induced by inelastic tunneling without optical pumping. A positive, steadily increasing bias voltage induces a step-like rise of the Stokes shifted optical signal emitted from the junction. This emission is strongly attenuated by reversing the applied bias voltage. At high bias voltage, the emission intensity depends non-linearly on the optical pump power. The enhanced emission can be modelled by rate equations taking into account hole injection from the tip (anode into the highest occupied orbital of the closest substrate-bound molecule (lower level and radiative recombination with an electron from above the Fermi level (upper level, hence feeding photons back by stimulated emission resonant with the gap mode. The system reflects many essential features of a superluminescent light emitting diode.

  10. Optical pumping in a microfabricated Rb vapor cell using a microfabricated Rb discharge light source

    Energy Technology Data Exchange (ETDEWEB)

    Venkatraman, V.; Kang, S.; Affolderbach, C.; Mileti, G., E-mail: [Laboratoire Temps-Fréquence, University of Neuchâtel, Neuchâtel 2000 (Switzerland); Shea, H. [Microsystems for Space Technologies Laboratory, Ecole Polytechnique Fédérale de Lausanne (EPFL), Neuchâtel 2002 (Switzerland)


    Miniature (optical pumping of alkali atoms, such as atomic clocks and magnetometers, today mostly employ vertical-cavity surface-emitting lasers as pump light sources. Here, we report on the demonstration of optical pumping in a microfabricated alkali vapor resonance cell using (1) a microfabricated Rb discharge lamp light source, as well as (2) a conventional glass-blown Rb discharge lamp. The microfabricated Rb lamp cell is a dielectric barrier discharge (DBD) light source, having the same inner cell volume of around 40 mm{sup 3} as that of the resonance cell, both filled with suitable buffer gases. A miniature (∼2 cm{sup 3} volume) test setup based on the M{sub z} magnetometer interrogation technique was used for observation of optical-radiofrequency double-resonance signals, proving the suitability of the microfabricated discharge lamp to introduce efficient optical pumping. The pumping ability of this light source was found to be comparable to or even better than that of a conventional glass-blown lamp. The reported results indicate that the micro-fabricated DBD discharge lamp has a high potential for the development of a new class of miniature atomic clocks, magnetometers, and quantum sensors.

  11. Superluminescence from an optically pumped molecular tunneling junction by injection of plasmon induced hot electrons. (United States)

    Braun, Kai; Wang, Xiao; Kern, Andreas M; Adler, Hilmar; Peisert, Heiko; Chassé, Thomas; Zhang, Dai; Meixner, Alfred J


    Here, we demonstrate a bias-driven superluminescent point light-source based on an optically pumped molecular junction (gold substrate/self-assembled molecular monolayer/gold tip) of a scanning tunneling microscope, operating at ambient conditions and providing almost three orders of magnitude higher electron-to-photon conversion efficiency than electroluminescence induced by inelastic tunneling without optical pumping. A positive, steadily increasing bias voltage induces a step-like rise of the Stokes shifted optical signal emitted from the junction. This emission is strongly attenuated by reversing the applied bias voltage. At high bias voltage, the emission intensity depends non-linearly on the optical pump power. The enhanced emission can be modelled by rate equations taking into account hole injection from the tip (anode) into the highest occupied orbital of the closest substrate-bound molecule (lower level) and radiative recombination with an electron from above the Fermi level (upper level), hence feeding photons back by stimulated emission resonant with the gap mode. The system reflects many essential features of a superluminescent light emitting diode.

  12. Mathematical model of an optically pumped molecular laser

    CSIR Research Space (South Africa)

    Botha, LR


    Full Text Available µm laser ring oscillator & pre-amplifier 1.9 µm Optically Pumped Molecular laser @ 4 µm 95:5 HBr Absorption cell Fast detector 2.064 µm ± 1 nm Feedback control box Feedback loop 1 P ie zo m o u nt Fast detector Feedback loop 2 Gas...

  13. Optically pumped 1550nm wavelength tunable MEMS VCSEL

    DEFF Research Database (Denmark)

    Sahoo, Hitesh Kumar; Ansbæk, Thor; Ottaviano, Luisa


    The paper presents the design and fabrication of an optically pumped 1550nm tunable MEMS VCSEL with anenclosed MEMS. The MEMS is defined in SOI and the active material, an InP wafer with quantum wells arebonded to the SOI and the last mirror is made from the deposition of dielectric materials...

  14. Electronic displays using optically pumped luminescent semiconductor nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Weiss, Shimon; Schlamp, Michael C.; Alivisatos, A. Paul


    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit tight of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  15. Electrical versus optical pumping of quantum dot amplifiers

    DEFF Research Database (Denmark)

    Berg, Tommy Winther; Bischoff, Svend; Mørk, Jesper


    of a reservoir of carriers in the WL opens up for the possibility of ultrafast gain recovery in QD devices. The strength of optical contra electrical pumping is that it reduces the bottleneck effect of a slow WL. Optical pumping thus allows significant improvement of the dynamical properties of QD devices....

  16. Optical pumping of hot phonons in GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Collins, C.L.; Yu, P.Y.


    Optical pumping of hot LO phonons in GaAs has been studied as a function of the excitation photon frequency. The experimental results are in good agreement with a model calculation which includes both inter- and intra-valley electron-phonon scatterings. The GAMMA-L and GAMMA-X intervalley electron-phonon interactions in GaAs have been estimated.

  17. Electronic displays using optically pumped luminescent semiconductor nanocrystals (United States)

    Weiss, Shimon; Schlamp, Michael C.; Alivisatos, A. Paul


    A multicolor electronic display is based on an array of luminescent semiconductor nanocrystals. Nanocrystals which emit light of different colors are grouped into pixels. The nanocrystals are optically pumped to produce a multicolor display. Different sized nanocrystals are used to produce the different colors. A variety of pixel addressing systems can be used.

  18. Study of 3He Rabi nutations by optically-pumped cesium magnetometers (United States)

    Koch, Hans-Christian; Bison, Georg; Grujić, Zoran Dragan; Heil, Werner; Kasprzak, Malgorzata; Knowles, Paul; Kraft, Andreas; Pazgalev, Anatoly; Schnabel, Allard; Voigt, Jens; Weis, Antoine


    We describe a method for recording the Rabi nutation of nuclear spin polarized 3He by optically pumped cesium magnetometers. The measurement is performed by detecting the time-dependent magnetic field produced by the 3He magnetization. The observed signals are compared to theoretical models and the results are used to precisely trace the evolution of the magnetization. This procedure represents a convenient way to control and measure the Rabi flip angle and the degree of spin polarization in experiments using 3He magnetometers. The method requires only very coarse knowledge of the applied magnetic field's magnitude.

  19. The Mesospheric Sodium Layer as a Remotely, Optically Pumped Magnetometer for Investigation of Birkeland Currents (United States)

    Matzka, J.; Johnsen, M. G.; Hoppe, U. P.; Serrano, A.


    By means of optical pumping, it is possible to use the naturally occurring sodium layer in the mesosphere to measure Earth's scalar magnetic field at 90 km above ground. This is an altitude not accessible by other means than rockets, which only will provide point measurements of very short time scales. We are planning to modify the sodium lidar at ALOMAR in Northern Norway to be able, for the first time, to measure and monitor the magnetic field in situ in the high latitude mesosphere over longer time scales. The planned modifications to the lidar instrument will allow alternating between the new magnetometer mode and its present mode for atmospheric temperatures and winds. The technique, which has been proposed earlier for measurements at low or mid-latitudes for studies of Earth's internal magnetic field, will in our project be applied to high latitudes in the auroral zone. This opens for a completely new domain of measurements of externally generated geomagnetic variations related to currents in the magnetosphere-ionosphere system. In particular, we aim to measure the magnetic field variations in close vicinity to Birkeland currents associated with particle precipitation events penetrating to altitudes below 90 km and small-scale, discrete auroral arcs. It is, furthermore, anticipated that it will be possible to detect horizontal current structures in the E-layer on much smaller length scales than it is presently possible from ground observations alone. During the project we plan take advantage of the rich space science infrastructure located in northern Norway, including ALOMAR, EISCAT and the Tromsø Geophysical Observatory magnetometer network. If possible, we also aim to make measurements in conjunction with overpasses of the SWARM satellites.

  20. Non-magnetic flexible heaters for spin-exchange optical pumping of 3He and other applications (United States)

    Ino, T.; Hayashida, H.; Kira, H.; Oku, T.; Sakai, K.


    Spin polarized 3He gas is currently widely used in various scientific fields and in medical diagnosis applications. The spin polarization of 3He nuclei can be achieved by spin-exchange optical pumping (SEOP). In SEOP, the 3He gas is enclosed in a glass cell together with alkali metals and is then heated to maintain the alkali metal vapor pressures at the appropriate levels. However, polarized 3He gas is highly sensitive to any inhomogeneity in its magnetic field, and any small field gradients caused by the heaters may cause degradation of the 3He polarization. To overcome this conflict between the heating process and the magnetic field, we have developed electrical heaters that essentially cause no magnetic fields. These heaters are thin and are flexible enough to be bent to within a radius of a few centimeters. These carefully designed heater elements and a double layer structure effectively eliminate magnetic field generation. The heaters were originally developed for SEOP applications, but can also be applied to other processes that need to avoid unwanted magnetic fields.

  1. Modeling polarization reversal in optically pumped rubidium vapors (United States)

    Dreiling, J. M.; Norrgard, E.; Gay, T. J.


    Rubidium atoms can be polarized by optical pumping with a resonant circularly polarized laser beam. Using Faraday rotation polarimetry [1], we have observed a flip in the sign of the Rb electron polarization when the wavelength of the pump laser is varied over the D1 absorption spectrum. This could occur if F Hitt, and T.J. Gay, Phys. Rev. Lett. 82, 4216 (1999).

  2. Optically pumped semiconductor lasers for atomic and molecular physics (United States)

    Burd, S.; Leibfried, D.; Wilson, A. C.; Wineland, D. J.


    Experiments in atomic, molecular and optical (AMO) physics rely on lasers at many different wavelengths and with varying requirements on spectral linewidth, power and intensity stability. Optically pumped semiconductor lasers (OPSLs), when combined with nonlinear frequency conversion, can potentially replace many of the laser systems currently in use. We are developing a source for laser cooling and spectroscopy of Mg+ ions at 280 nm, based on a frequency quadrupled OPSL with the gain chip fabricated at the ORC at Tampere Univ. of Technology, Finland. This OPSL system could serve as a prototype for many other sources used in atomic and molecular physics.

  3. Towards multiple quantum well optically pumped far infrared lasers


    Tan, H.A.


    Optically pumped lasers based on GaAs/AlGaAs multiple quantum well (MQW) structures are a potential coherent source in the far infrared (FIR) wavelengths. The FIR (~ 30 to 300 µm) is a region within the electromagnetic spectrum that has seen relatively little development. No practical solid-state lasers have been possible in the FIR, which is also referred to as the terahertz (THz) wave, until the very recent demonstration of THz quantum cascade lasers. Other existing FIR lasers are either bu...

  4. Recent results of the pulsed optically pumped rubidium clock (United States)

    Levi, F.; Micalizio, S.; Godone, A.; Calosso, C.; Bertacco, E.


    A laboratory prototype of a pulsed optically pumped (POP) clock based on a rubidium cell with buffer gas is described. This clock has shown very interesting physical and metrological features, such as negligible light-shift, strongly reduced cavity-pulling and very good frequency stability. In this regard, an Allan deviation of σy(τ) = 1.2 τ-1/2 for measurement times up to τ = 105 s has been measured. These results confirm the interesting perspectives of such a frequency standard and make it very attractive for several technological applications, such as radionavigation.

  5. Optically-pumped lasing of semi-polar InGaN/GaN(1122) heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Strittmatter, A.; Teepe, M.; Yang, Z.; Chua, C.; Northrup, J.; Johnson, N.M. [Palo Alto Research Center, Palo Alto, CA (United States); Spiberg, P.; Brown, R.G.W. [Ostendo Technologies, Inc., Carlsbad, CA (United States); Ivantsov, V.; Syrkin, A.; Shapovalov, L.; Usikov, A. [TDI, Inc., an Oxford Instruments Company, Silver Spring, MD (United States)


    Results for long-wavelength emitters are presented for semi-polar InGaN/AlGaN/GaN heterostructures grown on GaN(11-22)/m-sapphire templates by metalorganic chemical vapor deposition. The semi-polar GaN layers were 10 to 25 {mu}m thick and grown by HVPE on sapphire substrates. X-ray diffraction measurements indicate high crystallographic quality that approaches that of GaN(0001) layers on sapphire. Growth studies on the semi-polar GaN templates established the high efficiency of indium incorporation into InGaN layers, with a wide growth-temperature window up to 800 C for green light emitting structures. Basic LEDs were fabricated with peak emission up to 527 nm wavelength. Further growth studies established conditions for growing reasonably smooth, undoped InGaN/GaN laser heterostructures suitable for optical pumping. Optically-pumped lasing was achieved at wavelengths from 400 nm up to 500 nm. The results demonstrate the viability of semi-polar GaN(11-22) on sapphire templates for long-wavelength nitride laser diodes (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Direct measurement of the spectral reflectance of OP-SDL gain elements under optical pumping (United States)

    Borgentun, Carl; Bengtsson, Jörgen; Larsson, Anders


    We report on a direct measurement method for acquiring highly precise reflectance spectra of gain elements for semiconductor disk lasers under optical pumping. The gain element acts as an active mirror, and the active mirror reflectance (AMR) was measured with a weak and tunable probe beam coincident on the gain element with a high-power pump beam. In particular, we measured the spectral AMR of a gain element designed to have a broad and flat AMR spectrum by being anti-resonant at the center wavelength and employing a parametrically optimized anti-reflection structure. We were able to confirm that this sophisticated gain element performs according to design, with an almost constant AMR of ˜103% over a wavelength range of nearly 35 nm, very well matching the simulated behavior. Such gain characteristics are useful for optically pumped semiconductor disk lasers (OP-SDLs) designed for broadband tuning and short-pulse generation through mode-locking. The measurement technique was also applied to a conventional resonant periodic gain element designed for fixed wavelength OP-SDL operation; its AMR spectrum is markedly different with a narrow peak, again in good agreement with the simulations.

  7. On the possibility of developing quasi-CW high-power high-pressure laser on 4p–4s transition of ArI with electron beam—optical pumping: quenching of 4s (3P2) lower laser level (United States)

    Ionin, A. A.; Kholin, I. V.; L’dov, A. Yu; Seleznev, L. V.; Ustinovskii, N. N.; Zayarnyi, D. A.


    A new electron beam-optical procedure is proposed for quasi-cw pumping of high-pressure large-volume He–Ar laser on the 4p[1/2]1–4s[3/2]20 argon atom transition at the wavelength of 912.5 nm. It consists of creation and maintenance of a necessary density of the 4s[3/2]20 metastable state in the gain medium by a fast electron beam and subsequent optical pumping of the upper laser level via the classical three-level scheme using a laser diode. Absorption probing is used to study collisional quenching of Ar* metastable in electron-beam-excited high-pressure He–Ar mixtures with a low content of argon. The rate constants for plasma-chemical reactions Ar*  +  He  +  Ar  >  Ar2*   +  He (3.6  ±  0.4)  ×  10‑33 cm6 s‑1, Ar*  +  2He  >  HeAr*  +  He (4.4  ±  0.9)  ×  10‑36 cm6 s‑1 and Ar*  +  He  >  Products  +  He (2.4  ±  0.3)  ×  10‑15 cm3 s‑1 were for the first time measured.

  8. Continuous-wave single-frequency 295 nm laser source by a frequency-quadrupled optically pumped semiconductor laser. (United States)

    Kaneda, Yushi; Fallahi, Mahmoud; Hader, Jörg; Moloney, Jerome V; Koch, Stephan W; Kunert, Bernardette; Stoltz, Wolfgang


    Up to 136 mW of cw single-frequency output at 295 nm was obtained from a frequency-quadrupled optically pumped semiconductor laser. The highly strained InGaAs quantum-well semiconductor laser operates at 1178 nm in a single frequency. The single-frequency intracavity-doubled 589 nm output is further converted to 295 nm in an external resonator using beta-BaB(2)O(4).

  9. Magnetocardiography measurements with 4He vector optically pumped magnetometers at room temperature (United States)

    Morales, S.; Corsi, M. C.; Fourcault, W.; Bertrand, F.; Cauffet, G.; Gobbo, C.; Alcouffe, F.; Lenouvel, F.; Le Prado, M.; Berger, F.; Vanzetto, G.; Labyt, E.


    In this paper, we present a proof of concept study which demonstrates for the first time the possibility of recording magnetocardiography (MCG) signals with 4He vector optically pumped magnetometers (OPM) operated in a gradiometer mode. Resulting from a compromise between sensitivity, size and operability in a clinical environment, the developed magnetometers are based on the parametric resonance of helium in a zero magnetic field. Sensors are operated at room temperature and provide a tri-axis vector measurement of the magnetic field. Measured sensitivity is around 210 f T (√Hz)-1 in the bandwidth (2 Hz; 300 Hz). MCG signals from a phantom and two healthy subjects are successfully recorded. Human MCG data obtained with the OPMs are compared to reference electrocardiogram recordings: similar heart rates, shapes of the main patterns of the cardiac cycle (P/T waves, QRS complex) and QRS widths are obtained with both techniques.

  10. Characteristics of stimulated emission from optically pumped freestanding GaN grown by hydride vapor-phase epitaxy

    CERN Document Server

    Lee, M H; Kim, S T; Chung, S H; Moon, D C


    In this study, we observed optically pumped stimulated emission at room temperature in quasi-bulk GaN prepared from thick-film GaN grown on a sapphire substrate by using hydride vapor-phase epitaxy and subsequent mechanical removal of the sapphire substrate. The stimulated emission from the surface and 1-mm-wide-cleaved cavity of the GaN was red-shifted compared to the spontaneous emission by increasing the optical pumping-power density, and the full width at half maximum (FWHM) of the peak decreased. The stimulated emission was demonstrated to have a highly TE-mode polarized nature, and the super-linear dependence of the integrated emission intensity on the excitation power indicated a threshold pump-power density of I sub t sub h = 2 MW/cm sup 2 for one set of stimulated emissions.

  11. The passive optically pumped Rb frequency standard: the laser approach (United States)

    Vanier, J.; Mandache, C.


    This paper outlines the progress made during the last few decades in the implementation of a frequency standard using the optical-microwave double resonance technique and laser optical pumping in a sealed cell containing an alkali atom vapor in a microwave cavity. An analysis is presented based on a three-level model, describing the basic phenomena taking place in that approach. The expected frequency stability is calculated. The various frequency shifts taking place are described and their importance is evaluated. Several laser systems generally used in this context are described as well as the various techniques for stabilizing them. The results obtained by several research groups are outlined, compared to the analysis, and evaluated in the context of the implementation of a practical frequency standard. Conclusions are drawn relative to the future of a realistic implementation of such a laser pumped frequency standard.

  12. Pulsed optically pumped atomic clock with zero-dead-time (United States)

    Lin, Haixiao; Lin, Jinda; Deng, Jianliao; Zhang, Song; Wang, Yuzhu


    By alternatively operating two pulsed optically pumped (POP) atomic clocks, the dead time in a single clock can be eliminated, and the local oscillator can be discriminated continuously. A POP atomic clock with a zero-dead-time (ZDT) method is then insensitive to the microwave phase noise. From τ = 0.01 to 1 s, the Allan deviation of the ZDT-POP clock is reduced as nearly τ-1, which is significantly faster than τ-1/2 of a conventional clock. During 1-40 s, the Allan deviation returns to τ-1/2. Moreover, the frequency stability of the ZDT-POP clock is improved by one order of magnitude compared with that of the conventional POP clock. We also analyze the main factors that limit the short-term frequency stability of the POP atomic clock.

  13. Towards loss compensated and lasing terahertz metamaterials based on optically pumped graphene. (United States)

    Weis, P; Garcia-Pomar, J L; Rahm, M


    We evidence by numerical calculations that optically pumped graphene is suitable for compensating inherent loss in terahertz (THz) metamaterials. We calculate the complex conductivity of graphene under optical pumping and determine the proper conditions for terahertz amplification in single layer graphene. It is shown that amplification in graphene occurs up to room temperature for moderate pump intensities at telecommunication wavelength λ = 1.5 μm. Furthermore, we investigate the coupling between a plasmonic split ring resonator (SRR) metamaterial and optically pumped graphene at a temperature T = 77 K and a pump intensity I = 300 mW/mm(2). We find that the loss of a SRR metamaterial can be compensated by optically stimulated amplification in graphene. Moreover, we show that a hybrid material consisting of asymmetric split-ring resonators and optically pumped graphene can emit coherent THz radiation at minimum output power levels of 60 nW/mm(2).

  14. Production of a nuclear spin polarized23Na-beam by optical pumping (United States)

    Dreves, W.; Kamke, W.; Broermann, W.; Fick, D.


    Nuclear spin polarization of an atomic23Na-beam was produced by a combination of optical pumping with a dye laser and a sextupole magnet and, alternatively, by optical pumping with two dye lasers. The maximum value measured for the vector polarization was P z=0.86+0.08, using beam foil spectroscopy. Further improvements of polarized ion sources based on this principle are discussed.

  15. Magnetic microscopic imaging with an optically pumped magnetometer and flux guides (United States)

    Kim, Young Jin; Savukov, Igor; Huang, Jen-Huang; Nath, Pulak


    By combining an optically pumped magnetometer (OPM) with flux guides (FGs) and by installing a sample platform on automated translation stages, we have implemented an ultra-sensitive FG-OPM scanning magnetic imaging system that is capable of detecting magnetic fields of ˜20 pT with spatial resolution better than 300 μm (expected to reach ˜10 pT sensitivity and ˜100 μm spatial resolution with optimized FGs). As a demonstration of one possible application of the FG-OPM device, we conducted magnetic imaging of micron-size magnetic particles. Magnetic imaging of such particles, including nano-particles and clusters, is very important for many fields, especially for medical cancer diagnostics and biophysics applications. For rapid, precise magnetic imaging, we constructed an automatic scanning system, which holds and moves a target sample containing magnetic particles at a given stand-off distance from the FG tips. We show that the device was able to produce clear microscopic magnetic images of 10 μm-size magnetic particles. In addition, we also numerically investigated how the magnetic flux from a target sample at a given stand-off distance is transmitted to the OPM vapor cell.

  16. Accurate optical measurement of nuclear polarization in optically pumped ^3He gas (United States)

    Bigelow, N. P.; Nacher, P. J.; Leduc, M.


    Large nuclear polarizations M (over 80 %) can now be achieved in gaseous ^3He by optical pumping. The gas is excited by an RF discharge and is oriented using a high power LNA laser which is lamp pumped and tuned to the 2 ^3S-2 ^3P transition at 1.08 μm. In this paper we describe an experiment in which we measure M with high absolute precision. Our method is based on a change as a function of M in the ratio of σ or π polarized light absorbed from a weak probe beam by the 2 ^3S metastable atoms. The probe was delivered by a diode pumped LNA laser and propagated perpendicular to the direction of the magnetization. Simultaneous measurement of M was made by monitoring the degree of circular polarization \\cal{P} of the optical line at 668 nm emitted by the discharge. Our measurements show a linear relationship between M and \\cal{P} for all accessible M values and for a wide range of experimental conditions (sample pressure, magnetic field, RF discharge level, etc.). This provides a second method of measurement of the ^3He nuclear polarization which is simple to operate and is calibrated and is calibrated over a pressure range of 0.15 to 6.5 torr. On peut maintenant produire par pompage optique de fortes polarisations nucléaires M (M supérieure à 80 % dans l' ^3He gazeux. Le gaz est excité par une décharge radiofréquence et orienté à l'aide d'un laser LNA de forte intensité qui est pompé par des lampes et accordé sur la transition 2 ^3S-2 ^3P à 1,08 μm. Dans cet article, nous décrivons une expérience où nous mesurons M avec une grande précision absolue. Notre méthode est fondée sur la variation en fonction de M de l'absorption par les atomes métastables d'un faisceau sonde de faible intensité polarisé linéairement. Nous mesurons le rapport des absorptions pour des polarisations π et σ. Le faisceau sonde est un laser LNA pompé par diode qui se propage perpendiculairement à la direction de l'aimantation. Simultanément, nous mesurons M par le

  17. Progress in ultra-compact green frequency doubled optically pumped surface emitting lasers (United States)

    Steegmueller, Ulrich; Kuehnelt, Michael; Unold, Heiko; Schwarz, Thomas; Schmitt, Michael; Auen, Karsten; Schulz, Roland; Walter, Christoph; Pietzonka, Ines; Illek, Stefan; Lindberg, Hans; Gomez-Iglesias, Alvaro; Furitsch, Michael; Lauer, Christian; Strauss, Uwe; Hoefer, Thomas


    Compact, stable and efficient green lasers are of great interest for many applications like mobile video projection, sensing, distance measurement and instrumentation. Those applications require medium values of output power in the 50mW range, good wall-plug efficiency above 5 % and stable operation over a wide temperature range. In this paper we present latest results from experimental investigations on ultra-compact green intracavity frequency doubled optically pumped semiconductor InGaAs disk lasers. The green laser setup has been limited to a few micro optical and semiconductor components built on a silicon backplane and fits within an envelope of less than 0.4 cc. An optical frequency looking scheme in order to fix the fundamental wavelength over varying operating conditions like changing output power and ambient temperature has been applied. The cavity has been optimized for fast modulation response and high efficiency using quasi-phase matching non-linear material. Recent data from cw and high-frequency characterization is presented.

  18. Single-resonance optical pumping spectroscopy and application in dressed-state measurement with atomic vapor cell at room temperature. (United States)

    Liang, Qiangbing; Yang, Baodong; Zhang, Tiancai; Wang, Junmin


    By monitoring the transmission of probe laser beam (also served as coupling laser beam) which is locked to a cycling hyperfine transition of cesium D(2) line, while pumping laser is scanned across cesium D(1) or D(2) lines, the single-resonance optical pumping (SROP) spectra are obtained with atomic vapor cell. The SROP spectra indicate the variation of the zero-velocity atoms population of one hyperfine fold of ground state, which is optically pumped into another hyperfine fold of ground state by pumping laser. With the virtue of Doppler-free linewidth, high signal-to-noise ratio (SNR), flat background and elimination of crossover resonance lines (CRLs), the SROP spectra with atomic vapor cell around room temperature can be employed to measure dressed-state splitting of ground state, which is normally detected with laser-cooled atomic sample only, even if the dressed-state splitting is much smaller than the Doppler-broaden linewidth at room temperature.

  19. Electron microscopic observations of Rb particles and pitting in 129Xe spin-exchange optical pumping cells (United States)

    Flower, C.; Freeman, M. S.; Plue, M.; Driehuys, B.


    High-volume production of hyperpolarized 129Xe by spin-exchange optical pumping (SEOP) has historically fallen short of theoretical predictions. Recently, this shortfall was proposed to be caused by the formation of alkali metal clusters during optical pumping. However, this hypothesis has yet to be verified experimentally. Here, we seek to detect the presence of alkali particles using a combination of both transmission (TEM) and scanning (SEM) electron microscopy. From TEM studies, we observe the presence of particles exhibiting sizes ranging from approximately 0.2 to 1 μm and present at densities of order 10 s of particles per 100 square microns. Particle formation was more closely associated with extensive cell usage history than short-term ( ≈ 1 h) SEOP exposure. From the SEM studies, we observe pits on the cell surface. These pits are remarkably smooth, were frequently found adjacent to Rb particles, and located predominantly on the front face of the cells; they range in size from 1 to 5 μm. Together, these findings suggest that Rb particles do form during the SEOP process and at times can impart sufficient energy to locally alter the Pyrex surface.

  20. Effect of periodic optical pumping on dynamics of passive mode-locked fiber laser (United States)

    Lee, Chung Ghiu; Kim, Joonyoung; Kim, Soeun


    We report on the effect of periodic optical pumping on a passively mode-locked fiber laser (MLFL) based on an erbium-doped fiber (EDF). We investigate the influence of various parameters (including average pump power into the fiber laser, the modulation frequency and duty cycle of the pump, and the polarization state of the light inside the cavity) on the transient response characteristic of the MLFL such as: relaxation oscillation (RO) build-up time (defined as the time delay from the onset of pumping to the generation of passively mode-locked pulses) and the power of the detected RF signal at the fundamental cavity-mode frequency (determined by the ring cavity length), which reflects the stability of mode-locking pulse train. We have found that the RO build-up time is inversely proportional to the average pump power while the RF power of the detected fundamental cavity mode (produced by the ring cavity) is proportional to the average pump power. A change in the duty cycle effectively leads the average pump power to vary, which in turn leads to changes in the transient response. The modulation frequency of the pump is rather related to the stability of the MLFL than its response time. Generally, the lower the modulation frequency, the more stable the mode-locked pulses generated in the fiber laser. Finally, the RO build-up time and, consequently, the pulse-generation time are highly sensitive to the state of polarization in the MLFL cavity.

  1. Low-threshold terahertz molecular laser optically pumped by a quantum cascade laser

    Directory of Open Access Journals (Sweden)

    A. Pagies


    Full Text Available We demonstrate a low-threshold, compact, room temperature, and continuous-wave terahertz molecular laser optically pumped by a mid-infrared quantum cascade laser. These characteristics are obtained, thanks to large dipole transitions of the active medium: NH3 (ammonia in gas state. The low-power (<60 mW laser pumping excites the molecules, thanks to intense mid-infrared transitions around 10.3 μm. The molecules de-excite by stimulated emission on pure inversion “umbrella-mode” quantum transitions allowed by the tunnel effect. The tunability of the quantum cascade laser gives access to several pure inversion transitions with different rotation states: we demonstrate the continuous-wave generation of ten laser lines around 1 THz. At 1.07 THz, we measure a power of 34 μW with a very low-threshold of 2 mW and a high differential efficiency of 0.82 mW/W. The spectrum was measured showing that the linewidth is lower than 1 MHz. To our knowledge, this is the first THz molecular laser pumped by a solid-state source and this result opens the way for compact, simple, and efficient THz source at room temperature for imaging applications.

  2. Continuous-wave Optically Pumped Lasing of Hybrid Perovskite VCSEL at Green Wavelength

    KAUST Repository

    Alias, Mohd Sharizal


    We demonstrate the lasing of a perovskite vertical-cavity surface-emitting laser at green wavelengths, which operates under continuous-wave optical pumping at room-temperature by embedding hybrid perovskite between dielectric mirrors deposited at low-temperature.

  3. Capacitive-mesh output couplers for optically pumped far-infrared lasers. (United States)

    Weitz, D A; Skocpol, W J


    The use of capacitive-mesh output couplers for optically pumped far-infrared molecular lasers has been extended throughout the far-infrared spectrum, between 42 microm and 1.2 mm, and the optimum grid constants have been found for several lines. At shorter wavelengths, performance has been improved by the use of a novel hybrid capacitive-mesh hole output coupler.

  4. Optical Pumping Experiments on Next Generation Light Sources

    Energy Technology Data Exchange (ETDEWEB)

    Moon, S J; Fournier, K B; Scott, H; Chung, H K; Lee, R W


    Laser-based plasma spectroscopic techniques have been used with great success to determine the line shapes of atomic transitions in plasmas, study the population kinetics of atomic systems embedded in plasmas, and look at the redistribution of radiation. However, the possibilities for optical lasers end for plasmas with n{sub e}>10{sup 22}cm{sup -3} as light propagation is severely altered by the plasma. The construction of the Tesla Test Facility(TTF) at DESY(Deutsche Elektronen-Synchrotron), a short pulse tunable free electron laser in the vacuum-ultraviolet and soft X-ray regime (VUV FEL), based on the SASE(self amplified spontaneous emission) process, will provide a major advance in the capability for dense plasma-related research. This source will provide 10{sup 13} photons in a 200 fs duration pulse that is tunable from {approx} 6nm to 100nm. Since an VUV FEL will not have the limitation associated with optical lasers the entire field of high density plasmas kinetics in laser produced plasma will then be available to study with tunable source. Thus, one will be able to use this and other FEL x-ray sources to pump individual transitions creating enhanced population in the excited states that can easily be monitored. We show two case studies illuminating different aspects of plasma spectroscopy.

  5. Molecular iodine laser with wide-band optical pumping by polychannel cumulative discharge of magnetoplasma compressor

    Energy Technology Data Exchange (ETDEWEB)

    Kamrukov, A.S.; Kashnikov, G.N.; Kozlov, N.P.; Kuznetsov, S.G.; Orlov, V.K.; Protasov, Yu.S.


    Lasing is achieved in iodine vapor in experiments with wide-band optical pumping by the emission of a polychannel cumulative discharge of a magnetoplasma compressor. The active medium was excited by radiation from a shock-heated plasma formed by collision and accumulation of high-velocity head-on plasma streams produced by six magnetoplasma compressors 1 arranged in groups of three on each side of discharge chamber 2. The inside diameter of the chamber was 120 mm, and length was 300 mm. Two identical cells 3 containing the active substance were placed inside the chamber parallel to its axis. The cells were made of stainless steel with three flat windows of MgF/sub 2/ through which the pumping radiation was coupled into the active medium. On the end flanges of the cells were either quartz windows for studying luminescence characteristics, or adjustable quartz mirrors to form an optical cavity (laser cells). Brightness of the shock-compressed plasma in the iodine absorption band was enhanced by a xenon atmosphere of 1 to 3 torr in the discharge chamber. The use of a cumulative discharge in low-pressure gas instead of a vacuum discharge enabled effective tuning of the plasma emission spectrum. The buffer gas in the working cells was perfluoromethane. Lasing was observed on 342.0 and 342.4 nm corresponding to transitions with vibrational numbers of 1 to 14 and 2 to 15. Lasing pulse duration at half-amplitude was 1 to 1.5

  6. Metastability exchange optical pumping in {sup 3}He gas up to 30 mT. Efficiency measurements and evidence of laser-induced nuclear relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Batz, Marion


    Advances in metastability exchange optical pumping (MEOP) of {sup 3}He at high laser powers, with its various applications, but also at high gas pressures p{sub 3} and high magnetic field strengths B, have provided strong motivation for revisiting the understanding and for investigating the limitations of this powerful technique. For this purpose, we present systematic experimental and theoretical studies of efficiency and of relaxation mechanisms in B{<=}30 mT and p{sub 3}=0.63-2.45 mbar. {sup 3}He nuclear polarisation is measured by light absorption in longitudinal configuration where weak light beams at 1083 nm parallel to magnetic field and cell axis with opposite circular polarisations are used to probe the distribution of populations in the metastable state. This method is systematically tested to evaluate potential systematic biases and is shown to be reliable for the study of OP dynamics despite the redistribution of populations by OP light. Nuclear polarisation loss associated to the emission of polarised light by the plasma discharge used for MEOP is found to decrease above 10 mT, as expected, due to hyperfine decoupling in highly excited states. However, this does not lead to improved MEOP efficiency at high laser power. We find clear evidence of additional laser-induced relaxation instead. The strong OP-enhanced polarisation losses, currently limiting MEOP performances, are quantitatively investigated using an angular momentum budget approach and a recently developed comprehensive model that describes the combined effects of OP, ME and relaxation, validated by comparison to experimental results.

  7. GaSb-based optically pumped semiconductor disk lasers emitting in the 2.0-2.8 µm wavelength range (United States)

    Rösener, Benno; Rattunde, Marcel; Moser, Rüdiger; Kaspar, Sebastian; Manz, Christian; Köhler, Klaus; Wagner, Joachim


    In recent years, optically pumped semiconductor disk lasers (OPSDLs) have attracted increasing interest due to their capability of delivering simultaneously high output power and excellent beam quality. Here we report on group-III-Sbbased OPSDLs allowing to cover the wavelength range around and above 2 μm. First the current state-of-the-art and recent progress for OPSDLs emitting in the 2.0-to-2.3 μm spectral range is presented, which includes power scaling through the use of multiple gain elements and as well as spectral tuning and line width narrowing, exploiting in both cases the versatility of the external cavity concept. Then, results on III-Sb-based OPSDLs emitting at 2.8 μm with a cw output power of up to 0.12 W and a peak output power in pulsed mode of >0.5 W, both data referring to roomtemperature operation, are presented. In both cases, the active region of the OPSDL chip consists of compressively strained GaInAsSb quantum well (QW) layers embedded between AlGaAsSb barrier and pump-light-absorbing layers. The emission wavelength is controlled by adjusting the composition of the quaternary QW material. The active region is grown on top of an epitaxial GaSb/AlAsSb Bragg mirror. For efficient heat extraction, SiC intra-cavity heat spreaders were bonded to the surface of the cleaved laser chips. An N-shaped resonator with one OPSDL chip acting as an end mirror and the second OPSDL chip as a folding mirror was used for power scaling, while a V-shaped resonator configuration with a birefringent tuner inserted into the collimated beam path of the resonator was employed for wavelength tuning. Optical pumping was achieved by standard fiber-coupled diode laser modules emitting at 980 nm.

  8. Nonlinear effects in optical pumping of a cold and slow atomic beam

    KAUST Repository

    Porfido, N.


    By photoionizing hyperfine (HF) levels of the Cs state 62P3/2 in a slow and cold atom beam, we find how their population depends on the excitation laser power. The long time (around 180μs) spent by the slow atoms inside the resonant laser beam is large enough to enable exploration of a unique atom-light interaction regime heavily affected by time-dependent optical pumping. We demonstrate that, under such conditions, the onset of nonlinear effects in the population dynamics and optical pumping occurs at excitation laser intensities much smaller than the conventional respective saturation values. The evolution of population within the HF structure is calculated by numerical integration of the multilevel optical Bloch equations. The agreement between numerical results and experiment outcomes is excellent. All main features in the experimental findings are explained by the occurrence of “dark” and “bright” resonances leading to power-dependent branching coefficients.

  9. Optically pumped DBR-free semiconductor disk lasers. (United States)

    Yang, Zhou; Albrecht, Alexander R; Cederberg, Jeffrey G; Sheik-Bahae, Mansoor


    We report high power distributed Bragg reflector (DBR)-free semiconductor disk lasers. With active regions lifted off and bonded to various transparent heatspreaders, the high thermal impedance and narrow bandwidth of DBRs are mitigated. For a strained InGaAs multi-quantum-well sample bonded to a single-crystalline chemical-vapor deposited diamond, a maximum CW output power of 2.5 W and a record 78 nm tuning range centered at λ≈1160 nm was achieved. Laser operation using a total internal reflection geometry is also demonstrated. Furthermore, analysis for power scaling, based on thermal management, is presented.

  10. Erbium Doped GaN Lasers by Optical Pumping (United States)


    thermal properties . The thermal conductivity GaN is very high (κ = 230 W/mK) and is more than one order of magnitude higher than YAG (κ = 14 W/mK...the ground state to a higher-lying inner 4f manifold in Er3+ ions without invoking a non- radiative energy transfer , hence generating a much smaller...installation of a high power 980 laser. The system is dedicated to the studies of the optical and lasing properties of Er:GaN crystals. The views

  11. Optically pumped VECSELs: review of technology and progress (United States)

    Guina, M.; Rantamäki, A.; Härkönen, A.


    Vertical-external-cavity surface-emitting lasers (VECSELs) are the most versatile laser sources, combining unique features such as wide spectral coverage, ultrashort pulse operation, low noise properties, high output power, high brightness and compact form-factor. This paper reviews the recent technological developments of VECSELs in connection with the new milestones that continue to pave the way towards their use in numerous applications. Significant attention is devoted to the fabrication of VECSEL gain mirrors in challenging wavelength regions, especially at the yellow and red wavelengths. The reviewed fabrication approaches address wafer-bonded VECSEL structures as well as the use of hybrid mirror structures. Moreover, a comprehensive summary of VECSEL characterization methods is presented; the discussion covers different stages of VECSEL development and different operation regimes, pointing out specific characterization techniques for each of them. Finally, several emerging applications are discussed, with emphasis on the unique application objectives that VECSELs render possible, for example in atom and molecular physics, dermatology and spectroscopy.

  12. Kinetic analysis of rare gas metastable production and optically pumped Xe lasers (United States)

    Demyanov, A. V.; Kochetov, I. V.; Mikheyev, P. A.; Azyazov, V. N.; Heaven, M. C.


    Optically pumped all-rare-gas lasers use metastable rare gas atoms as the lasing species in mixtures with He or Ar buffer gas. The metastables are generated in a glow discharge, and we report model calculations for the optimal production of Ne*, Ar*, Kr* and Xe*. Discharge efficiency was estimated by solving the Boltzmann equation. Laser efficiency, gain and output power of the CW optically pumped Xe laser were assessed as functions of heavier rare gas content, pressure, optical pump intensity and the optical path length. It was found that, for efficient operation the heavier rare gas content has to be of the order of one percent or less, and the total pressure—in the range 0.3–1.5 atm. Output power and specific discharge power increase approximately linearly with pump intensity over the output range from 300–500 W cm‑2. Ternary mixtures Xe:Ar:He were found to be the most promising. Total laser efficiency was found to be nearly the same for pumping the 2p8 or 2p9 state, reaching 61%–70% for a pump intensity of ~720 W cm‑2 when the Xe fraction was in the range 0.001 ÷ 0.01 and Ar fraction—0.1 ÷ 0.5. However, when the 2p8 state was pumped, the maximum total efficiency occurred at larger pressures than for pumping of the 2p9 state. The discharge power density required to sustain a sufficient Xe* number density was in the range of tens of watts per cubic centimeter for 50% Ar in the mixture.

  13. Spatio-temporal Theory of Lasing Action in Optically-Pumped Rotationally Excited Molecular Gases (United States)


    6Departamento de Fı́sica Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049, Madrid, Spain ∗ Abstract: We investigate...De Lucia, “Millimeter wave spectroscopic studies of collision-induced energy transfer processes in the 13CH3F laser,” IEEE J. Quantum Electron. transfer in optically pumped far-infrared lasers,” IEEE J. Quantum Electron. QE-23, 2069–2077 (1989). 8. H. O. Everitt and F. C. De Lucia, “A time

  14. Optically pumped tunable HBr laser in the mid-infrared region. (United States)

    Koen, Wayne; Jacobs, Cobus; Bollig, Christoph; Strauss, Hencharl J; Esser, M J Daniel; Botha, Lourens R


    An optically pumped tunable HBr laser has been demonstrated for the first time. The pump source was a single-frequency Ho:YLF laser and amplifier system, which was locked to the 2064 nm absorption line of HBr. Laser oscillation was demonstrated on 19 molecular transition lines, which included both the R-branch (3870-4015 nm) and the P-branch (4070-4453 nm), by the use of an intra-cavity diffraction grating. The highest output energy was 2.4 mJ at 4133 nm.

  15. Analytical Solutions of Temporal Evolution of Populations in Optically-Pumped Atoms with Circularly Polarized Light

    Directory of Open Access Journals (Sweden)

    Heung-Ryoul Noh


    Full Text Available We present an analytical calculation of temporal evolution of populations for optically pumped atoms under the influence of weak, circularly polarized light. The differential equations for the populations of magnetic sublevels in the excited state, derived from rate equations, are expressed in the form of inhomogeneous second-order differential equations with constant coefficients. We present a general method of analytically solving these differential equations, and obtain explicit analytical forms of the populations of the ground state at the lowest order in the saturation parameter. The obtained populations can be used to calculate lineshapes in various laser spectroscopies, considering transit time relaxation.

  16. True-green (11-22) plane optically pumped laser with cleaved m-plane facets (United States)

    Sizov, Dmitry; Bhat, Rajaram; Heberle, Albert; Visovsky, Nick; Zah, Chung-en


    We present a detailed experimental study of optical property of green InGaN quantum wells and optically pumped lasers, with cleaved m-plane facets and a lasing wavelength in the range of 520-530 nm, grown on semipolar (11-22) planes. Taking advantage of low transparency carrier density of the lowest-energy valence band and overcoming low differential gain by minimizing the optical loss of the laser structure, we demonstrated a low threshold pumping power of 120 mW.

  17. Depolarization of nuclear spin polarized 129Xe gas by dark rubidium during spin-exchange optical pumping (United States)

    Antonacci, M. A.; Burant, Alex; Wagner, Wolfgang; Branca, Rosa T.


    Continuous-flow spin-exchange optical pumping (SEOP) continues to serve as the most widespread method of polarizing 129Xe for magnetic resonance experiments. Unfortunately, continuous-flow SEOP still suffers from as-yet unidentified inefficiencies that prevent the production of large volumes of xenon with a nuclear spin polarization close to theoretically calculated values. In this work we use a combination of ultra-low field nuclear magnetic resonance spectroscopy and atomic absorption spectroscopy (AAS) measurements to study the effects of dark Rb vapor on hyperpolarized 129Xe in situ during continuous-flow SEOP. We find that dark Rb vapor in the optical cell outlet has negligible impact on the final 129Xe polarization at typical experimental conditions, but can become significant at higher oven temperatures and lower flow rates. Additionally, in the AAS spectra we also look for a signature of paramagnetic Rb clusters, previously identified as a source of xenon depolarization and a cause for SEOP inefficiency, for which we are able to set an upper limit of 8.3 × 1015 Rb dimers per cm3.

  18. Systematic Effects in Laser-Induced Fluorescence Measurments of Ion Density and Temperature Caused by Optical Pumping (United States)

    Langin, Thomas; Strickler, Trevor; McQuillen, Patrick; Killian, Thomas


    Ultracold neutral plasmas of strontium are generated by photoionizing laser-cooled atoms. The plasma evolution is probed by laser induced fluorescence (LIF) via the 5s2S1/2-5p2P1/2 ion transition. Spectra are obtained by recording LIF intensity at varying laser detunings. The ion temperature, T, is then measured by fitting a Voigt profile to obtain the Doppler width. However, for linearly (circularly) polarized light, 5p2P1/2 ions have a 7% (33%) chance of decaying to the dark metastable 5d 2D3/2 state (dark opposite spin state). Near resonance, where ions are more likely to scatter multiple photons during the LIF process, the observed signal will be depressed due to optical pumping. This causes an artificial broadening in the spectra and thus artificially high T measurements. Moreover, the loss of ions throughout the excitation process, if not corrected for, will result in artificially low density measurements. We have developed, and experimentally verified, a method for simulating the LIF process in order to determine the LIF-probe durations and intensities for which these effects becomes significant. This work was supported by the National Science Foundation and the Department of Energy (PHY-0714603), the Air Force Office of Scientific Research (FA9550-12-1-0267), the Department of Defense (NDSEG Fellowship), and Shell

  19. Optically pumped distributed feedback dye lasing with slide-coated TiO₂ inverse-opal slab as Bragg reflector. (United States)

    Han, Sung Gu; Lim, Jongchul; Shin, Jinsub; Lee, Sung-Min; Park, Taiho; Yoon, Jongseung; Woo, Kyoungja; Lee, Hyunjung; Lee, Wonmok


    We demonstrate an optical amplification of organic dye within a TiO2 inverse-opal (IO) distributed feedback (DFB) reflector prepared by a slide-coating method. Highly reflective TiO2 IO film was fabricated by slide coating the binary aqueous dispersions of polystyrene microspheres and charge-stabilized TiO2 nanoparticles on a glass slide and subsequently removing the polymer-opal template. TiO2 IO film was infiltrated, in turn, with the solutions of DCM, a fluorescent dye in various solvents with different indices of refraction. Optical pumping by frequency-doubled Nd:YAG laser resulted in amplified spontaneous emission in each dye solution. In accordance with the semi-empirical simulation by the FDTD method, DCM in ethanol showed the best emission/stopband matching for the TiO2 IO film used in this study. Therefore, photo excitation of a DCM/ethanol cavity showed a single-mode DFB lasing at 640 nm wavelength at moderate pump energy.

  20. Laser Cooling and Trapping of Neutral Mercury Atoms Using an Optically-Pumped External-Cavity Semiconductor Laser (United States)

    Paul, Justin; Lytle, Christian; Jones, R. Jason


    The level structure of the Hg atom is similar to other alkaline earth-like atoms, offering the possibility to realize an extremely high quality resonance factor (Q) on the ``clock'' transition (1S0- 3P0) when confined in an optical lattice at the Stark-shift free wavelength. A key feature of the Hg system is the reduced uncertainty due to black-body induced Stark shifts, making it an interesting candidate as an optical frequency standard. One challenge to laser-cooling neutral Hg atoms is finding a reliable source for cooling on the 1S0-3 P1 transition at 253.7 nm. We employ an optically pumped semiconductor laser (OPSEL) operating at 1015 nm, whose frequency is quadrupled in two external-cavity doubling stages to generate over 120 mW at 253.7 nm. With this new laser source we have trapped Hg199 from a background vapor in a standard MOT. We trap up to 2 × 106 atoms with a 1/e2 radius of our MOT of ~310 microns, corresponding to a density of 1.28 × 1010 atoms/cm3. We report on the progress of our Hg system and plans for precision lattice-based spectroscopy of the clock transition. Support for this work is supported through the U.S. Air Force Office of Scientific Research (AFOSR) through grant no. FA9550-09-1-0563.

  1. Optically Pumped Lasing of Ar(4p -->4s) Excited in Linear Microplasma Arrays at Atmospheric Pressure (United States)

    Rawlins, Wilson; Galbally-Kinney, Kristin; Davis, Steven; Hoskinson, Alan; Hopwood, Jeffrey


    The optically pumped rare-gas metastable laser is a chemically inert analogue to alkali laser systems. These devices require efficient generation of electronically excited metastable atoms in a continuous-wave electric discharge in flowing gas mixtures at elevated pressure. Linear arrays of microstrip resonators are well suited for this task. We have observed CW optical gain and lasing at 912 nm using linear micro-discharge arrays to generate metastable rare-gas atoms at atmospheric pressure. Ar(4s) metastables are generated in flowing Ar/He mixtures by low-power, CW linear array microplasmas operating near 900 MHz and 1 atm. The metastables are optically excited to selected states in the Ar(4p) manifold by a tunable, CW Ti:S laser. Collisional energy transfer within the manifold produces a population inversion. The Ar(4s) concentration and the optical gain are probed by tunable diode laser spectroscopy. Supported by the Air Force Research Laboratory and High Energy Laser Joint Technology Office.

  2. Collinear laser spectroscopy of manganese isotopes using optical pumping in ISCOOL

    CERN Multimedia

    Marsh, B A; Neyens, G; Flanagan, K; Rajabali, M M; Reponen, M; Campbell, P; Procter, T J

    Recently, optical pumping of ions has been achieved inside an ion beam cooler-buncher. By illuminating the central axis of the cooler with laser light, subsequent decay populates selected ionic metastable states. This population enhancement is retained as the ion beam is delivered to an experimental station. In the case of collinear laser spectroscopy, transitions can then be excited from a preferred metastable level, rather than the ground-state. This proposal seeks to establish and develop the technique for ISCOOL. As a test of efficiency, this will be applied to the study of $^{55-66}$Mn isotopes using collinear laser spectroscopy-expanding an earlier study where the benefit of the technique was demonstrated. This will provide nuclear spins, magnetic-dipole and electric-quadrupole moments and changes in mean-square charge radii across N = 40 shell closure candidate and into a region where an onset of deformation, and a new "island of inversion" is predicted.

  3. Low-frequency, self-sustained oscillations in inductively coupled plasmas used for optical pumping (United States)

    Coffer, J.; Encalada, N.; Huang, M.; Camparo, J.


    We have investigated very low frequency, on the order of one hertz, self-pulsing in alkali-metal inductively-coupled plasmas (i.e., rf-discharge lamps). This self-pulsing has the potential to significantly vary signal-to-noise ratios and (via the ac-Stark shift) resonant frequencies in optically pumped atomic clocks and magnetometers (e.g., the atomic clocks now flying on GPS and Galileo global navigation system satellites). The phenomenon arises from a nonlinear interaction between the atomic physics of radiation trapping and the plasma's electrical nature. To explain the effect, we have developed an evaporation/condensation theory (EC theory) of the self-pulsing phenomenon.

  4. Dye linked conjugated homopolymers: using conjugated polymer electroluminescence to optically pump porphyrin-dye emission

    DEFF Research Database (Denmark)

    Nielsen, K.T.; Spanggaard, H.; Krebs, Frederik C


    Zinc-porphyrin dye molecules were incorporated into the backbone of a conjugated polymer material by a method, which allowed for the incorporation of only one zinc-porphyrin dye molecule into the backbone of each conjugated polymer molecule. The electronic properties of the homopolymer were....... Electroluminescent devices of the homopolymer itself and of the zinc-porphyrin containing polymer were prepared and the nature of the electroluminescence was characterized. The homopolymer segments were found to optically pump the emission of the zinc-porphyrin dye moities. The homopolymer exhibits blue......-green emission and the zinc-porphyrin linked homopolymers emit near-infrared/infrared light. This was demonstrated to be due to electroluminescence pumping of the zinc-porphyrin moieties that were covalently linked to homopolymer material. When only one zinc-porphyrin dye was incorporated into the backbone...

  5. Continuous-wave optically pumped green perovskite vertical-cavity surface-emitter

    KAUST Repository

    Alias, Mohd Sharizal


    We report an optically pumped green perovskite vertical-cavity surface-emitter operating in continuous-wave (CW) with a power density threshold of ~89 kW/cm2. The device has an active region of CH3NH3PbBr3 embedded in a dielectric microcavity; this feat was achieved with a combination of optimal spectral alignment of the optical cavity modes with the perovskite optical gain, an adequate Q-factor of the microcavity, adequate thermal stability, and improved material quality with a smooth, passivated, and annealed thin active layer. Our results signify a way towards efficient CW perovskite emitter operation and electrical injection using low-cost fabrication methods for addressing monolithic optoelectronic integration and lasing in the green gap.

  6. Stabilization of He2(A(sup 3)Sigma(sub u)(+)) molecules in liquid helium by optical pumping for vacuum UV laser (United States)

    Zmuidzinas, J. S. (Inventor)


    A technique is disclosed for achieving large populations of metastable spin-aligned He2(a 3 Sigma u +) molecules in superfluid helium to obtain lasing in the vacuum ultraviolet wavelength regime around 0.0800 micron m by electronically exciting liquid (superfluid) helium with a comparatively low-current electron beam and spin aligning the metastable molecules by means of optical pumping with a modestly-powered (100mW) circularly-polarized continuous wave laser operating at, for example, 0.9096 or 0.4650 micron m. Once a high concentration of spin-aligned He2 (a 3 Sigma u +) is achieved with lifetimes of a few milliseconds, a strong microwave signal destroys the spin alignment and induces a quick collisional transition of He2 (a 3 Sigma u +) molecules to the a 1 Sigma u + state and thereby a lasing transition to the X 1 Sigma g + state.

  7. Orientation of /sup 199m/Hg by optical pumping detected by gamma - radiation anisotropy

    CERN Document Server

    Bonn, J; Kluge, H J; Lode, D; Otten, E W


    /sup 199m/Hg was produced and mass separated at the ISOLDE facility (CERN). Nuclear orientation achieved by optical pumping via the resonance line 6s/sup 2/ /sup 1/S/sub 0/ to 6S6p/sup 3/P/sub 1/, lambda =2537 AA was monitored by means of the anisotropy of the gamma -radiation emitted in the cascade /sup 199m/Hg(I=13/2/sup +/) to /sup 191/Hg(I=5/2/sup -/) to /sup 199/Hg(I=1/2/sup -/). Maximum anisotropies of 35% (2,8%) were found in the M4(E2) transition. A Zeeman scanning of the /sup 3/P/sub 1/ state yielded the positions of F=13/2 and the F=15/2 hfs components relative to the reference isotope /sup 204/Hg at 15.13(15) GHz and -2.86(15) GHz respectively. Isotopic shift and the quadrupole interaction constant were deduced from these values using the known A factor. From the B factor the spectroscopic quadruplment was calculated as Q/sub s/=1.54(44) barn. (30 refs).

  8. Characterization of elastic interactions in GaAs/Si composites by optically pumped nuclear magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Ryan M.; Tokarski, John T.; McCarthy, Lauren A.; Bowers, Clifford R., E-mail: [Department of Chemistry, University of Florida, Gainesville, Florida 32611 (United States); Stanton, Christopher J. [Department of Physics, University of Florida, Gainesville, Florida 32611 (United States)


    Elastic interactions in GaAs/Si bilayer composite structures were studied by optically pumped nuclear magnetic resonance (OPNMR). The composites were fabricated by epoxy bonding of a single crystal of GaAs to a single crystal of Si at 373 K followed by selective chemical etching of the GaAs at room temperature to obtain a series of samples with GaAs thickness varying from 37 μm to 635 μm, while the Si support thickness remained fixed at 650 μm. Upon cooling to below 10 K, a biaxial tensile stress developed in the GaAs film due to differential thermal contraction. The strain perpendicular to the plane of the bilayer and localized near the surface of the GaAs was deduced from the quadrupolar splitting of the Gallium-71 OPNMR resonance. Strain relaxation by bowing of the composite was observed to an extent that depended on the relative thickness of the GaAs and Si layers. The variation of the strain with GaAs layer thickness was found to be in good agreement with a general analytical model for the elastic relationships in composite media.

  9. Probing Primordial Magnetic Fields with 21-cm Line Observations of the High-redshift Intergalactic Medium (United States)

    Oklopcic, Antonija; Gluscevic, V.; Hirata, C. M.; Mishra, A.; Venumadhav, T. N.


    Coherent magnetic fields with strengths of the order of 10^(-5) G are observed on scales of individual galaxies, including the Milky Way. They are thought to be organized and maintained by a dynamo mechanism. However, the nature and origin of the seed magnetic field, required for the dynamo effect to take place, are still unknown. Here, we propose a method of probing the magnetic field in the intergalactic medium before the Epoch of Reionization through observations of redshifted 21-cm radiation of neutral hydrogen. The 21-cm line is created during the spin-flip transition between the hyperfine levels of the hydrogen ground state. The upper hyperfine level is a triplet consisting of atomic states with three different projections of the total angular momentum vector. Anisotropic 21-cm radiation, resulting from perturbations in the high-redshift IGM, unevenly populates triplet sublevels. If an atom is located in an external magnetic field, it precesses between the three states; this causes an additional anisotropy in the 21-cm radiation, which could be imprinted in the 21-cm power spectrum. In order to evaluate the effect of the magnetic field, we need to consider in full detail all mechanisms that affect the distribution of atoms in hyperfine sublevels, such as the interaction of hydrogen atoms with the 21-cm radiation, optical pumping by Lyman-alpha photons, and spin-exchange in hydrogen-hydrogen collisions. Preliminary calculations suggest that this method could be sensitive to extremely weak magnetic fields, of the order of 10^(-17) G.

  10. High-field/high-pressure ESR. (United States)

    Sakurai, T; Okubo, S; Ohta, H


    We present a historical review of high-pressure ESR systems with emphasis on our recent development of a high-pressure, high-field, multi-frequency ESR system. Until 2000, the X-band system was almost established using a resonator filled with dielectric materials or a combination of the anvil cell and dielectric resonators. Recent developments have shifted from that in the low-frequency region, such as X-band, to that in multi-frequency region. High-pressure, high-field, multi-frequency ESR systems are classified into two types. First are the systems that use a vector network analyzer or a quasi-optical bridge, which have high sensitivity but a limited frequency region; the second are like our system, which has a very broad frequency region covering the THz region, but lower sensitivity. We will demonstrate the usefulness of our high-pressure ESR system, in addition to its experimental limitations. We also discuss the recent progress of our system and future plans. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. High Magnetic Fields in Chemistry (United States)

    Steiner, U. E.; Gilch, P.

    Recent applications of large ( 1 T - 30 T) magnetic fields in modern chemical research are reviewed. Magnetic field effects of chemical relevance appear on the levels of quantum mechanics, thermodynamics, and oscopic forces. Quantum mechanical magnetic field effects are governed by the Zeeman interaction and are borne out as static and dynamic effects in spectroscopy and in chemical kinetics. Magnetic circular dichroism (MCD) spectroscopy and magnetic fluorescence quenching in the gas phase serve to illustrate the former, while radical pair spin chemistry is representative of the latter. The principles of the radical pair mechanism are outlined and high-field applications are illustrated in some detail for photo-induced electron transfer reactions of some transition metal complexes. Thermodynamic effects concern the magnetization of chemical samples, which is the focus of magnetochemistry or — more modern — molecular magnetism, and the equilibrium of chemical reactions. Representative examples of both aspects are described. Finally, the exploitation of orientational forces caused by the magnetic anisotropy of larger particles (from omolecules to micro-crystals) is exemplified. Crystal growth in a magnetic field may hold a potential for achieving better control of the quality of protein crystals for structural analysis.

  12. High Field Atherosclerotic Plaque MRI


    Yuan, Chun; Wang, Jinnan; Balu, Niranjan


    Manifestations of atherosclerotic plaque in different arterial beds range from perfusion deficits to overt ischemia such as stroke and myocardial infarction. Atherosclerotic plaque composition is known to be associated with its propensity to rupture and cause vascular events. MRI of atherosclerotic plaque using clinical 1.5T scanners can detect plaque composition. Plaque MRI at higher field strengths offers both opportunities and challenges to improving the high spatial-resolution and contras...

  13. A measurement of the absolute neutron beam polarization produced by an optically pumped sup 3 He neutron spin filter

    CERN Document Server

    Rich, D R; Crawford, B E; Delheij, P P J; Espy, M A; Haseyama, T; Jones, G; Keith, C D; Knudson, J; Leuschner, M B; Masaike, A; Masuda, Y; Matsuda, Y; Penttilae, S I; Pomeroy, V R; Smith, D A; Snow, W M; Szymanski, J J; Stephenson, S L; Thompson, A K; Yuan, V


    The capability of performing accurate absolute measurements of neutron beam polarization opens a number of exciting opportunities in fundamental neutron physics and in neutron scattering. At the LANSCE pulsed neutron source we have measured the neutron beam polarization with an absolute accuracy of 0.3% in the neutron energy range from 40 meV to 10 eV using an optically pumped polarized sup 3 He spin filter and a relative transmission measurement technique. sup 3 He was polarized using the Rb spin-exchange method. We describe the measurement technique, present our results, and discuss some of the systematic effects associated with the method.

  14. Optically pumped lasing in solution-processed perovskite semiconducting materials: Self-assembled Fabry-Pérot microcavity (United States)

    Sasaki, Fumio; Zhou, Ying; Sonoda, Yoriko; Azumi, Reiko; Mochizuki, Hiroyuki; Nguyen, Van-Cao; Yanagi, Hisao


    Optically pumped lasing has been observed in solution-processed perovskite semiconducting materials, CH3NH3PbX3 (X = Cl, Br, I). Self-assembled Fabry-Pérot (FP) cavities have been easily obtained by using a simple “cast-capping method”, where we can obtain single-crystal-like optical cavities. The observed spectra show clear multimode lasing of the FP cavities under pulsed optical excitation. The mode intervals are well explained by the optical constants with large dispersions of the materials. The obtained refractive index around the lasing area coincides with the results in the previous reports.

  15. Wafer-scale crack-free AlGaN on GaN through two-step selective-area growth for optically pumped stimulated emission (United States)

    Ko, Young-Ho; Bae, Sung-Bum; Kim, Sung-Bock; Kim, Dong Churl; Leem, Young Ahn; Cho, Yong-Hoon; Nam, Eun-Soo


    Crack-free AlGaN template has been successfully grown over entire 2-in. wafer by using 2-step selective-area growth (SAG). The GaN truncated structure was obtained by vertical growth mode with low growth temperature. AlGaN of second step was grown under lateral growth mode. Low pressure enhanced the relative ratio of lateral to vertical growth rate as well as absolute overall growth rate. High V/III ratio was favorable for lateral growth mode. Crack-free planar AlGaN was obtained under low pressure of 30 Torr and high V/III ratio of 4400. The AlGaN was crack-free over entire 2-in. wafer and had quite uniform Al-mole fraction. The dislocation density of the AlGaN with 20% Al-composition was as low as ~7.6×108 /cm2, measured by cathodoluminescence. GaN/AlGaN multi-quantum well (MQW) with cladding and waveguide layers were grown on the crack-free AlGaN template with low dislocation density. It was confirmed that the MQW on the AlGaN template emitted the stimulated emission at 355.5 nm through optical pumping experiment. The AlGaN obtained by 2-step SAG would provide high crystal quality for highly-efficient optoelectronic devices as well as the ultraviolet laser diode.

  16. Towards high efficiency heliostat fields (United States)

    Arbes, Florian; Wöhrbach, Markus; Gebreiter, Daniel; Weinrebe, Gerhard


    CSP power plants have great potential to substantially contribute to world energy supply. To set this free, cost reductions are required for future projects. Heliostat field layout optimization offers a great opportunity to improve field efficiency. Field efficiency primarily depends on the positions of the heliostats around the tower, commonly known as the heliostat field layout. Heliostat shape also influences efficiency. Improvements to optical efficiency results in electricity cost reduction without adding any extra technical complexity. Due to computational challenges heliostat fields are often arranged in patterns. The mathematical models of the radial staggered or spiral patterns are based on two parameters and thus lead to uniform patterns. Optical efficiencies of a heliostat field do not change uniformly with the distance to the tower, they even differ in the northern and southern field. A fixed pattern is not optimal in many parts of the heliostat field, especially when used as large scaled heliostat field. In this paper, two methods are described which allow to modify field density suitable to inconsistent field efficiencies. A new software for large scale heliostat field evaluation is presented, it allows for fast optimizations of several parameters for pattern modification routines. It was used to design a heliostat field with 23,000 heliostats, which is currently planned for a site in South Africa.

  17. Idea Generation in Highly Institutionalized Fields

    DEFF Research Database (Denmark)

    Agoguè, Marine; Boxenbaum, Eva

    The early phase of innovation processes in highly institutionalized fields relies on the capabilities of actors to generate new ideas that break with the field frame. Informed by a dominant logic, a field frame shapes collective cognition and can thus prevent the generation of new ideas and block...

  18. High field MRI in the diagnosis of multiple sclerosis: high field-high yield?

    Energy Technology Data Exchange (ETDEWEB)

    Wattjes, Mike P.; Barkhof, Frederik [VU University Medical Center, MS Center Amsterdam, Department of Radiology, Amsterdam (Netherlands)


    Following the approval of the U.S. Food and Drug Administration (FDA), high field magnetic resonance imaging (MRI) has been increasingly incorporated into the clinical setting. Especially in the field of neuroimaging, the number of high field MRI applications has been increased dramatically. Taking advantage on increased signal-to-noise ratio (SNR) and chemical shift, higher magnetic field strengths offer new perspectives particularly in brain imaging and also challenges in terms of several technical and physical consequences. Over the past few years, many applications of high field MRI in patients with suspected and definite multiple sclerosis (MS) have been reported including conventional and quantitative MRI methods. Conventional pulse sequences at 3 T offers higher lesion detection rates when compared to 1.5 T, particularly in anatomic regions which are important for the diagnosis of patients with MS. MR spectroscopy at 3 T is characterized by an improved spectral resolution due to increased chemical shift allowing a better quantification of metabolites. It detects significant axonal damage already in patients presenting with clinically isolated syndromes and can quantify metabolites of special interest such as glutamate which is technically difficult to quantify at lower field strengths. Furthermore, the higher susceptibility and SNR offer advantages in the field of functional MRI and diffusion tensor imaging. The recently introduced new generation of ultra-high field systems beyond 3 T allows scanning in submillimeter resolution and gives new insights into in vivo MS pathology on MRI. The objectives of this article are to review the current knowledge and level of evidence concerning the application of high field MRI in MS and to give some ideas of research perspectives in the future. (orig.)

  19. Synchrotron Applications of High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)



    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF.

  20. Neutron Scattering and High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Winn, Barry L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Stone, Matthew B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)


    The workshop “Neutron Scattering and High Magnetic Fields” was held September 4-5, 2014 at the Oak Ridge National Laboratory (ORNL). The workshop was held in response to a recent report by the National Research Council of the National Academy of Sciences entitled “High Magnetic Field Science and Its Application in the United States: Current Status and Future Directions.”1 This report highlights the fact that neutron scattering measurements carried out in high magnetic fields provide important opportunities for new science. The workshop explored the range of the scientific discoveries that could be enabled with neutron scattering measurements at high fields (25 Tesla or larger), the various technologies that might be utilized to build specialized instruments and sample environment equipment to enable this research at ORNL, and possible routes to funding and constructing these facilities and portable high field sample environments.

  1. High-field measurements on YBCO

    Energy Technology Data Exchange (ETDEWEB)

    Smith, J.L.; Fowler, C.M.; Freeman, B.L.; Goettee, J.D.; Hults, W.L.; King, J.C.; Rickel, D.G. [Los Alamos National Lab., NM (United States); Brooks, J.S.; Mankiewich, P.M.; De Obaldia, E.I.; Skocpol, W.J. [Boston Univ., MA (United States); O`Malley, M.L. [AT& T Bell Labs., Holmdel, NJ (United States)


    The authors have performed resistance measurements on thin films of the high-temperature superconductor YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) in applied magnetic fields to above 200 T (2 MegaOersted) at temperatures as low as 2.5 K. The fields are produced by an explosively driven flux-compression system. The authors can see a particularly clear onset, without replotting the data, of the {open_quotes}hydrodynamic{close_quotes} flow of vortices probably because of the very fast increasing field. The low-temperature {open_quotes}critical field{close_quotes} for the field parallel to the c-axis of the sample is 135 T. The data in the other direction are still preliminary. The authors discuss possible interpretation of the results.

  2. Development of optically pumped DBR-free semiconductor disk lasers (Conference Presentation) (United States)

    Yang, Zhou; Albrecht, Alexander R.; Cederberg, Jeffrey G.; Sheik-Bahae, Mansoor


    Semiconductor disk lasers (SDLs) are attractive for applications requiring good beam quality, wavelength versatility, and high output powers. Typical SDLs utilize the active mirror geometry, where a semiconductor DBR is integrated with the active region by growth or post-growth bonding. This imposes restrictions for the SDL design, like material system choice, thermal management, and effective gain bandwidth. In DBR-free geometry, these restrictions can be alleviated. An integrated gain model predicts DBR-free geometry with twice the gain bandwidth of typical SDLs, which has been experimentally verified with active regions near 1 μm and 1.15 μm. The lift-off and bonding technique enables the integration of semiconductor active regions with arbitrary high quality substrates, allowing novel monolithic geometries. Bonding an active region onto a straight side of a commercial fused silica right angle prism, and attaching a high reflectivity mirror onto the hypotenuse side, with quasi CW pumping at 780 nm, lasing operation was achieved at 1037 nm with 0.2 mW average power at 1.6 mW average pump power. Laser dynamics show that thermal lens generation in the active region bottlenecks the laser efficiency. Investigations on total internal reflection based monolithic ring cavities are ongoing. These geometries would allow the intracavity integration of 2D materials or other passive absorbers, which could be relevant for stable mode locking. Unlike typical monolithic microchip SDLs, with the evanescent wave coupling technique, these monolithic geometries allow variable coupling efficiency.

  3. High magnetic fields science and technology

    CERN Document Server

    Miura, Noboru


    This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological syst

  4. Collisional Dynamics, Lasing and Stimulated Raman Scattering in Optically Pumped Cesium and Potassium Vapors (United States)


    system of rate equations with terms describing radiative rates, driving rates (form iΩjρij) and transition rates (form iωijρij) where the Ω are the Rabi ...longer than the cell. The flat high reflector and output coupler ( Lattice Electro Optics, Inc. ROC = 25 cm) form a stable 48 cm cavity. We tested...The potential terms in the Hamiltonian can be written using the Rabi frequency, Ωij = Eijµij h , and the frequency terms can be written as ∆nm = ωnm

  5. Large-Scale Statistics for Threshold Optimization of Optically Pumped Nanowire Lasers. (United States)

    Alanis, Juan Arturo; Saxena, Dhruv; Mokkapati, Sudha; Jiang, Nian; Peng, Kun; Tang, Xiaoyan; Fu, Lan; Tan, Hark Hoe; Jagadish, Chennupati; Parkinson, Patrick


    Single nanowire lasers based on bottom-up III-V materials have been shown to exhibit room-temperature near-infrared lasing, making them highly promising for use as nanoscale, silicon-integrable, and coherent light sources. While lasing behavior is reproducible, small variations in growth conditions across a substrate arising from the use of bottom-up growth techniques can introduce interwire disorder, either through geometric or material inhomogeneity. Nanolasers critically depend on both high material quality and tight dimensional tolerances, and as such, lasing threshold is both sensitive to and a sensitive probe of such inhomogeneity. We present an all-optical characterization technique coupled to statistical analysis to correlate geometrical and material parameters with lasing threshold. For these multiple-quantum-well nanolasers, it is found that low threshold is closely linked to longer lasing wavelength caused by losses in the core, providing a route to optimized future low-threshold devices. A best-in-group room temperature lasing threshold of ∼43 μJ cm-2 under pulsed excitation was found, and overall device yields in excess of 50% are measured, demonstrating a promising future for the nanolaser architecture.

  6. Molecular dynamics in high electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Apostol, M., E-mail:; Cune, L.C.


    Highlights: • New method for rotation molecular spectra in high electric fields. • Parametric resonances – new features in spectra. • New elementary excitations in polar solids from dipolar interaction (“dipolons”). • Discussion about a possible origin of the ferroelectricity from dipolar interactions. - Abstract: Molecular rotation spectra, generated by the coupling of the molecular electric-dipole moments to an external time-dependent electric field, are discussed in a few particular conditions which can be of some experimental interest. First, the spherical-pendulum molecular model is reviewed, with the aim of introducing an approximate method which consists in the separation of the azimuthal and zenithal motions. Second, rotation spectra are considered in the presence of a static electric field. Two particular cases are analyzed, corresponding to strong and weak fields. In both cases the classical motion of the dipoles consists of rotations and vibrations about equilibrium positions; this motion may exhibit parametric resonances. For strong fields a large macroscopic electric polarization may appear. This situation may be relevant for polar matter (like pyroelectrics, ferroelectrics), or for heavy impurities embedded in a polar solid. The dipolar interaction is analyzed in polar condensed matter, where it is shown that new polarization modes appear for a spontaneous macroscopic electric polarization (these modes are tentatively called “dipolons”); one of the polarization modes is related to parametric resonances. The extension of these considerations to magnetic dipoles is briefly discussed. The treatment is extended to strong electric fields which oscillate with a high frequency, as those provided by high-power lasers. It is shown that the effect of such fields on molecular dynamics is governed by a much weaker, effective, renormalized, static electric field.

  7. Optical pump-THz probe measurements of self-assembled h-BN/G heterostructures (United States)

    Murali Krishna, M. Bala; Catherine, C.; Harada, T.; Soumya, V.; Taha-Tijerrina, J.; Nguyen, P.; Chang, P.; Ajayan, P. M.; Narayanan, N. T.; Dani, K. M.


    Two dimensional materials have attracted significant interest in recent times due to properties like large electron mobility, extreme thermal conductivity and high young's modulus. The potential of combining different two-dimensional materials to form new heterostructures with new functionality offers intriguing possibilities. Here, we study the opto-electronic properties of new types of solids consisting of randomly stacked layers of hexagonal boron nitride (h-BN) and graphene (G). We prepare these artificially stacked h-BN/G solids with different ratios of h-BN and G by mixing dispersions of exfoliated h-BN layers and graphene in different concentrations and allowing the exfoliated flakes to form the h-BN/G solids via van der Waals interaction. We study the ultrafast photocarrier dynamics in these solids by pumping with femtosecond visible-near-infrared pulses of light, and probing the transient photo-conductivity with sub-picosecond Terahertz pulses. As we tune the ratio of h-BN and G in the new h-BN/G solids, we not only observe opto-electronic properties that tune from the insulating h-BN phase to semi-metallic G phase, but we also see unique behavior, distinct from either phase, for certain h-BN/G ratios in between the two extreme phases.

  8. Dynamic nuclear polarization at high magnetic fields. (United States)

    Maly, Thorsten; Debelouchina, Galia T; Bajaj, Vikram S; Hu, Kan-Nian; Joo, Chan-Gyu; Mak-Jurkauskas, Melody L; Sirigiri, Jagadishwar R; van der Wel, Patrick C A; Herzfeld, Judith; Temkin, Richard J; Griffin, Robert G


    Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (microw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (gamma(e)gamma(l)), being approximately 660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (> or =5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms-the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in microw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.

  9. Physics of semiconductors in high magnetic fields

    CERN Document Server

    Miura, Noboru


    This book summarizes most of the fundamental physical phenomena which semiconductors and their modulated structures exhibit in high magnetic fields. Readers can learn not only the basic theoretical background but also the present state of the art from the most advanced data in this rapidly growing research area.

  10. Strain sensors for high field pulse magnets

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Christian [Los Alamos National Laboratory; Zheng, Yan [Los Alamos National Laboratory; Easton, Daniel [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory


    In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective of this preliminary study is to characterize the performance of various strain sensing technologies at liquid nitrogen temperatures (-196 C). Four sensor types are considered in this investigation: fiber Bragg gratings (FBG), resistive foil strain gauges (RFSG), piezoelectric polymers (PVDF), and piezoceramics (PZT). Three operational conditions are considered for each sensor: bond integrity, sensitivity as a function of temperature, and thermal cycling effects. Several experiments were conducted as part of this study, investigating adhesion with various substrate materials (stainless steel, aluminum, and carbon fiber), sensitivity to static (FBG and RFSG) and dynamic (RFSG, PVDF and PZT) load conditions, and sensor diagnostics using PZT sensors. This work has been conducted in collaboration with the National High Magnetic Field Laboratory (NHMFL), and the results of this study will be used to identify the set of sensing technologies that would be best suited for integration within high field pulsed magnets at the NHMFL facility.

  11. High-performance phase-field modeling

    KAUST Repository

    Vignal, Philippe


    Many processes in engineering and sciences involve the evolution of interfaces. Among the mathematical frameworks developed to model these types of problems, the phase-field method has emerged as a possible solution. Phase-fields nonetheless lead to complex nonlinear, high-order partial differential equations, whose solution poses mathematical and computational challenges. Guaranteeing some of the physical properties of the equations has lead to the development of efficient algorithms and discretizations capable of recovering said properties by construction [2, 5]. This work builds-up on these ideas, and proposes novel discretization strategies that guarantee numerical energy dissipation for both conserved and non-conserved phase-field models. The temporal discretization is based on a novel method which relies on Taylor series and ensures strong energy stability. It is second-order accurate, and can also be rendered linear to speed-up the solution process [4]. The spatial discretization relies on Isogeometric Analysis, a finite element method that possesses the k-refinement technology and enables the generation of high-order, high-continuity basis functions. These basis functions are well suited to handle the high-order operators present in phase-field models. Two-dimensional and three dimensional results of the Allen-Cahn, Cahn-Hilliard, Swift-Hohenberg and phase-field crystal equation will be presented, which corroborate the theoretical findings, and illustrate the robustness of the method. Results related to more challenging examples, namely the Navier-Stokes Cahn-Hilliard and a diusion-reaction Cahn-Hilliard system, will also be presented. The implementation was done in PetIGA and PetIGA-MF, high-performance Isogeometric Analysis frameworks [1, 3], designed to handle non-linear, time-dependent problems.

  12. Wuhan pulsed high magnetic field center


    Li, Liang; Peng, Tao; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; Duan, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan


    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  13. High Field Pulse Magnets with New Materials (United States)

    Li, L.; Lesch, B.; Cochran, V. G.; Eyssa, Y.; Tozer, S.; Mielke, C. H.; Rickel, D.; van Sciver, S. W.; Schneider-Muntau, H. J.


    High performance pulse magnets using the combination of CuNb conductor and Zylon fiber composite reinforcement with bore sizes of 24, 15 and 10 mm have been designed, manufactured and tested to destruction. The magnets successfully reached the peak fields of 64, 70 and 77.8 T respectively with no destruction. Failures occurred near the end flanges at the layer. The magnet design, manufacturing and testing, and the mode of the failure are described and analyzed.

  14. Charge carrier dynamics of GaAs/AlGaAs asymmetric double quantum wells at room temperature studied by optical pump terahertz probe spectroscopy (United States)

    Afalla, Jessica; Ohta, Kaoru; Tokonami, Shunrou; Prieto, Elizabeth Ann; Catindig, Gerald Angelo; Cedric Gonzales, Karl; Jaculbia, Rafael; Vasquez, John Daniel; Somintac, Armando; Salvador, Arnel; Estacio, Elmer; Tani, Masahiko; Tominaga, Keisuke


    Two asymmetric double quantum wells of different coupling strengths (barrier widths) were grown via molecular beam epitaxy, both samples allowing tunneling. Photoluminescence was measured at 10 and 300 K to provide evidence of tunneling, barrier dependence, and structural uniformity. Carrier dynamics at room temperature was investigated by optical pump terahertz probe (OPTP) spectroscopy. Carrier population decay rates were obtained and photoconductivity spectra were analyzed using the Drude model. This work demonstrates that carrier, and possibly tunneling dynamics in asymmetric double quantum well structures may be studied at room temperature through OPTP spectroscopy.

  15. High field superconductor development and understanding

    Energy Technology Data Exchange (ETDEWEB)

    Larbalestier, David C. [Florida State Univ., Tallahassee, FL (United States); Lee, Peter J. [Florida State Univ., Tallahassee, FL (United States); Tarantini, Chiara [Florida State Univ., Tallahassee, FL (United States)


    All present circular accelerators use superconducting magnets to bend and to focus the particle beams. The most powerful of these machines is the large hadron collider (LHC) at CERN. The main ring dipole magnets of the LHC are made from Nb-Ti but, as the machine is upgraded to higher luminosity, more powerful magnets made of Nb3Sn will be required. Our work addresses how to make the Nb3Sn conductors more effective and more suitable for use in the LHC. The most important property of the superconducting conductor used for an accelerator magnet is that it must have very high critical current density, the property that allows the generation of high magnetic fields in small spaces. Nb3Sn is the original high field superconductor, the material which was discovered in 1960 to allow a high current density in the field of about 9 T. For the high luminosity upgrade of the LHC, much higher current densities in fields of about 12 Tesla will be required. The critical value of the current density is of order 2600 A/mm2 in a field of 12 Tesla. But there are very important secondary factors that complicate the attainment of this critical current density. The first is that the effective filament diameter must be no larger than about 40 µm. The second factor is that 50% of the cross-section of the Nb3Sn conductor that is pure copper must be protected from any poisoning by any Sn leakage through the diffusion barrier that protects the package of niobium and tin from which the Nb3Sn is formed by a high temperature reaction. These three, somewhat conflicting requirements, mean that optimization of the conductor is complex. The work described in this contract report addresses these conflicting requirements. They show that very sophisticated characterizations can uncover the way to satisfy all 3 requirements and they also suggest that the ultimate optimization of Nb3Sn is still not yet in sight

  16. High-intensity, focused ultrasonic fields

    DEFF Research Database (Denmark)

    Jensen, Leif Bjørnø


    The use of extracorporeal shock wave lithotripsy (ESWL) for disintegration of body stones has increased considerably during recent years. A worldwide activity in this field is reflected in a growing number of international publications and in the development and manufacturing of several ESWL...... machines marketed by companies in Germany and France, in particular. Two main types of ESWL systems are prevailing, the spark gap-based and the piezoelectric disk-based systems. This paper is introduced by a brief reconsideration of the features of pressure waves in water produced by an electrical...... distribution, etc. involving nonlinearity, diffraction, and absorption in the high-intensity focused ultrasonic fields produced by an ellipsoid as well as a spherical cap focusing geometry. Data from the development of an ESWL of the piezoelectric disk type are reported including demands to transducers...

  17. Efficient polarization of high-angular-momentum systems

    CERN Document Server

    Rochester, Simon; Raizen, Mark; Pustelny, Szymon; Auzinsh, Marcis; Budker, Dmitry


    We propose methods of optical pumping that are applicable to open, high-angular-momentum transitions in atoms and molecules, for which conventional optical pumping would lead to significant population loss. Instead of applying circularly polarized cw light, as in conventional optical pumping, we propose to use techniques for coherent population transfer (e.g., adiabatic fast passage) to arrange the atoms so as to increase the entropy removed from the system with each spontaneous decay from the upper state. This minimizes the number of spontaneous-emission events required to produce a stretched state, thus reducing the population loss due to decay to other states. To produce a stretched state in a manifold with angular momentum J, conventional optical pumping requires about 2J spontaneous decays per atom; one of our proposed methods reduces this to about log_2(2J), while another of the methods reduces it to about one spontaneous decay, independent of J.

  18. [Neurofunctional MRI at high magnetic fields]. (United States)

    Speck, O; Turner, R


    Functional magnetic resonance imaging (fMRI) examinations are limited in their sensitivity due to the low activation-induced signal change. Within short tolerable scan times the spatial resolution is thus limited. fMRI is a reliable tool in neuroscience as well as for clinical applications such as presurgical mapping of brain function. The fMRI sensitivity improves greatly (more than linearly) with increasing magnetic field strengths. For many years this was the main driving force in the push towards higher field strengths, such as 7 T. The sensitivity gain is greatest for high spatial resolution and fMRI with very high sub-millimeter resolution becomes feasible. Current results demonstrate that the localization of the blood oxygenation level dependent (BOLD) signal is better than previously assumed. High-field fMRI not only allows quantitative improvements but also opens the way to new information content, such as columnar and layer-dependent functional structures of the cortex. This may pave the way for further information, e.g. the directionality of cortico-cortical connections; however, these possibilities also pose new challenges. New methods for processing such high resolution data are required which do not require spatial smoothing and preserve the high information content. Common spatial resolutions of 2-3 mm are still very well suited for examinations at 3 T where they benefit from the low signal void, lower geometrical distortion and reduced acoustic noise. To achieve higher resolution at 7 T parallel imaging and geometric distortion correction are essential and permit the best congruence with structural data. The echo time at 7 T should be adjusted to about 20-25 ms. Data processing for single subjects or patients should be performed with little or no smoothing to retain resolution. Group studies could achieve good correlation with local normalization. New methods for information extraction, such as multivariate pattern analysis may allow

  19. A high performance field-reversed configuration

    Energy Technology Data Exchange (ETDEWEB)

    Binderbauer, M. W.; Tajima, T.; Steinhauer, L. C.; Garate, E.; Tuszewski, M.; Smirnov, A.; Gota, H.; Barnes, D.; Deng, B. H.; Thompson, M. C.; Trask, E.; Yang, X.; Putvinski, S.; Rostoker, N.; Andow, R.; Aefsky, S.; Bolte, N.; Bui, D. Q.; Ceccherini, F.; Clary, R. [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States); and others


    Conventional field-reversed configurations (FRCs), high-beta, prolate compact toroids embedded in poloidal magnetic fields, face notable stability and confinement concerns. These can be ameliorated by various control techniques, such as introducing a significant fast ion population. Indeed, adding neutral beam injection into the FRC over the past half-decade has contributed to striking improvements in confinement and stability. Further, the addition of electrically biased plasma guns at the ends, magnetic end plugs, and advanced surface conditioning led to dramatic reductions in turbulence-driven losses and greatly improved stability. Together, these enabled the build-up of a well-confined and dominant fast-ion population. Under such conditions, highly reproducible, macroscopically stable hot FRCs (with total plasma temperature of ∼1 keV) with record lifetimes were achieved. These accomplishments point to the prospect of advanced, beam-driven FRCs as an intriguing path toward fusion reactors. This paper reviews key results and presents context for further interpretation.

  20. High Performance Clocks and Gravity Field Determination (United States)

    Müller, J.; Dirkx, D.; Kopeikin, S. M.; Lion, G.; Panet, I.; Petit, G.; Visser, P. N. A. M.


    Time measured by an ideal clock crucially depends on the gravitational potential and velocity of the clock according to general relativity. Technological advances in manufacturing high-precision atomic clocks have rapidly improved their accuracy and stability over the last decade that approached the level of 10^{-18}. This notable achievement along with the direct sensitivity of clocks to the strength of the gravitational field make them practically important for various geodetic applications that are addressed in the present paper. Based on a fully relativistic description of the background gravitational physics, we discuss the impact of those highly-precise clocks on the realization of reference frames and time scales used in geodesy. We discuss the current definitions of basic geodetic concepts and come to the conclusion that the advances in clocks and other metrological technologies will soon require the re-definition of time scales or, at least, clarification to ensure their continuity and consistent use in practice. The relative frequency shift between two clocks is directly related to the difference in the values of the gravity potential at the points of clock's localization. According to general relativity the relative accuracy of clocks in 10^{-18} is equivalent to measuring the gravitational red shift effect between two clocks with the height difference amounting to 1 cm. This makes the clocks an indispensable tool in high-precision geodesy in addition to laser ranging and space geodetic techniques. We show how clock measurements can provide geopotential numbers for the realization of gravity-field-related height systems and can resolve discrepancies in classically-determined height systems as well as between national height systems. Another application of clocks is the direct use of observed potential differences for the improved recovery of regional gravity field solutions. Finally, clock measurements for space-borne gravimetry are analyzed along with

  1. Crystal field interactions studied by high-field magnetization

    Energy Technology Data Exchange (ETDEWEB)

    Radwanski, R.J.; Franse, J.J.M. (Van der Waals-Zeeman Lab., Univ. Amsterdam (Netherlands))


    The effect of crystalline electric field (CEF) interactions of the 4f ions on the magnetization process is reviewed for some intermetallic compounds. Special emphasis is given to metamagnetic transitions. The transitions in Ho{sub 2}Co{sub 17} are exchange-driven transitions associated with the formation of a non-collinear magnetic structure in contrast to the transition found in DyCo{sub 2}Si{sub 2} that is of a level-crossing type. The transition found in Pr{sub 2}Fe{sub 14}B results from a competition between lower and higher order crystal field terms. The formation of the rare earth moment under the action of CEF and exchange interactions as well as of external fields is analyzed. (orig.).

  2. Nonlinear relaxation field in charged systems under high electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Morawetz, K


    The influence of an external electric field on the current in charged systems is investigated. The results from the classical hierarchy of density matrices are compared with the results from the quantum kinetic theory. The kinetic theory yields a systematic treatment of the nonlinear current beyond linear response. To this end the dynamically screened and field-dependent Lenard-Balescu equation is integrated analytically and the nonlinear relaxation field is calculated. The classical linear response result known as Debye - On-Sager relaxation effect is only obtained if asymmetric screening is assumed. Considering the kinetic equation of one specie the other species have to be screened dynamically while the screening with the same specie itself has to be performed statically. Different other approximations are discussed and compared. (author)

  3. "Molecular" MR imaging at high fields. (United States)

    Gore, John C; Zu, Zhongliang; Wang, Ping; Li, Hua; Xu, Junzhong; Dortch, Richard; Gochberg, Daniel F


    Magnetic resonance imaging (MRI) and spectroscopy (MRS) have contributed considerably to clinical radiology, and a variety of MR techniques have been developed to evaluate pathological processes as well as normal tissue biology at the cellular and molecular level. However, in comparison to nuclear imaging, MRI has relatively poor sensitivity for detecting true molecular changes or for detecting the presence of targeted contrast agents, though these remain under active development. In recent years very high field (7T and above) MRI systems have been developed for human studies and these provide new opportunities and technical challenges for molecular imaging. We identify 5 types of intrinsic contrast mechanisms that do not require the use of exogenous agents but which can provide molecular and cellular information. We can derive information on tissue composition by (i) imaging different nuclei, especially sodium (ii) exploiting chemical shift differences as in MRS (iii) exploiting specific relaxation mechanisms (iv) exploiting tissue differences in the exchange rates of molecular species such as amides or hydroxyls and (v) differences in susceptibility. The increased signal strength at higher fields enables higher resolution images to be acquired, along with increased sensitivity to detecting subtle effects caused by molecular changes in tissues. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. High sensitivity field asymmetric ion mobility spectrometer. (United States)

    Chavarria, Mario A; Matheoud, Alessandro V; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni


    A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 10 12 V/A with an effective equivalent input noise level down to about 1 fA/Hz 1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

  5. High sensitivity field asymmetric ion mobility spectrometer (United States)

    Chavarria, Mario A.; Matheoud, Alessandro V.; Marmillod, Philippe; Liu, Youjiang; Kong, Deyi; Brugger, Jürgen; Boero, Giovanni


    A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s.

  6. Plant Responses to High Frequency Electromagnetic Fields

    Directory of Open Access Journals (Sweden)

    Alain Vian


    Full Text Available High frequency nonionizing electromagnetic fields (HF-EMF that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc. are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor, and growth reduced (stem elongation and dry weight after low power (i.e., nonthermal HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism.

  7. Plant Responses to High Frequency Electromagnetic Fields (United States)

    Vian, Alain; Davies, Eric; Gendraud, Michel; Bonnet, Pierre


    High frequency nonionizing electromagnetic fields (HF-EMF) that are increasingly present in the environment constitute a genuine environmental stimulus able to evoke specific responses in plants that share many similarities with those observed after a stressful treatment. Plants constitute an outstanding model to study such interactions since their architecture (high surface area to volume ratio) optimizes their interaction with the environment. In the present review, after identifying the main exposure devices (transverse and gigahertz electromagnetic cells, wave guide, and mode stirred reverberating chamber) and general physics laws that govern EMF interactions with plants, we illustrate some of the observed responses after exposure to HF-EMF at the cellular, molecular, and whole plant scale. Indeed, numerous metabolic activities (reactive oxygen species metabolism, α- and β-amylase, Krebs cycle, pentose phosphate pathway, chlorophyll content, terpene emission, etc.) are modified, gene expression altered (calmodulin, calcium-dependent protein kinase, and proteinase inhibitor), and growth reduced (stem elongation and dry weight) after low power (i.e., nonthermal) HF-EMF exposure. These changes occur not only in the tissues directly exposed but also systemically in distant tissues. While the long-term impact of these metabolic changes remains largely unknown, we propose to consider nonionizing HF-EMF radiation as a noninjurious, genuine environmental factor that readily evokes changes in plant metabolism. PMID:26981524

  8. High-Gain High-Field Fusion Plasma (United States)

    Li, Ge


    A Faraday wheel (FW)—an electric generator of constant electrical polarity that produces huge currents—could be implemented in an existing tokamak to study high-gain high-field (HGHF) fusion plasma, such as the Experimental Advanced Superconducting Tokamak (EAST). HGHF plasma can be realized in EAST by updating its pulsed-power system to compress plasma in two steps by induction fields; high gains of the Lawson trinity parameter and fusion power are both predicted by formulating the HGHF plasma. Both gain rates are faster than the decrease rate of the plasma volume. The formulation is checked by earlier ATC tests. Good agreement between theory and tests indicates that scaling to over 10 T at EAST may be possible by two-step compressions with a compression ratio of the minor radius of up to 3. These results point to a quick new path of fusion plasma study, i.e., simulating the Sun by EAST. PMID:26507314

  9. Magnetic field effect in highly pure, highly fluorescent conjugated polymers

    Energy Technology Data Exchange (ETDEWEB)

    Graupner, W.; Sacher, M.; Graupner, M.; Zenz, C.; Grampp, G.; Hermetter, A.; Leising, G.


    The authors report on the magnetic field effect (MFE) on the photoluminescence in films of a highly fluorescent conjugated laddertype poly(paraphenylene) (LPPP). They observe no MFE for the pure material, however, the introduction of a very small content of chemical defects via photo-oxidation leads to a MFE proportional to the amount of defects. The chemically induced increase in MFE is correlated with a change in other properties of the LPPP films, such as photoluminescence emission and excitation spectra, transient photoluminescence and infrared spectra.

  10. High magnetic field ohmically decoupled non-contact technology (United States)

    Wilgen, John [Oak Ridge, TN; Kisner, Roger [Knoxville, TN; Ludtka, Gerard [Oak Ridge, TN; Ludtka, Gail [Oak Ridge, TN; Jaramillo, Roger [Knoxville, TN


    Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.

  11. Particularities of optical pumping effects in cold and ultra-slow beams of Na and Cs in the case of cyclic transitions

    KAUST Repository

    Bruvelis, M.


    The time-dependent population dynamics of hyperfine (HF) levels of n2p3/2 states is examined for cyclic transitions in alkali atoms. We study a slow and cold atomic beam of Na (n = 3) and Cs (n = 6), taking into account the long interaction time of light with atoms (~200 μs) inside the resonant laser beam. Simple analytical expressions for the populations of the excited states and for the intensities of the absorption lines are derived for a three-level system model. We show that at moderate pump laser power the mixing of HF levels is sufficient to form a flow of population from a cyclic transition to partially open transitions. We discuss various phenomena associated with the evolution of optical pumping that cannot be explained by general analysis of two-level system model.

  12. Tests of a polarized source of hydrogen and deuterium based on a spin-exchange optical pumping and a storage cell for polarized deuterium (United States)

    Holt, R. J.; Gilman, R.; Kinney, E. R.; Kowalczyk, R. S.; Napolitano, J.; Young, L.; Mishnev, S. I.; Nikolenko, D. M.; Popov, S. G.; Rachek, I. A.; Temnykh, A. B.; Toporkov, D. K.; Tsentalovich, E. P.; Vesnovsky, D. K.; Wojtsekhowski, B. B.; Zelevinsky, V. G.


    A novel laser-driven polarized source of hydrogen and deuterium which is based on the principle of spin-exchange optical pumping has been developed at Argonne. The advantages of this method over conventional polarized sources for internal target experiments is discussed. At present, the laser-driven polarized source delivers hydrogen 8×1016 atoms/s with a polarization of 24% and deuterium at 6×1016 atoms/s with a polarization of 25%. A passive storage cell for polarized deuterium was tested in the VEPP-3 electron storage ring. The storage cell was found to increase the target thickness by approximately a factor of three and no less in polarization was observed.

  13. Measurements of loss and gain of optically pumped InGaAs semiconductor lasers based on the photoluminescence spectra from dual facets (United States)

    Jia, Y.; Yu, Q.-N.; Lu, W.; Zhang, J.; Zhang, X.; Ning, Y.-Q.; Wu, J.


    In this paper, the loss and gain characteristics of optically-pumped InGaAs/GaAs quantum well lasers are measured based on the photoluminescence spectra from dual facets of a single laser device. The device is pumped by 808nm fiber coupled semiconductor lasers controlled with pulsing signal and beam shaping system to reduce the thermal effect. The result of loss spectra is consistent with gain spectra well. In addition, the special double-peak configuration in the loss and gain spectra is observed and analyzed, in term of the strain mechanism and band structure of InGaAs quantum well. The results will be very helpful to the study and design of the InGaAs semiconductor lasers

  14. Ultrafast outflows disappear in high radiation fields (United States)

    Pinto, C.; Alston, W.; Parker, M. L.; Fabian, A. C.; Gallo, L. C.; Buisson, D. J. K.; Walton, D. J.; Kara, E.; Jiang, J.; Lohfink, A.; Reynolds, C. S.


    Ultrafast outflows (UFOs) are the most extreme winds launched by active galactic nuclei (AGN) due to their mildly-relativistic speeds (˜0.1 - 0.3c) and are thought to significantly contribute to galactic evolution via AGN feedback. Their nature and launching mechanism are however not well understood. Recently, we have discovered the presence of a variable UFO in the narrow-line Seyfert 1 IRAS 13224-3809. The UFO varies in response to the brightness of the source. In this work we perform flux-resolved X-ray spectroscopy to study the variability of the UFO and found that the ionisation parameter is correlated with the luminosity. In the brightest states the gas is almost completely ionised by the powerful radiation field and the UFO is hardly detected. This agrees with our recent results obtained with principal component analysis. We might have found the tip of the iceberg: the high ionisation of the outflowing gas may explain why it is commonly difficult to detect UFOs in AGN and possibly suggest that we may underestimate their actual feedback. We have also found a tentative correlation between the outflow velocity and the luminosity, which is expected from theoretical predictions of radiation-pressure driven winds. This trend is rather marginal due to the Fe XXV-XXVI degeneracy. Further work is needed to break such degeneracy through time-resolved spectroscopy.

  15. Investigating High Field Gravity using Astrophysical Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Bloom, Elliott D.; /SLAC


    The purpose of these lectures is to introduce particle physicists to astrophysical techniques. These techniques can help us understand certain phenomena important to particle physics that are currently impossible to address using standard particle physics experimental techniques. As the subject matter is vast, compromises are necessary in order to convey the central ideas to the reader. Many general references are included for those who want to learn more. The paragraphs below elaborate on the structure of these lectures. I hope this discussion will clarify my motivation and make the lectures easier to follow. The lectures begin with a brief review of more theoretical ideas. First, elements of general relativity are reviewed, concentrating on those aspects that are needed to understand compact stellar objects (white dwarf stars, neutron stars, and black holes). I then review the equations of state of these objects, concentrating on the simplest standard models from astrophysics. After these mathematical preliminaries, Sec. 2(c) discusses 'The End State of Stars'. Most of this section also uses the simplest standard models. However, as these lectures are for particle physicists, I also discuss some of the more recent approaches to the equation of state of very dense compact objects. These particle-physics-motivated equations of state can dramatically change how we view the formation of black holes. Section 3 focuses on the properties of the objects that we want to characterize and measure. X-ray binary systems and Active Galactic Nuclei (AGN) are stressed because the lectures center on understanding very dense stellar objects, black hole candidates (BHCs), and their accompanying high gravitational fields. The use of x-ray timing and gamma-ray experiments is also introduced in this section. Sections 4 and 5 review information from x-ray and gamma-ray experiments. These sections also discuss the current state of the art in x-ray and gamma-ray satellite

  16. Threats to ultra-high-field MRI (United States)

    Le Bihan, Denis


    In 2004 the European Commission (EC) adopted a directive restricting occupational exposure to electromagnetic fields. This directive (2004/40/CE), which examines the possible health risks of the electromagnetic fields from mobile phones, Wi-Fi, Bluetooth and other devices, concluded that upper limits on radiation and applied electromagnetic fields are necessary to prevent workers from suffering any undue acute health effects. But although not initially intended, the biggest impact of the directive could be on magnetic resonance imaging (MRI), which is used in hospitals worldwide to produce images of unrivalled quality of the brain and other soft tissues.

  17. Highly educated but in the wrong field?

    DEFF Research Database (Denmark)

    Reimer, David; Steinmetz, Stephanie


      This paper investigates the impact of gender differences in tertiary education, i.e., field of study and level of tertiary degree, on two selected labour market risks: unemployment and low-status jobs. Using Labour Force Survey data from the year 2000, results of the logistic regression models...... and non-linear decomposition analyses generally confirm our expectation that the field of study explains a sizable portion of the gender gap in unemployment and low-status jobs in both countries. However, the level of tertiary degree earned explains only part of the female disadvantage behind holding...... a low-status job in Spain. The analyses also show that compared to men, women with a degree in a predominantly male field of study seem to be systematically disadvantaged in both Germany and Spain, particularly with respect to unemployment. Overall, the analyses reveal that gender differentiation...

  18. Plasma instabilities in high electric fields

    DEFF Research Database (Denmark)

    Morawetz, K.; Jauho, Antti-Pekka


    expression is derived for the nonequilibrium dielectric function epsilon(K, omega). For certain values of momenta K and frequency omega, Imepsilon(K, omega) becomes negative, implying a plasma instability. This new instability exists only for strong electric fields, underlining its nonequilibrium origin....

  19. High Field Magnetization of Tb Single Crystals

    DEFF Research Database (Denmark)

    Roeland, L. W.; Cock, G. J.; Lindgård, Per-Anker


    The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenologica...... data on Tb. The conduction-electron polarization at zero field and temperature is (0.33+or-0.05) mu B/ion, and the susceptibility is greater than the Pauli susceptibility calculated from the band-structure.......The magnetization of Tb single crystals was measured in magnetic fields to 34T along the hard direction at temperature of 1.8, 4.2, 65.5 and 77K, and along with easy direction at 4.2 and 77K. The data are compared with the results of a self-consistent spin wave calculation using a phenomenological...... Hamiltonian including isotropic exchange interactions, effective single-ion anisotropy and magnetoelastic contributions. The parameters of this Hamiltonian were determined by fitting the theoretical results for the spin wave dispersion and energy gap as a function of temperature and magnetic field to existing...

  20. Dielectric shimming : exploiting dielectric interactions in High Field MRI

    NARCIS (Netherlands)

    Brink, Wyger Maurits


    This thesis reports on the utility of high permittivity dielectric materials for adjusting the radiofrequency (RF) field in high field MR. The performance-driven trend towards higher static magnetic field strengths drives MR operation into the regime where the dimensions of the body section being

  1. Flatland Electrons in High Magnetic Fields (United States)

    Shayegan, M.

    This paper provides a review of recent developments in the physics of two-dimensional carrier systems in perpendicular magnetic fields. The emphasis is on many-body phenomena in very clean GaAs/AlGaAs heterostructures, probed via magnetotransport measurements. Topics that are discussed include the integer and fractional quantum Hall effects, Wigner crystallization, composite Fermions, Skyrmions, stripe and bubble phases in single layer systems, and electron-hole pairing and Bose-Einstein condensation in interacting bilayer systems.

  2. Radiofrequency solutions in clinical high field magnetic resonance

    NARCIS (Netherlands)

    Andreychenko, A.|info:eu-repo/dai/nl/341697672


    Magnetic resonance imaging (MRI) and spectroscopy (MRS) benefit from the sensitivity gain at high field (≥7T). However, high field brings also certain challenges associated with growing frequency and spectral dispersion. Frequency growth results in degraded performance of large volume radiofrequency

  3. High field electrical behaviour in lithium–phospho–vanadate glass ...

    Indian Academy of Sciences (India)

    High field electrical behaviour; lithium–phospho–vanadate glass system. 1. Introduction. High field electrical switching behaviour is one of the fascinating properties in oxide glasses, since it exhibits reversible threshold and irreversible memory states. Several investigations have been initiated to study switching in glasses ...

  4. High-order-harmonic generation from field-distorted orbitals

    DEFF Research Database (Denmark)

    Spiewanowski, Maciek; Etches, Adam; Madsen, Lars Bojer


    We investigate the effect on high-order-harmonic generation of the distortion of molecular orbitals by the driving laser field. Calculations for high-order-harmonic generation including orbital distortion are performed for N2. Our results allow us to suggest that field distortion is the reason why...

  5. High School Students' Representations and Understandings of Electric Fields (United States)

    Cao, Ying; Brizuela, Bárbara M.


    This study investigates the representations and understandings of electric fields expressed by Chinese high school students 15 to 16 years old who have not received high school level physics instruction. The physics education research literature has reported students' conceptions of electric fields post-instruction as indicated by students'…

  6. Magnetic probe array with high sensitivity for fluctuating field. (United States)

    Kanamaru, Yuki; Gota, Hiroshi; Fujimoto, Kayoko; Ikeyama, Taeko; Asai, Tomohiko; Takahashi, Tsutomu; Nogi, Yasuyuki


    A magnetic probe array is constructed to measure precisely the spatial structure of a small fluctuating field included in a strong confinement field that varies with time. To exclude the effect of the confinement field, the magnetic probes consisting of figure-eight-wound coils are prepared. The spatial structure of the fluctuating field is obtained from a Fourier analysis of the probe signal. It is found that the probe array is more sensitive to the fluctuating field with a high mode number than that with a low mode number. An experimental demonstration of the present method is attempted using a field-reversed configuration plasma, where the fluctuating field with 0.1% of the confinement field is successfully detected.

  7. Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field (United States)

    Bojarevics, V.; Easter, S.; Pericleous, K.


    Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case.

  8. Electron transport in reduced graphene oxides in high electric field (United States)

    Jian, Wen-Bin; Lai, Jian-Jhong; Wang, Sheng-Tsung; Tsao, Rui-Wen; Su, Min-Chia; Tsai, Wei-Yu; Rosenstein, Baruch; Zhou, Xufeng; Liu, Zhaoping

    Due to a honeycomb structure, charge carriers in graphene exhibit quasiparticles of linear energy-momentum dispersion and phenomena of Schwinger pair creation may be explored. Because graphene is easily broken in high electric fields, single-layer reduced graphene oxides (rGO) are used instead. The rGO shows a small band gap while it reveals a graphene like behavior in high electric fields. Electron transport in rGO exhibits two-dimensional Mott's variable range hopping. The temperature behavior of resistance in low electric fields and the electric field behavior of resistance at low temperatures are all well explained by the Mott model. At temperatures higher than 200 K, the electric field behavior does not agree with the model while it shows a power law behavior with an exponent of 3/2, being in agreement with the Schwinger model. Comparing with graphene, the rGO is more sustainable to high electric field thus presenting a complete high-electric field behavior. When the rGO is gated away from the charge neutral point, the turn-on electric field of Schwinger phenomena is increased. A summary figure is given to present electric field behaviors and power law variations of resistances of single-layer rGO, graphene, and MoS2.

  9. High magnetic field {mu}SR instrument scientific case

    Energy Technology Data Exchange (ETDEWEB)

    Amato, A


    In order to gain more insight into the specific behavior of materials, it is often necessary to perform measurements as a function of different external parameters. Despite its high sensitivity to internal fields, this simple observation also applies for the {mu}SR technique. The most common parameter which can be tuned during an experiment is the sample temperature. By using a range of cryostats, temperatures between 0.02 and 900 K can be covered at the PSI {mu}SR Facility. On the other hand, and by using high-energy muons, pressures as high as 10'000 bars can nowadays be reached during {mu}SR experiments. As will be demonstrated in the following Sections, the magnetic field is an additional external parameter playing a fundamental role when studying the ground state properties of materials in condensed matter physics and chemistry. However, the availability of high magnetic fields for {mu}SR experiments is still rather limited. Hence, if on one hand the high value of the gyromagnetic ratio of the muon provides the high magnetic sensitivity of the method, on the other hand it can lead to very high muon-spin precession frequencies when performing measurements in applied fields (the muon-spin precession frequency in a field of 1 Tesla s 135.5 MHz). Consequently, the use of ultra-fast detectors and electronics is mandatory when measuring in magnetic fields exceeding 1 Tesla. If such fields are very intense when compared to the Earth magnetic field < 10{sup -4} Tesla), the energy associated with them is still modest in view of the thermal energy. Hence, the Zeeman energy splitting of a free electron in a magnetic field of 1 Tesla corresponds to a thermal energy as low as 0.67 Kelvin. It is worth mentioning that nowadays magnetic fields of the order of 10 to 15 Tesla are quite common in condensed matter laboratories and have opened up vast new exciting experimental possibilities. (author)

  10. Advanced measurements and techniques in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, L.J.; Rickel, D.G. [Los Alamos National Lab., NM (United States); Lacerda, A.H. [Florida State Univ., Tallahassee, FL (United States); Kim, Y. [Northeastern Univ., Boston, MA (United States)


    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). High magnetic fields present a unique environment for studying the electronic structure of materials. Two classes of materials were chosen for experiments at the national high Magnetic Field Laboratory at Los Alamos: highly correlated electron systems and semiconductors. Magnetotransport and thermodynamic experiments were performed on the renormalized ground states of highly correlated electron systems (such as heavy fermion materials and Kondo insulators) in the presence of magnetic fields that are large enough to disrupt the many-body correlations. A variety of optical measurements in high magnetic fields were performed on semiconductor heterostructures including GaAs/AlGaAs single heterojunctions (HEMT structure), coupled double quantum wells (CDQW), asymmetric coupled double quantum wells (ACDQW), multiple quantum wells and a CdTe single crystal thin film.

  11. Improving Magnet Designs With High and Low Field Regions

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Bahl, Christian Robert Haffenden; Smith, Anders


    A general scheme for increasing the difference in magnetic flux density between a high and a low magnetic field region by removing unnecessary magnet material is presented. This is important in, e.g., magnetic refrigeration where magnet arrays have to deliver high field regions in close proximity...... to low field regions. Also, a general way to replace magnet material with a high permeability soft magnetic material where appropriate is discussed. As an example, these schemes are applied to a two dimensional concentric Halbach cylinder design resulting in a reduction of the amount of magnet material...

  12. Magnetostructural transitions in a frustrated magnet at high fields. (United States)

    Tsurkan, V; Zherlitsyn, S; Felea, V; Yasin, S; Skourski, Yu; Deisenhofer, J; von Nidda, H-A Krug; Lemmens, P; Wosnitza, J; Loidl, A


    Ultrasound and magnetization studies of bond-frustrated ZnCr(2)S(4) spinel are performed in static magnetic fields up to 18 T and in pulsed fields up to 62 T. At temperatures below the antiferromagnetic transition at T(N1)≈14  K, the sound velocity as a function of the magnetic field reveals a sequence of steps followed by plateaus indicating a succession of crystallographic structures with constant stiffness. At the same time, the magnetization evolves continuously with a field up to full magnetic polarization without any plateaus in contrast to geometrically frustrated chromium oxide spinels. The observed high-field magnetostructural states are discussed within a H-T phase diagram taking into account the field and temperature evolution of three coexisting spin structures and subsequent lattice transformations induced by the magnetic field.

  13. Strong magnetic fields in normal galaxies at high redshift (United States)

    Bernet, Martin L.; Miniati, Francesco; Lilly, Simon J.; Kronberg, Philipp P.; Dessauges-Zavadsky, Miroslava


    The origin and growth of magnetic fields in galaxies is still something of an enigma. It is generally assumed that seed fields are amplified over time through the dynamo effect, but there are few constraints on the timescale. It was recently demonstrated that field strengths as traced by rotation measures of distant (and hence ancient) quasars are comparable to those seen today, but it was unclear whether the high fields were in the unusual environments of the quasars themselves or distributed along the lines of sight. Here we report high-resolution spectra that demonstrate that the quasars with strong MgII absorption lines are unambiguously associated with larger rotation measures. Because MgII absorption occurs in the haloes of normal galaxies along the sightlines to the quasars, this association requires that organized fields of surprisingly high strengths are associated with normal galaxies when the Universe was only about one-third of its present age.

  14. Probing High Temperature Superconductors with Magnetometry in Ultrahigh Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Li, Lu [Univ. of Michigan, Ann Arbor, MI (United States)


    The objective of this research is to investigate the high-field magnetic properties of high temperature superconductors, materials that conduct electricity without loss. A technique known as high-resolution torque magnetometry that was developed to directly measure the magnetization of high temperature superconductors. This technique was implemented using the 65 Tesla pulsed magnetic field facility that is part of the National High Magnetic Field Laboratory at Los Alamos National Laboratory. This research addressed unanswered questions about the interplay between magnetism and superconductivity, determine the electronic structure of high temperature superconductors, and shed light on the mechanism of high temperature superconductivity and on potential applications of these materials in areas such as energy generation and power transmission. Further applications of the technology resolve the novel physical phenomena such as correlated topological insulators, and spin liquid state in quantum magnets.

  15. High-field EPR spectroscopy of thermal donors in silicon

    DEFF Research Database (Denmark)

    Dirksen, R.; Rasmussen, F.B.; Gregorkiewicz, T.


    Thermal donors generated in p-type boron-doped Czochralski-grown silicon by a 450 degrees C heat treatment have been studied by high-field magnetic resonance spectroscopy. In the experiments conducted at a microwave frequency of 140 GHz and in a magnetic field of approximately 5 T four individual...

  16. High magnetic fields in couplers of x-band acceleratingstructures

    CERN Document Server

    Dolgashev, V A


    Recent high power tests of x-band accelerating structures at SLAC have shown that Coupler models were matched with an automated procedure that uses the commercial To reduce the high magnetic fields new couplers were designed. These couplers and typical results for couplers with sharp and rounded irises are discussed in code HFSS. This matching procedure is based on calculation of reflection from have 3 mm radius waveguide-to-coupler-cell iris and maximum magnetic field below is consistent with a model of pulsed heating due to high magnetic fields. The magnetic fields, 3D electrodynamics models of the couplers were built and matched. matching, the magnetic and electric fields in the couplers were calculated for typical observed damage is located in the region of high magnetic fields. To calculate these on sharp (approx 80 micron radius) edges of the waveguide-to-coupler-cell irises. For operation parameters. Highest magnetic fields on the order of 1 MA/m were found some input couplers, electric fields on these...

  17. NDT of fiber-reinforced composites with a new fiber-optic pump-probe laser-ultrasound system. (United States)

    Pelivanov, Ivan; Buma, Takashi; Xia, Jinjun; Wei, Chen-Wei; O'Donnell, Matthew


    Laser-ultrasonics is an attractive and powerful tool for the non-destructive testing and evaluation (NDT&E) of composite materials. Current systems for non-contact detection of ultrasound have relatively low sensitivity compared to contact peizotransducers. They are also expensive, difficult to adjust, and strongly influenced by environmental noise. Moreover, laser-ultrasound (LU) systems typically launch only about 50 firings per second, much slower than the kHz level pulse repetition rate of conventional systems. As demonstrated here, most of these drawbacks can be eliminated by combining a new generation of compact, inexpensive, high repetition rate nanosecond fiber lasers with new developments in fiber telecommunication optics and an optimally designed balanced probe beam detector. In particular, a modified fiber-optic balanced Sagnac interferometer is presented as part of a LU pump-probe system for NDT&E of aircraft composites. The performance of the all-optical system is demonstrated for a number of composite samples with different types and locations of inclusions.

  18. Alignment of molecular materials in high magnetic fields

    NARCIS (Netherlands)

    Christianen, P.C.M.; Shklyarevskiy, O.I.; Boamfa, M.I.; Maan, J.C.


    The potential of using high magnetic fields to align functional molecular materials is discussed, illustrated by magnetic orientation of two different types of materials. Alignment of side chain polymer liquid crystals leads to macroscopically ordered, transparant and strongly birefringent material.

  19. Overlay control methodology comparison: field-by-field and high-order methods (United States)

    Huang, Chun-Yen; Chiu, Chui-Fu; Wu, Wen-Bin; Shih, Chiang-Lin; Huang, Chin-Chou Kevin; Huang, Healthy; Choi, DongSub; Pierson, Bill; Robinson, John C.


    Overlay control in advanced integrated circuit (IC) manufacturing is becoming one of the leading lithographic challenges in the 3x and 2x nm process nodes. Production overlay control can no longer meet the stringent emerging requirements based on linear composite wafer and field models with sampling of 10 to 20 fields and 4 to 5 sites per field, which was the industry standard for many years. Methods that have emerged include overlay metrology in many or all fields, including the high order field model method called high order control (HOC), and field by field control (FxFc) methods also called correction per exposure. The HOC and FxFc methods were initially introduced as relatively infrequent scanner qualification activities meant to supplement linear production schemes. More recently, however, it is clear that production control is also requiring intense sampling, similar high order and FxFc methods. The added control benefits of high order and FxFc overlay methods need to be balanced with the increased metrology requirements, however, without putting material at risk. Of critical importance is the proper control of edge fields, which requires intensive sampling in order to minimize signatures. In this study we compare various methods of overlay control including the performance levels that can be achieved.

  20. Mitigated-force carriage for high magnetic field environments (United States)

    Ludtka, Gerard M.; Ludtka, Gail M.; Wilgen, John B.; Murphy, Bart L.


    A carriage for high magnetic field environments includes a plurality of work-piece separators disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla for supporting and separating a plurality of work-pieces by a preselected, essentially equal spacing, so that, as a first work-piece is inserted into the magnetic field, a second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

  1. Magnetic field management of substations in high rise buildings

    Energy Technology Data Exchange (ETDEWEB)

    Farag, A.S.; Al-Shehri, A.M. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia); Cheng, T.C.; Du, Y.; Hu, L.; Penn, D. [Univ. of Southern California, LADWP, Los Angeles, CA (United States)


    The electric and magnetic field issue has become an area of increasing public concern. Utilities have been carrying out extensive projects to characterize and manage the magnetic fields around their substations in an effort to answer public concerns over the possible health hazard caused by these fields. This paper describes various techniques available for managing magnetic field strength levels in substations. The design guideline aids in the planning, design, construction of substation facilities. Low-frequency magnetic field is directly associated with current-carrying sources and its magnitude is proportional to the distance from the sources. Distribution substations in high-rise buildings are very close to public areas and the magnetic fields imposed by these substations might be relatively higher than that imposed by outdoor substations. Options to manage these substations fields are considered in this paper. Techniques to manage magnetic fields in substations such as: source relocation, compaction, rephasing, return-current control, passive and active shielding are discussed. Several techniques were applied to reduce the magnetic fields in the conference room located in the main floor above a substation located in the basement of the main office high-rise building of LADWP. 10 refs, 14 figs, 3 tabs

  2. High-field spin dynamics of antiferromagnetic quantum spin chains

    DEFF Research Database (Denmark)

    Enderle, M.; Regnault, L.P.; Broholm, C.


    The characteristic internal order of macroscopic quantum ground states in one-dimensional spin systems is usually not directly accessible, but reflected in the spin dynamics and the field dependence of the magnetic excitations. In high magnetic fields quantum phase transitions are expected. We...... present recent work on the high-field spin dynamics of the S = I antiferromagnetic Heisenberg chains NENP (Haldane ground state) and CsNiCl3 (quasi-1D HAF close to the quantum critical point), the uniform S = 1/2 chain CTS, and the spin-Peierls system CuGeO3. (C) 2000 Elsevier Science B,V. All rights...

  3. Design of High Field Solenoids made of High Temperature Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Bartalesi, Antonio; /Pisa U.


    This thesis starts from the analytical mechanical analysis of a superconducting solenoid, loaded by self generated Lorentz forces. Also, a finite element model is proposed and verified with the analytical results. To study the anisotropic behavior of a coil made by layers of superconductor and insulation, a finite element meso-mechanic model is proposed and designed. The resulting material properties are then used in the main solenoid analysis. In parallel, design work is performed as well: an existing Insert Test Facility (ITF) is adapted and structurally verified to support a coil made of YBa{sub 2}Cu{sub 3}O{sub 7}, a High Temperature Superconductor (HTS). Finally, a technological winding process was proposed and the required tooling is designed.

  4. Large field-of-view transmission line resonator for high field MRI

    DEFF Research Database (Denmark)

    Zhurbenko, Vitaliy; Johannesson, Kristjan Sundgaard; Boer, Vincent


    Transmission line resonators is often a preferable choice for coils in high field magnetic resonance imaging (MRI), because they provide a number of advantages over traditional loop coils. The size of such resonators, however, is limited to shorter than half a wavelength due to high standing wave...... ratio, which leads to inhomogeneous field distribution along the resonator. In this work, it is demonstrated that the resonator length can be extended to over half a wavelength with the help of series capacitors. The approach allows for reduced standing wave ratio and improved field homogeneity....... Achieved magnetic field distribution is compared to the conventional transmission line resonator. Imaging experiments are performed using 7 Tesla MRI system. The developed resonator is useful for building coils with large field-of-view....

  5. Magnetoresistance peculiarities of bismuth wires in high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Condrea, E., E-mail: [Institute of Electronic Engineering and Nanotechnologies, Academy of Science of Moldova, 2028 Chisinau, Republic of Moldova (Moldova, Republic of); International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, 51-421 Wroclaw (Poland); Gilewski, A. [International Laboratory of High Magnetic Fields and Low Temperatures, Gajowicka 95, 51-421 Wroclaw (Poland); MagNet, 50-421 Wroclaw (Poland); Nicorici, A. [Institute of Electronic Engineering and Nanotechnologies, Academy of Science of Moldova, 2028 Chisinau, Republic of Moldova (Moldova, Republic of)


    Magnetoresistance measurements of Bi wires performed in the magnetic field oriented along the bisector axis revealed unexpected anomalous peaks in a high magnetic field far above the quantum limit of the electrons. By combining a magnetic field and an uniaxial strain, we obtained a modification of the electronic structure; as a result, the quantum limit for light and heavy electrons is changed in a different way. For the case where heavy electrons are in the quantum limit, a correlation between the exit of the lowest Landau level of light electrons and the Lifshitz transition was found. - Highlights: • Glass-coated single-crystalline Bi wires attain high limit of elastic strain of up to 3.0%. • Selective modification of the electronic structure of Bi wires is obtained by combining a high magnetic field and uniaxial strain. • The correlation between the exit of the lowest Landau level of electrons and Lifshitz transition was found.

  6. [Survey of risks related to static magnetic fields in ultra high field MRI]. (United States)

    Möller, H E; von Cramon, D Y


    In magnetic resonance imaging (MRI), substantial improvements with respect to sensitivity are expected due to the development of so-called ultra high field scanners, i. e., whole-body scanners with a magnetic field strength of 7 T or above. Users of this technology need to evaluate this benefit for potential risks since commercially available systems are not certified as a medical device for human use. This review provides a detailed survey of static field bioeffects related to the exposure of subjects being scanned, to occupational exposure, and to exposure of the general public under consideration of current standards and directives. According to present knowledge, it is not expected that exposure of human subjects to static magnetic fields of 7 T implies a specific risk of damage or disease provided that known contraindications are observed. The available database does not permit definition of exact thresholds for harmful effects. However, experience from previous application of ultra high field MRI indicates that transient phenomena, such as vertigo, nausea, metallic taste, or magneto-phosphenes, are more frequently observed. In particular, movements in the field or the gradient of the fringe field seem to lead to detectable effects. Besides such observations, there is a strong demand for systematic investigation of potential interaction mechanisms related to static field exposure during MRI examinations.

  7. High-field formation and field ion microscopy of monatomic carbon chains

    Energy Technology Data Exchange (ETDEWEB)

    Ksenofontov, V A; Mazilova, T I; Mikhailovskij, I M; Sadanov, E V; Velicodnaja, O A; Mazilov, A A [National Scientific Center, Kharkov Institute of Physics and Technology, Academicheskaja, 1, 61108 Kharkov (Ukraine)


    By methods of field ion microscopy and mass spectrometry, the presence of linear carbon chains at the surface of carbon fibers after high-voltage treatment using a pulse generator with pulse duration of 10 ns was revealed. The carbon chains attached to the specimen tips can be produced in situ in a field ion microscope using low-temperature pulsed evaporation by electric fields of the order of 80 V nm{sup -1}. These nanowires are perfectly resolved in the field ion microscope. An analysis of the cluster images and determination of the field-enhancement factors strongly indicate that the field produced clusters are linear chains of one carbon atom in diameter. The process of field evaporation at the pulse voltage loading is sporadic with an anomalously large instant rate of evaporation corresponding to explosive removal of about 10{sup 11} atomic layers s{sup -1}. Atomic C chains are produced during the high-field unraveling of nanofibers at 4.2 and 77 K.

  8. Homogenous BSCCO-2212 Round Wires for Very High Field Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Scott Campbell


    The performance demands on modern particle accelerators generate a relentless push towards higher field magnets. In turn, advanced high field magnet development places increased demands on superconducting materials. Nb3Sn conductors have been used to achieve 16 T in a prototype dipole magnet and are thought to have the capability for {approx}18 T for accelerator magnets (primarily dipoles but also higher order multipole magnets). However there have been suggestions and proposals for such magnets higher than 20 T. The High Energy Physics Community (HEP) has identified important new physics opportunities that are enabled by extremely high field magnets: 20 to 50 T solenoids for muon cooling in a muon collider (impact: understanding of neutrinos and dark matter); and 20+ T dipoles and quadrupoles for high energy hadron colliders (impact: discovery reach far beyond present). This proposal addresses the latest SBIR solicitation that calls for grant applications that seek to develop new or improved superconducting wire technologies for magnets that operate at a minimum of 12 Tesla (T) field, with increases up to 15 to 20 T sought in the near future (three to five years). The long-term development of accelerator magnets with fields greater than 20 T will require superconducting wires having significantly better high-field properties than those possessed by current Nb{sub 3}Sn or other A15 based wires. Given the existing materials science base for Bi-2212 wire processing, we believe that Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212) round wires can be produced in km-long piece lengths with properties suitable to meet both the near term and long term needs of the HEP community. The key advance will be the translation of this materials science base into a robust, high-yield wire technology. While the processing and application of A15 materials have advanced to a much higher level than those of the copper oxide-based, high T{sub c} (HTS) counterparts, the HTS materials have

  9. Calculation of electric fields induced by body and head motion in high-field MRI (United States)

    Liu, Feng; Zhao, Huawei; Crozier, Stuart


    In modern magnetic resonance imaging (MRI), patients are exposed to strong, nonuniform static magnetic fields outside the central imaging region, in which the movement of the body may be able to induce electric currents in tissues which could be possibly harmful. This paper presents theoretical investigations into the spatial distribution of induced electric fields and currents in the patient when moving into the MRI scanner and also for head motion at various positions in the magnet. The numerical calculations are based on an efficient, quasi-static, finite-difference scheme and an anatomically realistic, full-body, male model. 3D field profiles from an actively shielded 4 T magnet system are used and the body model projected through the field profile with a range of velocities. The simulation shows that it possible to induce electric fields/currents near the level of physiological significance under some circumstances and provides insight into the spatial characteristics of the induced fields. The results are extrapolated to very high field strengths and tabulated data shows the expected induced currents and fields with both movement velocity and field strength.

  10. Effect of magnetic field inhomogeneity on ion cyclotron motion coherence at high magnetic field. (United States)

    Vladimirov, Gleb; Kostyukevich, Yury; Hendrickson, Christopher L; Blakney, Greg T; Nikolaev, Eugene


    A three-dimensional code based on the particle-in-cell algorithm modified to account for the inhomogeneity of the magnetic field was applied to determine the effect of Z(1), Z(2), Z(3), Z(4), X, Y, ZX, ZY, XZ(2) YZ(2), XY and X(2)-Y(2) components of an orthogonal magnetic field expansion on ion motion during detection in an FT-ICR cell. Simulations were performed for magnetic field strengths of 4.7, 7, 14.5 and 21 Tesla, including experimentally determined magnetic field spatial distributions for existing 4.7 T and 14.5 T magnets. The effect of magnetic field inhomogeneity on ion cloud stabilization ("ion condensation") at high numbers of ions was investigated by direct simulations of individual ion trajectories. Z(1), Z(2), Z(3) and Z(4) components have the largest effect (especially Z(1)) on ion cloud stability. Higher magnetic field strength and lower m/z demand higher relative magnetic field homogeneity to maintain cloud coherence for a fixed time period. The dependence of mass resolving power upper limit on Z(1) inhomogeneity is evaluated for different magnetic fields and m/z. The results serve to set the homogeneity requirements for various orthogonal magnetic field components (shims) for future FT-ICR magnet design.

  11. Exposure to high-frequency transient electromagnetic fields. (United States)

    Skotte, J H


    The purpose of this study was to assess exposure to high-frequency transient (HFT) electromagnetic fields in occupational and residential environments. Exposure to HFT electromagnetic fields was measured with personal dosimeters for 301 volunteers (396 measurements) in periods of 24 h in both occupational and residential environments. The study included electrical utility workers (generation, transmission, distribution, substation), office and industrial workers, and people living near high-power transmission lines. The measure of exposure to HFT fields was specified as the proportion of time (parts per million) in which the electric field exceeds a nominal threshold level of 200 V.m-1 at 5-20 MHz. Recently the specification of the HFT channel of the dosimeter has been found to be incomplete; therefore a testing of the threshold level and the sensitivity to electromagnetic fields from radio-telephones was carried out. The percentage of measurements with a mean workday exposure above 0.1 ppm was 6.5-9.4% for the utility groups and 0.9% for all the nonwork measurements. It is likely that the use of radio-telephones has contributed significantly to the number of HFT events in some of the measurements, especially for the generation workers. The nominal threshold level of the dosimeter was found to vary considerably depending on the polarization of the field (20-400 V.m-1 at 13.56 MHz for one instrument). Generally speaking, HFT fields appeared infrequently. The workday exposure to HFT fields and 50 Hz magnetic fields ranked the groups differently. There is a need for developing instrumentation for HFT field measurements further.

  12. Magnetoresistance peculiarities of bismuth wires in high magnetic field (United States)

    Condrea, E.; Gilewski, A.; Nicorici, A.


    Magnetoresistance measurements of Bi wires performed in the magnetic field oriented along the bisector axis revealed unexpected anomalous peaks in a high magnetic field far above the quantum limit of the electrons. By combining a magnetic field and an uniaxial strain, we obtained a modification of the electronic structure; as a result, the quantum limit for light and heavy electrons is changed in a different way. For the case where heavy electrons are in the quantum limit, a correlation between the exit of the lowest Landau level of light electrons and the Lifshitz transition was found.

  13. Disintegration and field evaporation of thiolate polymers in high electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Nickerson, B.S., E-mail:; Karahka, M.; Kreuzer, H.J.


    High electrostatic fields cause major changes in polymers, structural (e.g. electrostriction) and electronic (e.g. reduction of the “band gap” with final metallization). Using density functional theory we have studied field effects on amino-alkane-thiols and perfluoro-alkane-thiols adsorbed on a metal substrate. Our results agree well with the APT fragmentation spectra obtained by Stoffers, Oberdorfer and Schmitz and shed light on disintegration pathways. We demonstrate that in SAMs the HOMO/LUMO gap is again reduced as a function of the field strength and vanishes at evaporation. We also follow the field dependence of the dielectric constant and polarizability. - Highlights: • Simple model of thiolate polymers is used to understand trends leading to field evaporation. • Potential energy curves followed by dipole moment, electric polarizability and dielectric constant are examined. • Features including coil, tilt and electrostriction are featured alongside evaporated species and HOMO/LUMO gap.

  14. High-field thermal transport properties of REBCO coated conductors (United States)

    Bonura, Marco; Senatore, Carmine


    The use of REBCO coated conductors (CCs) is envisaged for many applications, extending from power cables to high-field magnets. Whatever the case, thermal properties of REBCO tapes play a key role for the stability of superconducting devices. In this work, we present the first study on the longitudinal thermal conductivity (κ) of REBCO CCs in magnetic fields up to 19 T applied both parallel and perpendicularly to the thermal-current direction. Copper-stabilized tapes from six industrial manufacturers have been investigated. We show that zero-field κ of CCs can be calculated with an accuracy of +/- 15% from the residual resistivity ratio of the stabilizer and the Cu/non-Cu ratio. Measurements performed at high fields have allowed us to evaluate the consistency of the procedures generally used for estimating in-field κ in the framework of the Wiedemann-Franz law from an electrical characterization of the materials. In-field data are intended to provide primary ingredients for the thermal stability analysis of high-temperature superconductor-based magnets.

  15. Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

    Directory of Open Access Journals (Sweden)

    Ilya eLisenker


    Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

  16. High-intensity polarized H- ion source for the RHIC SPIN physics (United States)

    Zelenski, A.; Atoian, G.; Raparia, D.; Ritter, J.; Kolmogorov, A.; Davydenko, V.


    A novel polarization technique had been successfully implemented for the RHIC polarized H- ion source upgrade to higher intensity and polarization. In this technique a proton beam inside the high magnetic field solenoid is produced by ionization of the atomic hydrogen beam (from external source) in the He-gas ionizer cell. Further proton polarization is produced in the process of polarized electron capture from the optically-pumped Rb vapour. The use of high-brightness primary beam and large cross-sections of charge-exchange cross-sections resulted in production of high intensity H- ion beam of 85% polarization. High beam brightness and polarization resulted in 75% polarization at 23 GeV out of AGS and 60-65% beam polarization at 100-250 GeV colliding beams in RHIC. The status of un-polarized magnetron type (Cs-vapour loaded) BNL source is also discussed.

  17. Diffusion of minority carriers against electric field (high injection level) (United States)

    Gert, A. V.; Dmitriev, A. P.; Levinshtein, M. E.; Yuferev, V. S.; Palmour, J. W.


    A one-dimensional analytic model describing the motion of minority carriers against the electric field direction under the conditions of high injection level is developed. The results of the model can also be used to estimate the motion of carriers against the field in the case of an arbitrary injection level. The model makes it possible to describe, in good agreement with the results of computer simulation, the modulation of the collector layer resistance in a high voltage SiC bipolar transistor.

  18. Low-field MRI can be more sensitive than high-field MRI (United States)

    Coffey, Aaron M.; Truong, Milton L.; Chekmenev, Eduard Y.


    MRI signal-to-noise ratio (SNR) is the key factor for image quality. Conventionally, SNR is proportional to nuclear spin polarization, which scales linearly with magnetic field strength. Yet ever-stronger magnets present numerous technical and financial limitations. Low-field MRI can mitigate these constraints with equivalent SNR from non-equilibrium ‘hyperpolarization' schemes, which increase polarization by orders of magnitude independently of the magnetic field. Here, theory and experimental validation demonstrate that combination of field independent polarization (e.g. hyperpolarization) with frequency optimized MRI detection coils (i.e. multi-turn coils using the maximum allowed conductor length) results in low-field MRI sensitivity approaching and even rivaling that of high-field MRI. Four read-out frequencies were tested using samples with identical numbers of 1H and 13C spins. Experimental SNRs at 0.0475 T were ∼40% of those obtained at 4.7 T. Conservatively, theoretical SNRs at 0.0475 T 1.13-fold higher than those at 4.7 T were possible despite an ∼100-fold lower detection frequency, indicating feasibility of high-sensitivity MRI without technically challenging, expensive high-field magnets. The data at 4.7 T and 0.0475 T was obtained from different spectrometers with different RF probes. The SNR comparison between the two field strengths accounted for many differences in parameters such as system noise figures and variations in the probe detection coils including Q factors and coil diameters.

  19. Electric and magnetic field measurements in a high voltage center. (United States)

    Safigianni, Anastasia S; Spyridopoulos, Anastasios I; Kanas, Vasilis L


    This paper investigates the electric and magnetic fields inside a large high voltage center constituted both of 400/150 and 150/20 kV substation areas. Results of previous field measurements and calculations in substations, made by the authors of this paper or other researchers, are presented first. The basic data distinguishing the examined center from previously examined substations follow. The main results of the field measurements in the areas of the above-mentioned center are presented in relevant diagrams. General conclusions arising from the comparison of the measured field values with relevant reference levels in force for safe public and occupational exposure as well as with the results of previous research are finally given.

  20. Field high-throughput phenotyping: the new crop breeding frontier. (United States)

    Araus, José Luis; Cairns, Jill E


    Constraints in field phenotyping capability limit our ability to dissect the genetics of quantitative traits, particularly those related to yield and stress tolerance (e.g., yield potential as well as increased drought, heat tolerance, and nutrient efficiency, etc.). The development of effective field-based high-throughput phenotyping platforms (HTPPs) remains a bottleneck for future breeding advances. However, progress in sensors, aeronautics, and high-performance computing are paving the way. Here, we review recent advances in field HTPPs, which should combine at an affordable cost, high capacity for data recording, scoring and processing, and non-invasive remote sensing methods, together with automated environmental data collection. Laboratory analyses of key plant parts may complement direct phenotyping under field conditions. Improvements in user-friendly data management together with a more powerful interpretation of results should increase the use of field HTPPs, therefore increasing the efficiency of crop genetic improvement to meet the needs of future generations. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Field-effect transistor having a superlattice channel and high carrier velocities at high applied fields (United States)

    Chaffin, deceased, Roger J.; Dawson, Ralph; Fritz, Ian J.; Osbourn, Gordon C.; Zipperian, Thomas E.


    A field effect transistor comprises a semiconductor having a source, a drain, a channel and a gate in operational relationship. The semiconductor is a strained layer superlattice comprising alternating quantum well and barrier layers, the quantum well layers and barrier layers being selected from the group of layer pairs consisting of InGaAs/AlGaAs, InAs/InAlGaAs, and InAs/InAlAsP. The layer thicknesses of the quantum well and barrier layers are sufficiently thin that the alternating layers constitute a superlattice which has a superlattice conduction band energy level structure in k-vector space which includes a lowest energy .GAMMA.-valley and a next lowest energy L-valley, each k-vector corresponding to one of the orthogonal directions defined by the planes of said layers and the directions perpendicular thereto. The layer thicknesses of the quantum well layers are selected to provide a superlattice L.sub.2D -valley which has a shape which is substantially more two-dimensional than that of said bulk L-valley.

  2. High School Students' Understandings and Representations of the Electric Field

    CERN Document Server

    Cao, Ying


    This study investigates the understandings and representations of the electric field expressed by Chinese high school students ages 15 to 16 who have not yet received high school-level physics instruction. The literature has reported students' ideas of the electric field post-instruction as indicated by their performance on textbook-style questionnaires. However, by relying on measures such as questionnaires, previous research has inadequately captured the thinking process that led students to answer questions in the ways that they did. The present study portrays the beginning of this process by closely examining students' understandings pre-instruction. The participants in this study were asked to engage in a lesson that included informal group tasks that involved playing a Web-based hockey game that replicated an electric field and drawing comic strips that used charges as characters. The lesson was videotaped, students' work was collected, and three students were interviewed afterward to ascertain more det...

  3. Nb3Sn High Field Magnets for the High Luminosity LHC Upgrade Project

    Energy Technology Data Exchange (ETDEWEB)

    Ambrosio, Giorgio


    The High Luminosity upgrade of the Large Hadron Collider at CERN requires a new generation of high field superconducting magnets. High field large aperture quadrupoles (MQXF) are needed for the low-beta triplets close to the ATLAS and CMS detectors, and high field two-in-one dipoles (11 T dipoles) are needed to make room for additional collimation. The MQXF quadrupoles, with a field gradient of 140 T/m in 150 mm aperture, have a peak coil field of 12.1 T at nominal current. The 11 T dipoles, with an aperture of 60 mm, have a peak coil field of 11.6 T at nominal current. Both magnets require Nb3Sn conductor and are the first applications of this superconductor to actual accelerator magnets.

  4. Disintegration and field evaporation of thiolate polymers in high electric fields. (United States)

    Nickerson, B S; Karahka, M; Kreuzer, H J


    High electrostatic fields cause major changes in polymers, structural (e.g. electrostriction) and electronic (e.g. reduction of the "band gap" with final metallization). Using density functional theory we have studied field effects on amino-alkane-thiols and perfluoro-alkane-thiols adsorbed on a metal substrate. Our results agree well with the APT fragmentation spectra obtained by Stoffers, Oberdorfer and Schmitz and shed light on disintegration pathways. We demonstrate that in SAMs the HOMO/LUMO gap is again reduced as a function of the field strength and vanishes at evaporation. We also follow the field dependence of the dielectric constant and polarizability. Copyright © 2015 Elsevier B.V. All rights reserved.


    This study presents the field evaluation of a high-volume dichotomous sampler that collects coarse (PM10-2.5) and fine (PM2.5) particulate matter. The key feature of this device is the utilization of a round-nozzle virtual impactor with a 50% cutpoint at 2.5 5m to split PM10 into...

  6. Survey of high field superconducting material for accelerator magnets

    Energy Technology Data Exchange (ETDEWEB)

    Scahlan, R.; Greene, A.F.; Suenaga, M.


    The high field superconductors which could be used in accelerator dipole magnets are surveyed, ranking these candidates with respect to ease of fabrication and cost as well as superconducting properties. Emphasis is on Nb/sub 3/Sn and NbTi. 27 refs., 2 figs. (LEW)

  7. National Program on High Field Accelerator Magnet R&D

    Energy Technology Data Exchange (ETDEWEB)

    Apollinari, G. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Cooley, L. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Zlobin, A. V. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Caspi, S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gourlay, S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Prestemon, S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Larbalestier, D. [National High Magnetic Field Laboratory, Tallahassee, FL (United States); Gupta, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wanderer, P. [Brookhaven National Lab. (BNL), Upton, NY (United States)


    A National High-Field Magnet (HFM) Program is proposed as a thrust of the updated DOE-HEP General Accelerator R&D Program. The program responds to Recommendation 24 of the 2014 Particle Physics Project Prioritization Panel (P5) Report.

  8. Multibeam synthesis of high-power subcycle field waveforms (United States)

    Serebryannikov, E. E.; Panchenko, V. Ya.; Zheltikov, A. M.


    We identify physical scenarios whereby high-peak-power subcycle attosecond field waveforms can be synthesized by coherently combining a multibeam high-order harmonic output generated by a laser driver consisting of a pair of few-cycle pulses with different carrier frequencies. With the relative amplitudes, phases, and group delays of these driver pulses carefully adjusted in each of the driver beams toward confining the recollisions of highest-ponderomotive-energy electrons to an extremely short time gate within a fraction of the driver field cycle, the phase-matched multibeam high-harmonic output can be tailored to yield an intense isolated subgigawatt sub-10-attosecond field waveform. As a general tendency, propagation effects are shown to limit the minimum pulse width of the multibeam high-harmonic output. Still, with appropriate optimization of the gas pressure and the beam geometry, ≈10 -as field waveforms can be synthesized at the expense of one to two orders of magnitude of the output radiation energy.

  9. High mobility polymer gated organic field effect transistor using zinc ...

    Indian Academy of Sciences (India)

    Mater. Sci., Vol. 37, No. 1, February 2014, pp. 95–99. c Indian Academy of Sciences. High mobility polymer gated organic field effect transistor using zinc phthalocyanine. K R RAJESH. ∗. , V KANNAN, M R KIM, Y S CHAE and J K RHEE. Millimeter- Wave Innovation Technology Research Centre (MINT), Dongguk University,.

  10. High mobility polymer gated organic field effect transistor using zinc ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 1. High mobility polymer gated organic field effect transistor using zinc ... fabricated using evaporated zinc phthalocyanine as the active layer. Parylene film prepared by chemical vapour deposition was used as the organic gate insulator. The annealing of the ...

  11. High school students' representations and understandings of electric fields (United States)

    Cao, Ying; Brizuela, Bárbara M.


    This study investigates the representations and understandings of electric fields expressed by Chinese high school students 15 to 16 years old who have not received high school level physics instruction. The physics education research literature has reported students' conceptions of electric fields postinstruction as indicated by students' performance on textbook-style questions. It has, however, inadequately captured student ideas expressed in other situations yet informative to educational research. In this study, we explore students' ideas of electric fields preinstruction as shown by students' representations produced in open-ended activities. 92 participant students completed a worksheet that involved drawing comic strips about electric charges as characters of a cartoon series. Three students who had spontaneously produced arrow diagrams were interviewed individually after class. We identified nine ideas related to electric fields that these three students spontaneously leveraged in the comic strip activity. In this paper, we describe in detail each idea and its situated context. As most research in the literature has understood students as having relatively fixed conceptions and mostly identified divergences in those conceptions from canonical targets, this study shows students' reasoning to be more variable in particular moments, and that variability includes common sense resources that can be productive for learning about electric fields.

  12. Self propagating high temperature synthesis of ferrites in magnetic fields

    CERN Document Server

    Affleck, L


    Self propagating high temperature synthesis (SHS) reactions have been performed on mixtures of BaO sub 2 , Fe and Fe sub 2 O sub 3 to form barium ferrite, BaFe sub 1 sub 2 O sub 1 sub 9. Reactions were conducted in zero field and in an applied magnetic field of 1.1 T with the aim of exploring the influence of the field. The temperature and velocity of the reactions were measured and the products, both post-SHS and post-annealing, were characterised by techniques including X-ray diffraction, Moessbauer spectroscopy, vibrating sample magnetometry and electron microprobe analysis. The applied magnetic field was found to lead to hotter and faster reactions, a greater degree of conversion of the reactants, a needle-like microstructure in the post-SHS product, and a reduced coercive field (approx 20-30 %) in the annealed product, compared to zero field. Sodium perchlorate was used as an internal oxidising agent, and found to produce similar effects. Correlations were observed between the temperature reached in the ...

  13. Electron-electron interactions in graphene field-induced quantum dots in a high magnetic field

    DEFF Research Database (Denmark)

    Orlof, A.; Shylau, Artsem; Zozoulenko, I. V.


    We study the effect of electron-electron interaction in graphene quantum dots defined by an external electrostatic potential and a high magnetic field. To account for the electron-electron interaction, we use the Thomas-Fermi approximation and find that electron screening causes the formation...

  14. High-field phase-diagram of Fe arsenide superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Y.J.; Jaroszynski, J.; Yamamoto, A.; Gurevich, A.; Riggs, S.C.; Boebinger, G.S.; Larbalestier, D. [National High Magnetic Field Laboratory, Florida State University, Tallahassee-FL 32310 (United States); Wen, H.H. [Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Zhigadlo, N.D.; Katrych, S.; Bukowski, Z.; Karpinski, J. [Laboratory for Solid State Physics, ETH Zuerich, CH-8093 Zuerich (Switzerland); Liu, R.H.; Chen, H.; Chen, X.H. [Hefei National Laboratory for Physical Science a Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Balicas, L., E-mail: balicas@magnet.fsu.ed [National High Magnetic Field Laboratory, Florida State University, Tallahassee-FL 32310 (United States)


    Here, we report an overview of the phase-diagram of single-layered and double-layered Fe arsenide superconductors at high magnetic fields. Our systematic magneto-transport measurements of polycrystalline SmFeAsO{sub 1-x}F{sub x} at different doping levels confirm the upward curvature of the upper critical magnetic field H{sub c2}(T) as a function of temperature T defining the phase boundary between the superconducting and metallic states for crystallites with the ab planes oriented nearly perpendicular to the magnetic field. We further show from measurements on single-crystals that this feature, which was interpreted in terms of the existence of two superconducting gaps, is ubiquitous among both series of single- and double-layered compounds. In all compounds explored by us the zero temperature upper critical field H{sub c2}(0), estimated either through the Ginzburg-Landau or the Werthamer-Helfand-Hohenberg single gap theories, strongly surpasses the weak-coupling Pauli paramagnetic limiting field. This clearly indicates the strong-coupling nature of the superconducting state and the importance of magnetic correlations for these materials. Our measurements indicate that the superconducting anisotropy, as estimated through the ratio of the effective masses gamma = (m{sub c}/m{sub ab}){sup 1/2} for carriers moving along the c-axis and the ab-planes, respectively, is relatively modest as compared to the high-T{sub c} cuprates, but it is temperature, field and even doping dependent. Finally, our preliminary estimations of the irreversibility field H{sub m}(T), separating the vortex-solid from the vortex-liquid phase in the single-layered compounds, indicates that it is well described by the melting of a vortex lattice in a moderately anisotropic uniaxial superconductor.

  15. Magnetic resonance imaging and spectroscopy at ultra high fields

    Energy Technology Data Exchange (ETDEWEB)

    Neuberger, Thomas


    The goal of the work presented in this thesis was to explore the possibilities and limitations of MRI / MRS using an ultra high field of 17.6 tesla. A broad range of specific applications and MR methods, from MRI to MRSI and MRS were investigated. The main foci were on sodium magnetic resonance spectroscopic imaging of rodents, magnetic resonance spectroscopy of the mouse brain, and the detection of small amounts of iron labeled stem cells in the rat brain using MRI Sodium spectroscopic imaging was explored since it benefits tremendously from the high magnetic field. Due to the intrinsically low signal in vivo, originating from the low concentrations and short transverse relaxation times, only limited results have been achieved by other researchers until now. Results in the literature include studies conducted on large animals such as dogs to animals as small as rats. No studies performed on mice have been reported, despite the fact that the mouse is the most important laboratory animal due to the ready availability of transgenic strains. Hence, this study concentrated on sodium MRSI of small rodents, mostly mice (brain, heart, and kidney), and in the case of the brain on young rats. The second part of this work concentrated on proton magnetic resonance spectroscopy of the rodent brain. Due to the high magnetic field strength not only the increasing signal but also the extended spectral resolution was advantageous for such kind of studies. The difficulties/limitations of ultra high field MRS were also investigated. In the last part of the presented work detection limits of iron labeled stem cells in vivo using magnetic resonance imaging were explored. The studies provided very useful benchmarks for future researchers in terms of the number of labeled stem cells that are required for high-field MRI studies. Overall this work has shown many of the benefits and the areas that need special attention of ultra high fields in MR. Three topics in MRI, MRS and MRSI were

  16. Mechanical design of a high field common coil magnet

    CERN Document Server

    Caspi, S; Dietderich, D R; Gourlay, S A; Gupta, R; McInturff, A; Millos, G; Scanlan, R M


    A common coil design for high field 2-in-1 accelerator magnets has been previously presented as a "conductor-friendly" option for high field magnets applicable for a Very Large Hadron Collider. This paper presents the mechanical design for a 14 tesla 2-in-1 dipole based on the common coil design approach. The magnet will use a high current density Nb/sub 3/Sn conductor. The design addresses mechanical issues particular to the common coil geometry: horizontal support against coil edges, vertical preload on coil faces, end loading and support, and coil stresses and strains. The magnet is the second in a series of racetrack coil magnets that will provide experimental verification of the common coil design approach. (9 refs).

  17. Mechanical design of a high field common coil magnet

    Energy Technology Data Exchange (ETDEWEB)

    Caspi, S.; Chow, K.; Dietderich, D.; Gourlay, S.; Gupta, R.; McInturff, A.; Millos, G.; Scanlan, R.


    A common coil design for high field 2-in-1 accelerator magnets has been previously presented as a 'conductor-friendly' option for high field magnets applicable for a Very Large Hadron Collider. This paper presents the mechanical design for a 14 tesla 2-in-1 dipole based on the common coil design approach. The magnet will use a high current density Nb{sub 3}Sn conductor. The design addresses mechanical issues particular to the common coil geometry: horizontal support against coil edges, vertical preload on coil faces, end loading and support, and coil stresses and strains. The magnet is the second in a series of racetrack coil magnets that will provide experimental verification of the common coil design approach.


    Haninger, T; Kleinau, P; Haninger, S


    The new albedo dosemeter-type AWST-TL-GD 04 has been calibrated in the CERF neutron field (Cern-EU high-energy Reference Field). This type of albedo dosemeter is based on thermoluminescent detectors (TLDs) and used by the individual monitoring service of the Helmholtz Zentrum München (AWST) since 2015 for monitoring persons, who are exposed occupationally against photon and neutron radiation. The motivation for this experiment was to gain a field specific neutron correction factor Nn for workplaces at high-energy particle accelerators. Nn is a dimensionless factor relative to a basic detector calibration with 137Cs and is used to calculate the personal neutron dose in terms of Hp(10) from the neutron albedo signal. The results show that the sensitivity of the albedo dosemeter for this specific neutron field is not significantly lower as for fast neutrons of a radionuclide source like 252Cf. The neutron correction factor varies between 0.73 and 1.16 with a midrange value of 0.94. The albedo dosemeter is therefore appropriate to monitor persons, which are exposed at high-energy particle accelerators. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email:

  19. Control and data acquisition systems for high field superconducting wigglers

    CERN Document Server

    Batrakov, A; Karpov, G; Kozak, V; Kuzin, M; Kuper, E; Mamkin, V; Mezentsev, N A; Repkov, V V; Selivanov, A; Shkaruba, V A


    This paper describes the control and DAQ system of superconducting wigglers with magnetic field range up to 10.3 T. The first version of the system controls a 7 T superconducting wiggler prepared for installation at Bessy-II (Germany). The second one controls a 10 T wiggler which is under testing now at the SPring-8 site (Japan). Both systems are based on VME apparatus. The set of specialized VME modules is elaborated to arrange wiggler power supply control, full time wiggler monitoring, and magnetic field high accuracy measurement and field stabilization. The software for the control of the wigglers is written in C language for VxWorks operation system for a Motorola-162 VME controller. The task initialization, stops and acquisition of the data can be done from the nearest personal computer (FTP host for VME), or from the remote system as well.

  20. Rf Gun with High-Current Density Field Emission Cathode

    Energy Technology Data Exchange (ETDEWEB)

    Jay L. Hirshfield


    High current-density field emission from an array of carbon nanotubes, with field-emission-transistor control, and with secondary electron channel multiplication in a ceramic facing structure, have been combined in a cold cathode for rf guns and diode guns. Electrodynamic and space-charge flow simulations were conducted to specify the cathode configuration and range of emission current density from the field emission cold cathode. Design of this cathode has been made for installation and testing in an existing S-band 2-1/2 cell rf gun. With emission control and modulation, and with current density in the range of 0.1-1 kA/cm2, this cathode could provide performance and long-life not enjoyed by other currently-available cathodes

  1. Behavior of InP:Fe under high electric field (United States)

    Turki, K.; Picoli, G.; Viallet, J. E.


    The behavior of semi-insulating InP:Fe under high electric field is investigated. The current-voltage (I-V) characteristics are studied on both long liquid-encapsulated Czochralski-grown samples and short epitaxial-grown layers. These characteristics show a linear regime at low voltages followed, for higher voltages, by a nonlinear behavior and a current breakdown. The critical electric field at which the nonlinearity begins is found to be independent of the sample thickness, the material compensation, and the nature of the contacts, and is equal to 10 kV/cm. This fact rules out the usual explanation in terms of Lampert's injection theory. In the nonlinear regime, a slow transient response (≊1 s at room temperature) is observed only for long samples. The time constant of this effect exhibits a thermal activation energy (≊0.64 eV) close to that of the iron-related deep level. Field-dependent effects on the thermal emission rate and the capture cross section are discussed. Considering a field enhancement of the capture cross section, we propose a model to explain both the nonlinear characteristics and the slow dynamic behavior of long samples. The current breakdown observed at higher fields is attributed to an impact ionization of the deep levels and not to a trap-filled-limit voltage as previously reported.

  2. Dosimetry in radiation fields around high-energy proton accelerators

    CERN Document Server

    Agosteo, S; Silari, M; Theis, C


    Radiation dosimetry at high-energy proton accelerators is a difficult task because of the complexity of the stray radiation field. A good knowledge of this mixed radiation field is very important to be able to select the type of detectors (active and/or passive) to be employed for routine area monitoring and to choose the personal dosimeter legally required for estimating the effective dose received by individuals. At the same time, the response function of the detectors to the mixed field must be thoroughly understood. A proper calibration of a device, which may involve a complex series of measurements in various reference fields, is needed. Monte Carlo simulations provide a complementary – and sometimes the principal – mean of determining the response function. The ambient dose equivalent rates during operation range from a few hundreds of μSv per year to a few mSv per year. To measure such rates one needs detectors of high sensitivity and/or capable of integrating over long periods. The main challenge...

  3. Raman spectroscopy of graphite in high magnetic fields (United States)

    Kim, Younghee; Lombardo, Antonio; Kalugin, Nikolai G.; Kono, Junichiro; Ferrari, Andrea C.; Smirnov, Dmitry


    Recently, much attention has been paid to electron-phonon coupling in graphene. In particular, significant re-normalization and broadening of long-wavelength optical phonons are predicted to occur through resonant interaction with Landau-quantized Dirac fermions. We report here on a high-field magneto-Raman spectroscopy study of highly-oriented pyrolytic graphite (HOPG) and natural graphite at temperatures down to 5 K and in magnetic fields up to 45 T. The E2 g graphite phonon line exhibits anticrossing-like behavior at approximately 30 T, which we attribute to the magneto-phonon resonance (MPR) of graphite's massless holes at the H-point. Additionally, we observed features related to inter-Landau-level transitions at the K-point of graphite. We also observed weak graphene-like signatures of MPR, indicating the existence of graphene flakes on the graphite surface.

  4. Development of high magnetic fields for energy research

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, J.D.; Campbell, L.J.; Modler, R.; Movshovich, R. [Los Alamos National Lab., NM (United States); Lawrence, J.M. [Univ. of California, Irvine, CA (United States); Awschalom, D.D. [Univ. of California, Santa Barbara, CA (United States)


    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The primary purpose of work has been to develop the scientific basis for DOE support of a program that would build a novel, nondestructive 100-tesla magnet that would be available as a user facility for cutting-edge, energy-related research and technology at very high magnetic fields.

  5. Key techniques of the high precision gravity field system (United States)

    Xu, Weimin; Chen, Shi; Lu, Hongyan; Shi, Lei


    Ground-based gravity time series provide a direct method to monitor all sources of mass changes from local to global scale. But the effectively infinite spatial sensitivity of gravity measurements make it difficult to isolate the signal of interest. The high precision gravity field system is an alternative approach of modeling mass changes under-ground. The field system, consists of absolute gravity, gravity and gravity gradient, GNSS, leveling and climate hydrology measurements, can improve the signal-to-noise ratio for many applications by removing contributions of unwanted signal from elevation changes, air pressure changes, local hydrology, and others. The networks of field system combination, such as field-profile in more than 100 kilometers, can be used in critical zone with high seismic risk for monitoring earth dynamics, volcanic and seismic phenomena. The system is constituted by 9 typical observation stations in 3*3 array (or 4 in 2*2 array) in 60 square meters field, each station is designed for integrated measurements, including absolute gravity, gravity gradient, elevation changes, air pressure and hydrology. Time-lapse gravity changes resulting from absolute gravimeter (FG5 or A10) with standard deviation less than 2 μGal, without the contributions of Earth tides, loading and polar motion. Additional measurements such as air pressure change, local hydrology and soil moisture are indispensable. The elevation changes resulting from GNSS (on the base station) and leveling (between stations) with precision less than 10 mm. The gravity gradient is the significant measurement for delimiting the location of the related mass changes underground the station, which is measured by Scintrex CG-5 gravimeters in different height (80cm in the test field), with precision less than 10 E. It is necessary to improve the precision of gravity gradient measurements by certain method in field experiment for the high precision measurement system. Acknowledgment: This

  6. Strong-field relativistic processes in highly charged ions

    Energy Technology Data Exchange (ETDEWEB)

    Postavaru, Octavian


    In this thesis we investigate strong-field relativistic processes in highly charged ions. In the first part, we study resonance fluorescence of laser-driven highly charged ions in the relativistic regime by solving the time-dependent master equation in a multi-level model. Our ab initio approach based on the Dirac equation allows for investigating highly relativistic ions, and, consequently, provides a sensitive means to test correlated relativistic dynamics, bound-state quantum electrodynamic phenomena and nuclear effects by applying coherent light with x-ray frequencies. Atomic dipole or multipole moments may be determined to unprecedented accuracy by measuring the interference-narrowed fluorescence spectrum. Furthermore, we investigate the level structure of heavy hydrogenlike ions in laser beams. Interaction with the light field leads to dynamic shifts of the electronic energy levels, which is relevant for spectroscopic experiments. We apply a fully relativistic description of the electronic states by means of the Dirac equation. Our formalism goes beyond the dipole approximation and takes into account non-dipole effects of retardation and interaction with the magnetic field components of the laser beam. We predicted cross sections for the inter-shell trielectronic recombination (TR) and quadruelectronic recombination processes which have been experimentally confirmed in electron beam ion trap measurements, mainly for C-like ions, of Ar, Fe and Kr. For Kr{sup 30}+, inter-shell TR contributions of nearly 6% to the total resonant photorecombination rate were found. (orig.)

  7. The Mechanical Design Optimization of a High Field HTS Solenoid

    Energy Technology Data Exchange (ETDEWEB)

    Lalitha, SL; Gupta, RC


    This paper describes the conceptual design optimization of a large aperture, high field (24 T at 4 K) solenoid for a 1.7 MJ superconducting magnetic energy storage device. The magnet is designed to be built entirely of second generation (2G) high temperature superconductor tape with excellent electrical and mechanical properties at the cryogenic temperatures. The critical parameters that govern the magnet performance are examined in detail through a multiphysics approach using ANSYS software. The analysis results formed the basis for the performance specification as well as the construction of the magnet.

  8. Electric Field Simulations and Analysis for High Voltage High Power Medium Frequency Transformer

    Directory of Open Access Journals (Sweden)

    Pei Huang


    Full Text Available The electronic power transformer (EPT raises concerns for its notable size and volume reduction compared with traditional line frequency transformers. Medium frequency transformers (MFTs are important components in high voltage and high power energy conversion systems such as EPTs. High voltage and high power make the reliable insulation design of MFT more difficult. In this paper, the influence of wire type and interleaved winding structure on the electric field distribution of MFT is discussed in detail. The electric field distributions for six kinds of typical non-interleaved windings with different wire types are researched using a 2-D finite element method (FEM. The electric field distributions for one non-interleaved winding and two interleaved windings are also studied using 2-D FEM. Furthermore, the maximum electric field intensities are obtained and compared. The results show that, in this case study, compared with foil conductor, smaller maximum electric field intensity can be achieved using litz wire in secondary winding. Besides, interleaving can increase the maximum electric field intensity when insulation distance is constant. The proposed method of studying the electric field distribution and analysis results are expected to make a contribution to the improvement of electric field distribution in transformers.

  9. The High Field Path to Practical Fusion Energy (United States)

    Mumgaard, Robert; Whyte, D.; Greenwald, M.; Hartwig, Z.; Brunner, D.; Sorbom, B.; Marmar, E.; Minervini, J.; Bonoli, P.; Irby, J.; Labombard, B.; Terry, J.; Vieira, R.; Wukitch, S.


    We propose a faster, lower cost development path for fusion energy enabled by high temperature superconductors, devices at high magnetic field, innovative technologies and modern approaches to technology development. Timeliness, scale, and economic-viability are the drivers for fusion energy to combat climate change and aid economic development. The opportunities provided by high-temperature superconductors, innovative engineering and physics, and new organizational structures identified over the last few years open new possibilities for realizing practical fusion energy that could meet mid-century de-carbonization needs. We discuss re-factoring the fusion energy development path with an emphasis on concrete risk retirement strategies utilizing a modular approach based on the high-field tokamak that leverages the broader tokamak physics understanding of confinement, stability, and operational limits. Elements of this plan include development of high-temperature superconductor magnets, simplified immersion blankets, advanced long-leg divertors, a compact divertor test tokamak, efficient current drive, modular construction, and demountable magnet joints. An R&D plan culminating in the construction of an integrated pilot plant and test facility modeled on the ARC concept is presented.

  10. Compliance with High-Intensity Radiated Fields Regulations - Emitter's Perspective (United States)

    Statman, Joseph; Jamnejad, Vahraz; Nguyen, Lee


    NASA's Deep Space Network (DSN) uses high-power transmitters on its large antennas to communicate with spacecraft of NASA and its partner agencies. The prime reflectors of the DSN antennas are parabolic, at 34m and 70m in diameter. The DSN transmitters radiate Continuous Wave (CW) signals at 20 kW - 500 kW at X-band and S-band frequencies. The combination of antenna reflector size and high frequency results in a very narrow beam with extensive oscillating near-field pattern. Another unique feature of the DSN antennas is that they (and the radiated beam) move mostly at very slow sidereal rate, essentially identical in magnitude and at the opposite direction of Earth rotation.The DSN is in the process of revamping its documentation to provide analysis of the High Intensity Radiation Fields (HIRF) environment resulting from radio frequency radiation from DSN antennas for comparison to FAA regulations regarding certification of HIRF protection as outlined in the FAA regulations on HIRF protection for aircraft electrical and electronic systems (Title 14, Code of Federal Regulations (14 CFR) [section sign][section sign] 23.1308, 25.1317, 27.1317, and 29.1317).This paper presents work done at JPL, in consultation with the FAA. The work includes analysis of the radiated field structure created by the unique DSN emitters (combination of transmitters and antennas) and comparing it to the fields defined in the environments in the FAA regulations. The paper identifies areas that required special attention, including the implications of the very narrow beam of the DSN emitters and the sidereal rate motion. The paper derives the maximum emitter power allowed without mitigation and the mitigation zones, where required.Finally, the paper presents summary of the results of the analyses of the DSN emitters and the resulting DSN process documentation.

  11. Enhanced Field Emission Studies on Niobium Surfaces Relevant to High Field Superconducting Radio-Frequency Devices

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Tong [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States)


    Enhanced field emission (EFE) presents the main impediment to higher acceleration gradients in superconducting niobium (Nb) radiofrequency cavities for particle accelerators. The strength, number and sources of EFE sites strongly depend on surface preparation and handling. The main objective of this thesis project is to systematically investigate the sources of EFE from Nb, to evaluate the best available surface preparation techniques with respect to resulting field emission, and to establish an optimized process to minimize or eliminate EFE. To achieve these goals, a scanning field emission microscope (SFEM) was designed and built as an extension to an existing commercial scanning electron microscope (SEM). In the SFEM chamber of ultra high vacuum, a sample is moved laterally in a raster pattern under a high voltage anode tip for EFE detection and localization. The sample is then transferred under vacuum to the SEM chamber equipped with an energy-dispersive x-ray spectrometer for individual emitting site characterization. Compared to other systems built for similar purposes, this apparatus has low cost and maintenance, high operational flexibility, considerably bigger scan area, as well as reliable performance. EFE sources from planar Nb have been studied after various surface preparation, including chemical etching and electropolishing, combined with ultrasonic or high-pressure water rinse. Emitters have been identified, analyzed and the preparation process has been examined and improved based on EFE results. As a result, field-emission-free or near field-emission-free surfaces at ~140 MV/m have been consistently achieved with the above techniques. Characterization on the remaining emitters leads to the conclusion that no evidence of intrinsic emitters, i.e., no fundamental electric field limit induced by EFE, has been observed up to ~140 MV/m. Chemically etched and electropolished Nb are compared and no significant difference is observed up to ~140 MV/m. To

  12. Field experimental observations of highly graded sediment plumes. (United States)

    Jensen, Jacob Hjelmager; Saremi, Sina; Jimenez, Carlos; Hadjioannou, Louis


    A field experiment in the waters off the south-eastern coast of Cyprus was carried out to study near-field formation of sediment plumes from dumping. Different loads of sediment were poured into calm and limpid waters one at the time from just above the sea surface. The associated plumes, gravitating towards the seafloor, were filmed simultaneously by four divers situated at different depths in the water column, and facing the plume at different angles. The processes were captured using GoPro-Hero-series cameras. The high-quality underwater footage from near-surface, mid-depth and near-bed positions gives unique insight into the dynamics of the descending plume and near-field dispersion processes, and enables good understanding of flow and sediment transport processes involved from-release-to-deposition of the load in a non-scaled environment. The high resolution images and footages are available through the link provided herein. Observations support the development of a detailed multi-fractional sediment plume model. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Advances in High-Field BOLD fMRI

    Directory of Open Access Journals (Sweden)

    Markus Barth


    Full Text Available This review article examines the current state of BOLD fMRI at a high magnetic field strength of 7 Tesla. The following aspects are covered: a short description of the BOLD contrast, spatial and temporal resolution, BOLD sensitivity, localization and spatial specificity, technical challenges as well as an outlook on future developments are given. It is shown that the main technical challenges of performing BOLD fMRI at high magnetic field strengths—namely development of array coils, imaging sequences and parallel imaging reconstruction—have been solved successfully. The combination of these developments has lead to the availability of high-resolution BOLD fMRI protocols that are able to cover the whole brain with a repetition time (TR shorter than 3 s. The structural information available from these high-resolution fMRI images itself is already very detailed, which helps to co-localize structure and function. Potential future applications include whole-brain connectivity analysis on a laminar resolution and single subject examinations.

  14. High-field electrical and thermal transport in suspended graphene. (United States)

    Dorgan, Vincent E; Behnam, Ashkan; Conley, Hiram J; Bolotin, Kirill I; Pop, Eric


    We study the intrinsic transport properties of suspended graphene devices at high fields (≥1 V/μm) and high temperatures (≥1000 K). Across 15 samples, we find peak (average) saturation velocity of 3.6 × 10(7) cm/s (1.7 × 10(7) cm/s) and peak (average) thermal conductivity of 530 W m(-1) K(-1) (310 W m(-1) K(-1)) at 1000 K. The saturation velocity is 2-4 times and the thermal conductivity 10-17 times greater than in silicon at such elevated temperatures. However, the thermal conductivity shows a steeper decrease at high temperature than in graphite, consistent with stronger effects of second-order three-phonon scattering. Our analysis of sample-to-sample variation suggests the behavior of "cleaner" devices most closely approaches the intrinsic high-field properties of graphene. This study reveals key features of charge and heat flow in graphene up to device breakdown at ~2230 K in vacuum, highlighting remaining unknowns under extreme operating conditions.

  15. Dissipation in high-temperature superconductors in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.H.; Gray, K.E.; Kampwirth, R.T.; McDonald, D.B.; McKay, D.M.


    The absence of a Lorentz force dependence on dissipation in the highly anisotropic highly high-temperature superconductor, Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub x}, has been measured over a wide range of current densities in broadened resistive transitions, current-voltage characteristics, magnetoresistances, and critical current densities, J{sub c}. The magnetoresistances are very useful to find out the correct temperature and field dependences of the activation energy. As an alternative to flux motion, we consider a Josephson-coupling model which is consistent with the broadened resistive transitions and the lack of Lorentz-force dependence. We found that the Josephson-coupling model agrees with the temperature dependences of the activation energy and J{sub c} and is better matched to the weak field dependence of J{sub c} than the flux creep model. Possible origins of Josephson junctions in high-quality films and single crystals are discussed. 12 refs., 6 figs.


    Energy Technology Data Exchange (ETDEWEB)

    Gianluigi Ciovati


    One of the most interesting phenomenon occurring in superconducting radio-frequency (SRF) cavities made of bulk niobium is represented by a sharp decrease of the quality factor above peak surface magnetic field of about 90 mT and is referred to as "high field Q-slope" or "Q-drop". This phenomenon was observed first in 1997 and since then some effort was devoted to the understanding of the causes behind it. Still, no clear physical interpretation of the Q-drop has emerged, despite several attempts. In this contribution, I will review the experimental results for various cavities measured in many laboratories and I will try to identify common features and differences related to the Q-drop.

  17. High electric field dielectric studies of aqueous myoglobin solutions. (United States)

    Jones, G P; Davies, A E; van der Sluijs, M J


    High field dielectric measurements of the Piekara factor deltaepsilon/E2 have been carried out for a range of concentrations of horse heart myoglobin in water at 293K. Using the literature value for the dipole moment of myoglobin and the established theory for the classical orientational dipolar non-linear effect predicts a value of deltaepsilon/E2 one order of magnitude greater than that for water. The measured effect, however, was found to be one order of magnitude less than for water. This difference is explained as being most probably due to the existence of antiparallel molecular dipole pairs in the myoglobin solution. The possibility of a positive deltaepsilon due to a field induced conformational change of the myoglobin cannot, however, be ruled out.

  18. High-resolution field shaping utilizing a masked multileaf collimator. (United States)

    Williams, P C; Cooper, P


    Multileaf collimators (MLCs) have become an important tool in the modern radiotherapy department. However, the current limit of resolution (1 cm at isocentre) can be too coarse for acceptable shielding of all fields. A number of mini- and micro-MLCs have been developed, with thinner leaves to achieve approved resolution. Currently however, such devices are limited to modest field sizes and stereotactic applications. This paper proposes a new method of high-resolution beam collimation by use of a tertiary grid collimator situated below the conventional MLC. The width of each slit in the grid is a submultiple of the MLC width. A composite shaped field is thus built up from a series of subfields, with the main MLC defining the length of each strip within each subfield. Presented here are initial findings using a prototype device. The beam uniformity achievable with such a device was examined by measuring transmission profiles through the grid using a diode. Profiles thus measured were then copied and superposed to generate composite beams, from which the uniformity achievable could be assessed. With the average dose across the profile normalized to 100%, hot spots up to 5.0% and troughs of 3% were identified for a composite beam of 2 x 5.0 mm grids, as measured at Dmax for a 6 MV beam. For a beam composed from 4 x 2.5 mm grids, the maximum across the profile was 3.0% above the average, and the minimum 2.5% below. Actual composite profiles were also formed using the integrating properties of film, with the subfield indexing performed using an engineering positioning stage. The beam uniformity for these fields compared well with that achieved in theory using the diode measurements. Finally sine wave patterns were generated to demonstrate the potential improvements in field shaping and conformity using this device as opposed to the conventional MLC alone. The scalloping effect on the field edge commonly seen on MLC fields was appreciably reduced by use of 2 x 5.0 mm

  19. High Field Side MHD Activity During Local Helicity Injection (United States)

    Pachicano, J. L.; Bongard, M. W.; Fonck, R. J.; Perry, J. M.; Reusch, J. A.; Richner, N. J.


    MHD is an essential part of understanding the mechanism for local helicity injection (LHI) current drive. The new high field side (HFS) LHI system on the Pegasus ST permits new tests of recent NIMROD simulations. In that model, LHI current streams in the plasma edge undergo large-scale reconnection events, leading to current drive. This produces bursty n = 1 activity around 30 kHz on low field side (LFS) Mirnov coils, consistent with experiment. The simulations also feature coherent injector streams winding down the center column. Improvements to the core high-resolution poloidal Mirnov array with Cat7A Ethernet cabling and differentially driven signal processing eliminated EMI-driven switching noise, enabling detailed spectral analysis. Preliminary results from the recovered HFS poloidal Mirnov coils suggest n = 1 activity is present at the top of the vessel core, but does not persist down the centerstack. HFS LHI experiments can exhibit an operating regime where the high amplitude MHD is abruptly reduced by more than an order of magnitude on LFS Mirnov coils, leading to higher plasma current and improved particle confinement. This reduction is not observed on the HFS midplane magnetics. Instead, they show broadband turbulence-like magnetic features with near consistent amplitude in a frequency range of 90-200 kHz. Work supported by US DOE Grant DE-FG02-96ER54375.

  20. Tunable-frequency high-field electron paramagnetic resonance (United States)

    Krzystek, J.; Zvyagin, S. A.; Ozarowski, Andrew; Trofimenko, S.; Telser, Joshua


    A tunable-frequency methodology based on backward wave oscillator sources in high-frequency and -field EPR (HFEPR) is described. This methodology is illustrated by an application to three non-Kramers transition metal ion complexes and one Kramers ion complex. The complexes are of: Ni(II) ( S = 1) as found in dichlorobistriphenylphosphanenickel(II), Mn(III) ( S = 2) as found in mesotetrasulfonatoporphyrinatomanganese(III) chloride, Fe(II) ( S = 2) as found in ferrous sulfate tetrahydrate, and Co(II) ( S = 3/2) as found in azido(tris(3- tert-butylpyrazol-1-yl)hydroborate)cobalt(II). The above Ni(II) and Mn(III) complexes have been studied before by HFEPR using the multifrequency methodology based on Gunn oscillator sources, but not by the present method, while the Fe(II) and Co(II) complexes presented here have not been studied by any form of HFEPR. Highly accurate spin Hamiltonian parameters can be obtained by the experimental methodology described here, in combination with automated fitting procedures. This method is particularly successful in determining g-matrix parameters, which are very difficult to extract for high-spin systems from single frequency (or a very limited set of multi-frequency) HFEPR spectra, but is also able to deliver equally accurate values of the zero-field splitting tensor. The experimental methods involve either conventional magnetic field modulation or an optical modulation of the sub-THz wave beam. The relative merits of these and other experimental methods are discussed.

  1. Constraints from high redshift supernovae upon scalar field cosmologies

    Energy Technology Data Exchange (ETDEWEB)

    Frieman, J.A. [NASA/Fermilab Astrophysics Center, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, Illinois60510 (United States)]|[Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois60637 (United States); Waga, I. [Universidade Federal do Rio de Janeiro, Instituto de Fisica, Rio de Janeiro, RJ, 21945-970 (Brazil)


    Recent observations of high-redshift type Ia supernovae have placed stringent constraints on the cosmological constant {Lambda}. We explore the implications of these SNe observations for cosmological models in which a classically evolving scalar field currently dominates the energy density of the Universe. Such models have been shown to share the advantages of {Lambda} models: compatibility with the spatial flatness predicted by inflation; a Universe older than the standard Einstein{endash}de Sitter model; and, combined with cold dark matter, predictions for large-scale structure formation in good agreement with data from galaxy surveys. Compared to the cosmological constant, these scalar field models are consistent with the SNe observations for a lower matter density, {Omega}{sub m0}{approximately}0.2, and a higher age, H{sub 0}t{sub 0}{approx_gt}1. Combined with the fact that scalar field models imprint a distinctive signature on the cosmic microwave background anisotropy, they remain currently viable and should be testable in the near future. {copyright} {ital 1998} {ital The American Physical Society}

  2. High magnetic field magnetization of a new triangular lattice antiferromagnet

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, H. D. [Univ. of Tennessee, Knoxville, TN (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States). National High Magnetic Field Lab. (MagLab); Stritzinger, Laurel Elaine Winter [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Harrison, Neil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)


    In CsV(MoO4)2, the magnetic V3+ ions with octahedral oxygen-coordination form a geometrically frustrated triangular lattice. So fare, there is no magnetic properties reported on it. Recently, we successfully grew single crystals of CsV(MoO4)2 by using flux method. The susceptibility shows a sharp drop around 24 K, representing a long range magnetic ordering. To understand the physical properties of this new triangular lattice antiferromagnet (TLAF), we pursued high field magnetization measurements to answer two questions: (i) what is the saturation field, which will be very useful to calculate the exchange interaction of the system? (ii) Will it exhibit spin state transition, such as the up up down phase with 1/3-saturation moment as other TLAFs? Recently, we performed VSM measurements in Cell 8, Tallahassee, NHMFL, the results show that the magnetization reaches 0.38 MuB at 34 T, which is just 19% of the full moment of 2 MuB for V3+ (3d2) ions. Apparently we need higher field to reach 1/3 value or full moment.

  3. High temperature superconducting axial field magnetic coupler: realization and test (United States)

    Belguerras, L.; Mezani, S.; Lubin, T.; Lévêque, J.; Rezzoug, A.


    Contactless torque transmission through a large airgap is required in some industrial applications in which hermetic isolation is necessary. This torque transmission usually uses magnetic couplers, whose dimension strongly depends on the airgap flux density. The use of high temperature superconducting (HTS) coils to create a strong magnetic field may constitute a solution to reduce the size of the coupler. It is also possible to use this coupler to replace a torque tube in transmitting the torque produced by a HTS motor to its load. This paper presents the detailed construction and tests of an axial field HTS magnetic coupler. Pancake coils have been manufactured from BSCCO tape and used in one rotor of the coupler. The second rotor is mainly composed of NdFeB permanent magnets. Several tests have been carried out showing that the constructed coupler is working properly. A 3D finite element (FE) model of the studied coupler has been developed. Airgap magnetic field and torque measurements have been carried out and compared to the FE results. It has been shown that the measured and the computed quantities are in satisfactory agreement.

  4. High magnetic field properties of Fe-pnictide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kurth, Fritz


    The recent discovery of high-temperature superconductivity in Fe-based materials triggered worldwide efforts to investigate their fundamental properties. Despite a lot of similarities to cuprates and MgB{sub 2}, important differences like near isotropic behaviour in contrast to cuprates and the peculiar pairing symmetry of the order parameter (OP) have been reported. The OP symmetry of Fe-based superconductors (FBS) was theoretically predicted to be of so-called s± state prior to various experimental works. Still, most of the experimental results favour the s± scenario; however, definitive evidence has not yet been reported. Although no clear understanding of the superconducting mechanisms yet exists, potential applications such as high-field magnets and Josephson devices have been explored. Indeed, a lot of reports about FBS tapes, wires, and even SQUIDs have been published to this date. In this thesis, the feasibility of high-field magnet applications of FBS is addressed by studying their transport properties, involving doped BaFe{sub 2}As{sub 2} (Ba-122) and LnFeAs(O,F) [Ln=Sm and Nd]. Particularly, it is important to study physical properties in a sample form (i.e. thin films) that is close to the conditions found in applications. However, the realisation of epitaxial FBS thin films is not an easy undertaking. Recent success in growing epitaxial FBS thin films opens a new avenue to delve into transport critical current measurements. The information obtained through this research will be useful for exploring high-field magnet applications. This thesis consists of 7 chapters: Chapter 1 describes the motivation of this study, the basic background of superconductivity, and a brief summary of the thin film growth of FBS. Chapter 2 describes experimental methods employed in this study. Chapter 3 reports on the fabrication of Co-doped Ba-122 thin films on various substrates. Particular emphasis lies on the discovery of fluoride substrates to be beneficial for

  5. Low-threshold ( le 92 A/cm sup 2 ) 1. 6. mu. m strained-layer single quantum well laser diodes optically pumped by a 0. 8. mu. m laser diode

    Energy Technology Data Exchange (ETDEWEB)

    Zah, C.E.; Bhat, R.; Cheung, K.W.; Andreadakis, N.C.; Favire, F.J.; Menocal, S.G.; Yablonovitch, E.; Hwang, D.M.; Koza, M.; Gmitter, T.J.; Lee, T.P. (Bellcore, 331 Newman Springs Road, Red Bank, New Jersey 07701 (USA))


    To explore the ultimate threshold current limit in long-wavelength semiconductor lasers, In{sub {ital x}}Ga{sub 1{minus}{ital x}}As/InP strained-layer single quantum well laser diodes were studied for the first time by optically pumping with a 0.8 {mu}m laser diode. Low-threshold ({le}92 A/cm{sup 2}) cw operation was obtained and the lasing wavelength (1.62 {mu}m) corresponding to the transition from the first quantization state of a 25 A In{sub 0.8}Ga{sub 0.2}As well was observed. By taking the carrier collection efficiency ({le}77%) into account, the actual threshold current density could be as low as 70 A/cm{sup 2}.

  6. High-Magnetic-Field and High-Pressure Effects in Monocrystalline URu2Si2

    NARCIS (Netherlands)

    Boer, F.R. de; Franse, J.J.M.; Louis, E.; Menovsky, A.A.; Mydosh, J.A.; Palstra, T.T.M.; Rauchschwalbe, U.; Schlabitz, W.; Steglich, F.; Visser, A. de


    High-field magnetisation and high-pressure resistivity measurements have been performed on monocrystalline samples of the superconducting compound URu2Si2 just above Tc. At 1.4 K, well below the magnetic ordering temperature of about 17.5K, two sharp transitions at 36 and 40 T have been observed in

  7. Progress with High-Field Superconducting Magnets for High-Energy Colliders (United States)

    Apollinari, Giorgio; Prestemon, Soren; Zlobin, Alexander V.


    One of the possible next steps for high-energy physics research relies on a high-energy hadron or muon collider. The energy of a circular collider is limited by the strength of bending dipoles, and its maximum luminosity is determined by the strength of final focus quadrupoles. For this reason, the high-energy physics and accelerator communities have shown much interest in higher-field and higher-gradient superconducting accelerator magnets. The maximum field of NbTi magnets used in all present high-energy machines, including the LHC, is limited to ˜10 T at 1.9 K. Fields above 10 T became possible with the use of Nb3Sn superconductors. Nb3Sn accelerator magnets can provide operating fields up to ˜15 T and can significantly increase the coil temperature margin. Accelerator magnets with operating fields above 15 T require high-temperature superconductors. This review discusses the status and main results of Nb3Sn accelerator magnet research and development and work toward 20-T magnets.

  8. Whole-globe biomechanics using high-field MRI. (United States)

    Voorhees, Andrew P; Ho, Leon C; Jan, Ning-Jiun; Tran, Huong; van der Merwe, Yolandi; Chan, Kevin; Sigal, Ian A


    The eye is a complex structure composed of several interconnected tissues acting together, across the whole globe, to resist deformation due to intraocular pressure (IOP). However, most work in the ocular biomechanics field only examines the response to IOP over smaller regions of the eye. We used high-field MRI to measure IOP induced ocular displacements and deformations over the whole globe. Seven sheep eyes were obtained from a local abattoir and imaged within 48 h using MRI at multiple levels of IOP. IOP was controlled with a gravity perfusion system and a cannula inserted into the anterior chamber. T2-weighted imaging was performed to the eyes serially at 0 mmHg, 10 mmHg, 20 mmHg and 40 mmHg of IOP using a 9.4 T MRI scanner. Manual morphometry was conducted using 3D visualization software to quantify IOP-induced effects at the globe scale (e.g. axial length and equatorial diameters) or optic nerve head scale (e.g. canal diameter, peripapillary sclera bowing). Measurement sensitivity analysis was conducted to determine measurement precision. High-field MRI revealed an outward bowing of the posterior sclera and anterior bulging of the cornea due to IOP elevation. Increments in IOP from 10 to 40 mmHg caused measurable increases in axial length in 6 of 7 eyes of 7.9 ± 5.7% (mean ± SD). Changes in equatorial diameter were minimal, 0.4 ± 1.2% between 10 and 40 mmHg, and in all cases less than the measurement sensitivity. The effects were nonlinear, with larger deformations at normal IOPs (10-20 mmHg) than at elevated IOPs (20-40 mmHg). IOP also caused measurable increases in the nasal-temporal scleral canal diameter of 13.4 ± 9.7% between 0 and 20 mmHg, but not in the superior-inferior diameter. This study demonstrates that high-field MRI can be used to visualize and measure simultaneously the effects of IOP over the whole globe, including the effects on axial length and equatorial diameter, posterior sclera displacement and bowing, and even

  9. Anisotropic high field superconductinng behavior in MgB_2 (United States)

    Gurevich, Alexander


    I will discuss new effects resulting from the two-gap superconductivity in MgB_2, focusing on: 1. Current-induced interband breakdown and dynamic interband phase textures caused by nonequilibrium charge imbalance [1], 2. Anomalous enhancement of the upper critical field H_c2(T) by nonmagnetic impurities in dirty two-gap superconductors. A theory of H_c2 based on generalized two-gap Usadel equations, which include both intra and interband scattering channels and paramagnetic pairbreaking is presented. Solutions of these equations show that H_c2(T) can exhibit a strong upward curvature and an unusual temperature dependence of the anisotropy parameter H_c2^||/H_c2^⊥, which can both increase and decrease with T depending on the ratio of the intraband electron diffusivities D_π/D_σ [2]. The theory explains recent high-field transport experiments on resistive MgB2 films in which the upper critical field was increased by 3-10 times as compared to single crystals [3], H_c2 exceeding 50 Tesla for H||ab and 35T for H⊥ ab. The results suggest that nonmagnetic impurities due to selective atomic substitution on Mg and B sites can increase H_c2 of MgB2 to a much greater extend than in one-gap superconductors. [1]. A. Gurevich and V.M. Vinokur, PRL 90, 047004 (2003). [2]. A. Gurevich, PRB 67, 1845151 (2003) and unpublished. [3]. A. Gurevich et al. Supercond. Sci. Technol. (2003, to appear). *In collaboration with V.M. Vinokur, V. Braccini, S. Patnaik, X. Song, D.C. Larbalestier, C.B. Eom, X. Pan, X. Xi, V. Ferrando, C. Ferdighini, A. Siri, K.H. Kim and C. Mielke. Work supported by NSF Nanostructured Materials and Interfaces MRSEC at the University of Wisconsin.

  10. Dynamics of Coulomb correlations in semiconductors in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Fromer, Neil Alan [Univ. of California, Berkeley, CA (United States)


    Current theories have been successful in explaining many nonlinear optical experiments in undoped semiconductors. However, these theories require a ground state which is assumed to be uncorrelated. Strongly correlated systems of current interest, such as a two dimensional electron gas in a high magnetic field, cannot be explained in this manner because the correlations in the ground state and the low energy collective excitations cause a breakdown of the conventional techniques. We perform ultrafast time-resolved four-wave mixing on $n$-modulation doped quantum wells, which contain a quasi-two dimensional electron gas, in a large magnetic field, when only a single Landau level is excited and also when two levels are excited together. We find evidence for memory effects and as strong coupling between the Landau levels induced by the electron gas. We compare our results with simulations based on a new microscopic approach capable of treating the collective effects and correlations of the doped electrons, and find a good qualitative agreement. By looking at the individual contributions to the model, we determine that the unusual correlation effects seen in the experiments are caused by the scattering of photo-excited electron-hole pairs with the electron gas, leading to new excited states which are not present in undoped semiconductors, and also by exciton-exciton interactions mediated by the long-lived collective excitations of the electron gas, inter-Landau level magnetoplasmons.

  11. Birkeland current effects on high-latitude groundmagnetic field perturbations

    CERN Document Server

    Laundal, K M; Lehtinen, N; Gjerloev, J W; Østgaard, N; Tenfjord, P; Reistad, J P; Snekvik, K; Milan, S E; Ohtani, S; Anderson, B J


    Magnetic perturbations on ground at high latitudes are directly associated only with the divergence-free component of the height-integrated horizontal ionospheric current, $\\textbf{J}_{\\perp,df}$. Here we show how $\\textbf{J}_{\\perp,df}$ can be expressed as the total horizontal current $\\textbf{J}_\\perp$ minus its curl-free component, the latter being completely determined by the global Birkeland current pattern. Thus in regions where $\\textbf{J}_\\perp = 0$, the global Birkeland current distribution alone determines the local magnetic perturbation. We show with observations from ground and space that in the polar cap, the ground magnetic field perturbations tend to align with the Birkeland current contribution in darkness but not in sunlight. We also show that in sunlight, the magnetic perturbations are typically such that the equivalent overhead current is anti-parallel to the convection, indicating that the Hall current system dominates. Thus the ground magnetic field in the polar cap relates to different c...

  12. High-Speed and Wide-Field Photometry with TORTORA

    Directory of Open Access Journals (Sweden)

    G. Greco


    Full Text Available We present the photometric analysis of the extended sky fields observed by the TORTORA optical monitoring system. The technology involved in the TORTORA camera is based on the use of a fast TV-CCD matrix with an image intensifier. This approach can both significantly reduce the readout noise and shorten the focal length following to monitor relatively large sky regions with high temporal resolution and adequate detection limit. The performance of the system has been tested using the relative magnitudes of standard stars by means of long image sequences collected at different airmasses and at various intensities of the moon illumination. As expected from the previous laboratory measurements, artifact sources are negligible and do not affect the photometric results. The following analysis is based on a large sample of images acquired by the TORTORA instrument since July 2006.

  13. Diffuse axonal injury at ultra-high field MRI.

    Directory of Open Access Journals (Sweden)

    Christoph Moenninghoff

    Full Text Available Diffuse axonal injury (DAI is a specific type of traumatic brain injury caused by shearing forces leading to widespread tearing of axons and small vessels. Traumatic microbleeds (TMBs are regarded as a radiological marker for DAI. This study aims to compare DAI-associated TMBs at 3 Tesla (T and 7 T susceptibility weighted imaging (SWI to evaluate possible diagnostic benefits of ultra-high field (UHF MRI.10 study participants (4 male, 6 female, age range 20-74 years with known DAI were included. All MR exams were performed with a 3 T MR system (Magnetom Skyra and a 7 T MR research system (Magnetom 7 T, Siemens AG, Healthcare Sector, Erlangen, Germany each in combination with a 32-channel-receive coil. The average time interval between trauma and imaging was 22 months. Location and count of TMBs were independently evaluated by two neuroradiologists on 3 T and 7 T SWI images with similar and additionally increased spatial resolution at 7 T. Inter- and intraobserver reliability was assessed using the interclass correlation coefficient (ICC. Count and diameter of TMB were evaluated with Wilcoxon signed rank test.Susceptibility weighted imaging revealed a total of 485 TMBs (range 1-190, median 25 at 3 T, 584 TMBs (plus 20%, range 1-262, median 30.5 at 7 T with similar spatial resolution, and 684 TMBs (plus 41%, range 1-288, median 39.5 at 7 T with 10-times higher spatial resolution. Hemorrhagic DAI appeared significantly larger at 7 T compared to 3 T (p = 0.005. Inter- and intraobserver correlation regarding the counted TMB was high and almost equal 3 T and 7 T.7 T SWI improves the depiction of small hemorrhagic DAI compared to 3 T and may be supplementary to lower field strengths for diagnostic in inconclusive or medicolegal cases.

  14. High resolution, high speed, long working distance, large field of view confocal fluorescence microscope. (United States)

    Pacheco, Shaun; Wang, Chengliang; Chawla, Monica K; Nguyen, Minhkhoi; Baggett, Brend K; Utzinger, Urs; Barnes, Carol A; Liang, Rongguang


    Confocal fluorescence microscopy is often used in brain imaging experiments, however conventional confocal microscopes are limited in their field of view, working distance, and speed for high resolution imaging. We report here the development of a novel high resolution, high speed, long working distance, and large field of view confocal fluorescence microscope (H2L2-CFM) with the capability of multi-region and multifocal imaging. To demonstrate the concept, a 0.5 numerical aperture (NA) confocal fluorescence microscope is prototyped with a 3 mm × 3 mm field of view and 12 mm working distance, an array of 9 beams is scanned over the field of view in 9 different regions to speed up the acquisition time by a factor of 9. We test this custom designed confocal fluorescence microscope for future use with brain clarification methods to image large volumes of the brain at subcellular resolution. This multi-region and multi-spot imaging method can be used in other imaging modalities, such as multiphoton microscopes, and the field of view can be extended well beyond 12 mm × 12 mm.

  15. High Electron Confinement under High Electric Field in RF GaN-on-Silicon HEMTs

    Directory of Open Access Journals (Sweden)

    Farid Medjdoub


    Full Text Available We report on AlN/GaN high electron mobility transistors grown on silicon substrate with highly optimized electron confinement under a high electric field. The fabricated short devices (sub-10-nm barrier thickness with a gate length of 120 nm using gate-to-drain distances below 2 µm deliver a unique breakdown field close to 100 V/µm while offering high frequency performance. The low leakage current well below 1 µA/mm is achieved without using any gate dielectrics which typically degrade both the frequency performance and the device reliability. This achievement is mainly attributed to the optimization of material design and processing quality and paves the way for millimeter-wave devices operating at drain biases above 40 V, which would be only limited by the thermal dissipation.

  16. High-precision high field strength partitioning between garnet, amphibole, and alkaline melt, Kakanui, New Zealand

    NARCIS (Netherlands)

    Fulmer, E.J.; Nebel, O.; van Westrenen, W.


    The high field strength elements (HFSE: Zr, Hf, Nb, Ta, and W) are an important group of chemical tracers that are increasingly used to investigate magmatic differentiation processes. Successful modeling of these processes requires the availability of accurate mineral-melt partition coefficients

  17. Self-interacting scalar fields at high-temperature

    Energy Technology Data Exchange (ETDEWEB)

    Deur, Alexandre [University of Virginia, Charlottesville, VA (United States)


    We study two self-interacting scalar field theories in their high-temperature limit using path integrals on a lattice. We first discuss the formalism and recover known potentials to validate the method. We then discuss how these theories can model, in the high-temperature limit, the strong interaction and General Relativity. For the strong interaction, the model recovers the known phenomenology of the nearly static regime of heavy quarkonia. The model also exposes a possible origin for the emergence of the confinement scale from the approximately conformal Lagrangian. Aside from such possible insights, the main purpose of addressing the strong interaction here - given that more sophisticated approaches already exist - is mostly to further verify the pertinence of the model in the more complex case of General Relativity for which non-perturbative methods are not as developed. The results have important implications on the nature of Dark Matter. In particular, non-perturbative effects naturally provide flat rotation curves for disk galaxies, without need for non-baryonic matter, and explain as well other observations involving Dark Matter such as cluster dynamics or the dark mass of elliptical galaxies. (orig.)

  18. High-field magnetization of dilute rare earths in yttrium

    DEFF Research Database (Denmark)

    Touborg, P.; Høg, J.; Cock, G. J.


    Magnetization measurements have been performed on single crystals of Y containing small amounts of Tb, Dy, or Er at 4.2 K in fields up to 295 × 105 A/m (370 kOe). Crystal-field and molecular-field parameters obtained from measurements of the initial susceptibility versus temperature give a satisf...

  19. A Feasibility Study of High-Strength Bi-2223 Conductor for High-Field Solenoids. (United States)

    Godeke, A; Abraimov, D V; Arroyo, E; Barret, N; Bird, M D; Francis, A; Jaroszynski, J; Kurteva, D V; Markiewicz, W D; Marks, E L; Marshall, W S; McRae, D M; Noyes, P D; Pereira, R C P; Viouchkov, Y L; Walsh, R P; White, J M


    We performed a feasibility study on a high-strength Bi2-x Pb x Sr2Ca2Cu3O10-x (Bi-2223) tape conductor for high-field solenoid applications. The investigated conductor, DI-BSCCO Type HT-XX, is a pre-production version of Type HT-NX, which has recently become available from Sumitomo Electric Industries (SEI). It is based on their DI-BSCCO Type H tape, but laminated with a high-strength Ni-alloy. We used stress-strain characterizations, single- and double-bend tests, easy- and hard-way bent coil-turns at various radii, straight and helical samples in up to 31.2 T background field, and small 20-turn coils in up to 17 T background field to systematically determine the electro-mechanical limits in magnet-relevant conditions. In longitudinal tensile tests at 77 K, we found critical stress- and strain-levels of 516 MPa and 0.57%, respectively. In three decidedly different experiments we detected an amplification of the allowable strain with a combination of pure bending and Lorentz loading to ≥ 0.92% (calculated elastically at the outer tape edge). This significant strain level, and the fact that it is multi-filamentary conductor and available in the reacted and insulated state, makes DI-BSCCO HT-NX highly suitable for very high-field solenoids, for which high current densities and therefore high loads are required to retain manageable magnet dimensions.

  20. RAPID COMMUNICATION: High performance superconducting wire in high applied magnetic fields via nanoscale defect engineering (United States)

    Wee, Sung Hun; Goyal, Amit; Zuev, Yuri L.; Cantoni, Claudia


    High temperature superconducting (HTS) wires capable of carrying large critical currents with low dissipation levels in high applied magnetic fields are needed for a wide range of applications. In particular, for electric power applications involving rotating machinery, such as large-scale motors and generators, a high critical current, Ic, and a high engineering critical current density, JE, in applied magnetic fields in the range of 3-5 Tesla (T) at 65 K are required. In addition, exceeding the minimum performance requirements needed for these applications results in a lower fabrication cost, which is regarded as crucial to realize or enable many large-scale bulk applications of HTS materials. Here we report the fabrication of short segments of a potential superconducting wire comprised of a 4 µm thick YBa2Cu3O7-δ (YBCO) layer on a biaxially textured substrate with a 50% higher Ic and JE than the highest values reported previously. The YBCO film contained columns of self-assembled nanodots of BaZrO3 (BZO) roughly oriented along the c-axis of YBCO. Although the YBCO film was grown at a high deposition rate, three-dimensional self-assembly of the insulating BZO nanodots still occurred. For all magnetic field orientations, minimum Ic and JE at 65 K, 3 T for the wire were 353 A cm-1 and 65.4 kA cm-2, respectively.

  1. Survey of Processing Methods for High Strength High Conductivity Wires for High Field Magnet Applications

    Energy Technology Data Exchange (ETDEWEB)

    Han, K.; Embury, J.D.


    This paper will deal with the basic concepts of attaining combination of high strength and high conductivity in pure materials, in-situ composites and macrocomposites. It will survey current attainments, and outline where some future developments may lie in developing wire products that are close to the theoretical strength of future magnet applications.

  2. Low and High-Frequency Field Potentials of Cortical Networks ... (United States)

    Neural networks grown on microelectrode arrays (MEAs) have become an important, high content in vitro assay for assessing neuronal function. MEA experiments typically examine high- frequency (HF) (>200 Hz) spikes, and bursts which can be used to discriminate between different pharmacological agents/chemicals. However, normal brain activity is additionally composed of integrated low-frequency (0.5-100 Hz) field potentials (LFPs) which are filtered out of MEA recordings. The objective of this study was to characterize the relationship between HF and LFP neural network signals, and to assess the relative sensitivity of LFPs to selected neurotoxicants. Rat primary cortical cultures were grown on glass, single-well MEA chips. Spontaneous activity was sampled at 25 kHz and recorded (5 min) (Multi-Channel Systems) from mature networks (14 days in vitro). HF (spike, mean firing rate, MFR) and LF (power spectrum, amplitude) components were extracted from each network and served as its baseline (BL). Next, each chip was treated with either 1) a positive control, bicuculline (BIC, 25μM) or domoic acid (DA, 0.3μM), 2) or a negative control, acetaminophen (ACE, 100μM) or glyphosate (GLY, 100μM), 3) a solvent control (H2O or DMSO:EtOH), or 4) a neurotoxicant, (carbaryl, CAR 5, 30μM ; lindane, LIN 1, 10μM; permethrin, PERM 25, 50μM; triadimefon, TRI 5, 65μM). Post treatment, 5 mins of spontaneous activity was recorded and analyzed. As expected posit

  3. Transport studies in high-performance field reversed configuration plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, S., E-mail:; Barnes, D. C.; Dettrick, S. A.; Trask, E.; Tuszewski, M.; Deng, B. H.; Gota, H.; Gupta, D.; Hubbard, K.; Korepanov, S.; Thompson, M. C.; Zhai, K.; Tajima, T. [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States)


    A significant improvement of field reversed configuration (FRC) lifetime and plasma confinement times in the C-2 plasma, called High Performance FRC regime, has been observed with neutral beam injection (NBI), improved edge stability, and better wall conditioning [Binderbauer et al., Phys. Plasmas 22, 056110 (2015)]. A Quasi-1D (Q1D) fluid transport code has been developed and employed to carry out transport analysis of such C-2 plasma conditions. The Q1D code is coupled to a Monte-Carlo code to incorporate the effect of fast ions, due to NBI, on the background FRC plasma. Numerically, the Q1D transport behavior with enhanced transport coefficients (but with otherwise classical parametric dependencies) such as 5 times classical resistive diffusion, classical thermal ion conductivity, 20 times classical electron thermal conductivity, and classical fast ion behavior fit with the experimentally measured time evolution of the excluded flux radius, line-integrated density, and electron/ion temperature. The numerical study shows near sustainment of poloidal flux for nearly 1 ms in the presence of NBI.

  4. High-field magnetic transition in Er sub 2 Fe sub 14 B

    Energy Technology Data Exchange (ETDEWEB)

    Radwanski, R.J.; Boer, F.R. de (Natuurkundig Lab., Univ. van Amsterdam (Netherlands)); Zhong, X.P.; Yang, F.M.; Li, J.Y. (Magnetism Lab., Inst. of Physics, Academia Sinica, Beijing (China)); Kohashi, T.; Ono, M.; Date, M. (Dept. of Physics, Osaka Univ. (Japan)); Yamagishi, A. (Research Center for Extreme Materials, Osaka Univ. (Japan))


    Field-induced transitions in quasi-ternary Er{sub 2}Fe{sub 14}B compounds have been revealed by means of magnetization measurements at high magnetic fields. The high-field studies for Er{sub 2}Fe{sub 14}B, in particular the modest differential high-field susceptibility and the formation of a non-collinear magnetic structure at 42 T, do not confirm the substantial canted magnetic structure at low fields. (orig.).

  5. ADX: a high field, high power density, advanced divertor and RF tokamak (United States)

    LaBombard, B.; Marmar, E.; Irby, J.; Terry, J. L.; Vieira, R.; Wallace, G.; Whyte, D. G.; Wolfe, S.; Wukitch, S.; Baek, S.; Beck, W.; Bonoli, P.; Brunner, D.; Doody, J.; Ellis, R.; Ernst, D.; Fiore, C.; Freidberg, J. P.; Golfinopoulos, T.; Granetz, R.; Greenwald, M.; Hartwig, Z. S.; Hubbard, A.; Hughes, J. W.; Hutchinson, I. H.; Kessel, C.; Kotschenreuther, M.; Leccacorvi, R.; Lin, Y.; Lipschultz, B.; Mahajan, S.; Minervini, J.; Mumgaard, R.; Nygren, R.; Parker, R.; Poli, F.; Porkolab, M.; Reinke, M. L.; Rice, J.; Rognlien, T.; Rowan, W.; Shiraiwa, S.; Terry, D.; Theiler, C.; Titus, P.; Umansky, M.; Valanju, P.; Walk, J.; White, A.; Wilson, J. R.; Wright, G.; Zweben, S. J.


    The MIT Plasma Science and Fusion Center and collaborators are proposing a high-performance Advanced Divertor and RF tokamak eXperiment (ADX)—a tokamak specifically designed to address critical gaps in the world fusion research programme on the pathway to next-step devices: fusion nuclear science facility (FNSF), fusion pilot plant (FPP) and/or demonstration power plant (DEMO). This high-field (⩾6.5 T, 1.5 MA), high power density facility (P/S ˜ 1.5 MW m-2) will test innovative divertor ideas, including an ‘X-point target divertor’ concept, at the required performance parameters—reactor-level boundary plasma pressures, magnetic field strengths and parallel heat flux densities entering into the divertor region—while simultaneously producing high-performance core plasma conditions that are prototypical of a reactor: equilibrated and strongly coupled electrons and ions, regimes with low or no torque, and no fuelling from external heating and current drive systems. Equally important, the experimental platform will test innovative concepts for lower hybrid current drive and ion cyclotron range of frequency actuators with the unprecedented ability to deploy launch structures both on the low-magnetic-field side and the high-magnetic-field side—the latter being a location where energetic plasma-material interactions can be controlled and favourable RF wave physics leads to efficient current drive, current profile control, heating and flow drive. This triple combination—advanced divertors, advanced RF actuators, reactor-prototypical core plasma conditions—will enable ADX to explore enhanced core confinement physics, such as made possible by reversed central shear, using only the types of external drive systems that are considered viable for a fusion power plant. Such an integrated demonstration of high-performance core-divertor operation with steady-state sustainment would pave the way towards an attractive pilot plant, as envisioned in the ARC concept

  6. Microscopy with microlens arrays: high throughput, high resolution and light-field imaging. (United States)

    Orth, Antony; Crozier, Kenneth


    We demonstrate highly parallelized fluorescence scanning microscopy using a refractive microlens array. Fluorescent beads and rat femur tissue are imaged over a 5.5 mm x 5.5 mm field of view at a pixel throughput of up to 4 megapixels/s and a resolution of 706 nm. We also demonstrate the ability to extract different perspective views of a pile of microspheres.

  7. Impact of high electromagnetic field levels on childhood leukemia incidence. (United States)

    Teepen, Jop C; van Dijck, Jos A A M


    The increasing exposure to electromagnetic fields (EMFs) has raised concern, as increased exposure may result in an increased risk of childhood leukemia (CL). Besides a short introduction of CL and EMF, our article gives an evaluation of the evidence of a causal relation between EMF and CL by critically appraising the epidemiological and biological evidence. The potential impact is also estimated by the population attributable risk. The etiology of CL is largely unknown, but is probably multifactorial. EMF may be one of the environmental exposures involved. Three pooled analyses of case-control studies showed a 1.4- to 1.7-fold increased CL risk for extremely low-frequency EMF (ELF-EMF) exposure levels above 0.3 μT. Several biases may have played a role in these studies, but are unlikely to fully explain the increased risk. For effects of radiofrequency ELF evidence is lacking. None of the proposed biological mechanisms by which ELF-EMF might cause CL have been confirmed. The estimated overall population attributable risk was 1.9%, with the highest estimates in Northern America and Brazil (4.2% and 4.1%, respectively). The potential impact of EMF exposure on public health is probably limited, although in some countries exposure might be relatively high and thus might have a more substantial impact. We recommend nationwide surveys to gain more insight into the contemporary exposure levels among children. Reducing exposure from power lines near densely populated areas and schools is advised. Future epidemiological studies should focus on limiting bias. Copyright © 2012 UICC.

  8. Analytical possibilities of highly focused ion beams in biomedical field (United States)

    Ren, M. Q.; Ji, X.; Vajandar, S. K.; Mi, Z. H.; Hoi, A.; Walczyk, T.; van Kan, J. A.; Bettiol, A. A.; Watt, F.; Osipowicz, T.


    At the Centre for Ion Beam Applications (CIBA), a 3.5 MV HVEE Singletron™ accelerator serves to provide MeV ion beams (mostly protons or He+) to six state-of-the-art beam lines, four of which are equipped with Oxford triplet magnetic quadrupole lens systems. This facility is used for a wide range of research projects, many of which are in the field of biomedicine. Here we presented a discussion of currently ongoing biomedical work carried out using two beamlines: The Nuclear Microscopy (NM) beamline is mainly used for trace elemental quantitative mapping using a combination of Particle Induced X-ray Emission (PIXE), to measure the trace elemental concentration of inorganic elements, Rutherford Backscattering Spectrometry (RBS), to characterise the organic matrix, and Scanning Transmission Ion Microscopy (STIM) to provide information on the lateral areal density variations of the specimen. Typically, a 2.1 MeV proton beam, focused to 1-2 μm spot size with a current of 100 pA is used. The high resolution single cell imaging beamline is equipped with direct STIM to image the interior structure of single cells with proton and alpha particles of sub-50 nm beam spot sizes. Simultaneously, forward scattering transmission ion microscopy (FSTIM) is utilized to generate images with improved contrast of nanoparticles with higher atomic numbers, such as gold nanoparticles, and fluorescent nanoparticles can be imaged using Proton Induced Fluorescence (PIF). Lastly, in this facility, RBS has been included as an option if required to determine the depth distribution of nanoparticles in cells, albeit with reduced spatial resolution.

  9. High-Throughput Phase-Field Design of High-Energy-Density Polymer Nanocomposites. (United States)

    Shen, Zhong-Hui; Wang, Jian-Jun; Lin, Yuanhua; Nan, Ce-Wen; Chen, Long-Qing; Shen, Yang


    Understanding the dielectric breakdown behavior of polymer nanocomposites is crucial to the design of high-energy-density dielectric materials with reliable performances. It is however challenging to predict the breakdown behavior due to the complicated factors involved in this highly nonequilibrium process. In this work, a comprehensive phase-field model is developed to investigate the breakdown behavior of polymer nanocomposites under electrostatic stimuli. It is found that the breakdown strength and path significantly depend on the microstructure of the nanocomposite. The predicted breakdown strengths for polymer nanocomposites with specific microstructures agree with existing experimental measurements. Using this phase-field model, a high throughput calculation is performed to seek the optimal microstructure. Based on the high-throughput calculation, a sandwich microstructure for PVDF-BaTiO3 nanocomposite is designed, where the upper and lower layers are filled with parallel nanosheets and the middle layer is filled with vertical nanofibers. It has an enhanced energy density of 2.44 times that of the pure PVDF polymer. The present work provides a computational approach for understanding the electrostatic breakdown, and it is expected to stimulate future experimental efforts on synthesizing polymer nanocomposites with novel microstructures to achieve high performances. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Brushless exciters using a high temperature superconducting field winding (United States)

    Garces, Luis Jose [Schenectady, NY; Delmerico, Robert William [Clifton Park, NY; Jansen, Patrick Lee [Scotia, NY; Parslow, John Harold [Scotia, NY; Sanderson, Harold Copeland [Tribes Hill, NY; Sinha, Gautam [Chesterfield, MO


    A brushless exciter for a synchronous generator or motor generally includes a stator and a rotor rotatably disposed within the stator. The rotor has a field winding and a voltage rectifying bridge circuit connected in parallel to the field winding. A plurality of firing circuits are connected the voltage rectifying bridge circuit. The firing circuit is configured to fire a signal at an angle of less than or at an angle greater than The voltage rectifying bridge circuit rectifies the AC voltage to excite or de-excite the field winding.

  11. Field Independence, Impulsiveness, High School Training, and Academic Achievement (United States)

    Feij, Jan A.


    Investigates the relationship between performance on field-independence tests and two variables which may be thought of as important determinants of performance on a variety of cognitive tasks: impulsiveness and previous education. (Author/RC)

  12. High dynamic range electric field sensor for electromagnetic pulse detection

    National Research Council Canada - National Science Library

    Lin, Che-Yun; Wang, Alan X; Lee, Beom Suk; Zhang, Xingyu; Chen, Ray T


    ...) polymer Y-fed directional coupler for electromagnetic wave detection. This electrode-less, all optical, wideband electrical field sensor is fabricated using standard processing for E-O polymer photonic devices...

  13. Ultrafast carrier dynamics in graphene under a high electric field. (United States)

    Tani, Shuntaro; Blanchard, François; Tanaka, Koichiro


    We investigated ultrafast carrier dynamics in graphene with near-infrared transient absorption measurement after intense half-cycle terahertz pulse excitation. The terahertz electric field efficiently drives the carriers, inducing large transparency in the near-infrared region. Theoretical calculations using the Boltzmann transport equation quantitatively reproduce the experimental findings. This good agreement suggests that the intense terahertz field should promote a remarkable impact ionization process and increase the carrier density.

  14. Effect of high solenoidal magnetic fields on breakdown voltages of high vacuum 805 MHz cavities

    Energy Technology Data Exchange (ETDEWEB)

    Moretti, A.; Bross, A.; Geer, S.; Qian, Z.; /Fermilab; Norem, J.; /Argonne; Li, D.; Zisman, M.; /LBL, Berkeley; Torun, Y.; /IIT, Chicago; Rimmer, R.; /Jefferson Lab; Errede,; /Illinois U., Urbana


    There is an on going international collaboration studying the feasibility and cost of building a muon collider or neutrino factory [1,2]. An important aspect of this study is the full understanding of ionization cooling of muons by many orders of magnitude for the collider case. An important muon ionization cooling experiment, MICE [3], has been proposed to demonstrate and validate the technology that could be used for cooling. Ionization cooling is accomplished by passing a high-emittance muon beam alternately through regions of low Z material, such as liquid hydrogen, and very high accelerating RF Cavities within a multi-Tesla solenoidal field. To determine the effect of very large solenoidal magnetic fields on the generation of dark current, x-rays and on the breakdown voltage gradients of vacuum RF cavities, a test facility has been established at Fermilab in Lab G. This facility consists of a 12 MW 805 MHz RF station and a large warm bore 5 T solenoidal superconducting magnet containing a pill box type cavity with thin removable window apertures. This system allows dark current and breakdown studies of different window configurations and materials. The results of this study will be presented. The study has shown that the peak achievable accelerating gradient is reduced by a factor greater than 2 when solenoidal field of greater than 2 T are applied to the cavity.

  15. Dynamic shielding of the magnetic fields

    Directory of Open Access Journals (Sweden)

    RAU, M.


    Full Text Available The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applications of the dynamic control of the magnetic field are: control of the magnetic field of the military ships, control of parasite magnetic field produced by power transformers and the electrical networks, protection of the mass spectrometers, electronic microscopes, SQUID and optical pumping magnetometers for applications in biomagnetism.

  16. Biological and Agricultural Studies on Application of Discharge Plasma and Electromagnetic Fields 5. Effects of High Electric Fields on Animals (United States)

    Isaka, Katsuo

    The biological effects of extremely low frequency electric fields on animals are reviewed with emphasis on studies of the nervous system, behavior, endocrinology, and blood chemistry. First, this paper provides a histrical overview of studies on the electric field effects initiated in Russia and the United States mainly regarding electric utility workers in high voltage substations and transmission lines. Then, the possible mechanisms of electric field effects are explained using the functions of surface electric fields and induced currents in biological objects. The real mechanisms have not yet been identified. The thresholds of electric field perception levels for rats, baboons, and humans are introduced and compared. The experimental results concerning the depression of melatonin secretion in rats exposed to electric fields are described.

  17. High-speed non-intrusive measurements of fuel velocity fields at high-pressure injectors (United States)

    Gürtler, Johannes; Schlüßler, Raimund; Fischer, Andreas; Czarske, Jürgen


    Using a single high-speed camera and a frequency modulated laser, a novel approach is presented for fast velocity field measurements in unsteady spray flows. The velocity range is from zero up to several 100 m/s, which requires a high measurement rate and a large dynamic. Typically, flow measurements require to seed tracer particles to the fluid. A paradigm shift to seeding-free measurements is presented. The light scattered at the phase boundaries of the fluid droplets is evaluated. In order to validate the high-speed measurement system, a detailed uncertainty analysis is performed by means of measurements as well as simulations. Thereby, variations of the scattered light intensity, which are based on the high temporal velocity gradients, are found to be the main contribution to the uncertainty. The eventually measurement results, obtained at a measurement rate of 500 kHz, exhibit spray velocities ranging from 0 m/s up to 400 m/s in less than 1 ms, and the detection of unsteady and irregular flow phenomena with a characteristic time of several μs is achieved. This demonstrates the high measurement rate, the high temporal resolution and the large measurement range of the proposed high-speed measurement system.

  18. Generation and measurement of pulsed high magnetic field

    CERN Document Server

    Jana, S


    Pulsed magnetic field has been generated by discharging a capacitor bank through a 5-layer air-core solenoid. The strength of the magnetic field at its peak has been measured using the voltage induced in various pick-up coils, and also from the Zeeman splitting of an ion having a known g value. Synchronizing a xenon flash at the peak of the magnetic field, this lab-made instrument has been made well suited to study the Zeeman effect, etc. at a temperature of 25 K. As an application of this setup, we have investigated the Zeeman splitting of the sup 4 I sub 9 sub / sub 2-> sup 4 G sub 5 sub / sub 2 transition of the Nd sup 3 sup + -doped CsCdCl sub 3 crystal at 7.8 T, and determined the splitting factors.

  19. Novel Josephson circuit elements for high magnetic field parity detection (United States)

    Cassidy, Maja

    Evidence for Majorana modes in semiconductor nanowires to date has relied on DC transport measurements that probe their zero-energy characteristics. However, in order to unambiguously demonstrate the non-Abelian nature of Majoranas, it is necessary to braid them and measure their parity. Superconducting transmon qubits have been shown to be sensitive parity detectors, however traditional designs are incompatible with the strong magnetic fields required for the creation of Majoranas in nanowires. In this talk I will discuss our development of novel superconducting circuit elements such as CPW resonators, tunnel junctions, transmon qubits and on chjp microwave sources that survive magnetic fields in excess of 1T.

  20. Prospects of development of highly mineralized high-temperature resources of the Tarumovskoye geothermal field (United States)

    Alkhasov, A. B.; Alkhasova, D. A.; Ramazanov, A. Sh.; Kasparova, M. A.


    The promising nature of integrated processing of high-temperature geothermal brines of the Tarumovskoye geothermal field is shown. Thermal energy of a geothermal brine can be converted to the electric power at a binary geothermal power plant (GPP) based on low-boiling working substance. The thermodynamic Rankine cycles are considered which are implemented in the GPP secondary loop at different evaporation temperatures of the working substance―isobutane. Among them, the most efficient cycle from the standpoint of attaining a maximum power is the supercritical one which is close to the so-called triangular cycle with an evaporation pressure of p e = 5.0 MPa. The used low-temperature brine is supplied from the GPP to a chemical plant, where main chemical components (lithium carbonate, burnt magnesia, calcium carbonate, and sodium chloride) are extracted from it according to the developed technology of comprehensive utilization of geothermal brines of chloride-sodium type. The waste water is delivered to the geotechnological complex and other consumers. For producing valuable inorganic materials, the electric power generated at the GPP is used. Owing to this, the total self-sufficiency of production and independence from external conditions is achieved. The advantages of the proposed geotechnological complex are the full utilization of the heat potential and the extraction of main chemical components of multiparameter geothermal resources. In this case, there is no need for reverse pumping, which eliminates the significant capital costs for building injection wells and a pumping station and the operating costs for their service. A characteristic of the modern state of the field and estimated figures of the integrated processing of high-temperature brines of well no. 6 are given, from which it follows that the proposed technology has a high efficiency. The comprehensive development of the field resources will make it possible to improve the economic structure of the

  1. Robustness of various metals against high THz field induced damage

    DEFF Research Database (Denmark)

    Zhu, Jianfei; Iwaszczuk, Krzysztof; Tarekegne, Abebe Tilahun


    We investigate various metals for their robustness against damage caused by strong THz field. Even though the damage process is not of a thermal nature we observe a correlation between robustness and the melting temperature. Influence of the substrate material on the damage pattern is also studied....

  2. High Fidelity Modeling of Field Reversed Configuration (FRC) Thrusters (United States)


    expedited through the hiring of two new employees, Dr. Eder Sousa (recent graduate of U. of Washington) and Dr. Artan Qerushi (formerly at Tri- Alpha ...Effect on Field-Reversed Configuration Thruster Efficiency, Journal of Propulsion and Power, Vol 30, No. 6, Nov- Dec 2014. - Qerushi, A, “Overview of

  3. Multilayers for high Tc superconducting electric field effect devices

    NARCIS (Netherlands)

    Joosse, K.; Joosse, K.; Gerritsma, G.J.; Rogalla, Horst; Boguslavskij, Y.M.; Boguslavskij, Y.M.; de Vaal, J.W.


    Epitaxial multilayers, consisting of a PrBa2Cu3O7-x buffer layer, ultrathin YBa2Cu3O7-x and SrTiO3, have been grown for application in electric field effect devices. Different analytical techniques indicate a sharp interface between the layers and good dielectric properties of the SrTiO3-layer.

  4. Ultra High Field MRI-Guided Deep Brain Stimulation

    NARCIS (Netherlands)

    Forstmann, Birte U; Isaacs, Bethany R; Temel, Yasin


    Deep brain stimulation (DBS) is a neurosurgical treatment for neurological disorders often planned with 1.5-T or 3-T MRI. The clinical efficacy of DBS can be improved using ultrahigh-field (UHF) MRI for planning by increasing the level of precision required for an individualized approach.

  5. High-Field Magnetization of Light Rare-Earth Metals

    DEFF Research Database (Denmark)

    McEwen, K.A.; Cock, G.J.; Roeland, L.W.


    The magnetization of single crystals of Eu, Sm, Nd, Pr, and Pr-Nd alloys has been measured in fields up to 37 T (370 kG). The results give new information on the magnetic properties of these metals. Of particular interest is a first-order transition from a nonmagnetic to a metamagnetic phase...

  6. Impact of high electromagnetic field levels on childhood leukemia incidence

    NARCIS (Netherlands)

    Teepen, J.C.; Dijck, J.A. van


    The increasing exposure to electromagnetic fields (EMFs) has raised concern, as increased exposure may result in an increased risk of childhood leukemia (CL). Besides a short introduction of CL and EMF, our article gives an evaluation of the evidence of a causal relation between EMF and CL by

  7. The new installation at the Nijmegen High Field Magnet Laboratory

    NARCIS (Netherlands)

    Perenboom, J.A.A.J.; Wiegers, S.A.J.; Christianen, P.C.M.; Zeitler, U.; Maan, J.C.


    For research in the highest continuous and pulsed magnetic fields large, complex and powerful installations are needed. A new 20 MW installation has been built at the University of Nijmegen. The ultra-low ripple power converter, delivering 40 kA at up to 500 V, provides the capability to perform

  8. The effect of high voltage, high frequency pulsed electric field on slain ovine cortical bone. (United States)

    Asgarifar, Hajarossadat; Oloyede, Adekunle; Zare, Firuz


    High power, high frequency pulsed electric fields known as pulsed power (PP) has been applied recently in biology and medicine. However, little attention has been paid to investigate the application of pulse power in musculoskeletal system and its possible effect on functional behavior and biomechanical properties of bone tissue. This paper presents the first research investigating whether or not PP can be applied safely on bone tissue as a stimuli and what will be the possible effect of these signals on the characteristics of cortical bone by comparing the mechanical properties of this type of bone pre and post expose to PP and in comparison with the control samples. A positive buck-boost converter was applied to generate adjustable high voltage, high frequency pulses (up to 500 V and 10 kHz). The functional behavior of bone in response to pulse power excitation was elucidated by applying compressive loading until failure. The stiffness, failure stress (strength) and the total fracture energy (bone toughness) were determined as a measure of the main bone characteristics. Furthermore, an ultrasonic technique was applied to determine and comprise bone elasticity before and after pulse power stimulation. The elastic property of cortical bone samples appeared to remain unchanged following exposure to pulse power excitation for all three orthogonal directions obtained from ultrasonic technique and similarly from the compression test. Nevertheless, the compressive strength and toughness of bone samples were increased when they were exposed to 66 h of high power pulsed electromagnetic field compared to the control samples. As the toughness and the strength of the cortical bone tissue are directly associated with the quality and integrity of the collagen matrix whereas its stiffness is primarily related to bone mineral content these overall results may address that although, the pulse power stimulation can influence the arrangement or the quality of the collagen network

  9. High impact ionization rate in silicon by sub-picosecond THz electric field pulses (Conference Presentation)

    DEFF Research Database (Denmark)

    Tarekegne, Abebe Tilahun; Iwaszczuk, Krzysztof; Hirori, Hideki


    Summary form only given. Metallic antenna arrays fabricated on high resistivity silicon are used to localize and enhance the incident THz field resulting in high electric field pulses with peak electric field strength reaching several MV/cm on the silicon surface near the antenna tips. In such hi...... carrier dynamics in other semiconductors....

  10. Nitrogen detected TROSY at high field yields high resolution and sensitivity for protein NMR. (United States)

    Takeuchi, Koh; Arthanari, Haribabu; Shimada, Ichio; Wagner, Gerhard


    Detection of (15)N in multidimensional NMR experiments of proteins has sparsely been utilized because of the low gyromagnetic ratio (γ) of nitrogen and the presumed low sensitivity of such experiments. Here we show that selecting the TROSY components of proton-attached (15)N nuclei (TROSY (15)NH) yields high quality spectra in high field magnets (>600 MHz) by taking advantage of the slow (15)N transverse relaxation and compensating for the inherently low (15)N sensitivity. The (15)N TROSY transverse relaxation rates increase modestly with molecular weight but the TROSY gain in peak heights depends strongly on the magnetic field strength. Theoretical simulations predict that the narrowest line width for the TROSY (15)NH component can be obtained at 900 MHz, but sensitivity reaches its maximum around 1.2 GHz. Based on these considerations, a (15)N-detected 2D (1)H-(15)N TROSY-HSQC ((15)N-detected TROSY-HSQC) experiment was developed and high-quality 2D spectra were recorded at 800 MHz in 2 h for 1 mM maltose-binding protein at 278 K (τc ~ 40 ns). Unlike for (1)H detected TROSY, deuteration is not mandatory to benefit (15)N detected TROSY due to reduced dipolar broadening, which facilitates studies of proteins that cannot be deuterated, especially in cases where production requires eukaryotic expression systems. The option of recording (15)N TROSY of proteins expressed in H2O media also alleviates the problem of incomplete amide proton back exchange, which often hampers the detection of amide groups in the core of large molecular weight proteins that are expressed in D2O culture media and cannot be refolded for amide back exchange. These results illustrate the potential of (15)NH-detected TROSY experiments as a means to exploit the high resolution offered by high field magnets near and above 1 GHz.

  11. Ultrasound versus high field magnetic resonance imaging in rheumatoid arthritis

    DEFF Research Database (Denmark)

    Tan, York Kiat; Østergaard, Mikkel; Bird, Paul


    Over the past decade there have been significant advances in the field of musculoskeletal imaging, especially in the application of ultrasound (US) and magnetic resonance imaging (MRI) to the management of rheumatoid arthritis (RA). Both modalities offer significant advantages over the previous...... standards of clinical examination and radiography, and allow direct visualisation of both joint inflammation and structural damage. Although measuring similar pathology, each of these imaging tools has its own benefits and limitations; understanding these will help researchers and clinicians to determine...

  12. Numerical simulation of screening current distribution in HTS tape of high field magnet


    Itoh, Ryusei; Oga, Yuki; Noguchi, So; Igarashi, Hajime; Ueda, Hiroshi


    In recent years, properties of high temperature superconducting (HTS) tapes, especially in-field performance and mechanical strength, have been continuously improved. The HTS tapes have been widely used for high field (>20 T) magnet researches and there are several technical challenges including field attenuation of an HTS magnet by screening currents induced within the HTS tapes. Several publications reported that the screening currents, induced by penetration of self magnetic fields into HT...

  13. High-field conductor testing at the FENIX facility (United States)

    Shen, S. S.; Chaplin, M. R.; Felker, B.; Hassenzahl, W. V.; Kishiyama, K. I.; Parker, J. M.


    The Fusion Engineering International experiments (FENIX) Test Facility, which was commissioned at the end of 1991, is the first facility in the world capable of testing prototype conductors for the International Thermonuclear Experimental Reactor (ITER) superconducting magnets. The FENIX facility provides test conditions that simulate the ITER magnet operating environment; more importantly, it also accommodates specific experiments to determine the operational margins for the prototype conductors. The FENIX facility generates magnetic fields close to 14 T, and transport currents over 40 kA for testing the prototype conductors. This paper describes an experimental program that measures critical currents, current-sharing temperatures, forced-flow properties, and cyclic effects.

  14. High-field (high-frequency) EPR spectroscopy and structural characterization of a novel manganese(III) corrole


    Bendix, Jesper; Gray, Harry B.; Golubkov, Galina; Gross, Zeev


    The X-ray structure, magnetic susceptibility, and high-field (high-frequency) EPR spectrum of manganese 5,10,15-tris(pentafluorophenyl) corrole unambiguously establish that the complex contains an isolated, slightly rhombic, manganese(III) center.

  15. High Field Studies for CLIC Accelerating Structures Development

    CERN Document Server

    Profatilova, I


    Compact Linear Collider RF structures need to be able to achieve the very high average accelerating gradient of 100 MV/m. One of the main challenges in reaching such high accelerating gradients is to avoid vacuum electrical breakdown within CLIC accelerating structures. Accelerating structure tests are carried out in the klystron-based test stands known as the XBoxes. In order to investigate vacuum breakdown phenomena and its statistical characteristics in a simpler system and get results in a faster way, pulsed dc systems have been developed at CERN. To acquire sufficient breakdown data in a reasonable period of time, high repetition rate pulse generators are used in the systems for breakdown studies, so-called pulsed dc system. This paper describes the pulsed dc systems and the two high repetition rate circuits, which produce high-voltage pulses for it, available at CERN.

  16. Modelling high arctic percent vegetation cover using field digital images and high resolution satellite data (United States)

    Liu, Nanfeng; Treitz, Paul


    In this study, digital images collected at a study site in the Canadian High Arctic were processed and classified to examine the spatial-temporal patterns of percent vegetation cover (PVC). To obtain the PVC of different plant functional groups (i.e., forbs, graminoids/sedges and mosses), field near infrared-green-blue (NGB) digital images were classified using an object-based image analysis (OBIA) approach. The PVC analyses comparing different vegetation types confirmed: (i) the polar semi-desert exhibited the lowest PVC with a large proportion of bare soil/rock cover; (ii) the mesic tundra cover consisted of approximately 60% mosses; and (iii) the wet sedge consisted almost exclusively of graminoids and sedges. As expected, the PVC and green normalized difference vegetation index (GNDVI; (RNIR - RGreen)/(RNIR + RGreen)), derived from field NGB digital images, increased during the summer growing season for each vegetation type: i.e., ∼5% (0.01) for polar semi-desert; ∼10% (0.04) for mesic tundra; and ∼12% (0.03) for wet sedge respectively. PVC derived from field images was found to be strongly correlated with WorldView-2 derived normalized difference spectral indices (NDSI; (Rx - Ry)/(Rx + Ry)), where Rx is the reflectance of the red edge (724.1 nm) or near infrared (832.9 nm and 949.3 nm) bands; Ry is the reflectance of the yellow (607.7 nm) or red (658.8 nm) bands with R2's ranging from 0.74 to 0.81. NDSIs that incorporated the yellow band (607.7 nm) performed slightly better than the NDSIs without, indicating that this band may be more useful for investigating Arctic vegetation that often includes large proportions of senescent vegetation throughout the growing season.

  17. New probe of magnetic fields in the prereionization epoch. I. Formalism (United States)

    Venumadhav, Tejaswi; Oklopčić, Antonija; Gluscevic, Vera; Mishra, Abhilash; Hirata, Christopher M.


    We propose a method of measuring extremely weak magnetic fields in the intergalactic medium prior to and during the epoch of cosmic reionization. The method utilizes the Larmor precession of spin-polarized neutral hydrogen in the triplet state of the hyperfine transition. This precession leads to a systematic change in the brightness temperature fluctuations of the 21-cm line from the high-redshift universe, and thus the statistics of these fluctuations encode information about the magnetic field the atoms are immersed in. The method is most suited to probing fields that are coherent on large scales; in this paper, we consider a homogenous magnetic field over the scale of the 21-cm fluctuations. Due to the long lifetime of the triplet state of the 21-cm transition, this technique is naturally sensitive to extremely weak field strengths, of order 10-19 G at a reference redshift of ˜20 (or 10-21 G if scaled to the present day). Therefore, this might open up the possibility of probing primordial magnetic fields just prior to reionization. If the magnetic fields are much stronger, it is still possible to use this method to infer their direction, and place a lower limit on their strength. In this paper (Paper I in a series on this effect), we perform detailed calculations of the microphysics behind this effect, and take into account all the processes that affect the hyperfine transition, including radiative decays, collisions, and optical pumping by Lyman-α photons. We conclude with an analytic formula for the brightness temperature of linear-regime fluctuations in the presence of a magnetic field, and discuss its limiting behavior for weak and strong fields.

  18. Flow field design for high-pressure PEM electrolysis cells

    DEFF Research Database (Denmark)

    Olesen, Anders Christian; Kær, Søren Knudsen

    micro-channels and porous media, our research group has developed an Euler-Euler model in the computational fluid dynamics modelling framework of ANSYS CFX. In addition to two-phase flow, the model accounts for turbulence, species transport in the gas phase, heat transport in all three phases (i......With the increasing interest in producing hydrogen through water electrolysis, the importance of understanding the transport phenomena governing its operation increases. To ensure optimal operating conditions for PEM electrolysis, it is particularly important to understand how the liquid feed.......e. solid, gas and liquid), as well as charge transport of electrons and ions. Our recent improvements have focused on the models ability to account for phase change and electrochemistry as well as the modelling of two-phase flow regimes. For comparison, an interdigitated and parallel channel flow field...

  19. High field magnet program at Brookhaven National Laboratory

    CERN Document Server

    Ghosh, A; Muratore, J; Parker, B; Sampson, W; Wanderer, P J; Willen, E


    The magnet program at Brookhaven National Laboratory (BNL) is focussed on superconducting magnets for particle accelerators. The effort includes magnet production at the laboratory and in industry, magnet R&D, and test facilities for magnets and superconductors. Nearly 2000 magnets-dipoles, quadrupoles, sextupoles and correctors for the arc and insertion regions-were produced for the Relativistic Heavy Ion Collider (RHIC), which is being commissioned. Currently, production of helical dipoles for the polarized proton program at RHIC, insertion region dipoles for the Large Hadron Collider (LHC) at CERN, and an insertion magnet system for the Hadron-Elektron-Ring- Analage (HERA) collider at Deutsches Elektronen-Synchrotron (DESY) is underway. The R&D effort is exploring dipoles with fields above 10 T for use in post-LHC colliders. Brittle superconductors-Nb/sub 3/Sn or HTS-are being used for these magnets. The superconductor test facility measures short-sample currents and other characteristics of sample...

  20. New high dielectric constant materials for tailoring the B1+ distribution at high magnetic fields. (United States)

    Haines, K; Smith, N B; Webb, A G


    The spatial distribution of electromagnetic fields within the human body can be tailored using external dielectric materials. Here, we introduce a new material with high dielectric constant, and also low background MRI signal. The material is based upon metal titanates, which can be made into a geometrically-formable suspension in de-ionized water. The material properties of the suspension are characterized from 100 to 400 MHz. Results obtained at 7 T show a significant increase in image intensity in areas such as the temporal lobe and base of the brain with the new material placed around the head, and improved performance compared to purely water-based gels. 2010 Elsevier Inc. All rights reserved.

  1. High Frequency Electromagnetic Field Induces Lipocalin 2 Expression in

    Directory of Open Access Journals (Sweden)

    Amaneh Mohammadi Roushandeh


    Full Text Available Objective(sNeutrophil gelatinase-associated lipocalin (NGAL/Lcn2, comprise a group of small extracellular proteins with a common β-sheet-dominated 3-dimensional structure. In the past, it was assumed that the predominant role of lipocalin was acting as transport proteins. Recently it has been found that oxidative stress induces Lcn2 expression. It has been also proved that electromagnetic field (EMF produces reactive oxygen species (ROS in different tissues. Expression of Lcn2 following exposure to electromagnetic field has been investigated in this study. Materials and MethodsBalb/c mice (8 weeks old were exposed to 3 mT, 50 HZ EMF for 2 months, 4 hr/day. Afterwards, the mice were sacrificed by cervical dislocation and livers were removed. The liver specimens were stained with Haematoxylin- Eosin (H&E and analyzed under an optical microscope. Total RNA was extracted from liver and reverse transcription was performed by SuperScript III reverse transcriptase with 1 µg of total RNA. Assessment of Lcn2 expression was performed by semiquantitative and real time- PCR.ResultsThe light microscopic studies revealed that the number of lymphocyte cells was increased compared to control and dilation of sinosoids was observed in the liver. Lcn2 was up-regulated in the mice exposed to EMF both in mRNA and protein levels.ConclusionTo the extent of our knowledge, this is the first report dealing with up-regulation of Lcn2 in liver after exposure to EMF. The up-regulation might be a compensatory response that involves cell defense pathways and protective effects against ROS. However, further and complementary studies are required in this regards.

  2. Continuous online field deployable high precision and high resolution water isotope analysis from ice cores (United States)

    Gkinis, Vasileios; Popp, Trevor; Johnsen, Sigfus; Blunier, Thomas; Stowasser, Christopher; Kettner, Ernesto


    One of the most important features of ice cores as climate and atmospheric paleoarchives is their potential for high temporal resolution. The measurement of chemical impurities in ice cores that fully exploits this high resolution has become standard with the advent of Continuous Flow Analysis (CFA) from continuously melted ice core segments, often performed in the field. Meanwhile, the measurement of water stable isotopic composition (deuterium and oxygen-18) continues, for the most part, to be performed offline via discrete sampling with traditional mass spectroscopy. These offline procedures are time consuming, expensive, and do not fully exploit the temporal resolution available in the ice core. Here we describe a new method and the first results for the determination of water isotopic content measured from a continuous melted rod with a commercially available near-infrared cavity ring down spectrometer (CRDS; coupled to a CFA system both in the field on the Greenland ice sheet and in the laboratory. For the measurement of water isotopes a carefully controlled fraction of the CFA melt stream is evaporated directly into the laser cavity for simultaneous analysis of both deuterium and oxygen-18 content. The details of the system have been tested with a deployment to the North Greenland Eemian Ice Drilling (NEEM) coupled to the University of Bern CFA system and in the laboratory with NGRIP ice coupled to the University of Copenhagen CFA system. The results show that the system already produces the highest interpretable resolution records that are comparable or somewhat less precise than traditional mass spectroscopy discrete sample methods. The enormous potential of the system is being realized in the density and resolution of the produced records in connection with other highly resolved series (e.g. chemical impurities), and also in the efficiency by which the records can be produced. Among other things, time series from this type of

  3. Field Evidence for a Low Permeability, High Storage Fault Core at the Santa Susana Field Laboratory (United States)

    Allègre, V.; Brodsky, E. E.; Parker, B. L.; Cherry, J. A.


    In situ measurements of hydrogeologic properties within fault zones are few, in part because of the challenges of measuring the scale-dependent quantities in fractured rock reservoirs. This work aims to fill the gap by utilizing a combination of tidal, barometric and seismic response analyses on pressure head time-series from the Santa Susana Field Laboratory in Southern California. The techniques sample different effective volumes and so allow us to investigate the scale-dependent structure near fault zones. Permeability and specific storage were inverted from tidal response at 14 locations, and specific storage was also computed from barometric efficiencies at 10 locations. In addition, we computed hydro-seismic transfer functions after nine local earthquakes and teleseismic events. We found that permeability computed from tidal response are quite homogeneous within about one and a half orders of magnitude over the site regardless of the presence of moderate to large faults. This result is consistent with the earlier aquifer tests using standard methods. The tidal responses also showed higher variability of specific storage inside the fault zones suggesting that fault damage zone generates a storage architecture. The storage from the tidal responses can be consistently interpreted for the tidal, barometric and seismic responses. However, the observations require that the permeability inside the fault zones at the spatial scale of the seismic response (~meters) is much lower than at the spatial scale of the tidal response (~10's of meters). The result suggests possible sensitivity to the low permeability fault core, which has been historically difficult to measure at the field scale.

  4. Nature of the Background Ultraviolet Radiation Field at High Redshifts

    Indian Academy of Sciences (India)


    thus necessary for the understanding of the early universe. AGNs are believed to be the major ... This ratio is insensitive to the particle density and the abundance of carbon, but is very sensitive to the ..... assuming the rest of the required flux to be of local, galactic origin, very high galactic flux is required. For most of the ...

  5. Bottom mounted seabed mooring frame for high current field

    Digital Repository Service at National Institute of Oceanography (India)

    AshokKumar, K.; Chandramohan, P.; Pednekar, P.S.; Diwan, S.G.

    and direction on the sea surface and at a fixed five layers. The company supplied frame was not suitable to use at the proposed measurement location, owing to random oscillation in the seabed, strong currents and high concentration of sediments in the water...

  6. Physical processes in high field insulating liquid conduction (United States)

    Mazarakis, Michael; Kiefer, Mark; Leckbee, Joshua; Anderson, Delmar; Wilkins, Frank; Obregon, Robert


    In the power grid transmission where a large amount of energy is transmitted to long distances, High Voltage DC (HVDC) transmission of up to 1MV becomes more attractive since is more efficient than the counterpart AC. However, two of the most difficult problems to solve are the cable connections to the high voltage power sources and their insulation from the ground. The insulating systems are usually composed of transformer oil and solid insulators. The oil behavior under HVDC is similar to that of a weak electrolyte. Its behavior under HVDC is dominated more by conductivity than dielectric constant. Space charge effects in the oil bulk near high voltage electrodes and impeded plastic insulators affect the voltage oil hold-off. We have constructed an experimental facility where we study the oil and plastic insulator behavior in an actual HVDC System. Experimental results will be presented and compared with the present understanding of the physics governing the oil behavior under very high electrical stresses. Sandia National Laboratories managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. D.O.E., NNSA under contract DE-NA-0003525.

  7. Cold induced peripheral vasodilation at high altitudes- a field study

    NARCIS (Netherlands)

    Daanen, H.A.M.; Ruiten, H.J.A. van


    A significant reduction in cold-induced vasodilation (CIVD) is observed at high altitudes. No agreement is found in the literature about acclimatization effects on CIVD. Two studies were performed to investigate the effect of altitude acclimatization on CIVD. In the first study 13 male subjects

  8. Field experimental observations of highly graded sediment plumes

    DEFF Research Database (Denmark)

    Hjelmager Jensen, Jacob; Saremi, Sina; Jimenez, Carlos


    , gravitating towards the seafloor, were filmed simultaneously by four divers situated at different depths in the water column, and facing the plume at different angles. The processes were captured using GoPro-Hero-series cameras. The high-quality underwater footage from near-surface, mid-depth and near...

  9. Generation of Unprecedented high Electric Fields with Pyroelectric Crystals (United States)

    Crimi, Sarah; Tornow, Werner; Corse, Zach


    Since a few years pyroelectric crystals in a deuterium gas environment have been used to produce neutrons via the ^2H(d,n)^3He reaction. The figure-of-merit for neutron production in the energy region of interest is about IE^3/2, where I is the deuterium ion current and E is the associated ion energy. Therefore, it is important to maximize E. Using single and double crystal arrangements with electric field enhancing nano-tips, the highest positive potentials reported in the literature were 115 keV [1] and 250 keV [2], respectively. Using longer LiTaO3 crystals than commonly employed (2.5 cm versus 1.0 cm) and without attaching a nano-tip, we have produced positive deuterium ion beams of energies up to 325 keV with a single crystal during the cooling phase from 130 ^oC to 0 ^oC. In a double crystal arrangement we have obtained positive ion energies of up to 390 keV. Details of our experimental approach will be presented.[4pt] [1] B. Naranjo et al., Nature 434, 1115 (2005).[0pt] [2] D. Gillich et al., Nucl. Instr. Meth. in Phys. Res. A 602, 306 (2009).

  10. Pelvic endometriosis: a comparison between low-field (0.2 T) and high-field (1.5 T) magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Minaif, Karine; Ajzen, Sergio [Universidade Federal de Sao Paulo (UNIFESP/EPM), SP (Brazil). Dept. of Imaging Diagnosis]. E-mail:; Shigueoka, David Carlos; Minami, Cintia Cristina Satie; Sales, Danilo Moulin; Szejnfeld, Jacob [Universidade Federal de Sao Paulo (UNIFESP/EPM), SP (Brazil). Dept. of Imaging Diagnosis. Unit of Abdomen; Ruano, Jose Maria Cordeiro [Universidade Federal de Sao Paulo (UNIFESP/EPM), SP (Brazil). Dept. of General Gynecology. Sector of Videlaparoscopy; Noguti, Alberto Sinhiti [Universidade Federal de Sao Paulo (UNIFESP/EPM), SP (Brazil). Dept. of General Gynecology


    Objective: to compare low-field (0.2 T) with high-field (1.5 T) magnetic resonance imaging in the assessment of pelvic endometriosis and adenomyosis. Materials and methods: twenty-seven female patients with clinically suspected endometriosis were prospectively evaluated by means of high-field and low-field magnetic resonance imaging. The reading of the images was performed by a single radiologist, initiating by the low-field, followed by the high-field images. High-field magnetic resonance imaging was utilized as the golden-standard. Results: among the 27 patients included in the present study, 18 (66.7%) had some type of lesion suggesting the presence of endometriosis demonstrated at high-field images. In 14 of these patients the diagnosis was correctly established by low-field magnetic resonance imaging. Endometriomas, tubal lesions, and endometriotic foci > 7 mm identified at the high-field images were also identified at low-field images with 100% accuracy, sensitivity and specificity. Among the nine patients diagnosed with adenomyosis by high-field images, eight were correctly diagnosed by low-field images with 88.9% accuracy, specificity and sensitivity. Conclusion: low-field magnetic resonance imaging demonstrated a low sensitivity in the detection of small endometriotic foci, high sensitivity in the detection of endometriomas and large endometriotic foci, and high accuracy in the detection of adenomyosis when compared with high-field magnetic resonance imaging. (author)

  11. Excitation-Dependent Carrier lifetime and Diffusion Length in Bulk CdTe Determined by Time-Resolved Optical Pump-Probe Techniques.

    Energy Technology Data Exchange (ETDEWEB)

    Kuciauskas, Darius [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Scajev, Patrik [Vilnius University; Miasojedovas, Saulius [Vilnius University; Mekys, Algirdas [Vilnius University; Lynn, Kelvin G. [Washington State University; Swain, Santosh K. [Washington State University; Jarasiunas, Kestutis [Vilnius University


    We applied time-resolved pump-probe spectroscopy based on free carrier absorption and light diffraction on a transient grating for direct measurements of the carrier lifetime and diffusion coefficient D in high-resistivity single crystal CdTe (codoped with In and Er). The bulk carrier lifetime t decreased from 670 +/-50 ns to 60 +/- 10 ns with increase of excess carrier density N from 10^16 to 5 x 10^18 cm-3 due to the excitation-dependent radiative recombination rate. In this N range, the carrier diffusion length dropped from 14 um to 6 um due to lifetime decrease. Modeling of in-depth (axial) and in-plane (lateral) carrier diffusion provided the value of surface recombination velocity S = 6 x 10^5 cm/s for the untreated surface. At even higher excitations, in the 10^19-3 x 10^20 cm-3 density range, D increase from 5 to 20 cm^2/s due to carrier degeneracy was observed.

  12. Behavior of Rubber Materials under Exposure to High Electric Fields

    DEFF Research Database (Denmark)

    Candela Garolera, Anna; Holbøll, Joachim; Henriksen, M,


    The effect of high electrical stress on rubber materials is investigated by performing breakdown tests and tracking resistance tests on selected samples. The study is focused on the relationship between the dielectric strength and the thickness of the samples, as well as the influence of the inte......The effect of high electrical stress on rubber materials is investigated by performing breakdown tests and tracking resistance tests on selected samples. The study is focused on the relationship between the dielectric strength and the thickness of the samples, as well as the influence...... of the interfaces between different layers of material. Tracking resistance tests are also performed on the rubber material. The purpose is to provide a complete study of the applicability of the rubber material in thunderstorm environments....

  13. Ultra-High Intensity Magnetic Field Generation in Dense Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, Nathaniel J. [Princeton Univ., NJ (United States)


    The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereas the efficient generation of electric current in low-­energy-­density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­energy-­density plasma the ideas for steady-­state current drive developed for low-­energy-­density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­energy-­density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new forms of current drive in regimes appropriate for new fusion concepts.

  14. Superconductor Requirements and Characterization for High Field Accelerator Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Barzi, E.; Zlobin, A. V.


    The 2014 Particle Physics Project Prioritization Panel (P5) strategic plan for U.S. High Energy Physics (HEP) endorses a continued world leadership role in superconducting magnet technology for future Energy Frontier Programs. This includes 10 to 15 T Nb3Sn accelerator magnets for LHC upgrades and a future 100 TeV scale pp collider, and as ultimate goal that of developing magnet technologies above 20 T based on both High Temperature Superconductors (HTS) and Low Temperature Superconductors (LTS) for accelerator magnets. To achieve these objectives, a sound conductor development and characterization program is needed and is herein described. This program is intended to be conducted in close collaboration with U.S. and International labs, Universities and Industry.

  15. Gendered Fields: Sports and Advanced Course Taking in High School


    Pearson, Jennifer; Crissey, Sarah R.; Riegle-Crumb, Catherine


    This study explores the association between sports participation and course taking in high school, specifically comparing subjects with varied gendered legacies—science and foreign language. Analyses of a nationally representative longitudinal sample (N=5,447) of U.S. adolescents from the National Longitudinal Study of Adolescent Health and the linked Adolescent Health and Academic Achievement transcript study show that male and female athletes are more likely than non-athletes to take both a...

  16. Field manual for identifying and preserving high-water mark data (United States)

    Feaster, Toby D.; Koenig, Todd A.


    This field manual provides general guidance for identifying and collecting high-water marks and is meant to be used by field personnel as a quick reference. The field manual describes purposes for collecting and documenting high-water marks along with the most common types of high-water marks. The manual provides a list of suggested field equipment, describes rules of thumb and best practices for finding high-water marks, and describes the importance of evaluating each high-water mark and assigning a numeric uncertainty value as part of the flagging process. The manual also includes an appendix of photographs of a variety of high-water marks obtained from various U.S. Geological Survey field investigations along with general comments about the logic for the assigned uncertainty values.

  17. Low temperature superconductor and aligned high temperature superconductor magnetic dipole system and method for producing high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Ramesh; Scanlan, Ronald; Ghosh, Arup K.; Weggel, Robert J.; Palmer, Robert; Anerella, Michael D.; Schmalzle, Jesse


    A dipole-magnet system and method for producing high-magnetic-fields, including an open-region located in a radially-central-region to allow particle-beam transport and other uses, low-temperature-superconducting-coils comprised of low-temperature-superconducting-wire located in radially-outward-regions to generate high magnetic-fields, high-temperature-superconducting-coils comprised of high-temperature-superconducting-tape located in radially-inward-regions to generate even higher magnetic-fields and to reduce erroneous fields, support-structures to support the coils against large Lorentz-forces, a liquid-helium-system to cool the coils, and electrical-contacts to allow electric-current into and out of the coils. The high-temperature-superconducting-tape may be comprised of bismuth-strontium-calcium-copper-oxide or rare-earth-metal, barium-copper-oxide (ReBCO) where the rare-earth-metal may be yttrium, samarium, neodymium, or gadolinium. Advantageously, alignment of the large-dimension of the rectangular-cross-section or curved-cross-section of the high-temperature-superconducting-tape with the high-magnetic-field minimizes unwanted erroneous magnetic fields. Alignment may be accomplished by proper positioning, tilting the high-temperature-superconducting-coils, forming the high-temperature-superconducting-coils into a curved-cross-section, placing nonconducting wedge-shaped-material between windings, placing nonconducting curved-and-wedge-shaped-material between windings, or by a combination of these techniques.

  18. A new support structure for high field magnets

    CERN Document Server

    Hafalia, R R; Caspi, S; Dietderich, D R; Gourlay, S A; Hannaford, R; Lietzke, A F; Liggins, N; McInturff, A D; Sabbi, G L; Scanlan, R M; O'Neill, J; Swanson, J H


    Pre-stress of superconducting magnets can be applied directly through the magnet yoke structure. We have replaced the collar functionality in our 14 Tesla R&D Nb//3Sn dipole magnets with an assembly procedure based on an aluminum shell and bladders. Bladders, placed between the coil pack and surrounding yoke inside the shell, are pressurized up to 10 ksi left bracket 70 MPa right bracket to create an interference gap. Keys placed into the interference gap replace the bladder functionality. Following the assembly, the bladders are deflated and removed. Strain gauges mounted directly on the shell are used to monitor the stress of the entire magnet structure, thereby providing a high degree of pre-stress control without the need for high tolerances. During assembly, a force of 8.2 multiplied by 10**5 lbs /ft left bracket 12 MN/m right bracket is generated by the bladders and the stress in the 1.57 double prime left bracket 40 mm right bracket aluminum shell reaches 20.3 ksi left bracket 140 MPa right bracket...

  19. High accuracy magnetic field mapping of the LEP spectrometer magnet

    CERN Document Server

    Roncarolo, F


    The Large Electron Positron accelerator (LEP) is a storage ring which has been operated since 1989 at the European Laboratory for Particle Physics (CERN), located in the Geneva area. It is intended to experimentally verify the Standard Model theory and in particular to detect with high accuracy the mass of the electro-weak force bosons. Electrons and positrons are accelerated inside the LEP ring in opposite directions and forced to collide at four locations, once they reach an energy high enough for the experimental purposes. During head-to-head collisions the leptons loose all their energy and a huge amount of energy is concentrated in a small region. In this condition the energy is quickly converted in other particles which tend to go away from the interaction point. The higher the energy of the leptons before the collisions, the higher the mass of the particles that can escape. At LEP four large experimental detectors are accommodated. All detectors are multi purpose detectors covering a solid angle of alm...

  20. High-field thermal transports properties of REBCO coated conductors

    CERN Document Server

    Bonura, M


    The use of REBCO coated conductors is envisaged for many applications, extending from power cables to high-field magnets. Whatever the case, thermal properties of REBCO tapes play a key role for the stability of superconducting devices. In this work, we present the first study on the longitudinal thermal conductivity (k) of REBCO coated conductors in magnetic fields up to 19 T applied both parallelly and perpendicularly to the thermal-current direction. Copper-stabilized tapes from six industrial manufacturers have been investigated. We show that zero-field k of coated conductors can be calculated with an accuracy of ‡ 15% from the residual resistivity ratio of the stabilizer and the Cu/non-Cu ratio. Measurements performed at high fields have allowed us to evaluate the consistency of the procedures generally used for estimating in-field k in the framework of the Wiedemann-Franz law from an electrical characterization of the materials. In-field data are intended to provide primary ingredients for the ...

  1. Influence of high frequency electric field on the dispersion of ion-acoustic waves in plasma

    Energy Technology Data Exchange (ETDEWEB)

    Turky, A.; Cercek, M.; Tavzes, R.


    The modification of the ion-acoustic wave dispersion under the action of a high frequency electric field was studied experimentally, the wave propagating along and against the plasma stream. The frequency of the field amounted to approximately half the electron plasma frequency. It was found that the phase velocity of the ion wave and the plasma drift velocity decrease as the effective high frequency field power increases.

  2. In vivo high field magnetic resonance imaging and spectroscopy of adult zebrafish

    NARCIS (Netherlands)

    Kabli, Samira


    This thesis contains the results of imaging of adult zebrafish by using different MR approaches. We present the first high resolution mMR images of adult zebrafish. To achieve high spatial resolution we used a magnetic field of 9.4T, in combination with strong magnetic field gradients (1000 mT/m)

  3. Ultra-high field MRI: Advancing systems neuroscience towards mesoscopic human brain function

    NARCIS (Netherlands)

    Dumoulin, Serge O; Fracasso, A.; Van der Zwaag, W.; Siero, Jeroen C W; Petridou, Natalia


    Human MRI scanners at ultra-high magnetic field strengths of 7 T and higher are increasingly available to the neuroscience community. A key advantage brought by ultra-high field MRI is the possibility to increase the spatial resolution at which data is acquired, with little reduction in image

  4. Estimating the Reliability of Electronic Parts in High Radiation Fields (United States)

    Everline, Chester; Clark, Karla; Man, Guy; Rasmussen, Robert; Johnston, Allan; Kohlhase, Charles; Paulos, Todd


    Radiation effects on materials and electronic parts constrain the lifetime of flight systems visiting Europa. Understanding mission lifetime limits is critical to the design and planning of such a mission. Therefore, the operational aspects of radiation dose are a mission success issue. To predict and manage mission lifetime in a high radiation environment, system engineers need capable tools to trade radiation design choices against system design and reliability, and science achievements. Conventional tools and approaches provided past missions with conservative designs without the ability to predict their lifetime beyond the baseline mission.This paper describes a more systematic approach to understanding spacecraft design margin, allowing better prediction of spacecraft lifetime. This is possible because of newly available electronic parts radiation effects statistics and an enhanced spacecraft system reliability methodology. This new approach can be used in conjunction with traditional approaches for mission design. This paper describes the fundamentals of the new methodology.

  5. Gendered Fields: Sports and Advanced Course Taking in High School. (United States)

    Pearson, Jennifer; Crissey, Sarah R; Riegle-Crumb, Catherine


    This study explores the association between sports participation and course taking in high school, specifically comparing subjects with varied gendered legacies-science and foreign language. Analyses of a nationally representative longitudinal sample (N=5,447) of U.S. adolescents from the National Longitudinal Study of Adolescent Health and the linked Adolescent Health and Academic Achievement transcript study show that male and female athletes are more likely than non-athletes to take both advanced foreign language and Physics, largely because of their higher academic orientation. However, the association between sports participation and course taking was strongest for girls' Physics coursework, suggesting that sports may provide girls with a unique opportunity to develop the skills and confidence to persevere in the masculine domain of science.

  6. Wilderness medicine at high altitude: recent developments in the field

    Directory of Open Access Journals (Sweden)

    Shah NM


    Full Text Available Neeraj M Shah,1 Sidra Hussain,2 Mark Cooke,3 John P O’Hara,3 Adrian Mellor3,4 1Division of Asthma, Allergy and Lung Biology, King’s College London, UK; 2School of Medicine, University College London, London, UK; 3Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, UK; 4Academic Department of Military Anaesthesia and Critical Care, Royal Centre for Defence Medicine, Birmingham, UK Abstract: Travel to high altitude is increasingly popular. With this comes an increased incidence of high-altitude illness and therefore an increased need to improve our strategies to prevent and accurately diagnose these. In this review, we provide a summary of recent advances of relevance to practitioners who may be advising travelers to altitude. Although the Lake Louise Score is now widely used as a diagnostic tool for acute mountain sickness (AMS, increasing evidence questions the validity of doing so, and of considering AMS as a single condition. Biomarkers, such as brain natriuretic peptide, are likely correlating with pulmonary artery systolic pressure, thus potential markers of the development of altitude illness. Established drug treatments include acetazolamide, nifedipine, and dexamethasone. Drugs with a potential to reduce the risk of developing AMS include nitrate supplements, propagators of nitric oxide, and supplemental iron. The role of exercise in the development of altitude illness remains hotly debated, and it appears that the intensity of exercise is more important than the exercise itself. Finally, despite copious studies demonstrating the value of preacclimatization in reducing the risk of altitude illness and improving performance, an optimal protocol to preacclimatize an individual remains elusive. Keywords: hypoxia, acute mountain sickness, acclimatization, biomarkers, preacclimatization

  7. Full-field, high-spatial-resolution detection of local structural damage from low-resolution random strain field measurements (United States)

    Yang, Yongchao; Sun, Peng; Nagarajaiah, Satish; Bachilo, Sergei M.; Weisman, R. Bruce


    Structural damage is typically a local phenomenon that initiates and propagates within a limited area. As such high spatial resolution measurement and monitoring is often needed for accurate damage detection. This requires either significantly increased costs from denser sensor deployment in the case of global simultaneous/parallel measurements, or increased measurement time and labor in the case of global sequential measurements. This study explores the feasibility of an alternative approach to this problem: a computational solution in which a limited set of randomly positioned, low-resolution global strain measurements are used to reconstruct the full-field, high-spatial-resolution, two-dimensional (2D) strain field and rapidly detect local damage. The proposed approach exploits the implicit low-rank and sparse data structure of the 2D strain field: it is highly correlated without many edges and hence has a low-rank structure, unless damage-manifesting itself as sparse local irregularity-is present and alters such a low-rank structure slightly. Therefore, reconstruction of the full-field, high-spatial-resolution strain field from a limited set of randomly positioned low-resolution global measurements is modeled as a low-rank matrix completion framework and damage detection as a sparse decomposition formulation, enabled by emerging convex optimization techniques. Numerical simulations on a plate structure are conducted for validation. The results are discussed and a practical iterative global/local procedure is recommended. This new computational approach should enable the efficient detection of local damage using limited sets of strain measurements.


    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L


    The Phase I work reported here responds to DoE'ss stated need " develop improved accelerator designs that can provide very high gradient (>200 MV/m for electrons...) acceleration of intense bunches of particles." Omega-P's approach to this goal is through use of a ramped train of annular electron bunches to drive a coaxial dielectric wakefield accelerator (CDWA) structure. This approach is a direct extension of the CDWA concept from acceleration in wake fields caused by a single drive bunch, to the more efficient acceleration that we predict can be realized from a tailored (or ramped) train of several drive bunches. This is possible because of a much higher transformer ratio for the latter. The CDWA structure itself has a number of unique features, including: a high accelerating gradient G, potentially with G > 1 GeV/m; continuous energy coupling from drive to test bunches without transfer structures; inherent transverse focusing forces for particles in the accelerated bunch; highly stable motion of high charge annular drive bunches; acceptable alignment tolerances for a multi-section system. What is new in the present approach is that the coaxial dielectric structure is now to be energized by-not one-but by a short train of ramped annular-shaped drive bunches moving in the outer coaxial channel of the structure. We have shown that this allows acceleration of an electron bunch traveling along the axis in the inner channel with a markedly higher transformer ratio T than for a single drive bunch. As described in this report, the structure will be a GHz-scale prototype with cm-scale transverse dimensions that is expected to confirm principles that can be applied to the design of a future THz-scale high gradient (> 500 MV/m) accelerator with mm-scale transverse dimensions. We show here a new means to significantly increase the transformer ratio T of the device, and thereby to significantly improve its suitability as a flexible and effective component in

  9. Zylon-reinforced high magnetic field coils for the K.U. Leuven pulsed field laboratory (United States)

    Rosseel, K.; Herlach, F.; Boon, W.; Bruynseraede, Y.


    PBO Zylon ® fibers have been used for the internal reinforcement of pulsed magnets. Due to the very high packing density (80%) of these fibers, vacuum impregnation of Zylon reinforced coils is difficult. Impregnation test were performed using pressure-vacuum impregnation and wet winding. A prototype series of coils for 60-70 T with 1-2 ms pulse duration was designed and wound, using wet winding for both the internal Zylon and external carbon fiber reinforcement. Special precautions were taken to avoid insulation breakdown at the transitions between conductor layers. Furthermore, axial movement of the conductor wires was restrained by strong axial compression of the coil with a steel shell casing. These modifications were incorporated into an 80 T coil made of Zylon and soft Cu. The design, construction and performance of this coil are discussed.

  10. Soil physical properties of high mountain fields under bauxite mining

    Directory of Open Access Journals (Sweden)

    Dalmo Arantes de Barros


    Full Text Available Mining contributes to the life quality of contemporary society, but can generate significant impacts, these being mitigated due to environmental controls adopted. This study aimed to characterize soil physical properties in high-altitude areas affected by bauxite mining, and to edaphic factors responses to restoration techniques used to recover mined areas in Poços de Caldas plateau, MG, Brazil. The experiment used 3 randomized block design involving within 2 treatments (before mining intervention and after environmental recovery, and 4 replicates (N=24. In each treatment, soil samples with deformed structures were determined: granulometry, water-dispersible clay content, flocculation index, particle density, stoniness level, water aggregate stability, and organic matter contend. Soil samples with preserved structures were used to determine soil density and the total volume of pores, macropores, and micropores. Homogenization of stoniness between soil layers as a result of soil mobilization was observed after the mined area recovery. Stoniness decreased in 0.10-0.20 m layer after recovery, but was similar in the 0-0.10 m layer in before and after samples. The recovery techniques restored organic matter levels to pre-mining levels. However, changes in soil, including an increase in soil flocculation degree and a decrease in water-dispersible clays, were still apparent post-recovery. Furthermore, mining operations caused structural changes to the superficial layer of soil, as demonstrated by an increase in soil density and a decrease in total porosity and macroporosity. Decreases in the water stability of aggregates were observed after mining operations.

  11. Precise Determination of Zero-Field Splitting Parameters of Hemin by High-Field and High-Frequency Electron Paramagnetic Resonance (United States)

    Okamoto, Tsubasa; Ohmichi, Eiji; Okubo, Susumu; Ohta, Hitoshi


    The zero-field splitting (ZFS) parameters of Fe(III) protoporphyrin IX chloride, or hemin, a model substance of hemoproteins, were determined precisely by high-field and high-frequency electron paramagnetic resonance (HFEPR). From multi-frequency measurements up to 700 GHz, multiple EPR absorptions were clearly resolved, and the rhombic component of ZFS was directly determined, for the first time, as |E| = 0.055 ± 0.005 cm-1, in addition to the axial component D = 6.90 ± 0.01 cm-1. This finding indicates the essential role of the rhombic symmetry of excited states in the ZFS parameters.

  12. Review of the Dynamics of Coalescence and Demulsification by High-Voltage Pulsed Electric Fields

    Directory of Open Access Journals (Sweden)

    Ye Peng


    Full Text Available The coalescence of droplets in oil can be implemented rapidly by high-voltage pulse electric field, which is an effective demulsification dehydration technological method. At present, it is widely believed that the main reason of pulse electric field promoting droplets coalescence is the dipole coalescence and oscillation coalescence in pulse electric field, and the optimal coalescence pulse electric field parameters exist. Around the above content, the dynamics of high-voltage pulse electric field promoting the coalescence of emulsified droplets is studied by researchers domestically and abroad. By review, the progress of high-voltage pulse electric field demulsification technology can get a better understanding, which has an effect of throwing a sprat to catch a whale on promoting the industrial application.

  13. Mirrorless Lasing in Optically Pumped Rubidium Vapor (United States)


    Ionization Potential 33690.81 cm-1 nRb = Rb Number Density 6.5x1013cm-3 - 5.2 x1014cm-3 γo = Calculated Small Signal Gain 2522 cm-1 - 20566 cm-1 tpb Lucatorto’s work. Finally, stimulated Raman scattering also has the potential to populate higher energy states that are subject to photoionization...should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of

  14. Computing Temperatures In Optically Pumped Laser Rods (United States)

    Farrukh, Usamah O.


    Computer program presents new model solving temperature-distribution problem for laser rods of finite length and calculates both radial and axial components of temperature distributions in these rods. Contains several self-checking schemes to prevent over-writing of memory blocks and to provide simple tracing of information in case of trouble. Written in Microsoft FORTRAN 77.

  15. Kerr effect at high electric field in the isotropic phase of mesogenic materials. (United States)

    Li, Bing-Xiang; Borshch, Volodymyr; Shiyanovskii, Sergij V; Liu, Shao-Bin; Lavrentovich, Oleg D


    The well-known Kerr effect in isotropic fluids consists in the appearance of uniaxial orientational order and birefringence that grows as the square of the applied electric field. We predict and observe that at a high electric field, the Kerr effect displays features caused by the nonlinear dependence of dielectric permittivity on the field-induced orientational order parameter. Namely, the field-induced birefringence grows faster than the square of the electric field and the dynamics of birefringence growth slows down as the field increases. As a function of temperature, the field-induced birefringence is inversely proportional to the departure from an asymptotic critical temperature, but this temperature is no longer a constant (corresponding to the lower limit of the supercooled isotropic phase) and increases proportionally to the square of the electric field.

  16. New perspectives in vacuum high voltage insulation. I. The transition to field emission

    CERN Document Server

    Diamond, W T


    Vacuum high-voltage insulation has been investigated for many years. Typically, electrical breakdown occurs between two broad-area electrodes at electric fields 100-1000 times lower than the breakdown field (about 5000 MV/m) between a well-prepared point cathode and a broad-area anode. Explanations of the large differences remain unsatisfactory, usually evoking field emission from small projections on the cathode that are subject to higher peak fields. The field emission then produces secondary effects that lead to breakdown. This article provides a significant resolution to this long standing problem. Field emission is not present at all fields, but typically starts after some process occurs at the cathode surface. Three effects have been identified that produce the transition to field emission: work function changes; mechanical changes produced by the strong electrical forces on the electrode surfaces; and gas desorption from the anode with sufficient density to support an avalanche discharge. Material adso...

  17. A Novel High Sensitivity Sensor for Remote Field Eddy Current Non-Destructive Testing Based on Orthogonal Magnetic Field

    Directory of Open Access Journals (Sweden)

    Xiaojie Xu


    Full Text Available Remote field eddy current is an effective non-destructive testing method for ferromagnetic tubular structures. In view of conventional sensors’ disadvantages such as low signal-to-noise ratio and poor sensitivity to axial cracks, a novel high sensitivity sensor based on orthogonal magnetic field excitation is proposed. Firstly, through a three-dimensional finite element simulation, the remote field effect under orthogonal magnetic field excitation is determined, and an appropriate configuration which can generate an orthogonal magnetic field for a tubular structure is developed. Secondly, optimized selection of key parameters such as frequency, exciting currents and shielding modes is analyzed in detail, and different types of pick-up coils, including a new self-differential mode pick-up coil, are designed and analyzed. Lastly, the proposed sensor is verified experimentally by various types of defects manufactured on a section of a ferromagnetic tube. Experimental results show that the proposed novel sensor can largely improve the sensitivity of defect detection, especially for axial crack whose depth is less than 40% wall thickness, which are very difficult to detect and identify by conventional sensors. Another noteworthy advantage of the proposed sensor is that it has almost equal sensitivity to various types of defects, when a self-differential mode pick-up coil is adopted.

  18. Very high-accuracy calibration of radiation pattern and gain of a near-field probe

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Nielsen, Jeppe Majlund; Breinbjerg, Olav


    In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission of the Europ......In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission...


    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Berro, Enrique; Loren-Aguilar, Pablo; Aznar-Siguan, Gabriela; Torres, Santiago; Camacho, Judit [Departament de Fisica Aplicada, Universitat Politecnica de Catalunya, c/Esteve Terrades, 5, 08860 Castelldefels (Spain); Althaus, Leandro G.; Corsico, Alejandro H. [Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, (1900) La Plata (Argentina); Kuelebi, Baybars; Isern, Jordi, E-mail: [Institute for Space Studies of Catalonia, c/Gran Capita 2-4, Edif. Nexus 104, 08034 Barcelona (Spain)


    High-field magnetic white dwarfs have been long suspected to be the result of stellar mergers. However, the nature of the coalescing stars and the precise mechanism that produces the magnetic field are still unknown. Here, we show that the hot, convective, differentially rotating corona present in the outer layers of the remnant of the merger of two degenerate cores can produce magnetic fields of the required strength that do not decay for long timescales. Using a state-of-the-art Monte Carlo simulator, we also show that the expected number of high-field magnetic white dwarfs produced in this way is consistent with that found in the solar neighborhood.

  20. Unipolar and Bipolar High-Magnetic-Field Sensors Based on Surface Acoustic Wave Resonators (United States)

    Polewczyk, V.; Dumesnil, K.; Lacour, D.; Moutaouekkil, M.; Mjahed, H.; Tiercelin, N.; Petit Watelot, S.; Mishra, H.; Dusch, Y.; Hage-Ali, S.; Elmazria, O.; Montaigne, F.; Talbi, A.; Bou Matar, O.; Hehn, M.


    While surface acoustic wave (SAW) sensors have been used to measure temperature, pressure, strains, and low magnetic fields, the capability to measure bipolar fields and high fields is lacking. In this paper, we report magnetic surface acoustic wave sensors that consist of interdigital transducers made of a single magnetostrictive material, either Ni or TbFe2 , or based on exchange-biased (Co /IrMn ) multilayers. By controlling the ferromagnet magnetic properties, high-field sensors can be obtained with unipolar or bipolar responses. The issue of hysteretic response of the ferromagnetic material is especially addressed, and the control of the magnetic properties ensures the reversible behavior in the SAW response.

  1. Exposure to electromagnetic fields aboard high-speed electric multiple unit trains. (United States)

    Niu, D; Zhu, F; Qiu, R; Niu, Q


    High-speed electric multiple unit (EMU) trains generate high-frequency electric fields, low-frequency magnetic fields, and high-frequency wideband electromagnetic emissions when running. Potential human health concerns arise because the electromagnetic disturbances are transmitted mainly into the car body from windows, and from there to passengers and train staff. The transmission amount and amplitude distribution characteristics that dominate electromagnetic field emission need to be studied, and the exposure level of electromagnetic field emission to humans should be measured. We conducted a series of tests of the on board electromagnetic field distribution on several high-speed railway lines. While results showed that exposure was within permitted levels, the possibility of long-term health effects should be investigated.

  2. Dose equivalent measurements in a strongly pulsed high-energy radiation field

    CERN Document Server

    Mayer, S; Kyllonen, J E; Menzel, Hans Gregor; Otto, Thomas


    The stray radiation field outside the shielding of high-energy accelerators comprises neutrons, photons and charged particles with a wide range of energies. Often, accelerators operate by accelerating and ejecting short pulses of particles, creating an analogue, pulsed radiation field. The pulses can be as short as 10 mu s with high instantaneous fluence rates and dose rates. Measurements of average dose equivalent (rate) for radiation protection purposes in these fields present a challenge for instrumentation. The performance of three instruments (i.e. a recombination chamber, the Sievert Instrument and a HANDITEPC) measuring total dose equivalent is compared in a high-energy reference radiation field (CERF) and a strongly pulsed, high-energy radiation field at the CERN proton synchrotron (PS).

  3. A new approach for explanation of specimen rupture under high electric field. (United States)

    Mikhailovskij, I M; Wanderka, N; Storizhko, V E; Ksenofontov, V A; Mazilova, T I


    Failure of needle-shaped specimens under the action of high electric fields is one of the most serious problems in many field-ionization devices and methods. It was shown that the length of what was removed during discharge part of specimens in most of the cases was several orders greater than that of an initial radius of the specimen apex. Experimental results obtained in this work indicate that electrical breakdown in field-ion microscopes is initiated by the impact of nanoparticles detached from a point anode in a high electric field. A new approach for explanation of an observed specimen failure in a high electric field was proposed, where the formation and expansion of the cathode plasma play the key role in the mechanical rupture and melting of field-ion tips. The expanding plasma behaves as a dynamic capacitor plate characterized by a high velocity and increasing field strength at the specimen tip. The field rise rate at a constant voltage in a dynamic plasma-to-tip capacitor is of the order of >10(20)V/m/s. The present experimental data along with the ecton model of the vacuum breakdown allow the results to be discussed as a mechanical sample failure under the action of the superhigh positive field pulse induced by the cathode plasma expansion.

  4. High-spin chloro mononuclear MnIII complexes: a multifrequency high-field EPR study. (United States)

    Mantel, Claire; Chen, Hongyu; Crabtree, Robert H; Brudvig, Gary W; Pécaut, Jacques; Collomb, Marie-Noëlle; Duboc, Carole


    The isolation, structural characterization, and electronic properties of two six-coordinated chloromanganese (III) complexes, [Mn(terpy)(Cl)3] (1) and [Mn(Phterpy)(Cl)3] (2), are reported (terpy = 2,2':6'2"-terpyridine, Phterpy = 4'-phenyl-2,2':6',2"-terpyridine). These complexes complement a series of mononuclear azide and fluoride Mn(lll) complexes synthesized with neutral N-tridentate ligands, [Mn(L)(X)3] (X = F- or N3 and L = terpy or bpea [N,N-bis(2-pyridylmethyl)-ethylamine)], previously described. Similar to these previous complexes, 1 and 2 exhibit a Jahn-Teller distortion of the octahedron, characteristic of a high-spin Mn(III) complex (S = 2). The analysis of the crystallographic data shows that, in both cases, the manganese ion lies in the center of a distorted octahedron characterized by an elongation along the tetragonal axis. Their electronic properties were investigated by multifrequency EPR (190-475 GHz) performed in the solid state at different temperatures (5-15 K). This study confirms our previous results and further shows that: i) the sign of D is correlated with the nature of the tetragonal distortion; ii) the magnitude of D is not sensitive to the nature of the anions in our series of rhombic complexes, contrary to the porphyrinic systems; iii) the [E/D] values (0.124 for 1 and 0.085 for 2) are smaller compared to those found for the [Mn(L)(X)3] complexes (in the range of 0.146 to 0.234); and iv) the E term increases when the ligand-field strength of the equatorial ligands decreases.

  5. Electron transport in bulk GaN under ultrashort high-electric field transient (United States)

    Korotyeyev, V. V.; Kochelap, V. A.; Kim, K. W.


    We have investigated nonlinear electron transport in GaN induced by high-electric field transients by analyzing the temporal dependence of the electron drift velocity and temperature. For picosecond transients, our calculations have established that the electron dynamics retain almost all the features of the steady-state velocity-field characteristics including the portion with negative differential conductivity. It was also found that transient currents in GaN samples give rise to the THz re-emission effect—radiation of electromagnetic field, temporal and spectral properties of which directly relate to the velocity-field characteristics of the sample. The results clearly indicate that existing methods for the generation of high-electric field transients and subpicosecond signal measurements can be applied to the characterization of hot electron transport at ultrahigh fields while avoiding Joule self-heating, hot phonon accumulation and other undesirable effects.

  6. Recent developments in high-resolution global altimetric gravity field modeling

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Knudsen, Per; Berry, P. A .M.


    In recent years, dedicated effort has been made to improve high-resolution global marine gravity fields. One new global field is the Danish National Space Center (DNSC) 1-minute grid called DNSC08GRA, released in 2008. DNSC08GRA was derived from double-retracked satellite altimetry, mainly from...... the ERS-1 geodetic mission data, augmented with new retracked GEOSAT data which have significantly enhanced the range and hence the gravity field accuracy. DNSC08GRA is the first high-resolution global gravity field to cover the entire Arctic Ocean all the way to the North Pole. Comparisons with other...... older gravity fields show accuracy improvement of the order of 20-40% due to a combination of retracking, enhanced processing, and the use of the new EGM2008 geoid model. In coastal and polar regions, accuracy improved in many places by 40-50% (or more) compared with older global marine gravity fields....

  7. Tomographic reconstruction of circularly polarized high-harmonic fields: 3D attosecond metrology. (United States)

    Chen, Cong; Tao, Zhensheng; Hernández-García, Carlos; Matyba, Piotr; Carr, Adra; Knut, Ronny; Kfir, Ofer; Zusin, Dimitry; Gentry, Christian; Grychtol, Patrik; Cohen, Oren; Plaja, Luis; Becker, Andreas; Jaron-Becker, Agnieszka; Kapteyn, Henry; Murnane, Margaret


    Bright, circularly polarized, extreme ultraviolet (EUV) and soft x-ray high-harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. Although the resulting circularly polarized harmonics consist of relatively simple pairs of peaks in the spectral domain, in the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency, and polarization. We extend attosecond metrology techniques to circularly polarized light by simultaneously irradiating a copper surface with circularly polarized high-harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date.

  8. High-Intensity Nanosecond Pulsed Electric Field effects on Early Physiological Development in Arabidopsis thaliana


    Wisuwat Songnuan; Phumin Kirawanich


    The influences of pulsed electric fields on early physiological development in Arabidopsis thaliana were studied. Inside a 4-mm electroporation cuvette, pre-germination seeds were subjected to high-intensity, nanosecond electrical pulses generated using laboratory-assembled pulsed electric field system. The field strength was varied from 5 to 20 and the pulse width and the pulse number were maintained at 10 ns and 100, respectively, corresponding to the specific t...

  9. High field magnetization process in Er sub 2 (Fe, Al) sub 14 B

    Energy Technology Data Exchange (ETDEWEB)

    Kohashi, T.; Kindo, K.; Date, M. (Dept. of Physics, Osaka Univ. (Japan)); Boer, F.R. de; Radwanski, R.J.; Zhong, X.P. (Natuurkundig Lab., Univ. Amsterdam (Netherlands)); Yamagishi, A. (Research Center for Extreme Materials, Osaka Univ. (Japan))


    A magnetization study in pulsed high magnetic fields up to 50 T has been performed on magnetically aligned powder samples of ferrimagnetic Er{sub 2}Fe{sub 14-x}Al{sub x}B (x = 0, 1, 2) compounds and field-induced transitions have been observed. Free-energy calculations with one Fe and four Er sublattices have been performed and the field-induced transitions can satisfactorily be explained. (orig.).

  10. Studies on the reliability of high-field intra-operative MRI in brain glioma resection

    Directory of Open Access Journals (Sweden)

    Zhi-jun SONG


    Full Text Available Objective To evaluate the reliability of high-field intra-operative magnetic resonance imaging(iMRI in detecting the residual tumors during glioma resection.Method One hundred and thirty-one cases of brain glioma(69 males and 62 females,aged from 7 to 79 years with mean of 39.6 years hospitalized from Nov.2009 to Aug.2010 were involved in present study.All the patients were evaluated using magnetic resonance imaging(MRI before the operation.The tumors were resected under conventional navigation microscope,and the high-field iMRI was used for all the patients when the operators considered the tumor was satisfactorily resected,while the residual tumor was difficult to detect under the microscope,but resected after being revealed by high-field iMRI.Histopathological examination was performed.The patients without residual tumors recieved high-field MRI scan at day 4 or 5 after operation to evaluate the accuracy of high-field iMRI during operation.Results High quality intra-operative images were obtained by using high-field iMRI.Twenty-eight cases were excluded because their residual tumors were not resected due to their location too close to functional area.Combined with the results of intra-operative histopathological examination and post-operative MRI at the early recovery stage,the sensitivity of high-field iMRI in residual tumor diagnosis was 98.0%(49/50,the specificity was 94.3%(50/53,and the accuracy was 96.1%(99/103.Conclusion High-quality intra-operative imaging could be acquired by high-field iMRI,which maybe used as a safe and reliable method in detecting the residual tumors during glioma resection.

  11. Establishing resolution-improved NMR spectroscopy in high magnetic fields with unknown spatiotemporal variations (United States)

    Zhang, Zhiyong; Smith, Pieter E. S.; Cai, Shuhui; Zheng, Zhenyao; Lin, Yulan; Chen, Zhong


    A half-century quest for higher magnetic fields has been an integral part of the progress undergone in the Nuclear Magnetic Resonance (NMR) study of materials' structure and dynamics. Because 2D NMR relies on systematic changes in coherences' phases as a function of an encoding time varied over a series of independent experiments, it generally cannot be applied in temporally unstable fields. This precludes most NMR methods from being used to characterize samples situated in hybrid or resistive magnets that are capable of achieving extremely high magnetic field strength. Recently, "ultrafast" NMR has been developed into an effective and widely applicable methodology enabling the acquisition of a multidimensional NMR spectrum in a single scan; it can therefore be used to partially mitigate the effects of temporally varying magnetic fields. Nevertheless, the strong interference of fluctuating fields with the spatial encoding of ultrafast NMR still severely restricts measurement sensitivity and resolution. Here, we introduce a strategy for obtaining high resolution NMR spectra that exploits the immunity of intermolecular zero-quantum coherences (iZQCs) to field instabilities and inhomogeneities. The spatial encoding of iZQCs is combined with a J-modulated detection scheme that removes the influence of arbitrary field inhomogeneities during acquisition. This new method can acquire high-resolution one-dimensional NMR spectra in large inhomogeneous and fluctuating fields, and it is tested with fields experimentally modeled to mimic those of resistive and resistive-superconducting hybrid magnets.

  12. High field magnetization and specific heat of ErNi{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Kayzel, F.E.; Franse, J.J.M. [Univ. van Amsterdam (Netherlands). Van der Waals-Zeeman Lab.; Radwanski, R.J. [Centre for Solid State Physics, Krakow (Poland)


    High field magnetization studies of single crystalline ErNi{sub 5} in fields up to 38T at 1.5K along the main crystallographic directions have been performed. Along the easy direction, the hexagonal axis, the spontaneous magnetization, M{sub s}, amounts to 8.62{mu}{sub B}/f.u. The high-field susceptibility is very small and equal to 41 {times} 10{sup {minus}4}{mu}{sub B}/Tf.u. There exists a distinct difference between the curves along the a- and b-axis. The a-axis curve monotonously increases with field up to 38T. The b-axis curve coincides with the a-axis curve up to 12T but starts to deviate from it above this field, resulting in a value for the magnetization at 38T which is almost the full moment value. The specific beat of a newly-grown single-crystalline sample has been measured in zero field and in applied fields along the c-axis (B = 0.3, 1, 2, 5T). The zero-field measurements coincide with previously reported results The specific heat shows a rapid decrease of the ferrimagnetic order with applied field. Already in 1T, the sharp lambda-type of peak at the magnetic transition is decreased by two third and becomes a broad bump that coincides with the la measurement above 30K. Higher fields further suppress the transition.

  13. Study on technology of high-frequency pulsed magnetic field strength measurement. (United States)

    Chen, Yi-Mei; Liu, Zhi-Peng; Yin, Tao


    High-frequency transient weak magnetic field is always involved in researches about biomedical engineering field while common magnetic-field sensors cannot work properly at frequencies as high as MHz. To measure the value of MHz-level weak pulsed magnetic-field strength accurately, this paper designs a measurement and calibration method for pulsed magnetic-field. In this paper, a device made of Nonferromagnetic material was independently designed and applied to pulsed magnetic field measurement. It held an accurately relative position between the magnetic field generating coil and the detecting coil. By applying a sinusoidal pulse to the generator, collecting the induced electromotive force of the detector, the final magnetic field strength was worked out through algorithms written in Matlab according to Faraday's Law. Experiments were carried out for measurement and calibration. Experiments showed that, under good stability and consistency, accurate measurement of magnetic-field strength of a sinepulse magnetic-field can be achieved, with frequency at 0.5, 1, 1.5 MHz and strength level at micro-Tesla. Calibration results carried out a measuring relative error about 2.5%.

  14. GPU-accelerated FDTD modeling of radio-frequency field-tissue interactions in high-field MRI. (United States)

    Chi, Jieru; Liu, Feng; Weber, Ewald; Li, Yu; Crozier, Stuart


    The analysis of high-field RF field-tissue interactions requires high-performance finite-difference time-domain (FDTD) computing. Conventional CPU-based FDTD calculations offer limited computing performance in a PC environment. This study presents a graphics processing unit (GPU)-based parallel-computing framework, producing substantially boosted computing efficiency (with a two-order speedup factor) at a PC-level cost. Specific details of implementing the FDTD method on a GPU architecture have been presented and the new computational strategy has been successfully applied to the design of a novel 8-element transceive RF coil system at 9.4 T. Facilitated by the powerful GPU-FDTD computing, the new RF coil array offers optimized fields (averaging 25% improvement in sensitivity, and 20% reduction in loop coupling compared with conventional array structures of the same size) for small animal imaging with a robust RF configuration. The GPU-enabled acceleration paves the way for FDTD to be applied for both detailed forward modeling and inverse design of MRI coils, which were previously impractical.

  15. A Study on the Evaluation of Field Application of High-Fluidity Concrete Containing High Volume Fly Ash

    Directory of Open Access Journals (Sweden)

    Yun-Wang Choi


    Full Text Available In the recent concrete industry, high-fluidity concrete is being widely used for the pouring of dense reinforced concrete. Normally, in the case of high-fluidity concrete, it includes high binder contents, so it is necessary to replace part of the cement through admixtures such as fly ash to procure economic feasibility and durability. This study shows the mechanical properties and field applicability of high-fluidity concrete using mass of fly ash as alternative materials of cement. The high-fluidity concrete mixed with 50% fly ash was measured to manufacture concrete that applies low water/binder ratio to measure the mechanical characteristics as compressive strength and elastic modulus. Also, in order to evaluate the field applicability, high-fluidity concrete containing high volume fly ash was evaluated for fluidity, compressive strength, heat of hydration, and drying shrinkage of concrete.

  16. Lumbar Modic Changes - A Comparison Between Findings at Low-and High-field MRI

    DEFF Research Database (Denmark)

    Bendix, Tom; Sorensen, Joan S; Henriksson, Gustaf A C


    -81), with or without sciatica, seen in a Danish outpatient LBP clinic were included. All patients had MRI scans on both a high-field and a low-field MRI scanner. Two radiologists evaluated all lumbar endplates independently using a standardized evaluation protocol. Kappa statistics were used to analyze the inter...

  17. Isolating Flow-field Discontinuities while Preserving Monotonicity and High-order Accuracy on Cartesian Meshes (United States)


    19b. TELEPHONE NUMBER (Include area code) 01/09/2017 Briefing Charts 01 January 2017 - 31 January 2017 Isolating Flow -field Discontinuities while...Unclassified Unclassified Unclassified SAR 18 V. Sanakaran N/A Isolating Flow -field Discontinuities while Preserving Monotonicity and High-order

  18. Charge transport in poly(p-phenylene vinylene) at low temperature and high electric field

    NARCIS (Netherlands)

    Katsouras, I.; Najafi, A.; Asadi, K.; Kronemeijer, A. J.; Oostra, A. J.; Koster, L. J. A.; de Leeuw, D. M.; Blom, P. W. M.

    Charge transport in poly(2-methoxy, 5-(2'-ethyl-hexyloxy)-p-phenylene vinylene) (MEH-PPV)-based hole-only diodes is investigated at high electric fields and low temperatures using a novel diode architecture. Charge carrier densities that are in the range of those in a field-effect transistor are

  19. Neutron scattering study of the incommensurate high-field phase of CuGeO3

    DEFF Research Database (Denmark)

    Rønnow, H.M.; Enderle, M.; McMorrow, D.F.


    CuGeO3 is a good realization of a spin-Peierls system. Using neutron scattering, we have investigated the transition from the dimerized spin-Peierls phase to an incommensurately modulated high-field phase. The incommensurate period has been measured for fields up to 14.5 T and is found...

  20. High-field 3He-F interaction at the surface of fluorocarbon spheres

    DEFF Research Database (Denmark)

    Schuhl, A.; Chapellier, M.; Rasmussen, Finn Berg


    High-field experiments on the relaxation betweenF in small Teflon spheres andHe on the surface are reported. WithHe as a monolayer, coupling times are found to be less than 5 sec, in magnetic fields up to 3 T and temperatures down to 50 mK, where electronic centers are completely polarized...


    DEFF Research Database (Denmark)

    Mosekilde, Erik


    An analytical treatment of the uniformly propagating acoustoelectric high-field domain is presented in the limit of zero diffusion. Expressions for the electron density and the acoustic energy density as functions of the electric field are given. The domain velocity is determined. ©1968 The Ameri...... The American Institute of Physics...

  2. In-situ high field strength testing using a transportable reverberation chamber

    NARCIS (Netherlands)

    Leferink, Frank Bernardus Johannes


    A reverberation chamber can create very high field strength with moderate input power. Existing chambers are making use of a paddle wheel to change the resonant modes in the chamber. In the case of a stepper motor, the field is stable for some time, and this type of reverberation chamber is called

  3. Application of Nb3Sn superconductors in high-field accelerator magnets

    NARCIS (Netherlands)

    den Ouden, A.; Wessel, Wilhelm A.J.; Krooshoop, Hendrikus J.G.; ten Kate, Herman H.J.


    Last year a record central field of 11 T at first excitation at 4.4 K has been achieved with the experimental LHC model dipole magnet MSUT by utilising a high Jc powder-in-tube Nb3Sn conductor. This is the first real breakthrough towards fields well above 10 T at 4 K. The clear influence of

  4. High-field Faraday rotation in II-VI-based semimagnetic semiconductors

    NARCIS (Netherlands)

    Savchuk, AI; Fediv, [No Value; Nikitin, PI; Perrone, A; Tatzenko, OM; Platonov, VV

    The effects of d-d exchange interaction have been studied by measuring high-field Faraday rotation in II-VI-based semimagnetic semiconductors. For Cd1-xMnxTe crystals with x = 0.43 and at room temperature a saturation in magnetic field dependence of the Faraday rotation has been observed. In the

  5. Flexible, High Performance Microlens Array Technologies for Integral Field Spectrographs Project (United States)

    National Aeronautics and Space Administration — For the purposes of advancing integral field spectrograph (IFS) microlens capabilities, a new class of high-quality optics-grade nanostructured organic-inorganic...

  6. Static high-gradient magnetic fields affect the functionality of monocytic cells

    Czech Academy of Sciences Publication Activity Database

    Syrovets, T.; Schmidt, Z.; Buechele, B.; Zablotskyy, Vitaliy A.; Dejneka, Alexandr; Dempsey, N.; Simmet, T.


    Roč. 28, č. 1 (2014), s. 1-2 ISSN 0892-6638 Institutional support: RVO:68378271 Keywords : static high-gradient * magnet ic fields * affect the functionality * monocytic cells Subject RIV: BM - Solid Matter Physics ; Magnet ism

  7. High Resolution Multispectral Flow Imaging of Cells with Extended Depth of Field Project (United States)

    National Aeronautics and Space Administration — Proposed is the development the extended depth of field (EDF) or confocal like imaging capabilities of a breakthrough multispectral high resolution imaging flow...

  8. Landau level splitting in Cd3As2 under high magnetic fields

    National Research Council Canada - National Science Library

    Cao, Junzhi; Liang, Sihang; Zhang, Cheng; Liu, Yanwen; Huang, Junwei; Jin, Zhao; Chen, Zhi-Gang; Wang, Zhijun; Wang, Qisi; Zhao, Jun; Li, Shiyan; Dai, Xi; Zou, Jin; Xia, Zhengcai; Li, Liang; Xiu, Faxian


    .... Here we report the first transport experiment on Landau level splitting in TDS Cd3As2 single crystals under high magnetic fields, suggesting the removal of spin degeneracy by breaking time reversal symmetry...

  9. Does high field MRI allow an earlier diagnosis of multiple sclerosis?

    NARCIS (Netherlands)

    Wattjes, M.P.; Harzheim, M.; Lutterbey, G.G.; Hojati, F.; Simon, B.; Schmidt, S.; Schild, H.H.; Barkhof, F.


    Background :High field magnetic resonance imaging (MRI) provides higher lesion load measurements in patients presenting with clinically isolated syndromes (CIS) suggestive of demyelination and has impact upon the classification of these syndromes and potentially, the diagnosis of multiple sclerosis

  10. Microstrip Resonator for High Field MRI with Capacitor-Segmented Strip and Ground Plane

    DEFF Research Database (Denmark)

    Zhurbenko, Vitaliy; Boer, Vincent; Petersen, Esben Thade


    ) segmenting stripe and ground plane of the resonator with series capacitors. The design equations for capacitors providing symmetric current distribution are derived. The performance of two types of segmented resonators are investigated experimentally. To authors’ knowledge, a microstrip resonator, where both......High field MRI coils are often based on transmission line resonators. Due to relatively short wavelength of RF fields, such coils produce uneven field patterns. Here we show, that it is possible to manipulate magnetic field patterns of microstrip resonators in both planes (sagittal and transverse......, strip and ground plane are capacitor-segmented, is shown here for the first time....

  11. High-field magnetisation measurements on R sub 2 Fe sub 14 B single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Verhoef, R.; Franse, J.J.M.; Menovsky, A.A.; Radwanski, R.J. (Amsterdam Univ. (NL). Natuurkundig Lab.); Song-quan, J.; Fu-ming, Y. (Academia Sinica, Beijing (CN). Inst. of Physics); Li, H.S.; Gavigan, J.P. (Trinity Coll. Dublin (IE). Dept. of Pure and Applied Physics)


    High-field magnetisation measurements on single crystalline samples of Pr{sub 2}Fe{sub 14}B, Nd{sub 2}Fe{sub 14}B and Dy{sub 2}Fe{sub 14}B are presented and discussed within a two-sublattice model. Special attention is given to the high-field part of the curves (B{sub o} > 20 T).

  12. B0 mapping with multi-channel RF coils at high field. (United States)

    Robinson, Simon; Jovicich, Jorge


    Mapping the static magnetic field via the phase evolution over gradient echo scans acquired at two or more echo times is an established method. A number of possibilities exist, however, for combining phase data from multi-channel coils, denoising and thresholding field maps for high field applications. Three methods for combining phase images when no body/volume coil is available are tested: (i) Hermitian product, (ii) phase-matching over channels, and (iii) a new approach based on calculating separate field maps for each channel. The separate channel method is shown to yield field maps with higher signal-to-noise ratio than the Hermitian product and phase-matching methods and fewer unwrapping errors at low signal-to-noise ratio. Separate channel combination also allows unreliable voxels to be identified via the standard deviation over channels, which is found to be the most effective means of denoising field maps. Tests were performed using multichannel coils with between 8 and 32 channels at 3 T, 4 T, and 7 T. For application in the correction of distortions in echo-planar images, a formulation is proposed for reducing the local gradient of field maps to eliminate signal pile-up or swapping artifacts. Field maps calculated using these techniques, implemented in a freely available MATLAB toolbox, provide the basis for an effective correction for echo-planar imaging distortions at high fields. Copyright © 2011 Wiley-Liss, Inc.

  13. Formation and texture of Bi-2223 phase during sintering in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Lu, X.Y.; Nagata, A.; Watanabe, K.; Nojima, T.; Sugawara, K.; Hanada, S.; Kamada, S


    The formation and texture of Bi-2223 phase during sintering in high magnetic fields were investigated. Samples contained in silver crucibles were sintered at different temperatures from 835 to 860 deg. C for 120 h in a vertical tube furnace installed in a solenoid-type superconducting magnet. A vertical magnetic field, H{sub a} of 10 T can be applied parallel to the long axis of the furnace. It has been found that the mixed structures of the Bi-2223 and the Bi-2212 grains with their c-axis parallel to the magnetic field are formed in samples sintered at 850-855 deg. C in 10 T magnetic field. Below 845 deg. C sintering in 10 T, a high proportion of Bi-2223 phase is obtained, however no preferred orientation is observed. It is suggested that a liquid phase is important for the formation of the textured structure in magnetic fields.

  14. Effect of very high magnetic field on the optical properties of firefly light emitter oxyluciferin

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Weihang; Nakamura, Daisuke [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Wang, Yu [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences (China); Mochizuki, Toshimitsu [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, 2-2-9 Machiike-dai, Koriyama, Fukushima 963-0215 (Japan); Akiyama, Hidefumi [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Takeyama, Shojiro, E-mail: [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)


    Magnetic field effect on enzymatic reactions is under intensive study in the past decades. Recently, it was reported that firefly bioluminescence was suppressed and red-shifted significantly when exposed to external magnetic field. However in this work, by means of selective excitation, we confirmed that emission properties of firefly light emitter “oxyluciferin” are completely immune to external magnetic field of up to 53 T. These findings pose strong contrast to existing relevant results. Potential reasons for the discrepancies found and the underlying physics towards the understanding of firefly bioluminescence were discussed. - Highlights: • Effect of ultra-high magnetic field on the optical properties of firefly light emitter oxyluciferin was reported. • Emission properties of oxyluciferin were confirmed to be immune to external high magnetic fields up to 53 T. • .Potential reasons for the discrepancies between our results and previous reports and the underlying physics were discussed.

  15. High sensitive LPFG magnetic field sensor based on dual-peak resonance (United States)

    Gu, Zhengtian; Ling, Qiang; Lan, Jinlong; Gao, Kan


    A high sensitivity magnetic field sensor based on magnetic-fluid-clad LPFG structure with dual peak resonance is presented and experimentally investigated. Based on coupled mode theory, the sensing principle of this sensor is originated from the sensibility of the dual peak based LPFG to the environment refractive index. In experiment, a dual peak interval change was available to 38 nm with a magnetic field strength varying from 0 to 12 mT when the temperature was 17.3 °C, and the dual peak interval displays a cubic polynomial dependence with the magnetic field strength at the low field regime. The sensitivity of this sensor to the magnetic field can be available to 4.08 nm/mT, and it is one order and two orders of magnitude higher than that of the sensors based on MSM and SMS fiber structure, respectively. The novel sensor has many advantages of simple technology, structure stability and high sensitivity.

  16. High field septum magnet using a superconducting shield for the Future Circular Collider

    CERN Document Server



    A zero-field cooled superconducting shield is proposed to realize a high-field (3–4 T) septum magnet for the Future Circular Collider hadron-hadron (FCC-hh) ring. Three planned prototypes using different materials and technical solutions are presented, which will be used to evaluate the feasibility of this idea as a part of the FCC study. The numerical simulation methods are described to calculate the field patterns around such a shield. A specific excitation current configuration is presented that maintains a fairly homogeneous field outside of a rectangular shield in a wide range of field levels from 0 to 3 Tesla. It is shown that a massless septum configuration (with an opening in the shield) is also possible and gives satisfactory field quality with realistic superconducting material properties.

  17. Early Time Dynamics of Gluon Fields in High Energy Nuclear Collisions


    Kapusta, Joseph I.; Chen, Guangyao; Fries, Rainer J.; Li, Yang


    Nuclei colliding at very high energy create a strong, quasi-classical gluon field during the initial phase of their interaction. We present an analytic calculation of the initial space-time evolution of this field in the limit of very high energies using a formal recursive solution of the Yang-Mills equations. We provide analytic expressions for the initial chromo-electric and chromo-magnetic fields and for their energy-momentum tensor. In particular, we discuss event-averaged results for ene...

  18. Comparative High Field Magneto-transport Of Rare Earth Oxypnictides With Maximum Transition Temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Balakirev, Fedor F [Los Alamos National Laboratory; Migliori, A [MPA-NHMFL; Riggs, S [NHMFL-FSU; Hunte, F [NHMFL-FSU; Gurevich, A [NHMFL-FSU; Larbalestier, D [NHMFL-FSU; Boebinger, G [NHMFL-FSU; Jaroszynski, J [NHMFL-FSU; Ren, Z [CHINA; Lu, W [CHINA; Yang, J [CHINA; Shen, X [CHINA; Dong, X [CHINA; Zhao, Z [CHINA; Jin, R [ORNL; Sefat, A [ORNL; Mcguire, M [ORNL; Sales, B [ORNL; Christen, D [ORNL; Mandrus, D [ORNL


    We compare magnetotransport of the three iron-arsenide-based compounds ReFeAsO (Re=La, Sm, Nd) in very high DC and pulsed magnetic fields up to 45 and 54 T, respectively. Each sample studied exhibits a superconducting transition temperature near the maximum reported to date for that particular compound. While high magnetic fields do not suppress the superconducting state appreciably, the resistivity, Hall coefficient, and critical magnetic fields, taken together, suggest that the phenomenology and superconducting parameters of the oxypnictide superconductors bridges the gap between MgB{sub 2} and YBCO.

  19. The Investigation of Field Plate Design in 500 V High Voltage NLDMOS

    Directory of Open Access Journals (Sweden)

    Donghua Liu


    Full Text Available This paper presents a 500 V high voltage NLDMOS with breakdown voltage (VBD improved by field plate technology. Effect of metal field plate (MFP and polysilicon field plate (PFP on breakdown voltage improvement of high voltage NLDMOS is studied. The coeffect of MFP and PFP on drain side has also been investigated. A 500 V NLDMOS is demonstrated with a 37 μm drift length and optimized MFP and PFP design. Finally the breakdown voltage 590 V and excellent on-resistance performance (Rsp = 7.88 ohm * mm2 are achieved.

  20. Determining of the electric field strength using high frequency broadband measurements


    Vulević, Branislav D.


    Exposure of humans to electromagnetic fields of high frequency (above 100 kHz), i.e. radiofrequency radiation from the modern wireless systems, today inevitable is. The purpose of this paper is to highlight the importance of broadband measurements of the electric field of high frequency in order to fast and reliable assessment of human exposure. A practical method of ‘in situ’ measurement the electric field intensity which is related to the frequency range of 3 MHz to 18 GHz, is provided.

  1. High temperature study of flexible silicon-on-insulator fin field-effect transistors

    KAUST Repository

    Diab, Amer El Hajj


    We report high temperature electrical transport characteristics of a flexible version of the semiconductor industry\\'s most advanced architecture: fin field-effect transistor on silicon-on-insulator with sub-20 nm fins and high-κ/metal gate stacks. Characterization from room to high temperature (150 °C) was completed to determine temperature dependence of drain current (Ids), gate leakage current (Igs), transconductance (gm), and extracted low-field mobility (μ0). Mobility degradation with temperature is mainly caused by phonon scattering. The other device characteristics show insignificant difference at high temperature which proves the suitability of inorganic flexible electronics with advanced device architecture.

  2. A carbon nanotube field emission cathode with high current density and long-term stability

    Energy Technology Data Exchange (ETDEWEB)

    Calderon-Colon, Xiomara; Zhou, Otto [Curriculum in Applied Science and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States); Geng Huaizhi; Gao Bo [Xintek, Incorporated, 7020 Kit Creek Road, Research Triangle Park, NC (United States); An Lei; Cao Guohua [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (United States)


    Carbon nanotube (CNT) field emitters are now being evaluated for a wide range of vacuum electronic applications. However, problems including short lifetime at high current density, instability under high voltage, poor emission uniformity, and pixel-to-pixel inconsistency are still major obstacles for device applications. We developed an electrophoretic process to fabricate composite CNT films with controlled nanotube orientation and surface density, and enhanced adhesion. The cathodes have significantly enhanced macroscopic field emission current density and long-term stability under high operating voltages. The application of this CNT electron source for high-resolution x-ray imaging is demonstrated.

  3. Prediction model of sinoatrial node field potential using high order partial least squares. (United States)

    Feng, Yu; Cao, Hui; Zhang, Yanbin


    High order partial least squares (HOPLS) is a novel data processing method. It is highly suitable for building prediction model which has tensor input and output. The objective of this study is to build a prediction model of the relationship between sinoatrial node field potential and high glucose using HOPLS. The three sub-signals of the sinoatrial node field potential made up the model's input. The concentration and the actuation duration of high glucose made up the model's output. The results showed that on the premise of predicting two dimensional variables, HOPLS had the same predictive ability and a lower dispersion degree compared with partial least squares (PLS).

  4. Sampling of high amounts of bioaerosols using a high-volume electrostatic field sampler

    DEFF Research Database (Denmark)

    Madsen, A. M.; Sharma, Anoop Kumar


    and 315 mg dust (net recovery of the lyophilized dust) was sampled during a period of 7 days, respectively. The sampling rates of the electrostatic field samplers were between 1.34 and 1.96 mg dust per hour, the value for the Gravikon was between 0.083 and 0.108 mg dust per hour and the values for the GSP...

  5. Transport Jc Measurements of HTS Conductors under High Magnetic Field at LNCMI (United States)

    Chaud, Xavier; Debray, François; Mossang, Eric; Tixador, Pascal; Rey, Jean-Michel; Lecrevisse, Thibault; Bruzek, Christian-Eric

    The LNCMI, the national French high magnetic field facility, provides high fields generated mainly by resistive magnets. Because of the forecast increasing price of electricity, LNCMI has a strong incentive to participate to the development and characterizations of HTS conductors in view of their use for the generation of strong field. Latest YBCO coated conductors have improved properties showing a great potential with that respect, without excluding Bi2212 and MgB2 for particular cases. We present the existing set-up to measure short straight or VAMAS type coil samples at variable temperature and high field up to 30 T, and some measurements obtained on different HTS conductors, Bi2212 round wires and YBCO coated conductors. We also report on the first results obtained at 18 T with a pancake coil made of commercial YBCO coated conductor tapes on a newly developed solenoid test bench.

  6. High magnetic field science and its application in the United States current status and future directions

    CERN Document Server

    National Research Council of the National Academies


    The Committee to Assess the Current Status and Future Direction of High Magnetic Field Science in the United States was convened by the National Research Council in response to a request by the National Science Foundation. This report answers three questions: (1) What is the current state of high-field magnet science, engineering, and technology in the United States, and are there any conspicuous needs to be addressed? (2) What are the current science drivers and which scientific opportunities and challenges can be anticipated over the next ten years? (3) What are the principal existing and planned high magnetic field facilities outside of the United States, what roles have U.S. high field magnet development efforts played in developing those facilities, and what potentials exist for further international collaboration in this area? A magnetic field is produced by an electrical current in a metal coil. This current exerts an expansive force on the coil, and a magnetic field is "high" if it challenges the str...

  7. 27 Al MAS NMR Studies of HBEA Zeolite at Low to High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Jian Z.; Wan, Chuan; Vjunov, Aleksei; Wang, Meng; Zhao, Zhenchao; Hu, Mary Y.; Camaioni, Donald M.; Lercher, Johannes A.


    27Al single pulse (SP) MAS NMR spectra of HBEA zeolites with high Si/Al ratios of 71 and 75 were obtained at three magnetic field strengths of 7.05, 11.75 and 19.97 T. High field 27Al MAS NMR spectra acquired at 19.97 T show significantly improved spectral resolution, resulting in at least two well-resolved tetrahedral-Al NMR peaks. Based on the results obtained from 27Al MAS and MQMAS NMR acquired at 19.97 T, four different quadrupole peaks are used to deconvolute the 27Al SP MAS spectra acquired at vari-ous fields by using the same set of quadrupole coupling constants, asymmetric parameters and relative integrated peak intensities for the tetrahedral Al peaks. The line shapes of individual peaks change from typical quadrupole line shape at low field to essentially symmetrical line shapes at high field. We demonstrate that for fully hydrated HBEA zeolites the effect of second order quadrupole interaction can be ignored and quantitative spectral analysis can be performed by directly fitting the high field spectra using mixed Gaussian/Lorentzian line shapes. Also, the analytical steps described in our work allow direct assignment of spectral intensity to individual Al tetrahedral sites (T-sites) of zeolite HBEA. Finally, the proposed concept is suggested generally applicable to other zeo-lite framework types, thus, allowing a direct probing of Al distributions by NMR spectroscopic methods in zeolites with high confi-dence.

  8. High field magnetic behavior in Boron doped Fe{sub 2}VAl Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Venkatesh, Ch., E-mail: [Department of Physics, Indian Institute of Technology, Kharagpur (India); DCMP & MS, Tata Institute of Fundamental Research, Mumbai (India); Vasundhara, M., E-mail: [Materials Science and Technology Division, National Institute for Interdisciplinary Science and Technology, CSIR, Trivandrum 695019 (India); Srinivas, V. [Department of Physics, Indian Institute of Technology, Chennai (India); Rao, V.V. [Cryogenic Engineering Centre, Indian Institute of Technology, Kharagpur (India)


    We have investigated the magnetic behavior of Fe{sub 2}VAl{sub 1−x}B{sub x} (x=0, 0.03, 0.06 and 0.1) alloys under high temperature and high magnetic field conditions separately. Although, the low temperature DC magnetization data for the alloys above x>0 show clear magnetic transitions, the zero field cooled (ZFC) and field cooled (FC) curves indicate the presence of spin cluster like features. Further, critical exponent (γ) deduced from the initial susceptibility above the T{sub c}, does not agree with standard models derived for 3 dimensional long range magnetic systems. The deviation in γ values are consistent with the short range magnetic nature of these alloys. We further extend the analysis of magnetic behavior by carrying the magnetization measurements at high temperatures and high magnetic fields distinctly. We mainly emphasize the following observations; (i) The magnetic hysteresis loops show sharp upturns at lower fields even at 900 K for all the alloys. (ii) High temperature inverse susceptibility do not overlap until T=900 K, indicating the persistent short range magnetic correlations even at high temperatures. (iii) The Arrott's plot of magnetization data shows spontaneous moment (M{sub S}) for the x=0 alloy at higher magnetic fields which is absent at lower fields (<50 kOe), while the Boron doped samples show feeble M{sub S} at lower fields. The origin of this short range correlation is due to presence of dilute magnetic heterogeneous phases which are not detected from the X-ray diffraction method. - Highlights: • Short range magnetic character has been confirmed by the critical exponents analysis. • Magnetoresistace is about −14% with non-saturating tendency even at 150 kOe for Fe{sub 2}VAl alloy. • Boron doped Fe{sub 2}VAl alloys show a weak magnetism even at T=900 K.

  9. Megagauss field generation for high-energy-density plasma science experiments.

    Energy Technology Data Exchange (ETDEWEB)

    Rovang, Dean Curtis; Struve, Kenneth William; Porter, John Larry Jr.


    There is a need to generate magnetic fields both above and below 1 megagauss (100 T) with compact generators for laser-plasma experiments in the Beamlet and Petawatt test chambers for focused research on fundamental properties of high energy density magnetic plasmas. Some of the important topics that could be addressed with such a capability are magnetic field diffusion, particle confinement, plasma instabilities, spectroscopic diagnostic development, material properties, flux compression, and alternate confinement schemes, all of which could directly support experiments on Z. This report summarizes a two-month study to develop preliminary designs of magnetic field generators for three design regimes. These are, (1) a design for a relatively low-field (10 to 50 T), compact generator for modest volumes (1 to 10 cm3), (2) a high-field (50 to 200 T) design for smaller volumes (10 to 100 mm3), and (3) an extreme field (greater than 600 T) design that uses flux compression. These designs rely on existing Sandia pulsed-power expertise and equipment, and address issues of magnetic field scaling with capacitor bank design and field inductance, vacuum interface, and trade-offs between inductance and coil designs.

  10. GravityCam: ground-based wide-field high-resolution imaging and high-speed photometry (United States)

    Dominik, Martin; Mackay, Craig; Steele, Iain; Snodgrass, Colin; Hirsch, Michael; Gråe Jørgensen, Uffe; Hundertmark, Markus; Rebolo, Rafael; Horne, Keith; Bridle, Sarah; Sicardy, Bruno; Bramich, Daniel; Alsubai, Khalid


    The image blurring by the Earth's atmosphere generally poses a substantial limitation to ground-based observations. While opportunities in space are scarce, lucky imaging can correct over a much larger patch of sky and with much fainter reference stars. We propose the first of a new kind of versatile instruments, "GravityCam", composed of ~100 EMCCDs, that will open up two entirely new windows to ground-based astronomy: (1) wide-field high-resolution imaging, and (2) wide-field high-speed photometry. Potential applications include (a) a gravitational microlensing survey going 4 magnitudes deeper than current efforts, and thereby gaining a factor 100 in mass at the same sensitivity, which means probing down to Lunar mass or even below, (b) extra-solar planet hunting via transits in galactic bulge fields, with high time resolution well-suited for transit timing variation studies, (c) variable stars in crowded fields, with sensitivity to very short periods, (d) asteroseismology with many bright stars in one pointing, (e) serendipitous occultations of stars by small solar system bodies, giving access to the small end of the Kuiper Belt size distribution and potentially leading to the first detection of true Oort cloud objects, while predicted occultations at high time resolution can reveal atmospheres, satellites, or rings, (f) general data mining of the high-speed variable sky (down to 40 ms cadence).

  11. Combined passive and active shimming for in vivo MR spectroscopy at high magnetic fields (United States)

    Juchem, Christoph; Muller-Bierl, Bernd; Schick, Fritz; Logothetis, Nikos K.; Pfeuffer, Josef


    The use of high magnetic fields increases the sensitivity and spectral dispersion in magnetic resonance spectroscopy (MRS) of brain metabolites. Practical limitations arise, however, from susceptibility-induced field distortions, which are increased at higher magnetic field strengths. Solutions to this problem include optimized shimming, provided that active, i.e., electronic, shimming can operate over a sufficient range. To meet our shim requirements, which were an order of magnitude greater than the active shim capacity of our 7 T MR system, we developed a combined passive and active shim approach. Simple geometries of ferromagnetic shim elements were derived and numerically optimized to generate a complete set of second-order spherical harmonic shim functions in a modular manner. The major goals of the shim design were maximization of shim field accuracy and ease of practical implementation. The theoretically optimized ferro-shim geometries were mounted on a cylindrical surface and placed inside the magnet bore, surrounding the subject's head and the RF coil. Passive shimming generated very strong shim fields and eliminated the worst of the field distortions, after which the field was further optimized by flexible and highly accurate active shimming. Here, the passive-shimming procedure was first evaluated theoretically, then applied in phantom studies and subsequently validated for in vivo1H MRS in the macaque visual cortex. No artifacts due to the passive shim setup were observed; adjustments were reproducible between sessions. The modularity and the reduction to two pieces per shim term in this study is an important simplification that makes the method applicable also for passive shimming within single sessions. The feasibility of very strong, flexible and high-quality shimming via a combined approach of passive and active shimming is of great practical relevance for MR imaging and spectroscopy at high field strengths where shim power is limited or where

  12. [Effect of high-intensity alternating magnetic field 
on viscosity of sheep blood]. (United States)

    Tao, Pengxian; Wu, Xiangyang; Zhao, Lingzhi; Wang, Feng; Xia, Qi; Peng, Yan; Gao, Bingren


    To explore the changes of blood viscosity in high-intensity alternating magnetic field and the mechanisms.
 Methods: Five adult sheep were randomly selected and the blood samples were placed in high-intensity alternating magnetic field. Before and after exposure, the blood samples were taken and divided into 2 groups: a control group and a magnetic field group. The blood rheology and transmission electron microscopy (TEM) were performed.
 Results: Compared to the control group, the high shear viscosity of whole blood was decreased in the magnetic field group (P<0.05); the whole blood low shear viscosity and plasma viscosity were also decreased (both P<0.01). TEM showed the changes in red blood cell morphology and the double concave disc curvature. The radian of double concave disc and cell volume in the magnetic field group was larger than those in the control group.
 Conclusion: The high intensity alternating magnetic field may affect the distribution of surface charge and molecular current in blood cells, which in turn decrease the aggregation of cells and the blood viscosity.

  13. Low-field vortex dynamics in various high-Tc thin films

    Indian Academy of Sciences (India)

    Vortex dynamics; flux creep; high temperature superconductor; thin film; ac susceptibil- ity. PACS Nos 74.72.-h; 74.76.Bz; 74.60.Ge. 1. Introduction. Despite the predictions of fundamental new physics and intriguing vortex phenomena in high-Tc materials at very low fields [1–6], a vast majority of experimental vortex dynam-.

  14. High Performance Ambipolar Field-Effect Transistor of Random Network Carbon Nanotubes

    NARCIS (Netherlands)

    Bisri, Satria Zulkarnaen; Gao, Jia; Derenskyi, Vladimir; Gomulya, Widianta; Iezhokin, Igor; Gordiichuk, Pavlo; Herrmann, Andreas; Loi, Maria Antonietta


    Ambipolar field-effect transistors of random network carbon nanotubes are fabricated from an enriched dispersion utilizing a conjugated polymer as the selective purifying medium. The devices exhibit high mobility values for both holes and electrons (3 cm(2)/V.s) with a high on/off ratio (10(6)). The

  15. A new hybrid protection system for high-field superconducting magnets

    NARCIS (Netherlands)

    Ravaioli, Emanuele; Datskov, V.I.; Kirby, G.; ten Kate, Herman H.J.; Verweij, A.P.


    The new generation of high-field superconducting accelerator magnets poses a challenge concerning the protection of the magnet coil in the case of a quench. The very high stored energy per unit volume requires a fast and efficient quench heating system in order to avoid damage due to overheating. A

  16. High Field Linear Magnetoresistance Sensors with Perpendicular Anisotropy L10-FePt Reference Layer

    Directory of Open Access Journals (Sweden)

    X. Liu


    Full Text Available High field linear magnetoresistance is an important feature for magnetic sensors applied in magnetic levitating train and high field positioning measurements. Here, we investigate linear magnetoresistance in Pt/FePt/ZnO/Fe/Pt multilayer magnetic sensor, where FePt and Fe ferromagnetic layers exhibit out-of-plane and in-plane magnetic anisotropy, respectively. Perpendicular anisotropy L10-FePt reference layer with large coercivity and high squareness ratio was obtained by in situ substrate heating. Linear magnetoresistance is observed in this sensor in a large range between +5 kOe and −5 kOe with the current parallel to the film plane. This L10-FePt based sensor is significant for the expansion of linear range and the simplification of preparation for future high field magnetic sensors.

  17. Feasibility study of cellulose nanofiber alignment by high DC magnetic field (United States)

    Kim, Hyun Chan; Kang, Jinmo; Park, Jung Ho; Akther, Asma; Kim, Jaehwan


    Cellulose nanofiber (CNF) has taken center stage as a future material with high specific strength, specific modulus and environmentally friendly behavior. However, natural CNFs are so randomly oriented that once CNFs are used in composites, their mechanical properties are not the same as expected from the CNFs. Thus, CNF alignment is important in fabricating composites and fibers. Interestingly, CNFs have negative diamagnetic anisotropy. In the presence of high magnetic field, the fiber axis of CNF can be aligned perpendicular to the applied field. This paper reports a preliminary study of CNF alignment by high dc magnetic field. The CNF emulsion is prepared by aqueous counter collision method and centrifugation. The CNF emulsion is placed in the high dc magnet and cured for a certain time. The alignment of CNF is investigated by scanning electron microscopy, mechanical tensile test.

  18. Microstructure and superconducting properties of Bi-2223/Ag tapes fabricated in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Lu, X Y [Faculty of Engineering and Resource Science, Akita University, Akita 010-8502 (Japan); Nagata, A [Faculty of Engineering and Resource Science, Akita University, Akita 010-8502 (Japan); Sugawara, K [Faculty of Engineering and Resource Science, Akita University, Akita 010-8502 (Japan); Watanabe, K [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Nojima, T [Center for Low Temperature Science, Tohoku University, Sendai 980-8577 (Japan)


    The microstructure and superconducting properties of Bi-2223/Ag tapes fabricated in high magnetic fields were investigated. The results show that the partial-melting temperature has influence on the formation of Bi-2223 phase and the J{sub c}. The optimum partial-melting temperature is 855{sup 0}C. The magnetic field during sintering at 830{sup 0}C has no influence on the formation of Bi-2223 phase and the J{sub c}. However, the magnetic field during partial-melting process has obvious influence on the formation of Bi-2223 phase and the J{sub c}. The tape partially melted with 10 T magnetic field shows stronger c-axis alignment of Bi-2223 phase and higher J{sub c}value than that partially melted without magnetic field.

  19. Impact of Increased Football Field Width on Player High-Speed Collision Rate. (United States)

    Joseph, Jacob R; Khalsa, Siri S; Smith, Brandon W; Park, Paul


    High-acceleration head impact is a known risk for mild traumatic brain injury (mTBI) based on studies using helmet accelerometry. In football, offensive and defensive players are at higher risk of mTBI due to increased speed of play. Other collision sport studies suggest that increased playing surface size may contribute to reductions in high-speed collisions. We hypothesized that wider football fields lead to a decreased rate of high-speed collisions. Computer football game simulation was developed using MATLAB. Four wide receivers were matched against 7 defensive players. Each offensive player was randomized to one of 5 typical routes on each play. The ball was thrown 3 seconds into play; ball flight time was 2 seconds. Defensive players were delayed 0.5 second before reacting to ball release. A high-speed collision was defined as the receiver converging with a defensive player within 0.5 second of catching the ball. The simulation counted high-speed collisions for 1 team/season (65 plays/game for 16 games/season = 1040 plays/season) averaged during 10 seasons, and was validated against existing data using standard field width (53.3 yards). Field width was increased in 1-yard intervals up to 58.3 yards. Using standard field width, 188 ± 4 high-speed collisions were seen per team per season (18% of plays). When field width increased by 3 yards, high-speed collision rate decreased to 135 ± 3 per team per season (28% decrease; P football field width can lead to substantial decline in high-speed collisions, with potential for reducing instances of mTBI in football players. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Natural geochemical analogues of the near field of high-level nuclear waste repositories

    Energy Technology Data Exchange (ETDEWEB)

    Apps, J.A. [Lawrence Berkeley Lab., CA (United States)


    United States practice has been to design high-level nuclear waste (HLW) geological repositories with waste densities sufficiently high that repository temperatures surrounding the waste will exceed 100{degrees}C and could reach 250{degrees}C. Basalt and devitrified vitroclastic tuff are among the host rocks considered for waste emplacement. Near-field repository thermal behavior and chemical alteration in such rocks is expected to be similar to that observed in many geothermal systems. Therefore, the predictive modeling required for performance assessment studies of the near field could be validated and calibrated using geothermal systems as natural analogues. Examples are given which demonstrate the need for refinement of the thermodynamic databases used in geochemical modeling of near-field natural analogues and the extent to which present models can predict conditions in geothermal fields.

  1. Hydrodynamic analysis of the high electric fields and double layers in expanding inhomogeneous plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Goldsworthy, M.P.; Green, F.; Lalousis, P.; Stening, R.J.; Eliezer, S.; Hora, H.


    A genuine two-fluid model of plasmas with collisions permits the calculation of dynamic electric fields and double layers inside of plasmas including oscillations and damping. For the first time, a macroscopic model for coupling of electromagnetic and Langmuir waves was achieved with realistic damping. Starting points were laser-produced plasmas showing very high dynamic electric fields in nonlinear force-produced cavitons and inverted layers, in agreement with experiments. Applications for any inhomogeneous plasma as in laboratory or in astrophysical plasmas can then be followed up by a transparent hydrodynamic description. The authors find the rotation of plasmas in magnetic fields and a new second harmonic resonance. Explanation of inverted double layers, second harmonic emission from laser-produced plasmas, and laser acceleration of charged particles by the very high fields of the double layers is given.

  2. Landau level splitting in Cd3As2 under high magnetic fields. (United States)

    Cao, Junzhi; Liang, Sihang; Zhang, Cheng; Liu, Yanwen; Huang, Junwei; Jin, Zhao; Chen, Zhi-Gang; Wang, Zhijun; Wang, Qisi; Zhao, Jun; Li, Shiyan; Dai, Xi; Zou, Jin; Xia, Zhengcai; Li, Liang; Xiu, Faxian


    Three-dimensional topological Dirac semimetals (TDSs) are a new kind of Dirac materials that exhibit linear energy dispersion in the bulk and can be viewed as three-dimensional graphene. It has been proposed that TDSs can be driven to other exotic phases like Weyl semimetals, topological insulators and topological superconductors by breaking certain symmetries. Here we report the first transport experiment on Landau level splitting in TDS Cd3As2 single crystals under high magnetic fields, suggesting the removal of spin degeneracy by breaking time reversal symmetry. The detected Berry phase develops an evident angular dependence and possesses a crossover from non-trivial to trivial state under high magnetic fields, a strong hint for a fierce competition between the orbit-coupled field strength and the field-generated mass term. Our results unveil the important role of symmetry breaking in TDSs and further demonstrate a feasible path to generate a Weyl semimetal phase by breaking time reversal symmetry.

  3. A permanent magnet device for producing variable high magnetic field in three dimensions

    CERN Document Server

    Hwang, C S; Chang, P C; Chen, H H; Chang, C H; Huang Ming Hsiung


    By combining four parallel rows of permanent magnet blocks, a magnet device that can produce variable high magnetic field in three dimensions has been designed. In this device, the magnetic field direction and strength can be varied by shifting the four rows along their longitudinal direction and by varying the magnet gap between the top and bottom rows. With a magnet gap of 10 mm, the magnetic field strength at the center of the device is about 1.4 T along the longitudinal and two transverse directions. This device can be utilized in X-ray magnetic circular dichroism and X-ray magnetic linear dichroism experiments as well as in other applications where a variable high magnetic field in three dimensions is needed.

  4. Magnetic and Magneto-Optical Properties in Paramagnetic NdF3 Under High Magnetic Field (United States)

    Wang, Wei; Liu, Gong-Qiang


    In this paper, we first theoretically report the magnetic and magneto-optical properties in paramagnetic media under high external magnetic field. Considering the action of the external magnetic field He and indirect exchange interaction Hv, the characteristic of the magnetic saturation and the property of the Faraday rotation to be nonlinear with external magnetic field are presented in paramagnetic NdF3. In terms of our theory, the indirect exchange interaction plays an important role in the magnetization M and the Faraday rotation θ in NdF3 under high external magnetic field. The theory is in good agreement with experimental results. On the other hand, a reasonable explanation for the temperature dependence of the ratio of the Verdet constant to the magnetic susceptibility V/χ is obtained.

  5. A thermo-field bimetal deformable mirror for wavefront correction in high power lasers (United States)

    Huang, L.; Xue, Q.; Yan, P.; Gong, M. L.; Li, T. H.; Feng, Z. X.; Ma, X. K.


    A novel thermo-field bimetal deformable mirror (TBDM) is proposed, which is mainly composed of a face plate, a base plate and some thermal elements, such as thermoelectric coolers (TECs). The TBDM utilizes the continuous thermal field to bend the face plate, via the TECs heating or cooling. A prototype is described, and the first results are presented. The simplicity and ultra-low cost make the TBDM attractive in correcting aberrations in high power lasers.

  6. High-field magnetic transitions in the R sub 2 T sub 17 compounds

    Energy Technology Data Exchange (ETDEWEB)

    Franse, J.J.M.; Sinnema, S. (Amsterdam Univ. (NL). Natuurkundig Lab.); Radwanski, R.J. (University of Mining and Metallurgy, Krakow (PL). Solid State Physics Dept.)


    In the past few years high-field magnetic transitions have been extensively studied for a number of single crystalline samples of the R{sub 2}T{sub 17} series (R = rare earths, T = Co or Fe). The transitions observed in Ho{sub 2}Co{sub 17} and Dy{sub 2}Co{sub 17} are exchange-driven transitions connected with a breaking of the ferromagnetic structure and only occur in applied fields above 20 T.

  7. Influence of atoms with high ionization potentials on a discharge in crossed E and H fields

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, A.A.; Timchenko, N.N.; Khripunov, B.I.; Shapkin, V.V.


    We consider processes connected with the separation of elements in a fully ionized plasma centrifuge with a plasma gun discharge in crossed E and H fields. We analyze the influence of atoms with high ionization potentials on the separation parameters, the value of the transverse ion current, and the separation coefficient. We not the role played by the radial electric field in the gas ionization processes and in the resulting growth of ion acoustic instabilities.

  8. The spontaneous generation of magnetic fields at high temperature in a supersymmetric theory


    Demchik, V. I.; Skalozub, V. V.


    The spontaneous generation of magnetic and chromomagnetic fields at high temperature in the minimal supersymmetric standard model (MSSM) is investigated. The consistent effective potential including the one-loop and the daisy diagrams of all bosons and fermions is calculated and the magnetization of the vacuum is observed. The mixing of the generated fields due to the quark and s-quark loop diagrams and the role of superpartners are studied in detail. It is found that the contribution of thes...

  9. Nematic ordering in pyrochlore antiferromagnets: high-field phase of chromium spinel oxides


    Takata, Emika; Momoi, Tsutomu; Oshikawa, Masaki


    Motivated by recent observation of a new high field phase near saturation in chromium spinels $A$Cr$_2$O$_4$ ($A=$ Zn, Cd, Hg), we study the $S = 3/2$ pyrochlore Heisenberg antiferromagnet with biquadratic interactions. Magnon instability analysis at the saturation field reveals that a very small biquadratic interaction can induce magnon pairing in pyrochlore antiferromagnets, which leads to the emergence of a ferro-quadrupolar phase, or equivalently a spin nematic phase, below the saturation...

  10. High throughput phenotyping to accelerate crop breeding and monitoring of diseases in the field. (United States)

    Shakoor, Nadia; Lee, Scott; Mockler, Todd C


    Effective implementation of technology that facilitates accurate and high-throughput screening of thousands of field-grown lines is critical for accelerating crop improvement and breeding strategies for higher yield and disease tolerance. Progress in the development of field-based high throughput phenotyping methods has advanced considerably in the last 10 years through technological progress in sensor development and high-performance computing. Here, we review recent advances in high throughput field phenotyping technologies designed to inform the genetics of quantitative traits, including crop yield and disease tolerance. Successful application of phenotyping platforms to advance crop breeding and identify and monitor disease requires: (1) high resolution of imaging and environmental sensors; (2) quality data products that facilitate computer vision, machine learning and GIS; (3) capacity infrastructure for data management and analysis; and (4) automated environmental data collection. Accelerated breeding for agriculturally relevant crop traits is key to the development of improved varieties and is critically dependent on high-resolution, high-throughput field-scale phenotyping technologies that can efficiently discriminate better performing lines within a larger population and across multiple environments. Copyright © 2017. Published by Elsevier Ltd.


    Directory of Open Access Journals (Sweden)



    Full Text Available Introduction: The goal of this study was to evaluate the relationship between occupational exposure to extremely low frequency (ELF electromagnetic fields and risk of Hematological changes among workers at High- voltage substations. This is a case - control study. In the present study 79 worker exposed to electromagetic fields (EMFs were compared to 50 control subjects who were not occupationaly exposed to EMFs. Methods: To measurement the levels of exposure to Lf electric and magnetic fields the strength of electric and magnetic field was determined by Dosimetric method. Worker"s blood samples were collected and analyzed for identification of leukemia and other abnormalities. Questionnaire and physical examination were used to study the effects of ELF fields on worker"s health. Measurements showed a high strength of ELF fields at the work places i.e. Results: Mean value of RBC and Hematocrit decreased significantly among exposed workers compared to controls (P < 0.05, but MCV, MCH and MCHC increased. The value of Neutrophiles increased but Lymphocytes decreased significantly among workers considering their workhistory (P < 0.05. Discussion: Moreover, tow leukemics (ALL, AML and ten hypocromic anemias were found. In conclusion study groups are similar in personal characteristics, the difference in RBC, MCV, MCH has to attributed to ELF fields.

  12. Highly flexible and robust N-doped SiC nanoneedle field emitters

    KAUST Repository

    Chen, Shanliang


    Flexible field emission (FE) emitters, whose unique advantages are lightweight and conformable, promise to enable a wide range of technologies, such as roll-up flexible FE displays, e-papers and flexible light-emitting diodes. In this work, we demonstrate for the first time highly flexible SiC field emitters with low turn-on fields and excellent emission stabilities. n-Type SiC nanoneedles with ultra-sharp tips and tailored N-doping levels were synthesized via a catalyst-assisted pyrolysis process on carbon fabrics by controlling the gas mixture and cooling rate. The turn-on field, threshold field and current emission fluctuation of SiC nanoneedle emitters with an N-doping level of 7.58 at.% are 1.11 V μm-1, 1.55 V μm-1 and 8.1%, respectively, suggesting the best overall performance for such flexible field emitters. Furthermore, characterization of the FE properties under repeated bending cycles and different bending states reveal that the SiC field emitters are mechanically and electrically robust with unprecedentedly high flexibility and stabilities. These findings underscore the importance of concurrent morphology and composition controls in nanomaterial synthesis and establish SiC nanoneedles as the most promising candidate for flexible FE applications. © 2015 Nature Publishing Group All rights reserved.

  13. A Novel Dual-Electrode Plug to Achieve Intensive Electric Field for High Performance Ignition

    Directory of Open Access Journals (Sweden)

    Chih-Lung Shen


    Full Text Available A thorough analysis of electric field is carried out so as to verify that a novel dual-electrode plug can build intensive electric field and can improve the main drawbacks of feeble electric field and low ignition efficiency of the traditional plug. With intensive electric field, the proposed novel plug can achieve high performance ignition, resulting in fuel saving and exhaust reduction. Gauss law is applied for electric field analysis to show that intensive electric field can be built by the novel plug. Then, according to Faraday law a lower-voltage ignition feature accomplished by the plug is discussed. Compared with traditional plug, the novel dual-electrode plug has the following advantages. (1 Much higher energy density is built between the plug electrodes, lowering ignition voltage requirement. (2 Electromagnetic interference (EMI problem caused by high ignition voltage is readily resolved. (3 Ignition time delay can be improved. (4 The feature to save fuel consuming is achieved. (5 The exhaust of CO and HC is reduced significantly. Practical measurements are fulfilled to validate the electric field analysis and to demonstrate the features of the proposed dual-electrode plug.

  14. Determination of exposure to electric fields in extra high voltage substations. (United States)

    Lövstrand, K G


    Electrophysical effects related to extra high voltage are surveyed for the determination of the exposure of personnel to electric fields in substations. It is concluded that the electric field strengths and the electrical discharges to the personnel are the important electrophysical factors. Instruments for measuring the field strength at grounded surfaces and at nonzero potentials were constructed. Results are presented of measurements with these instruments in substations. A dummy was used for the measurement of the distribution of capacitive currents to a man. The dummy can also be used for measuring the effectiveness of special shielding clothes.

  15. Features of the galactic magnetic field regarding deflections of ultra-high-energy cosmic rays

    Energy Technology Data Exchange (ETDEWEB)

    Wirtz, Marcus; Erdmann, Martin; Mueller, Gero; Urban, Martin [III. Physikalisches Institut A, RWTH Aachen University (Germany)


    Most recent models of the galactic magnetic field have been derived from Faraday rotation measurements and imply strong deflections even for ultra-high energy cosmic rays. We investigate the characteristics of the different field parametrizations and point out similarities and interesting features. Among them are extragalactic regions which are invisible for an Earth bound observation and the transition from diffuse to ballistic behaviour in the 1 EeV energy regime. Applying this knowledge to a directional analysis, there are indications for deflection patterns by the galactic magnetic field in cosmic ray arrival directions measured by the Pierre Auger Observatory.

  16. Mitigation of extremely low frequency magnetic fields from electrical installations in high-rise buildings

    Energy Technology Data Exchange (ETDEWEB)

    Burnett, John; Duyaping, Patrick [Hong Kong Polytechnic Univ., Dept. of Building Services Engineering, Kowloon, Hong Kong (China)


    The health impacts on people exposed to power line generated magnetic fields remains somewhat controversial. Under certain circumstances, such extremely low frequency (ELF) magnetic fields also arise in high-rise buildings in Hong Kong, causing interference with sensitive equipment, and with it concerns about the potential health impacts on affected persons. Due to a general lack of awareness electrical design and installation engineers rarely consider the issue. This paper discusses the problem of ELF fields generated by a building's electrical distribution system, and provides simplified analytical techniques that lead to practical solutions for eliminating interference problems as well as reducing concerns about health impacts. (Author)

  17. High field volume coil with unbalance current distribution for MRI applications of rodents (United States)

    Marrufo, O. R.; Hernández, J.; Rodríguez, A. O.


    The development of transceiver volume coils for high field MRI is still a very dynamic field of investigation and development Temnikov has been recently proposed a new volume coil design, similar to the to the gradiometer coil. It is also claimed that it is possible to individually tune it with a single chip capacitor. This motivated the development of a coil prototype based on this idea for whole-body MRI of rodents at 7 Tesla. Electromagnetic simulations of the RF field generated by this coil design were previously performed to study its properties. Electromagnetic simulations were also conducted for a standard birdcage coil with similar dimensions for fare comparison. In all numerical simulations, an unbalanced currents distribution was assumed by applying half the current intensity to designated legs. This coil design operated in the transceiver mode and was linear-driven. The coil size was manufactured to accommodate small rodents. Numerical simulations showed a field uniformity improvement of our coil over the standard birdcage coil. A popular birdcage coil was also constructed to compare their performances. Phantom and rat images were acquired for both volume coils to prove the viability of this coil design for high field MRI applications and standard spin echo pulse sequences Thus, these preliminary results make this coil design a good candidate for MRI and MRS applications of high magnetic fields.

  18. High performance field emission and Nottingham effect observed from carbon nanotube yarn (United States)

    Choi, Young Chul; Kang, Jun-Tae; Park, Sora; Go, Eunsol; Jeon, Hyojin; Kim, Jae-Woo; Jeong, Jin-Woo; Park, Kyung-Ho; Song, Yoon-Ho


    Vertically aligned CNTs were synthesized on a four inch wafer, followed by the preparation of a CNT yarn. The yarn emitter was found to have an extremely high field enhancement factor, which was confirmed to have originated from multi-stage effect. In addition to superb field emission characteristics, the energy exchange during field emission, called Nottingham effect, was observed from the CNT yarn emitter. A CNT yarn was attached to the thermistor whose resistance depends on temperature. Then, the change of resistance was monitored during the field emission, which enabled us to calculate the energy exchange. It was found that the observed heating originated from both Nottingham and Joule heating. Nottingham heating was dominant at low current region while Joule heating became larger contribution at high current region. Very large Nottingham region of up to 33.35 mA was obtained, which is due presumably to the high performance field emission characteristics of a CNT yarn. This is believed to be an important observation for developing reliable field emission devices with suppressed Joule heating effect.

  19. An optical setup for electric field measurements in MRI with high spatial resolution (United States)

    Reiss, Simon; Bitzer, Andreas; Bock, Michael


    Electric field measurements in the magnetic resonance (MR) imaging environment are important to assess potentially dangerous radio-frequency (RF) heating in the vicinity of metallic structures such as coils, implants or catheters. So far, E-field measurements have been performed with dipole antennas that lag of limited spatial resolution and which are difficult to use in the magnet bore as they interfere with the RF transmit field of the MRI system. In this work an electro-optic sensor is presented that utilizes the Pockels effect to measure the E-field in a clinical MR system with high spatial resolution. This sensor consists of dielectric materials only and thus, it only minimally influences the measured E-field distribution. A 10 m long flexible optical fiber connects the small sensor head to a remote processing unit where the optical signal is transformed into an electrical output signal. Spatially resolved qualitative E-field measurements were performed in a 1.5 T clinical MR system in the vicinity of metallic samples and an active tracking catheter with a resolution of up to 1 mm. The near-field pattern of a resonant U-shaped metallic sample was clearly identified and compared with numerical simulations. A more complex field behavior was found for the tracking catheter where strong E-field enhancements were observed at the distal tip and at its proximal part outside the phantom solution. Due to its sub-mm spatial resolution the optical sensor approach provides detailed insight into the complex and difficult to access field distributions close to implants and metallic structures and has turned out to be promising tool for MRI field and safety inspections.

  20. Effects of magnetic fields during high voltage live-line maintenance (United States)

    Göcsei, Gábor; Kiss, István, Dr; Németh, Bálint


    In case of transmission and distribution networks, extra low frequency (typically 50 or 60 Hz) electric and magnetic fields have to be taken into consideration separately from each other. Health effects have been documented from exposures to both types of fields. Magnetic fields are qualified as possibly carcinogenic to humans (category “2B”) by WHO's cancer research institute, International Agency for Research on Cancer (IARC), so it is essential to protect the workers against their harmful effects. During live-line maintenance (LLM) electric fields can be shielded effectively by different kinds of conductive clothing, which are enclosed metal surfaces acting as a Faraday-cage. In practice laboratory measurements also prove their efficiency, the required shielding ratio is above 99% by the related standard.. A set of measurements have proved that regular conductive clothing used against the electric fields cannot shield the magnetic fields effectively at all. This paper introduces the possible risks of LLM from the aspect of the health effects of magnetic fields. Although in this case the principle of shielding the electric fields cannot be applied, new considerations in equipment design and technology can be used as a possible solution. Calculations and simulations based on the data of the Hungarian transmission network - which represents the European grid as a part of ENTSO-E - and high-current laboratory measurement results also prove the importance of the topic.

  1. Practical aspects of spherical near-field antenna measurements using a high-order probe

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Pivnenko, Sergey; Nielsen, Jeppe Majlund


    Two practical aspects related to accurate antenna pattern characterization by probe-corrected spherical near-field antenna measurements with a high-order probe are examined. First, the requirements set by an arbitrary high-order probe on the scanning technique are pointed out. Secondly, a channel...... balance calibration procedure for a high-order dual-port probe with non-identical ports is presented, and the requirements set by this procedure for the probe are discussed....

  2. High-Beta, Improved Confinement Reversed-Field Pinch Plasmas at High Density

    Energy Technology Data Exchange (ETDEWEB)

    Wyman, M. [University of Wisconsin, Madison; Chapman, B. E. [University of Wisconsin, Madison; Ahn, J. W. [University of Wisconsin, Madison; Almagri, A. [University of Wisconsin, Madison; Anderson, J. [University of Wisconsin, Madison; Bonomo, F. [Consorzio RFX, Italy; Brower, D. L. [University of California, Los Angeles; Combs, Stephen Kirk [ORNL; Craig, D. [University of Wisconsin, Madison; Hartog, D. J. Den [University of Wisconsin, Madison; Deng, B. [University of California, Los Angeles; Ding, W. X. [University of California, Los Angeles; Ebrahimi, F. [University of Wisconsin, Madison; Ennis, D. [University of Wisconsin, Madison; Fiksel, G. [University of Wisconsin, Madison; Foust, Charles R [ORNL; Franz, P. [EURATOM / ENEA, Italy; Gangadhara, S. [University of Wisconsin, Madison; Goetz, J. [University of Wisconsin, Madison; O' Connell, R, [University of Wisconsin, Madison; Oliva, S. [University of Wisconsin, Madison; Prager, S. C. [University of Wisconsin, Madison; Reusch, J. A. [University of Wisconsin, Madison; Sarff, J. S. [University of Wisconsin, Madison; Stephens, H. D. [University of Wisconsin, Madison; Yates, T. [University of California, Los Angeles


    In Madison Symmetric Torus Dexter et al., Fusion Technol. 19, 131 1991 discharges where improved confinement is brought about by modification of the current profile, pellet injection has quadrupled the density, reaching ne=41019 m 3. Without pellet injection, the achievable density in improved confinement discharges had been limited by edge-resonant tearing instability. With pellet injection, the total beta has been increased to 26%, and the energy confinement time is comparable to that at low density. Pressure-driven local interchange and global tearing are predicted to be linearly unstable. Interchange has not yet been observed experimentally, but there is possible evidence of pressure-driven tearing, an instability usually driven by the current gradient in the reversed-field pinch.

  3. Image-guided spinal injection procedures in open high-field MRI with vertical field orientation: feasibility and technical features

    Energy Technology Data Exchange (ETDEWEB)

    Streitparth, F.; Walter, T.; Wonneberger, U.; Wagner, M.; Hermann, K.G.; Hamm, B.; Teichgraeber, U. [Charite, Humboldt-Universitaet zu Berlin, Department of Radiology, Berlin (Germany); Chopra, S. [Charite-Universitaetsmedizin Berlin, Campus Virchow Klinikum, Department of General, Visceral, and Transplantation Surgery, Berlin (Germany); Wichlas, F. [Charite-Universitaetsmedizin Berlin, Campus Virchow Klinikum, Center for Musculoskeletal Surgery, Berlin (Germany)


    We prospectively evaluated the feasibility and technical features of MR-guided lumbosacral injection procedures in open high-field MRI at 1.0 T. In a CuSO{sub 4}.5H{sub 2}O phantom and five human cadaveric spines, fluoroscopy sequences (proton-density-weighted turbo spin-echo (PDw TSE), T1w TSE, T2w TSE; balanced steady-state free precession (bSSFP), T1w gradient echo (GE), T2w GE) were evaluated using two MRI-compatible 20-G Chiba-type needles. Artefacts were analysed by varying needle orientation to B{sub 0}, frequency-encoding direction and slice orientation. Image quality was described using the contrast-to-noise ratio (CNR). Subsequently, a total of 183 MR-guided nerve root (107), facet (53) and sacroiliac joint (23) injections were performed in 53 patients. In vitro, PDw TSE sequence yielded the best needle-tissue contrasts (CNR = 45, 18, 15, 9, and 8 for needle vs. fat, muscle, root, bone and sclerosis, respectively) and optimal artefact sizes (width and tip shift less than 5 mm). In vivo, PDw TSE sequence was sufficient in all cases. The acquisition time of 2 s facilitated near-real-time MRI guidance. Drug delivery was technically successful in 100% (107/107), 87% (46/53) and 87% (20/23) of nerve root, facet and sacroiliac joint injections, respectively. No major complications occurred. The mean procedure time was 29 min (range 19-67 min). MR-guided spinal injections in open high-field MRI are feasible and accurate using fast TSE sequence designs. (orig.)

  4. Evaluating well-mixed room and near-field-far-field model performance under highly controlled conditions. (United States)

    Arnold, Susan F; Shao, Yuan; Ramachandran, Gurumurthy


    Exposure judgments made without personal exposure data and based instead on subjective inputs tend to underestimate exposure, with exposure judgment accuracy not significantly more accurate than random chance. Therefore, objective inputs that contribute to more accurate decision making are needed. Models have been shown anecdotally to be useful in accurately predicting exposure but their use in occupational hygiene has been limited. This may be attributable to a general lack of guidance on model selection and use and scant model input data. The lack of systematic evaluation of the models is also an important factor. This research addresses the need to systematically evaluate two widely applicable models, the Well-Mixed Room (WMR) and Near-Field-Far-Field (NF-FF) models. The evaluation, conducted under highly controlled conditions in an exposure chamber, allowed for model inputs to be accurately measured and controlled, generating over 800 pairs of high quality measured and modeled exposure estimates. By varying conditions in the chamber one at a time, model performance across a range of conditions was evaluated using two sets of criteria: the ASTM Standard 5157 and the AIHA Exposure Assessment categorical criteria. Model performance for the WMR model was excellent, with ASTM performance criteria met for 88-97% of the pairs across the three chemicals used in the study, and 96% categorical agreement observed. Model performance for the NF-FF model, impacted somewhat by the size of the chamber was nevertheless good to excellent. NF modeled estimates met modified ASTM criteria for 67-84% of the pairs while 69-91% of FF modeled estimates met these criteria. Categorical agreement was observed for 72% and 96% of NF and FF pairs, respectively. These results support the use of the WMR and NF-FF models in guiding decision making towards improving exposure judgment accuracy.

  5. Far-field high resolution effects and manipulating of electromagnetic waves based on transformation optics (United States)

    Ji, XueBin; Zang, XiaoFei; Li, Zhou; Shi, Cheng; Chen, Lin; Cai, Bin; Zhu, YiMing


    Based on the transformation optics (TO) and the effective medium theory (EMT), a new illusion media with homogeneous and isotropic materials is proposed to realize the far-field high resolution effects. When two point sources with the separation distance of λ0 / 4 are covered with the illusion media (λ0 is the free-space wavelength), the corresponding far-field pattern is equivalent to the case of two point sources with the separation distance larger than λ0 / 2 in free space, leading to the far-field high resolution effects (in free space, the separation distance of λ0 / 4 is less than half-wavelength, and thus the two point sources cannot be distinguished from each other). Furthermore, such illusion media can be applied to design tunable high-directivity antenna and an angle-dependent floating carpet cloak. Full wave simulations are carried out to verify the performance of our device.

  6. Opportunities for chiral discrimination using high harmonic generation in tailored laser fields

    CERN Document Server

    Smirnova, Olga; Patchkovskii, Serguei


    Chiral discrimination with high harmonic generation (cHHG method) has been introduced in the recent work by R. Cireasa et al ( Nat. Phys. 11, 654 - 658, 2015). In its original implementation, the cHHG method works by detecting high harmonic emission from randomly oriented ensemble of chiral molecules driven by elliptically polarized field, as a function of ellipticity. Here we discuss future perspectives in the development of this novel method, the ways of increasing chiral dichroism using tailored laser pulses, new detection schemes involving high harmonic phase measurements, and concentration-independent approaches. Using the example of the epoxypropane molecule C$_3$H$_6$O (also known as 1,2-propylene oxide), we show theoretically that application of two-color counter-rotating elliptically polarized laser fields yields an order of magnitude enhancement of chiral dichroism compared to single color elliptical fields. We also describe how one can introduce a new functionality to cHHG: concentration-independen...

  7. Electroslag remelting of high-speed steel using a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Murgas, M.


    The electroslag remelting process was studied when the consumable electrode made from the powder of M2 type high-speed steel was used and the effect of outside magnetic field was applied. The electromagnetic forces that arise from the interaction between the outside direct magnetic field and the one-phase electric current of the electroslag remelting process by a monofilar scheme alter the mechanism of the electrode remelting and thus, affect the solidification of a high-speed steel and its structure. The cast cutting tips made from ingots produced by this technology had tool life to be comparable to that of standard ones made from the wrought steel of the identical chemical composition and heat treatment. It has been shown that a magnetic field also affects both the temperature ranges and the kinetics of phase transformation in a high-speed steel. This suggestion is proved by DTA measurements. (author)

  8. The world's smallest capacitive dilatometer, for high-resolution thermal expansion and magnetostriction in high magnetic fields. (United States)

    Küchler, R; Wörl, A; Gegenwart, P; Berben, M; Bryant, B; Wiedmann, S


    For the characterization of novel quantum phases of matter, it is often required to study materials under multi-extreme conditions, in particular down to very low temperatures and in very high magnetic fields. We developed the world's smallest high-resolution capacitive dilatometer suitable for temperatures down to 10 mK and usage in high magnetic fields up to 37.5 T. Despite the extreme miniaturization, the capacitive dilatometer can resolve length changes down to 0.01 Å. This is an unprecedented resolution in a capacitive dilatometer of this compact size. Many cryogenic devices have limited space. Due to the extremely reduced cell size (3 cm3, 12 g), implementation or new applications in many of these sample space lacking devices are now possible. As an important example, the minute device can now be rotated in any standard cryostat, including dilution refrigerators or the commercial physical property measurement system. The present super compact design provides also for high resolution thermal expansion and magnetostriction measurements in a 15.2 mm diameter tube, enabling its use in the 32 mm bore, 37.5 T Bitter magnet at the High Field Magnet Laboratory in Nijmegen down to a temperature of 300 mK.

  9. Magnetic resonance imaging of hindfoot involvement in patients with spondyloarthritides: Comparison of low-field and high-field strength units

    Energy Technology Data Exchange (ETDEWEB)

    Eshed, Iris; Althoff, Christian E. [Department of Radiology, Charite Medical School, Berlin (Germany); Feist, Eugen [Department of Rheumatology and Clinical Immunology, Charite Medical School, Berlin (Germany); Minden, Kirsten [Helios Clinics, 2nd Children' s Hospital Berlin-Buch, Rheumatology Unit, Berlin (Germany); German Rheumatology Research Center, Berlin (Germany); Schink, Tania [Department of Medical Biometry, Charite Medical School, Berlin (Germany); Hamm, Bernd [Department of Radiology, Charite Medical School, Berlin (Germany); Hermann, Kay-Geert A. [Department of Radiology, Charite Medical School, Berlin (Germany)], E-mail:


    Objective: To compare MRI evaluation of a painful hindfoot of patients with spondyloarthritides (SpA) on low-field (0.2 T) versus high-field (1.5 T) MRI. Materials and methods: Patients with SpA and hindfoot pain were randomly referred to either high-field or low-field MRI. Twenty-seven patients were evaluated (male/female: 17:10; mean age: 39 {+-} 1.4 years). Fifteen patients were examined by low-field and 12 by high-field MRI. Two patients (evaluated by high-field MRI) were excluded. Images were separately read by two radiologists who later reached a consensus. In each patient the prevalence of erosions, fluid, synovitis or bone marrow edema of the hindfoot joints, tendinosis or tenosynovitis of tendons, enthesitis of the plantar fascia and Achilles tendon and retrocalcaneal bursitis were recorded. Clinical and demographic parameters were comparable between both groups. Results: MRI evaluation of joints and tendons of the hindfoot revealed no significant differences in patients with SpA groups for all parameters. Analyzing all joints or tendons together, there was no statistically significant difference between the two groups. Conclusion: Low-field and high-field MRI provide comparable information for evaluation of inflammatory hindfoot involvement. Thus, low-field MRI can be considered as a reliable diagnostic tool for the detection of hindfoot abnormalities in SpA patients.

  10. High spectral resolution lidar to measure optical scattering properties of atmospheric aerosols. I - Theory and instrumentation (United States)

    Shipley, S. T.; Tracy, D. H.; Eloranta, E. W.; Roesler, F. L.; Weinman, J. A.; Trauger, J. T.; Sroga, J. T.


    A high spectral resolution lidar technique to measure optical scattering properties of atmospheric aerosols is described. Light backscattered by the atmosphere from a narrowband optically pumped oscillator-amplifier dye laser is separated into its Doppler broadened molecular and elastically scattered aerosol components by a two-channel Fabry-Perot polyetalon interferometer. Aerosol optical properties, such as the backscatter ratio, optical depth, extinction cross section, scattering cross section, and the backscatter phase function, are derived from the two-channel measurements.

  11. Shrink Tube Insulation Apparatus for Rebco Superconducting Tapes for Use in High Field Magnets

    CERN Document Server

    Whittington, Andrew

    An increasing number of applications require the use of high temperature superconductors (HTS) such as (RE=Rare Earth) Ba2Cu3O7-x (REBCO) coated conductors [1]. HTS conductors show particularly great potential for high field magnets applications [1] due to their high upper critical fields [2], But several groups have shown that REBCO coated conductors are prone to delamination failure [3] [4] [5]. Under relatively low transverse stress the HTS film separates from the substrate and the conductor degrades [6]. This is problematic due to high transverse stresses that occur in fully epoxy impregnated solenoids wound with this conductor. Application of thin walled heat shrink tubing introduces a weak plane around the conductor, preventing delamination degradation [7]. However, manual application of the shrink tubing is impractical, requiring three operators limited to insulating 100 m lengths or less of REBCO conductor. The high risk of damage to the conductor, also associated with this process, shows the need for...

  12. Random magnetic field and quasiparticle transport in the mixed state of high- Tc cuprates. (United States)

    Ye, J


    By a singular gauge transformation, the quasiparticle transport in the mixed state of high- Tc cuprates is mapped into a charge-neutral Dirac moving in short-range correlated random scalar and long-range correlated vector potential. A fully quantum mechanical approach to longitudinal and transverse thermal conductivities is presented. The semiclassical Volovik effect is presented in a quantum mechanical way. The quasiparticle scattering from the random magnetic field which was completely missed in all the previous semiclassical approaches is the dominant scattering mechanism at sufficient high magnetic field. The implications for experiments are discussed.

  13. Observation of thermoelectric currents in high-field superconductor-ferromagnet tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Kolenda, Stefan; Wolf, Michael J.; Beckmann, Detlef [Institut fuer Nanotechnologie, Karlsruher Institut fuer Technologie (Germany)


    We report on the experimental observation of thermoelectric currents in superconductor-ferromagnet tunnel junctions in high magnetic fields. The thermoelectric signals are due to a spin-dependent lifting of particle-hole symmetry, and are found to be in excellent agreement with recent theoretical predictions. The maximum Seebeck coefficient inferred from the data is about -100 μ V/K, much larger than commonly found in metalic structures. Our results directly give proof of the coupling of spin and heat transport in high-field superconductors.


    Energy Technology Data Exchange (ETDEWEB)



    The target system for a muon collider/neutrino factory requires the conjunction of an intense proton beam, a high-Z liquid target and a high-field solenoid magnet. We describe here the design parameters for a pulsed solenoid, including the magnet cryogenic system and power supply, that can generate transient fields of greater than 10T with a flat-tops on the order of 1 second. It is envisioned to locate this device at the Brookhaven AGS for proof-of-principle testing of a liquid-jet target system with pulses of le13 protons.

  15. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    Energy Technology Data Exchange (ETDEWEB)

    Bouda, N. R., E-mail:; Pritchard, J.; Weber, R. J.; Mina, M. [Department of Electrical and Computer engineering, Iowa State University, Ames, Iowa 50011 (United States)


    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  16. Low-frequency approximation for high-order harmonic generation by a bicircular laser field (United States)

    Milošević, D. B.


    We present low-frequency approximation (LFA) for high-order harmonic generation (HHG) process. LFA represents the lowest-order term of an expansion of the final-state interaction matrix element in powers of the laser-field frequency ω . In this approximation the plane-wave recombination matrix element which appears in the strong-field approximation is replaced by the exact laser-free recombination matrix element calculated for the laser-field dressed electron momenta. First, we have shown that the HHG spectra obtained using the LFA agree with those obtained solving the time-dependent Schrödinger equation. Next, we have applied this LFA to calculate the HHG rate for inert gases exposed to a bicircular field. The bicircular field, which consists of two coplanar counter-rotating fields having different frequencies (usually ω and 2 ω ), is presently an important subject of scientific research since it enables efficient generation of circularly polarized high-order harmonics (coherent soft x rays). Analyzing the photorecombination matrix element we have found that the HHG rate can efficiently be calculated using the angular momentum basis with the states oriented in the direction of the bicircular field components. Our numerical results show that the HHG rate for atoms having p ground state, for higher high-order harmonic energies, is larger for circularly polarized harmonics having the helicity -1 . For lower energies the harmonics having helicity +1 prevails. The transition between these two harmonic energy regions can appear near the Cooper minimum, which, in the case of Ar atoms, makes the selection of high-order harmonics having the same helicity much easier. This is important for applications (for example, for generation of attosecond pulse trains of circularly polarized harmonics).

  17. Scaling Features of High-Latitude Geomagnetic Field Fluctuations at Swarm Altitude: Impact of IMF Orientation (United States)

    De Michelis, Paola; Consolini, Giuseppe; Tozzi, Roberta; Marcucci, Maria Federica


    This paper attempts to explore the statistical scaling features of high-latitude geomagnetic field fluctuations at Swarm altitude. Data for this study are low-resolution (1 Hz) magnetic data recorded by the vector field magnetometer on board Swarm A satellite over 1 year (from 15 April 2014 to 15 April 2015). The first- and second-order structure function scaling exponents and the degree of intermittency of the fluctuations of the intensity of the horizontal component of the magnetic field at high northern latitudes have been evaluated for different interplanetary magnetic field orientations in the GSM Y-Z plane and seasons. In the case of the first-order structure function scaling exponent, a comparison between the average spatial distributions of the obtained values and the statistical convection patterns obtained using a Super Dual Auroral Radar Network dynamic model (CS10 model) has been also considered. The obtained results support the idea that the knowledge of the scaling features of the geomagnetic field fluctuations can help in the characterization of the different ionospheric turbulence regimes of the medium crossed by Swarm A satellite. This study shows that different turbulent regimes of the geomagnetic field fluctuations exist in the regions characterized by a double-cell convection pattern and in those regions near the border of the convective structures.

  18. Ultra-high field magnetic resonance imaging of the basal ganglia and related structures

    Directory of Open Access Journals (Sweden)

    Birgit Renske Plantinga


    Full Text Available Deep brain stimulation is a treatment for Parkinson’s disease and other related disorders, involving the surgical placement of electrodes in the deeply situated basal ganglia or thalamic structures. Good clinical outcome requires accurate targeting. However, due to limited visibility of the target structures on routine clinical MR images, direct targeting of structures can be challenging. Non-clinical MR scanners with ultra-high magnetic field (7T or higher have the potential to improve the quality of these images. This technology report provides an overview of the current possibilities of visualizing deep brain stimulation targets and their related structures with the aid of ultra-high field MRI. Reviewed studies showed improved resolution, contrast- and signal-to-noise ratios at ultra-high field. Sequences sensitive to magnetic susceptibility such as T2* and susceptibility weighted imaging and their maps in general showed the best visualization of target structures, including a separation between the subthalamic nucleus and the substantia nigra, the lamina pallidi medialis and lamina pallidi incompleta within the globus pallidus and substructures of the thalamus, including the ventral intermediate nucleus (Vim. This shows that the visibility, identification and even subdivision of the small deep brain stimulation targets benefit from increased field strength. Although ultra-high field MR imaging is associated with increased risk of geometrical distortions, it has been shown that these distortions can be avoided or corrected to the extent where the effects are limited. The availability of ultra-high field MR scanners for humans seems to provide opportunities for a more accurate targeting for deep brain stimulation in patients with Parkinson’s disease and related disorders.

  19. Possibility of critical field enhancement due to field penetration in high-Tc sponges and thin films (United States)

    Collings, E. W.; Markoworth, A. J.; Marken, K. R., Jr.


    Magnetic susceptibility measurements of a sample of sintered high-Tc ceramic superconductor of nominal composition Y1Ba2Cu3O(7-y) were conducted as a function of temperature from liquid-He temperatures to Tc. The fitted form of the susceptibility temperature dependence yielded a sample-particle size that was only a few times larger than the field-penetration depth. The particle size was much less than the grain size and commensurate with the thickness of the optical twins. The results of the enhancement studies are also discussed in the light of Bean's (1964) early experiments on Pb sponges (in this case wavelength much greater than particle size) which exhibited spectacular enhancements of Hc in association with flux trapping at or between the Pb filaments. It is predicted that it should be possible, using presently available film-deposition techniques, to produce high-Tc films possessing severalfold enhancements of H(c1) beyond the bulk value, and that, as with the Pb sponges, the magnetization loops, even when taken within what passes for the Meissner state in such materials, will be hysteretic.

  20. High field magnetization of R sub 2 T sub 17 compounds

    Energy Technology Data Exchange (ETDEWEB)

    Franse, J.J.M.; Kayzel, F.E.; Marquina, C.; Radwanski, R.J.; Verhoef, R. (Van der Waals-Zeeman Lab., Univ. Amsterdam (Netherlands))


    A summary is presented of high field magnetization studies on the R{sub 2}T{sub 17} compounds (R = rare earth, T = Fe, Co or Ni). The different types of transitions that have been observed in magnetization studies on single-crystal samples along different crystallographic directions are mentioned. By analysing the transition fields, valuable information is obtained either on the strength of the R-T coupling or on the crystal field interactions of the rare earth ions. In addition, experiments are reported on powdered samples that are free to rotate in the applied magnetic field. This experimental technique provides a rather simple experimental approach to the intersublattice coupling in ferrimagnetic R-T compounds. (orig.).

  1. Magnetic and structural phase transitions of MnBi under high magnetic fields

    Directory of Open Access Journals (Sweden)

    Keiichi Koyama, Yoshifuru Mitsui and Kazuo Watanabe


    Full Text Available High-field x-ray diffraction and magnetization measurements and differential thermal analysis (DTA were carried out for polycrystalline MnBi with an NiAs-type hexagonal structure to investigate its magnetic and structural phase transitions. The lattice parameter a rapidly decreases below the spin reorientation temperature TSR(=90 K in a zero magnetic field. The parameter c decreases gradually with decreasing temperature and exhibits an anomaly in the vicinity of TSR. By applying a magnetic field of 5 T, the parameter a increases by ~0.05% when Tfield up to 14 T.

  2. Self propagating high temperature synthesis of metal oxides. Reactions in external magnetic fields

    CERN Document Server

    Aguas, M D


    The preparation of metal oxides by Self-Propagating High-Temperature Synthesis is reported. The reactions are started with a point source of ignition; typically a hot wire. A synthesis wave is observed moving out from the point source and reactions terminate in seconds. Products obtained can be classified into ferrites (magnetic applications) and stannates (gas sensing applications). Ferrites were synthesised under variable external magnetic fields. The synthesis wave is hotter in the presence of an external magnetic field for hard ferrite synthesis. For spinel ferrites the opposite was observed. Materials synthesised in the field show differences in their bulk magnetic properties (coercivity and saturation magnetisation), structures and microstructures. Combustion reactions in large fields revealed changes in unit cell volume (shrinkage was observed for hard ferrites while expansion was observed for spinel ferrites). SHS synthesised hard ferrites show two distinct components; one has large grain structure co...


    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay l


    Results are reported on attempts to reduce the RF breakdown probability on copper accelerator structures by applying thin surface films that could suppress field emission of electrons. Techniques for application and testing of copper samples with films of metals with work functions higher than copper are described, principally for application of platinum films, since platinum has the second highest work function of any metal. Techniques for application of insulating films are also described, since these can suppress field emission and damage on account of dielectric shielding of fields at the copper surface, and on account of the greater hardness of insulating films, as compared with copper. In particular, application of zirconium oxide films on high-field portions of a 11.424 GHz SLAC cavity structure for breakdown tests are described.

  4. A new high performance field reversed configuration operating regime in the C-2 device

    Energy Technology Data Exchange (ETDEWEB)

    Tuszewski, M.; Smirnov, A.; Thompson, M. C.; Barnes, D.; Binderbauer, M. W.; Brown, R.; Bui, D. Q.; Clary, R.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Garate, E.; Glass, F. J.; Gota, H.; Guo, H.Y.; Gupta, D.; Gupta, S.; Kinley, J. S.; Knapp, K. [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States); and others


    Large field reversed configurations (FRCs) are produced in the C-2 device by combining dynamic formation and merging processes. The good confinement of these FRCs must be further improved to achieve sustainment with neutral beam (NB) injection and pellet fuelling. A plasma gun is installed at one end of the C-2 device to attempt electric field control of the FRC edge layer. The gun inward radial electric field counters the usual FRC spin-up and mitigates the n = 2 rotational instability without applying quadrupole magnetic fields. Better plasma centering is also obtained, presumably from line-tying to the gun electrodes. The combined effects of the plasma gun and of neutral beam injection lead to the high performance FRC operating regime, with FRC lifetimes up to 3 ms and with FRC confinement times improved by factors 2 to 4.

  5. Investigation of material properties by NMR in low and high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Rata, D.G.


    In this work the experiments have been performed at both low and high field. The experiments cover various domains from simple relaxation experiments in low field to diffusion and spin-diffusion in high field. The applications of low-field investigations are: - quality control of chemical products. - water content determination inside of the walls of buildings. - determination of multilayer polymer coatings on a concrete. In high-field NMR several alkane molecules swollen at equilibrium in cross-linked natural rubber samples have been investigated and analyzed based on the assumptions of the Vrentras theory. A small diffusion anisotropy of the order of 10% has been discovered because of a deformation of free volume under compression. The anisotropy increases with the cross-link density and the compression ratio. The results presented in this study show that the solvent size influences the anisotropy of the diffusion process through the size parameter. The spin-diffusion measurements have been performed on Stanyl samples with different aged samples, at controlled temperature conditions. (orig.)

  6. Highly Efficient and Scalable Separation of Semiconducting Carbon Nanotubes via Weak Field Centrifugation (United States)

    Reis, Wieland G.; Weitz, R. Thomas; Kettner, Michel; Kraus, Alexander; Schwab, Matthias Georg; Tomović, Željko; Krupke, Ralph; Mikhael, Jules


    The identification of scalable processes that transfer random mixtures of single-walled carbon nanotubes (SWCNTs) into fractions featuring a high content of semiconducting species is crucial for future application of SWCNTs in high-performance electronics. Herein we demonstrate a highly efficient and simple separation method that relies on selective interactions between tailor-made amphiphilic polymers and semiconducting SWCNTs in the presence of low viscosity separation media. High purity individualized semiconducting SWCNTs or even self-organized semiconducting sheets are separated from an as-produced SWCNT dispersion via a single weak field centrifugation run. Absorption and Raman spectroscopy are applied to verify the high purity of the obtained SWCNTs. Furthermore SWCNT - network field-effect transistors were fabricated, which exhibit high ON/OFF ratios (105) and field-effect mobilities (17 cm2/Vs). In addition to demonstrating the feasibility of high purity separation by a novel low complexity process, our method can be readily transferred to large scale production.

  7. MRI of the Musculoskeletal System: Advanced Applications using High and Ultrahigh Field MRI. (United States)

    Alizai, Hamza; Chang, Gregory; Regatte, Ravinder R


    In vivo MRI has revolutionized the diagnosis and treatment of musculoskeletal disorders over the past 3 decades. Traditionally performed at 1.5 T, MRI at higher field strengths offers several advantages over lower field strengths including increased signal-to-noise ratio, higher spatial resolution, improved spectral resolution for spectroscopy, improved sensitivity for X-nucleus imaging, and decreased image acquisition times. However, the physics of imaging at higher field strengths also presents technical challenges. These include B0 and B1+ field inhomogeneity, design and construction of dedicated radiofrequency (RF) coils for use at high field, increased chemical shift and susceptibility artifacts, increased RF energy deposition (specific absorption rate), increased metal artifacts, and changes in relaxation times compared with the lower field scanners. These challenges were overcome in optimizing high-field (HF) (3 T) MRI over a decade ago. HF MRI systems have since gained universal acceptance for clinical musculoskeletal imaging and have also been widely utilized for the study of musculoskeletal anatomy and physiology. Recently there has been an increasing interest in exploring musculoskeletal applications of ultrahigh field (UHF) (7 T) systems. However, technical challenges similar to those encountered when moving from 1.5 T to 3 T have to be overcome to optimize 7 T musculoskeletal imaging. In this narrative review, we discuss the many potential opportunities and technical challenges presented by the HF and UHF MRI systems. We highlight recent developments in in vivo imaging of musculoskeletal tissues that benefit most from HF imaging including cartilage, skeletal muscle, and bone. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  8. Modeling of Diamond Field-Emitter-Arrays for high brightness photocathode applications (United States)

    Kwan, Thomas; Huang, Chengkun; Piryatinski, Andrei; Lewellen, John; Nichols, Kimberly; Choi, Bo; Pavlenko, Vitaly; Shchegolkov, Dmitry; Nguyen, Dinh; Andrews, Heather; Simakov, Evgenya


    We propose to employ Diamond Field-Emitter-Arrays (DFEAs) as high-current-density ultra-low-emittance photocathodes for compact laser-driven dielectric accelerators capable of generating ultra-high brightness electron beams for advanced applications. We develop a semi-classical Monte-Carlo photoemission model for DFEAs that includes carriers' transport to the emitter surface and tunneling through the surface under external fields. The model accounts for the electronic structure size quantization affecting the transport and tunneling process within the sharp diamond tips. We compare this first principle model with other field emission models, such as the Child-Langmuir and Murphy-Good models. By further including effects of carrier photoexcitation, we perform simulations of the DFEAs' photoemission quantum yield and the emitted electron beam. Details of the theoretical model and validation against preliminary experimental data will be presented. Work ssupported by LDRD program at LANL.

  9. Broadband measurements of high-frequency electric field levels and exposure ratios determination

    Directory of Open Access Journals (Sweden)

    Vulević Branislav


    Full Text Available The exposure of people to high-frequency electromagnetic fields (over 100 kHz that emanate from modern wireless information transmission systems is inevitable in modern times. Due to the rapid development of new technologies, measuring devices and their connection to measuring systems, the first fifteen years of the 21st century are characterized by the appearance of different approaches to measurements. This prompts the need for the assessment of the exposure of people to these fields. The main purpose of this paper is to show how to determine the exposure ratios based on the results of broadband measurements of the high-frequency electric field in the range of 3 MHz to 18 GHz in the environment.

  10. On the Nature of High Field Charge Transport in Reinforced Silicone Dielectrics: Experiment and Simulation

    CERN Document Server

    Huang, Yanhui


    The high field charge injection and transport properties in reinforced silicone dielectrics were investigated by measuring the time-dependent space charge distribution and the current under dc conditions up to the breakdown field, and were compared with properties of other dielectric polymers. It is argued that the energy and spatial distribution of localized electronic states are crucial to determining these properties for polymer dielectrics. Tunneling to localized states likely dominates the charge injection process. A transient transport regime arises due to the relaxation of charge carriers into deep traps at the energy band tails, and is successfully verified by a Monte Carlo simulation using the multiple-hopping model. The charge carrier mobility is found to be highly heterogeneous due to non-uniform trapping. The slow moving electron packet exhibits a negative field dependent drift velocity possibly due to the spatial disorder of traps.

  11. Polarizing Oxygen Vacancies in Insulating Metal Oxides under a High Electric Field (United States)

    Youssef, Mostafa; Van Vliet, Krystyn J.; Yildiz, Bilge


    We demonstrate a thermodynamic formulation to quantify defect formation energetics in an insulator under a high electric field. As a model system, we analyzed neutral oxygen vacancies (color centers) in alkaline-earth-metal binary oxides using density functional theory, Berry phase calculations, and maximally localized Wannier functions. The work of polarization lowers the field-dependent electric Gibbs energy of formation of this defect. This is attributed mainly to the ease of polarizing the two electrons trapped in the vacant site, and secondarily to the defect induced reduction in bond stiffness and softening of phonon modes. The formulation and analysis have implications for understanding the behavior of insulating oxides in electronic, magnetic, catalytic, and electrocaloric devices under a high electric field.

  12. Electric field analysis of extra high voltage (EHV) underground cables using finite element method

    DEFF Research Database (Denmark)

    Kumar, Mantosh; Bhaskar, Mahajan Sagar; Padmanaban, Sanjeevikumar


    Transmission and Distribution of electric power through underground cables is a viable alternative to overhead lines, particularly in residential or highly populated areas. The electrical stresses are consequences of regular voltages and over voltages and the thermal stresses are related to heat...... produced inside the conductor due to flow of high rated current which is the main factors that affect its reliability. The performance of these underground power cables is important for proper operation of the power system. Long-term problems with them are related to the degradation of polymer materials...... used for the insulator due electrical, thermal or environmental stress. Most of these problems are related to the electric field stress on the insulation of the underground cables. The objective of the electric field analysis by using different numerical techniques is to find electric field stress...

  13. Dose equivalent measurements in mixed and time varying radiation fields around high-energy accelerators

    CERN Document Server

    Mayer, S


    Measurements of ambient dose equivalent in stray radiation fields behind the shielding of high-energy accelerators are a challenging task. Several radiation components (photons, neutrons, charged particles, muons, etc.), spanning a wide range of energies, contribute to the total dose equivalent. The radiation fields are produced by beam losses interacting with structural material during the acceleration or at the ejection to experimental areas or other accelerators. The particle beam is usually not continuous but separated in "bunches" or pulses, which further complicates dose measurements at high-energy accelerators. An ideal dosimeter for operational radiation protection should measure dose equivalent for any composition of radiation components in the entire energy range even when the field is strongly pulsed. The objective of this work was to find out if an ionisation chamber operated as a "recombination chamber" and a TEPC instrument using the variance-covariance method ("Sievert Instrument") are capable ...

  14. Development and field evaluation of a pipe renewal system for high pressure gas mains

    Energy Technology Data Exchange (ETDEWEB)

    Beckendorf, P. [Gas Research Institute, Chicago, IL (United States); Driver, F.T. [Insituform Technologies, Inc., Chesterfield, MO (United States); Lawrence, S. [Pacific Gas & Electric, San Ramon, CA (United States)


    This paper describes a cured-in-place pipe renewal product, the high pressure liner, for use in natural gas pipelines at up to 450 psig. The liner development, testing of liner strength and durability, state approval, and field evaluation results are summarized. Problems encountered during field testing included: (1) modifications required for end seals, including methods for installation and seal integrity pressure testing; (2) gas leakage betweem the liner and the pipe; (3) liner wrinkling at a 20 degree miter joint. These problems are being addressed by redesign and/or further study; overall, the initial field evaluation successfully advanced the development of a high pressure liner as a significantly lower cost alternative for pipeline renewal.

  15. Open Science CBS Neuroimaging Repository: Sharing ultra-high-field MR images of the brain. (United States)

    Tardif, Christine Lucas; Schäfer, Andreas; Trampel, Robert; Villringer, Arno; Turner, Robert; Bazin, Pierre-Louis


    Magnetic resonance imaging at ultra high field opens the door to quantitative brain imaging at sub-millimeter isotropic resolutions. However, novel image processing tools to analyze these new rich datasets are lacking. In this article, we introduce the Open Science CBS Neuroimaging Repository: a unique repository of high-resolution and quantitative images acquired at 7 T. The motivation for this project is to increase interest for high-resolution and quantitative imaging and stimulate the development of image processing tools developed specifically for high-field data. Our growing repository currently includes datasets from MP2RAGE and multi-echo FLASH sequences from 28 and 20 healthy subjects respectively. These datasets represent the current state-of-the-art in in-vivo relaxometry at 7 T, and are now fully available to the entire neuroimaging community. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. High accuracy electromagnetic field solvers for cylindrical waveguides and axisymmetric structures using the finite element method

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, Eric Michael [Stanford Univ., CA (United States)


    Some two-dimensional finite element electromagnetic field solvers are described and tested. For TE and TM modes in homogeneous cylindrical waveguides and monopole modes in homogeneous axisymmetric structures, the solvers find approximate solutions to a weak formulation of the wave equation. Second-order isoparametric lagrangian triangular elements represent the field. For multipole modes in axisymmetric structures, the solver finds approximate solutions to a weak form of the curl-curl formulation of Maxwell`s equations. Second-order triangular edge elements represent the radial (ρ) and axial (z) components of the field, while a second-order lagrangian basis represents the azimuthal (Φ) component of the field weighted by the radius ρ. A reduced set of basis functions is employed for elements touching the axis. With this basis the spurious modes of the curl-curl formulation have zero frequency, so spurious modes are easily distinguished from non-static physical modes. Tests on an annular ring, a pillbox and a sphere indicate the solutions converge rapidly as the mesh is refined. Computed eigenvalues with relative errors of less than a few parts per million are obtained. Boundary conditions for symmetric, periodic and symmetric-periodic structures are discussed and included in the field solver. Boundary conditions for structures with inversion symmetry are also discussed. Special corner elements are described and employed to improve the accuracy of cylindrical waveguide and monopole modes with singular fields at sharp corners. The field solver is applied to three problems: (1) cross-field amplifier slow-wave circuits, (2) a detuned disk-loaded waveguide linear accelerator structure and (3) a 90° overmoded waveguide bend. The detuned accelerator structure is a critical application of this high accuracy field solver. To maintain low long-range wakefields, tight design and manufacturing tolerances are required.

  17. Full-field parallel interferometry coherence probe microscope for high-speed optical metrology. (United States)

    Safrani, A; Abdulhalim, I


    Parallel detection of several achromatic phase-shifted images is used to obtain a high-speed, high-resolution, full-field, optical coherence probe tomography system based on polarization interferometry. The high enface imaging speed, short coherence gate, and high lateral resolution provided by the system are exploited to determine microbump height uniformity in an integrated semiconductor chip at 50 frames per second. The technique is demonstrated using the Linnik microscope, although it can be implemented on any polarization-based interference microscopy system.

  18. Enhanced Energy Density in Permanent Magnets using Controlled High Magnetic Field during Processing

    Energy Technology Data Exchange (ETDEWEB)

    Carter, William G [ORNL; Rios, Orlando [ORNL; Constantinides, Steven [ORNL


    This ORNL Manufacturing Demonstraction Facility (MDF) technical collaboration focused on the use of high magnetic field processing (>2Tesla) using energy efficient large bore superconducting magnet technology and high frequency electromagnetics to improve magnet performance and reduce the energy budget associated with Alnico thermal processing. Alnico, alloys containing Al, Ni, Co and Fe, represent a class of functional nanostructured alloys, and show the greatest potential for supplementing or replacing commercial Nd-based rare-earth alloy magnets.

  19. Widespread inflammation in CLIPPERS syndrome indicated by autopsy and ultra-high-field 7T MRI

    DEFF Research Database (Denmark)

    Blaabjerg, Morten; Ruprecht, Klemens; Sinnecker, Tim


    OBJECTIVE: To examine if there is widespread inflammation in the brain of patients with chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) syndrome by using histology and ultra-high-field MRI at 7.0T. METHODS: We performed a detailed neuropath...

  20. The Influence of Morphology on High-Performance Polymer Field-Effect Transistors

    DEFF Research Database (Denmark)

    Tsao, Hoi Nok; Cho, Don; Andreasen, Jens Wenzel


    The influence of molecular packing on the performance of polymer organic field-effect transistors is illustrated in this work. Both close -stacking distance and long-range order are important for achieving high mobilities. By aligning the polymers from solution, long-range order is induced...

  1. High-frequency field-deployable isotope analyzer for hydrological applications (United States)

    Elena S.F. Berman; Manish Gupta; Chris Gabrielli; Tina Garland; Jeffrey J. McDonnell


    A high-frequency, field-deployable liquid water isotope analyzer was developed. The instrument was deployed for 4 contiguous weeks in the H. J. Andrews Experimental Forest Long-term Ecological Research site in western Oregon, where it was used for real-time measurement of the isotope ratios of precipitation and stream water during three large storm events. We were able...

  2. High resolution imaging of dielectric surfaces with an evanescent field optical microscope

    NARCIS (Netherlands)

    van Hulst, N.F.; Segerink, Franciscus B.; Bölger, B.


    An evanescent field optical microscope (EFOM) is presented which employs frustrated total internal reflection o­n a localized scale by scanning a dielectric tip in close proximity to a sample surface. High resolution images of dielectric gratings and spheres containing both topographic and

  3. In-situ high field strength testing using a transportable reverberation chamber

    NARCIS (Netherlands)

    Leferink, Frank Bernardus Johannes


    A reverberation chamber can create very high fieldstrength with moderate input power. Existing chambers are making use of a paddle wheel to change the resonant modes in the chamber. In the case of a stepper motor, the field is stable for some time, and this type of reverberation chamber is called

  4. Photoconductivity and high-field effects in amorphous Se83Te15Zn2 ...

    Indian Academy of Sciences (India)


    indium electrodes at the bottom were used for the electri- cal contact. The thickness of the film was ~ 500 nm. The co-planar structure (length ~ 1⋅2 cm and electrode separa- tion ~ 0⋅12 mm for high-field measurements and 0⋅5 mm for photoconductivity measurements) was used for the present measurements. A vacuum ...

  5. OASIS high-resolution integral field spectroscopy of the SAURON ellipticals and lenticulars

    NARCIS (Netherlands)

    McDermid, R; Emsellem, E; Cappellari, M; Kuntschner, H; Bacon, R; Bureau, M; Copin, Y; Davies, RL; Falcon-Barroso, J; Ferruit, P; Krajnovic, D; Peletier, RF; Shapiro, K; Wernli, F; de Zeeuw, PT


    We present a summary of high-spatial resolution follow-up observations of the elliptical (E) and lenticular (SO) galaxies in the SAURON survey using the OASIS integral field spectrograph. The OASIS observations explore the central 8" x 10" regions of these galaxies using a spatial sampling four

  6. The value of high-field MRI (3 T) in the assessment of sellar lesions

    Energy Technology Data Exchange (ETDEWEB)

    Pinker, K. [Department of Diagnostic Radiology, Medical University Vienna, Waehringer Guertel 18-20, 1090 Vienna (Austria); Ba-Ssalamah, A. [Department of Diagnostic Radiology, Medical University Vienna, Waehringer Guertel 18-20, 1090 Vienna (Austria); Wolfsberger, S. [Department of Neurosurgery, Medical University Vienna (Austria); Mlynarik, V. [Department of Diagnostic Radiology, Medical University Vienna, Waehringer Guertel 18-20, 1090 Vienna (Austria); Knosp, E. [Department of Neurosurgery, Medical University Vienna (Austria); Trattnig, S. [Department of Diagnostic Radiology, Medical University Vienna, Waehringer Guertel 18-20, 1090 Vienna (Austria)]. E-mail:


    The aim of this study was the evaluation of the normal sellar anatomy in vitro and in vivo with high-field MRI and its application in the diagnosis of sellar pathologies in comparison to standard MRI. All high-field MR images were obtained using a 3 T Bruker Medspec 30/80 Scanner with a head birdcage transmit/receive coil and an actively shielded gradient system with a maximum gradient strength of 45 mT/m. Firstly an in vitro study of the sella turcica was performed to depict normal pituitary and sellar anatomy at high field. After a pilot-study this sequence-protocol was established: A RARE sequence (TR/TE = 7790/19 ms; matrix size, 512 x 512; RARE factor = 8, FOV, 200 mm) was used for T2-weighted coronal, axial and sagittal images. A 3D gradient echo sequence with magnetization-preparation (MP-RAGE, TR/TE/TI 33.5/7.6/800 ms, matrix size, 512 x 512; FOV, 200 mm, effective slice thickness, 1.88 mm; 3 averages) was used for acquisition of T1-weighted pre- and post-contrast images. Between January 2002 and March 200458 patients were enrolled in this study. Seven patients were examined for suspected microadenoma and in 51 patients 3T MRI was used to obtain additional information about the sellar lesion already known to be present from standard MRI. In 21 cases the accuracy of the imaging findings was assessed afterwards by comparison with intraoperative findings. The infiltration of the medial cavernous sinus wall was suspected on standard MRI on 15 sides (47%), on high-field MRI on 9 sides (28%) and could be verified by intraoperative findings on 6 sides (19%). Accordingly, sensitivity to infiltration was 83% for 3 T and 67% for standard MRI. Specificity was 84% for 3 T and 58% for standard MRI. Moreover, high-field MRI revealed microadenomas in 7 patients with a median diameter of 4 mm (range 2-9 mm). The segments of the cranial nerves were seen as mean 4 hypointense spots (range 2-5 spots) on high-field MRI in contrast to 3 spots (range 0-4 spots) on standard MRI

  7. A compact high-performance low-field NMR apparatus for measurements on fluids at very high pressures and temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Freedman, R.; Anand, V., E-mail:; Ganesan, K.; Tabrizi, P.; Torres, R. [Schlumberger Technology Corp., 110 Schlumberger Drive, Sugar Land, Texas 77478 (United States); Grant, B. [Grant Innovation, 618 Mesquite Drive, Cedar Creek, Texas 78612 (United States); Catina, D. [National Oilwell Varco, 10302 Mula Road, Stafford, Texas 77477 (United States); Ryan, D.; Borman, C.; Krueckl, C. [Schlumberger DBR Technology Center, 9450–17 Avenue NW, Edmonton, Alberta (Canada)


    We discuss an innovative new high-performance apparatus for performing low-field Nuclear Magnetic Resonance (NMR) relaxation times and diffusion measurements on fluids at very high pressures and high temperatures. The apparatus sensor design and electronics specifications allow for dual deployment either in a fluid sampling well logging tool or in a laboratory. The sensor and electronics were designed to function in both environments. This paper discusses the use of the apparatus in a laboratory environment. The operating temperature and pressure limits, and the signal-to-noise ratio (SNR) of the new system exceed by a very wide margin what is currently possible. This major breakthrough was made possible by a revolutionary new sensor design that breaks many of the rules of conventional high pressure NMR sensor design. A metallic sample holder capable of operating at high pressures and temperatures is provided to contain the fluid under study. The sample holder has been successfully tested for operation up to 36 Kpsi. A solenoid coil wound on a slotted titanium frame sits inside the metallic sample holder and serves as an antenna to transmit RF pulses and receive NMR signals. The metal sample holder is sandwiched between a pair of gradient coils which provide a linear field gradient for pulsed field gradient diffusion measurements. The assembly sits in the bore of a low-gradient permanent magnet. The system can operate over a wide frequency range without the need for tuning the antenna to the Larmor frequency. The SNR measured on a water sample at room temperature is more than 15 times greater than that of the commercial low-field system in our laboratory. Thus, the new system provides for data acquisition more than 200 times faster than was previously possible. Laboratory NMR measurements of relaxations times and diffusion coefficients performed at pressures up to 25 Kpsi and at temperatures up to 175 °C with crude oils enlivened with dissolved hydrocarbon gases

  8. A compact high-performance low-field NMR apparatus for measurements on fluids at very high pressures and temperatures (United States)

    Freedman, R.; Anand, V.; Grant, B.; Ganesan, K.; Tabrizi, P.; Torres, R.; Catina, D.; Ryan, D.; Borman, C.; Krueckl, C.


    We discuss an innovative new high-performance apparatus for performing low-field Nuclear Magnetic Resonance (NMR) relaxation times and diffusion measurements on fluids at very high pressures and high temperatures. The apparatus sensor design and electronics specifications allow for dual deployment either in a fluid sampling well logging tool or in a laboratory. The sensor and electronics were designed to function in both environments. This paper discusses the use of the apparatus in a laboratory environment. The operating temperature and pressure limits, and the signal-to-noise ratio (SNR) of the new system exceed by a very wide margin what is currently possible. This major breakthrough was made possible by a revolutionary new sensor design that breaks many of the rules of conventional high pressure NMR sensor design. A metallic sample holder capable of operating at high pressures and temperatures is provided to contain the fluid under study. The sample holder has been successfully tested for operation up to 36 Kpsi. A solenoid coil wound on a slotted titanium frame sits inside the metallic sample holder and serves as an antenna to transmit RF pulses and receive NMR signals. The metal sample holder is sandwiched between a pair of gradient coils which provide a linear field gradient for pulsed field gradient diffusion measurements. The assembly sits in the bore of a low-gradient permanent magnet. The system can operate over a wide frequency range without the need for tuning the antenna to the Larmor frequency. The SNR measured on a water sample at room temperature is more than 15 times greater than that of the commercial low-field system in our laboratory. Thus, the new system provides for data acquisition more than 200 times faster than was previously possible. Laboratory NMR measurements of relaxations times and diffusion coefficients performed at pressures up to 25 Kpsi and at temperatures up to 175 °C with crude oils enlivened with dissolved hydrocarbon gases

  9. The Sterilization Effect of Cooperative Treatment of High Voltage Electrostatic Field and Variable Frequency Pulsed Electromagnetic Field on Heterotrophic Bacteria in Circulating Cooling Water (United States)

    Gao, Xuetong; Liu, Zhian; Zhao, Judong


    Compared to other treatment of industrial circulating cooling water in the field of industrial water treatment, high-voltage electrostatic field and variable frequency pulsed electromagnetic field co-sterilization technology, an advanced technology, is widely used because of its special characteristics--low energy consumption, nonpoisonous and environmentally friendly. In order to get a better cooling water sterilization effect under the premise of not polluting the environment, some experiments about sterilization of heterotrophic bacteria in industrial circulating cooling water by cooperative treatment of high voltage electrostatic field and variable frequency pulsed electromagnetic field were carried out. The comparison experiment on the sterilization effect of high-voltage electrostatic field and variable frequency pulsed electromagnetic field co-sterilization on heterotrophic bacteria in industrial circulating cooling water was carried out by change electric field strength and pulse frequency. The results show that the bactericidal rate is selective to the frequency and output voltage, and the heterotrophic bacterium can only kill under the condition of sweep frequency range and output voltage. When the voltage of the high voltage power supply is 4000V, the pulse frequency is 1000Hz and the water temperature is 30°C, the sterilization rate is 48.7%, the sterilization rate is over 90%. Results of this study have important guiding significance for future application of magnetic field sterilization.

  10. Early Time Dynamics of Gluon Fields in High Energy Nuclear Collisions (United States)

    Kapusta, Joseph I.; Chen, Guangyao; Fries, Rainer J.; Li, Yang


    Nuclei colliding at very high energy create a strong, quasi-classical gluon field during the initial phase of their interaction. We present an analytic calculation of the initial space-time evolution of this field in the limit of very high energies using a formal recursive solution of the Yang-Mills equations. We provide analytic expressions for the initial chromo-electric and chromo-magnetic fields and for their energy-momentum tensor. In particular, we discuss event-averaged results for energy density and energy flow as well as for longitudinal and transverse pressure of this system. Our results are generally applicable if τ field exhibits hydrodynamic-like contributions that follow transverse gradients of the energy density. In addition, a rapidity-odd energy flow also emerges from the non-abelian analog of Gauss' Law and generates non-vanishing angular momentum of the field. We will discuss the space-time picture that emerges from our analysis and its implications for observables in heavy ion collisions.

  11. High-field electrical transport in amorphous phase-change materials (United States)

    Kaes, Matthias; Le Gallo, Manuel; Sebastian, Abu; Salinga, Martin; Krebs, Daniel


    Electrical transport in chalcogenide-based phase change materials is an active area of research owing to the prominent role played by these materials in the field of information technology. Here, we present transport measurements (IV curves) obtained on line-cells of as-deposited amorphous phase change materials (Ge2Sb2Te5, GeTe, Ag4In3Sb66Te27) over a wide voltage and temperature range (300 K to 160 K). The well defined geometry of our devices enables a description of the transport behavior in terms of conductivity vs. electric field. At higher temperatures (300 K ≥ T ≥ 220 K) and low to intermediate fields (F Poole-Frenkel emission from a two-center Coulomb potential. Based on this model, we observe a temperature dependence of the inter-trap distance, which we can relate to a temperature dependence in the occupation of the defect creating the Coulomb potential governing Poole-Frenkel emission. At higher fields and lower temperatures, the dependency of the IV curve on the electric field can be described by ln(I/I0) = (F/Fc)2. By combining this contribution with that of the Poole-Frenkel emission, we can show that the slope at high fields, Fc, is independent of temperature. We argue that models based on direct tunneling or thermally assisted tunneling from a single defect into the valence band cannot explain the observed behavior quantitatively.

  12. Index extraction for electromagnetic field evaluation of high power wireless charging system. (United States)

    Park, SangWook


    This paper presents the precise dosimetry for highly resonant wireless power transfer (HR-WPT) system using an anatomically realistic human voxel model. The dosimetry for the HR-WPT system designed to operate at 13.56 MHz frequency, which one of the ISM band frequency band, is conducted in the various distances between the human model and the system, and in the condition of alignment and misalignment between transmitting and receiving circuits. The specific absorption rates in the human body are computed by the two-step approach; in the first step, the field generated by the HR-WPT system is calculated and in the second step the specific absorption rates are computed with the scattered field finite-difference time-domain method regarding the fields obtained in the first step as the incident fields. The safety compliance for non-uniform field exposure from the HR-WPT system is discussed with the international safety guidelines. Furthermore, the coupling factor concept is employed to relax the maximum allowable transmitting power. Coupling factors derived from the dosimetry results are presented. In this calculation, the external magnetic field from the HR-WPT system can be relaxed by approximately four times using coupling factor in the worst exposure scenario.

  13. Swept Forward Magnetic Field Variability in High-Latitude Regions of Saturn's Magnetosphere (United States)

    Davies, E. H.; Masters, A.; Dougherty, M. K.; Hansen, K. C.; Coates, A. J.; Hunt, G. J.


    Swept forward field is the term given to configurations of magnetic field wherein the field lines deviate from the meridional planes of a planet in the direction of its rotation. Evidence is presented for swept-forward field configurations on Cassini orbits around Saturn from the first half of 2008. These orbits were selected on the basis of high inclination, spatial proximity, and temporal proximity, allowing for the observation of swept-forward field and resolution of dynamic effects using data from the Cassini magnetometer. Nine orbits are surveyed; all show evidence of swept-forward field, with typical sweep angle found to be 23°. Evidence is found for transient events that lead to temporary dramatic increases in sweep-forward angle. The Michigan Solar Wind Model is employed to investigate temporal correlation between the arrivals of solar wind shocks at Saturn with these transient events, with two shown to include instances corresponding with solar wind shock arrivals. Measurements of equatorial electron number density from anode 5 of the Cassini Plasma Spectrometer instrument are investigated for evidence of magnetospheric compression, corresponding with predicted shock arrivals. Potential mechanisms for the transfer of momentum from the solar wind to the magnetosphere are discussed.

  14. Structure transformations in cold rolled ferromagnetic alloys upon heating in high DC magnetic field (United States)

    Gervasyeva, I. V.; Milyutin, V. A.; Beaugnon, E.


    The processes of recovery and recrystallization in the coldrolled alloys Fe-3%Si, Fe-50%Ni, and Ni-30%Co subjected to annealing at temperatures below and above the Curie point under a high direct current (DC) magnetic field of 10-29 Т have been studied. It is established that application of external magnetic field in the course of heat treatment at temperatures below the recrystallization temperature and Curie point retards the processes of material softening. The formation of crystallographic texture initiated by magnetic field starts upon the recovery during the pre-recrystallization magnetic annealing. Then, in the course of subsequent annealing at the recrystallization temperatures without magnetic field, there takes place the development of preferable orientations. The magnetic field annealing favors the formation of such texture components in which the easy-magnetization axis coincides with the direction of the magnetic field applied. This is evidenced by the textures formed in the Fe-50%Ni alloy (easy axis) and Ni-30%Co alloy (easy axis).

  15. Influence of high magnetic field on the luminescence of Eu3+-doped glass ceramics (United States)

    Jiang, Wei; Zhang, Junpei; Chen, Weibo; Chen, Ping; Han, Junbo; Xu, Beibei; Zheng, Shuhong; Guo, Qiangbing; Liu, Xiaofeng; Qiu, Jianrong


    Rare earth (RE) doped materials have been widely exploited as the intriguing electronic configuration of RE ions offers diverse functionalities from optics to magnetism. However, the coupling of magnetism with photoluminescence (PL) in such materials has been rarely reported in spite of its fundamental significance. In the present paper, the effect of high pulsed magnetic field on the photoluminescence intensity of Eu3+-doped nano-glass-ceramics has been investigated. In our experiment, Eu-doped oxyfluoride glass and glass ceramic were prepared by the conventional melt-quenching process and controlled heat treatment. The results demonstrate that the integrated PL intensity of Eu3+ decreases with the enhancement of magnetic field, which can be interpreted in terms of cooperation effect of Zeeman splitting and magnetic field induced change in site symmetry. Furthermore, as a result of Zeeman splitting, both blue and red shift in the emission peaks of Eu3+ can be observed, and this effect becomes more prominent with the increase of magnetic field. Possible mechanisms associated with the observed magneto-optical behaviors are suggested. The results of the present paper may open a new gate for modulation of luminescence by magnetic field and remote optical detection of magnetic field.


    Directory of Open Access Journals (Sweden)

    B.I. Kuznetsov


    Full Text Available Purpose. Analyze the spatial and temporal distribution of the magnetic field of high voltage power lines with different design allowing and development of recommendations for the design of active screening systems by magnetic field of high voltage power lines. Methodology. Analysis of the spatial and temporal distribution of the magnetic field of high voltage power lines of different design allowing is made on the basis of Maxwell's equations solutions in the quasi-stationary approximation. Determination of the number, configuration, spatial arrangement and the compensation coil currents is formulated in the form of multiobjective optimization problem that is solved by multi-agent multiswarm stochastic optimization based on Pareto optimal solutions. Results of active screening system for the synthesis of various types of transmission lines with different numbers of windings controlled. The possibility of a significant reduction in the level of the flux density of the magnetic field source within a given region of space. Originality. For the first time an analysis of the spatial and temporal distribution of the magnetic field of power lines with different types and based on findings developed recommendations for the design of active screening system by magnetic field of high voltage power lines. Practical value. Practical recommendations on reasonable choice of the number and spatial arrangement of compensating windings of active screening system by magnetic field of high voltage power lines of different design allowing for the spatial and temporal distribution of the magnetic field. Results of active screening system synthesis of the magnetic field of industrial frequency generated by single-circuit 110 kV high voltage power lines with the supports have 330 - 1T «triangle» rotating magnetic field with full polarization in a residential five-storey building, located near the power lines. The system contains three compensating coil and reduces

  17. Spectroscopic study of partially-ordered semiconductor heterojunction under high pressure and high magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Yu, P.Y.; Martinez, G.; Zeman, J.; Uchida, K.


    Photoluminescence upconversion (PLU) is a phenomenon in which a sample emits photons with energy higher than that of the excitation photon. This effect has been observed in many materials including rare earth ions doped in insulating hosts and semiconductor heterostructures without using high power lasers as the excitation source. Recently, this effect has been observed also in partially CuPt-ordered GaInP{sub 2} epilayers grown on GaAs substrates. As a spectroscopic technique photoluminescence upconversion is particularly well suited for studying band alignment at heterojunction interface. The value of band-offset has been determined with meV precision using magneto-photoluminescence. Using the fact that the pressure coefficient of electrons in GaAs is higher than those in GaInP{sub 2} they have been able to manipulate the band-offset at the GaInP/GaAs interface. By converting the band-offset from Type I to Type II they were able to demonstrate that the efficiency of the upconversion process is greatly enhanced by a Type II band-offset.

  18. A method for unwrapping highly wrapped multi-echo phase images at very high field: UMPIRE. (United States)

    Robinson, Simon; Schödl, Horst; Trattnig, Siegfried


    To develop a method of unwrapping phase images from multi-echo scans that works even where there are several wraps between echoes, and which generates unwrapped phase images in addition to phase difference (PD) images. The difference between the echo spacings in an acquisition with three unevenly spaced echoes (an imposed delay) can be selected such that the phase evolution in that time is in the range -π to +π in all voxels of interest. Under this condition, an image of the difference between the phase evolutions in the two inter-echo periods, an estimate of ΔB0 , is free of wraps. This ΔB0 estimate can be used to identify and remove receiver phase offsets and wraps in phase images. The approach was tested on simulated data and high-resolution in vivo brain data acquired from six subjects at 7 Tesla. The method generated wrap-free phase images. It was able to remove more wraps than is possible with PD imaging and was faster and more reliable than spatial unwrapping. Unwrapping Multi-echo Phase Images with iRregular Echo spacings (UMPIRE) is conceptually simple, fast, reliable, and requires no fitting, thresholds, or operator intervention. Copyright © 2013 Wiley Periodicals, Inc.

  19. Statistical properties of Joule heating rate, electric field and conductances at high latitudes

    Directory of Open Access Journals (Sweden)

    A. T. Aikio


    Full Text Available Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox and from similar sunspot conditions (about 1.5 years before the sunspot minimum providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution. All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03–05 MLT for Kp≥3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity. An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp≥3. In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to auroral arcs as a result of ionosphere-magnetosphere coupling, as discussed by Aikio et al. (2004 In

  20. Statistical properties of Joule heating rate, electric field and conductances at high latitudes

    Directory of Open Access Journals (Sweden)

    A. T. Aikio


    Full Text Available Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox and from similar sunspot conditions (about 1.5 years before the sunspot minimum providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution.

    All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03–05 MLT for Kp≥3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity.

    An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp≥3. In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to

  1. Rigid ion model of high field transport in GaN. (United States)

    Yamakawa, Shinya; Akis, Richard; Faralli, Nicolas; Saraniti, Marco; Goodnick, Stephen M


    Here we report on high field transport in GaN based on the rigid ion model of the electron-phonon interaction within the cellular Monte Carlo (CMC) approach. Using the rigid pseudo-ion method for the cubic zinc-blende and hexagonal wurtzite structures, the anisotropic deformation potentials are derived from the electronic structure, the atomic pseudopotential and the full phonon dispersion and eigenvectors for both acoustic and optical modes. Several different electronic structure and lattice dynamics models are compared, as well as different models for the interpolation of the atomic pseudopotentials required in the rigid pseudo-ion method. Piezoelectric as well as anisotropic polar optical phonon scattering is accounted for as well. In terms of high field transport, the peak velocity is primarily determined by deformation potential scattering described through the rigid pseudo-ion model. The calculated velocity is compared with experimental data from pulsed I-V measurements. Good agreement is found using the rigid ion model to the measured velocity-field characteristics with the inclusion of dislocation and ionized impurity scattering. The crystal orientation of the electric field is investigated, where very little difference is observed in the velocity-field characteristics. We simulate the effects of nonequilibrium hot phonons on the energy relaxation as well, using a detailed balance between emission and absorption during the simulation, and an anharmonic decay of LO phonons to acoustic phonons, as reported previously. Nonequilibrium phonons are shown to result in a significant degradation of the velocity-field characteristics for high carrier densities, such as those encountered at the AlGaN/GaN interface due to polarization effects.

  2. Behavioral Effects on Rats of Motion within a High Static Magnetic Field (United States)

    Houpt, Thomas A.; Carella, Lee; Gonzalez, Dani; Janowitz, Ilana; Mueller, Anthony; Mueller, Kathleen; Neth, Bryan; Smith, James C.


    Some human subjects report vestibular disturbances such as vertigo, apparent motion, and nausea around or within high strength MRI systems operating at 4 T to 9.4 T. These vestibular effects have been ascribed to the consequences of movement through the high magnetic field. We have previously found that exposure to magnetic fields above 7 T suppresses rearing, causes locomotor circling, and induces conditioned taste aversion (CTA) in rodents. The present experiments were designed to test the effects on rats of motion through the magnetic field of the 14.1 T superconducting magnet. In experiment 1, we compared the effects of multiple rapid insertions and removals from the center of the magnet to the effects of continuous exposure. Repeated traversal of the magnetic field gradient with only momentary exposure to 14.1 T was sufficient to suppress rearing and induce a significant CTA. Repeated insertion and removal from the magnet, however, did not have a greater effect than a single 30-min exposure on either acute locomotor behavior or CTA acquisition. Prolonged exposure was required to induce locomotor circling. In the second series of experiments, we controlled the rate of insertion and removal by means of an electric motor. Locomotor circling appeared to be dependent on the speed of insertion and removal, but the suppression of rearing and the acquisition of CTA were independent of speed of insertion and removal. In experiment 3, we inserted rats into the center of the magnet and then rotated them about their rostral-caudal axis during a 30-min 14.1 T exposure. Rotation within the magnet did not modulate the behavioral effects of exposure. We conclude that, in rats, movement through the steep gradient of a high magnetic field has some behavioral effects, but sustained exposure to the homogenous center of the field is required for the full behavioral consequences. PMID:21118699

  3. First Cluster results of the magnetic field structure of the mid- and high-altitude cusps

    Directory of Open Access Journals (Sweden)

    P. J. Cargill

    Full Text Available Magnetic field measurements from the four Cluster spacecraft from the mid- and high-altitude cusp are presented. Cluster underwent two encounters with the mid-altitude cusp during its commissioning phase (24 August 2000. Evidence for field-aligned currents (FACs was seen in the data from all three operating spacecraft from northern and southern cusps. The extent of the FACs was of the order of 1 RE in the X-direction, and at least 300 km in the Y-direction. However, fine-scale field structures with scales of the order of the spacecraft separation (300 km were observed within the FACs. In the northern crossing, two of the spacecraft appeared to lie along the same magnetic field line, and observed very well matched signals. However, the third spacecraft showed evidence for structuring transverse to the field on scales of a few hundred km. A crossing of the high-altitude cusp from 13 February 2001 is presented. It is revealed to be a highly dynamic structure with the boundaries moving with velocities ranging from a few km/s to tens of km/s, and having structure on timescales ranging from less than one minute up to several minutes. The cusp proper is associated with the presence of a very disordered magnetic field, which is entirely different from the magnetosheath turbulence.

    Key words. Magnetospheric physics (current systems; magnetopause, cusp, and boundary layers – Space plasma physics (discontinuities

  4. Rigid ion model of high field transport in GaN (United States)

    Yamakawa, Shinya; Akis, Richard; Faralli, Nicolas; Saraniti, Marco; Goodnick, Stephen M.


    Here we report on high field transport in GaN based on the rigid ion model of the electron-phonon interaction within the cellular Monte Carlo (CMC) approach. Using the rigid pseudo-ion method for the cubic zinc-blende and hexagonal wurtzite structures, the anisotropic deformation potentials are derived from the electronic structure, the atomic pseudopotential and the full phonon dispersion and eigenvectors for both acoustic and optical modes. Several different electronic structure and lattice dynamics models are compared, as well as different models for the interpolation of the atomic pseudopotentials required in the rigid pseudo-ion method. Piezoelectric as well as anisotropic polar optical phonon scattering is accounted for as well. In terms of high field transport, the peak velocity is primarily determined by deformation potential scattering described through the rigid pseudo-ion model. The calculated velocity is compared with experimental data from pulsed I-V measurements. Good agreement is found using the rigid ion model to the measured velocity-field characteristics with the inclusion of dislocation and ionized impurity scattering. The crystal orientation of the electric field is investigated, where very little difference is observed in the velocity-field characteristics. We simulate the effects of nonequilibrium hot phonons on the energy relaxation as well, using a detailed balance between emission and absorption during the simulation, and an anharmonic decay of LO phonons to acoustic phonons, as reported previously. Nonequilibrium phonons are shown to result in a significant degradation of the velocity-field characteristics for high carrier densities, such as those encountered at the AlGaN/GaN interface due to polarization effects.

  5. Defibrillation success with high frequency electric fields is related to degree and location of conduction block. (United States)

    Weinberg, Seth H; Chang, Kelly C; Zhu, Renjun; Tandri, Harikrishna; Berger, Ronald D; Trayanova, Natalia A; Tung, Leslie


    We recently demonstrated that high frequency alternating current (HFAC) electric fields can reversibly block propagation in the heart by inducing an oscillating, elevated transmembrane potential (Vm) that maintains myocytes in a refractory state for the field duration and can terminate arrhythmias, including ventricular fibrillation (VF). To quantify and characterize conduction block (CB) induced by HFAC fields and to determine whether the degree of CB can be used to predict defibrillation success. Optical mapping was performed in adult guinea pig hearts (n = 14), and simulations were performed in an anatomically accurate rabbit ventricular model. HFAC fields (50-500 Hz) were applied to the ventricles. A novel power spectrum metric of CB-the loss of spectral power in the 1-30 Hz range, termed loss of conduction power (LCP)-was assessed during the HFAC field and compared with defibrillation success and VF vulnerability. LCP increased with field strength and decreased with frequency. Optical mapping experiments conducted on the epicardial surface showed that LCP and the size of CB regions were significantly correlated with VF initiation and termination. In simulations, subsurface myocardial LCP and CB sizes were more closely correlated with VF termination than surface values. Multilinear regression analysis of simulation results revealed that while CB on both the surface and the subsurface myocardium was predictive, subsurface myocardial CB was the better predictor of defibrillation success. HFAC fields induce a field-dependent state of CB, and defibrillation success is related to the degree and location of the CB. Copyright © 2013. Published by Elsevier Inc.

  6. High-k Dielectric Passivation for GaN Diode with a Field Plate Termination

    Directory of Open Access Journals (Sweden)

    Michitaka Yoshino


    Full Text Available Vertical structured Gallium nitride (GaN p-n junction diodes with improved breakdown properties have been demonstrated using high-k dielectric passivation underneath the field plate. Simulation results at a reverse voltage of 1 kV showed that the maximum electric field near the mesa-etched p-n junction edges covered with film of dielectric constant k = 10 was reduced to 2.0 MV/cm from 3.0 MV/cm (SiO2 (k = 3.9. The diodes were fabricated using the high-k mixed oxide of SiO2 and CeO2 with k = 12.3. I–V characteristics of the diode with a field plate showed a breakdown voltage above 2 kV with an increased avalanche resistance. This means that the electric field reduces at the periphery of the mesa-etched p-n junction and is uniformly formed across the whole p-n junction. It is clear that high-k dielectric film passivation and filed plate termination are essential techniques for GaN power devices.

  7. Scoping study for compact high-field superconducting net energy tokamaks (United States)

    Mumgaard, R. T.; Greenwald, M.; Freidberg, J. P.; Wolfe, S. M.; Hartwig, Z. S.; Brunner, D.; Sorbom, B. N.; Whyte, D. G.


    The continued development and commercialization of high temperature superconductors (HTS) may enable the construction of compact, net-energy tokamaks. HTS, in contrast to present generation low temperature superconductors, offers improved performance in high magnetic fields, higher current density, stronger materials, higher temperature operation, and simplified assembly. Using HTS along with community-consensus confinement physics (H98 =1) may make it possible to achieve net-energy (Q>1) or burning plasma conditions (Q>5) in DIII-D or ASDEX-U sized, conventional aspect ratio tokamaks. It is shown that, by operating at high plasma current and density enabled by the high magnetic field (B>10T), the required triple products may be achieved at plasma volumes under 20m3, major radii under 2m, with external heating powers under 40MW. This is at the scale of existing devices operated by laboratories, universities and companies. The trade-offs in the core heating, divertor heat exhaust, sustainment, stability, and proximity to known plasma physics limits are discussed in the context of the present tokamak experience base and the requirements for future devices. The resulting HTS-based design space is compared and contrasted to previous studies on high-field copper experiments with similar missions. The physics exploration conducted with such HTS devices could decrease the real and perceived risks of ITER exploitation, and aid in quickly developing commercially-applicable tokamak pilot plants and reactors.

  8. High frequency electric field levels: An example of determination of measurement uncertainty for broadband measurements

    Directory of Open Access Journals (Sweden)

    Vulević Branislav


    Full Text Available Determining high frequency electromagnetic field levels in urban areas represents a very complex task, having in mind the exponential growth of the number of sources embodied in public cellular telephony systems in the past twenty years. The main goal of this paper is a representation of a practical solution in the evaluation of measurement uncertainty for in-situ measurements in the case of spatial averaging. An example of the estimation of the uncertainty for electric field strength broadband measurements in the frequency range from 3 MHz to 18 GHz is presented.

  9. High-field magnetic resonance imaging of the human temporal lobe

    Directory of Open Access Journals (Sweden)

    Luis M. Colon-Perez


    Conclusions: Fresh ex vivo MR imaging, along with tractography, revealed complex intra-temporal structural variation corresponding to neuronal cell body layers, dendritic fields, and axonal projection systems evident histologically. This is the first study to describe in detail the human temporal lobe structural organization using high-field MR imaging and tractography. By preserving the 3-dimensional structures of the hippocampus and surrounding structures, specific changes in anatomy may inform us about the changes that occur in TLE in relation to the disease process and structural underpinnings in epilepsy-related memory dysfunction.


    Directory of Open Access Journals (Sweden)

    V. I. Gavrilova


    Full Text Available Currently, high-scale field surveys-based thematic mapping is not very widespread, though it provides detailed and accurate information about the study area, presented in representative cartographic form. In this paper, authors present the soil map and landscape map of Veslovsky peninsula (Kunashir island, Kuril islands based on wide field surveys led in summer of 2014. Veslovsky peninsula is located in the buffer zone of the Kuril nature reserve. The maps provide detailed information on the soil cover and the landscape differentiation of the study area.

  11. Peculiarities of high electric field conduction in p-type diamond (United States)

    Mortet, V.; Trémouilles, D.; Bulíř, J.; Hubík, P.; Heller, L.; Bedel-Pereira, E.; Soltani, A.


    The electrical properties of chemical vapour deposited p-type epitaxial diamond layers are studied in high electric field conditions. The quasi-static current-voltage characteristics have been measured using transmission-line pulse method with 100 ns pulses. Reproducible impurity impact ionization avalanche breakdown occurs at a critical electrical field in the range of 100-200 kV cm-1 depending on the acceptor concentration and temperature, leading to complete ionisation of neutral impurities. The current-voltage characteristics exhibit an S-shape with the bi-stable conduction characteristic of impurity impact ionisation.

  12. Installation for microwave investigations of high-temperature superconductivity in magnetic field

    CERN Document Server

    Akhvlediani, I G; Mamniashvili, G I; Chigvinadze, D G


    Paper describes advanced EPR-spectrometer RE 1306 designed to investigate into structure of magnetic flux in high-temperature superconductors (HTSC). To measure in low fields one uses power source generating current within 0-600 mA limits and 10-500 Gauss field. To ensure temperature studies of HTSC within up to approx 15 K range one used helium and nitrogen cold steam blowing through resonator of EPR-spectrometer. To stabilize specimen temperature prior to cold steams enter double tube one fixed one more heater

  13. Highly accurate analytical energy of a two-dimensional exciton in a constant magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Hoang, Ngoc-Tram D. [Department of Physics, Ho Chi Minh City University of Pedagogy 280, An Duong Vuong Street, District 5, Ho Chi Minh City (Viet Nam); Nguyen, Duy-Anh P. [Department of Natural Science, Thu Dau Mot University, 6, Tran Van On Street, Thu Dau Mot City, Binh Duong Province (Viet Nam); Hoang, Van-Hung [Department of Physics, Ho Chi Minh City University of Pedagogy 280, An Duong Vuong Street, District 5, Ho Chi Minh City (Viet Nam); Le, Van-Hoang, E-mail: [Atomic Molecular and Optical Physics Research Group, Ton Duc Thang University, 19 Nguyen Huu Tho Street, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam); Faculty of Applied Sciences, Ton Duc Thang University, 19 Nguyen Huu Tho Street, Tan Phong Ward, District 7, Ho Chi Minh City (Viet Nam)


    Explicit expressions are given for analytically describing the dependence of the energy of a two-dimensional exciton on magnetic field intensity. These expressions are highly accurate with the precision of up to three decimal places for the whole range of the magnetic field intensity. The results are shown for the ground state and some excited states; moreover, we have all formulae to obtain similar expressions of any excited state. Analysis of numerical results shows that the precision of three decimal places is maintained for the excited states with the principal quantum number of up to n=100.

  14. Initial studies of high latitude magnetic field data during different magnetospheric conditions (United States)

    Cersosimo, D. O.; Wanliss, J. A.


    We investigate the statistical properties of high-latitude magnetometer data for differing geomagnetic activity. This is achieved by characterizing changes in the nonlinear statistics of the geomagnetic field, by means of the Hurst exponent, measured from a single ground-based magnetometer station. The long-range statistical nature of the geomagnetic field at a local observation site can be described as a multifractional Brownian motion, thus suggesting the statistical structure required of mathematical models of magnetospheric activity. We also find that, in general, the average Hurst exponent for quiet magnetospheric intervals is smaller than that for more active intervals.

  15. Radiation Fields in High Energy Accelerators and their impact on Single Event Effects

    CERN Document Server

    García Alía, Rubén; Wrobel, Frédéric; Brugger, Markus

    Including calculation models and measurements for a variety of electronic components and their concerned radiation environments, this thesis describes the complex radiation field present in the surrounding of a high-energy hadron accelerator and assesses the risks related to it in terms of Single Event Effects (SEE). It is shown that this poses not only a serious threat to the respective operation of modern accelerators but also highlights the impact on other high-energy radiation environments such as those for ground and avionics applications. Different LHC-like radiation environments are described in terms of their hadron composition and energy spectra. They are compared with other environments relevant for electronic component operation such as the ground-level, avionics or proton belt. The main characteristic of the high-energy accelerator radiation field is its mixed nature, both in terms of hadron types and energy interval. The threat to electronics ranges from neutrons of thermal energies to GeV hadron...

  16. [Ultra-high-field MRI in the Chicken Embryo in Ovo - a Model for Experimental Ophthalmology]. (United States)

    Klose, Ronja; Streckenbach, Felix; Hadlich, Stefan; Stahnke, Thomas; Guthoff, Rudolf; Wree, Andreas; Frank, Marcus; Langner, Sönke; Stachs, Oliver; Lindner, Tobias


    Ultra-high-field MRI (UHF-MRI) is an outstanding technique for non-invasive and non-destructive imaging of soft tissues and can provide versatile contrasts and high resolution in the µm range. In vivo imaging of the embryonal chick eye with its filigree anatomical structures imposes these requirements. However, due to the short embryonal development cycle, chicken are a favourite animal model for embryonal research studies. Ultra-high-field MRI allows repeated and longitudinal in ovo investigations on the same embryo. In the present study, the limitations and opportunities of in ovo MR-imaging at 7 T were evaluated and the process of eye growth was described in detail. Georg Thieme Verlag KG Stuttgart · New York.

  17. High-frequency noise characterization of graphene field effect transistors on SiC substrates (United States)

    Yu, C.; He, Z. Z.; Song, X. B.; Liu, Q. B.; Dun, S. B.; Han, T. T.; Wang, J. J.; Zhou, C. J.; Guo, J. C.; Lv, Y. J.; Cai, S. J.; Feng, Z. H.


    Considering its high carrier mobility and high saturation velocity, a low-noise amplifier is thought of as being the most attractive analogue application of graphene field-effect transistors. The noise performance of graphene field-effect transistors at frequencies in the K-band remains unknown. In this work, the noise parameters of a graphene transistor are measured from 10 to 26 GHz and noise models are built with the data. The extrinsic minimum noise figure for a graphene transistor reached 1.5 dB, and the intrinsic minimum noise figure was as low as 0.8 dB at a frequency of 10 GHz, which were comparable with the results from tests on Si CMOS and started to approach those for GaAs and InP transistors. Considering the short development time, the current results are a significant step forward for graphene transistors and show their application potential in high-frequency electronics.

  18. GEM detector performance with innovative micro-TPC readout in high magnetic field (United States)

    Garzia, I.; Alexeev, M.; Amoroso, A.; Baldini Ferroli, R.; Bertani, M.; Bettoni, D.; Bianchi, F.; Calcaterra, A.; Canale, N.; Capodiferro, M.; Cassariti, V.; Cerioni, S.; Chai, J. Y.; Chiozzi, S.; Cibinetto, G.; Cossio, F.; Cotta Ramusino, A.; De Mori, F.; Destefanis, M.; Dong, J.; Evangelisti, F.; Evangelisti, F.; Farinelli, R.; Fava, L.; Felici, G.; Fioravanti, E.; Gatta, M.; Greco, M.; Lavezzi, L.; Leng, C. Y.; Li, H.; Maggiora, M.; Malaguti, R.; Marcello, S.; Melchiorri, M.; Mezzadri, G.; Mignone, M.; Morello, G.; Pacetti, S.; Patteri, P.; Pellegrino, J.; Pelosi, A.; Rivetti, A.; Rolo, M. D.; Savrié, M.; Scodeggio, M.; Soldani, E.; Sosio, S.; Spataro, S.; Tskhadadze, E.; Verma, S.; Wheadon, R.; Yan, L.


    Gas detector development is one of the pillars of the research in fundamental physics. Since several years, a new concept of detectors, called Micro Pattern Gas Detector (MPGD), allowed to overcome several problems related to other types of commonly used detectors, like drift chamber and micro strips detectors, reducing the rate of discharges and providing better radiation tolerance. Among the most used MPGDs are the Gas Electron Multipliers (GEMs). Invented by Sauli in 1997, nowadays GEMs have become an important reality for particle detectors in high energy physics. Commonly deployed as fast timing detectors and triggers, their fast response, high rate capability and high radiation hardness make them also suitable as tracking detectors. The readout scheme is one of the most important features in tracking technology. Analog readout based on the calculation of the center of gravity technique allows to overcome the limit imposed by digital pads, whose spatial resolution is limited by the pitch dimensions. However, the presence of high external magnetic fields can distort the electronic cloud and affect the performance. The development of the micro-TPC reconstruction method brings GEM detectors into a new prospective, improving significantly the spatial resolutionin presence of high magnetic fields. This innovative technique allows to reconstruct the 3-dimensional particle position, as Time Projection Chamber, but within a drift gap of a few millimeters. In these report, the charge centroid and micro-TPC methods are described in details. We discuss the results of several test beams performed with planar chambers in magnetic field. These results are one of the first developments of micro-TPC technique for GEM detectors, which allows to reach unprecedented performance in a high magnetic field of 1 T.

  19. Electric Power High-Voltage Transmission Lines: Design Options, Cost, and Electric and Magnetic Field Levels

    Energy Technology Data Exchange (ETDEWEB)

    Stoffel, J. B. [Argonne National Lab. (ANL), Argonne, IL (United States). Environmental Assessment Division. Electronics and Computing Technologies Division; Pentecost, E. D. [Argonne National Lab. (ANL), Argonne, IL (United States). Environmental Assessment Division; Roman, R. D. [Argonne National Lab. (ANL), Argonne, IL (United States). Environmental Assessment Division; Traczyk, P. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Environmental Assessment Division


    The aim of this report is to provide background information about (1) the electric and magnetic fields (EMFs) of high-voltage transmission lines at typical voltages and line configurations and (2) typical transmission line costs to assist preparers and reviewers of the section on alternatives in environmental documents. This report will give the reviewing individual a better appreciation of the factors affecting EMF strengths near high-voltage transmission lines and the approaches that might be used to reduce EMF impacts on humans and other biological species in the vicinity of high-voltage overhead or underground alternating-current (ac) or direct-current (dc) transmission lines.

  20. High-Density Near-Field Readout Using Diamond Solid Immersion Lens (United States)

    Shinoda, Masataka; Saito, Kimihiro; Kondo, Takao; Nakaoki, Ariyoshi; Furuki, Motohiro; Takeda, Minoru; Yamamoto, Masanobu; Schaich, Thomas J.; van Oerle, Bart M.; Godfried, Herman P.; Kriele, Paul A. C.; Houwman, Evert P.; Nelissen, Wim H. M.; Pels, Gert J.; Spaaij, Paul G. M.


    We investigated high-density near-field readout using a diamond solid immersion lens (SIL). A synthetic single-crystal chemical vapor deposition diamond provides a high refractive index and a high transmission for a wide wavelength range. Since the refractive index at a wavelength of 405 nm is 2.458, we could design a solid immersion lens with an effective numerical aperture of 2.34. Using the diamond SIL, we observed the eye pattern of a 150-GB-capacity (104.3 Gbit/in.2) disk with a track pitch of 130 nm and a bit length of 47.6 nm.

  1. Magnet design with high B(0) homogeneity for fast-field-cycling NMR applications. (United States)

    Lips, O; Privalov, A F; Dvinskikh, S V; Fujara, F


    The design, construction, and performance of a low-inductance solenoidal coil with high B(0) homogeneity for fast-field-cycling NMR is presented. It consists of six concentric layers. The conductor width is varied to minimize the B(0) inhomogeneity in the volume of the sample. This is done using an algorithm which takes the real shape of the conductor directly into account. The calculated coil geometry can be manufactured easily using standard computerized numeric control equipment, which keeps the costs low. The coil is liquid cooled and produces a B(0) field of 0.95 T at 800 A. The field inhomogeneity in a cylindrical volume (diameter 5 mm, length 10 mm) is about 10 ppm, and the inductance is 190 microH. Switching times below 200 micros can be achieved. During 6 months of operation the coil has shown good stability and reliability. Copyright 2001 Academic Press.

  2. Classical solutions in quantum field theory solitons and instantons in high energy physics

    CERN Document Server

    Weinberg, Erick J


    Classical solutions play an important role in quantum field theory, high energy physics and cosmology. Real-time soliton solutions give rise to particles, such as magnetic monopoles, and extended structures, such as domain walls and cosmic strings, that have implications for early universe cosmology. Imaginary-time Euclidean instantons are responsible for important nonperturbative effects, while Euclidean bounce solutions govern transitions between metastable states. Written for advanced graduate students and researchers in elementary particle physics, cosmology and related fields, this book brings the reader up to the level of current research in the field. The first half of the book discusses the most important classes of solitons: kinks, vortices and magnetic monopoles. The cosmological and observational constraints on these are covered, as are more formal aspects, including BPS solitons and their connection with supersymmetry. The second half is devoted to Euclidean solutions, with particular emphasis on ...

  3. Injection halos of hydrocarbons above oil-gas fields with super-high pressures

    Energy Technology Data Exchange (ETDEWEB)

    Bakhtin, V.V.


    We studied the origin of injection halos of hydrocarbons above oil-gas fields with anomalously high formation pressures (AHFP). Using fields in Azerbaydzhan and Chechen-Ingushetiya as an example, we demonstrate the effect of certain factors (in particular, faults and zones of increased macro- and micro-jointing) on the morpholoy of the halos. The intensity of micro-jointing (jointing permeability, three-dimensional density of micro-jointing) is directly connected with vertical dimensions of the halos. We measured halos based on transverse profiles across the Khayan-Kort field and studied the distribution of bitumen saturation within the injection halo. Discovery of injection halos during drilling has enabled us to improve the technology of wiring deep-seated exploratory wells for oil and gas in regions with development of AHFP.

  4. High field matching effects in superconducting Nb porous arrays catalyzed from anodic alumina templates

    DEFF Research Database (Denmark)

    Vinckx, W.; Vanacken, J.; Moshchalkov, V.V.


    Vortex pinning in a superconducting Nb thin film deposited on an anodically grown alumina template is investigated. Anodic oxidation of aluminium layers permits under specific conditions the formation of highly ordered porous alumina, a membrane-like structure consisting of triangular arrays...... of parallel pores. Its pore diameter and interpore distance are set by careful tuning of the anodization parameters. A superconducting Nb thin film is deposited directly onto the alumina film. The porous alumina acts as a template and it allows Nb to form a periodic pinning array during its growth. Pinning...... force vs. field measurements derived from magnetization measurements, show matching effects in fields up to 1 T. We demonstrate that the anodic alumina template with 50 nm interpore spacing provides enhanced vortex pinning in a large field and temperature range....

  5. Dynamic characteristics of non-ideal plasmas in an external high frequency electric field

    Energy Technology Data Exchange (ETDEWEB)

    Adamyan, V M [Department of Theoretical Physics, I. I. Mechnikov Odessa National University, 65026 Odessa (Ukraine); Djuric, Z [Silvaco Data System, Silvaco Technology Centre, Compass Point, St. Ives PE27 5JL (United Kingdom); Mihajlov, A A [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro); Sakan, N M [Institute of Physics, PO Box 57, 11001 Belgrade (Serbia and Montenegro); Tkachenko, I M [Department of Applied Mathematics, ETSII, Polytechnic University of Valencia, Camino de Vera s/n, Valencia 46022 (Spain)


    The dynamic electric conductivity, dielectric permeability and refraction and reflection coefficients of a completely ionized gaseous plasma in a high frequency (HF) external electric field are calculated. These results are obtained within the self-consistent field approach developed earlier for the static conductivity determination. The plasma electron density, N{sub e}, and temperature, T, varied within the following limits: 10{sup 19} {<=} N{sub e} {<=} 10{sup 21} cm{sup -3} and 2 x 10{sup 4} {<=} T {<=} 10{sup 6} K, respectively. The external electric field frequency, f, varied in the range 3 GHz{<=} f {<=} 0.05{omicron}{sub p}, where {omicron}{sub p} is the circular plasma frequency. Thus, the upper limit for f is either in the microwave or in the far infrared frequency band. The final results are shown in a parameterized form, suitable for laboratory applications.

  6. High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED. (United States)

    Ullmann, Johannes; Andelkovic, Zoran; Brandau, Carsten; Dax, Andreas; Geithner, Wolfgang; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Hannen, Volker; Kaufmann, Simon; König, Kristian; Litvinov, Yuri A; Lochmann, Matthias; Maaß, Bernhard; Meisner, Johann; Murböck, Tobias; Sánchez, Rodolfo; Schmidt, Matthias; Schmidt, Stefan; Steck, Markus; Stöhlker, Thomas; Thompson, Richard C; Trageser, Christian; Vollbrecht, Jonas; Weinheimer, Christian; Nörtershäuser, Wilfried


    Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209 Bi 82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron-nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209 Bi 82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.

  7. High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED (United States)

    Ullmann, Johannes; Andelkovic, Zoran; Brandau, Carsten; Dax, Andreas; Geithner, Wolfgang; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Hannen, Volker; Kaufmann, Simon; König, Kristian; Litvinov, Yuri A.; Lochmann, Matthias; Maaß, Bernhard; Meisner, Johann; Murböck, Tobias; Sánchez, Rodolfo; Schmidt, Matthias; Schmidt, Stefan; Steck, Markus; Stöhlker, Thomas; Thompson, Richard C.; Trageser, Christian; Vollbrecht, Jonas; Weinheimer, Christian; Nörtershäuser, Wilfried


    Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209Bi82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron-nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209Bi82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.

  8. Drag-Free Motion Control of Satellite for High-Precision Gravity Field Mapping

    DEFF Research Database (Denmark)

    Ziegler, Bent Lindvig; Blanke, Mogens


    High precision mapping of the geoid and the Earth's gravity field are of importance to a wide range of ongoing studies in areas like ocean circulation, solid Earth physics and ice sheet dynamics. Using a satellite in orbit around the Earth gives the opportunity to map the Earth's gravity field in 3...... dimensions with much better accuracy and spatial resolution than ever accomplished. To reach the desired quality of measurements, the satellite must fly in a low Earth orbit where disturbances from atmospheric drag and the Earth's magnetic field will perturb the satellite's motion. These effects...... will compromise measurement accuracy, unless they are accurately compensated by on-board thrusters. The paper concerns the design of a control system to performing such delicate drag compensation. A six degrees-of-freedom model for the satellite is developed with the model including dynamics of the satellite...

  9. Superconducting high-field wigglers and wave length shifter in budker INP

    CERN Document Server

    Batrakov, A M; Borovikov, V M


    Several high-field superconducting wigglers (SCW) and wavelength shifters (WLS) are fabricated in the Budker INP for generation of synchrotron radiation.Three-pole WLS with the magnetic field of 7.5 T are installed on LSU-CAMD and BESSY-II storage rings for shifting the radiation spectrum.WLS with the field of 10.3 T will be used for generation of slow positrons on SPring-8.Creation of a 13-pole 7 T wiggler for the BESSY-II and 45-pole 3.5 T wiggler for ELETRA now is finished.The main characteristics,design features and synchrotron radiation properties of SCW and WLS created in the Budker INP are presented in this article.

  10. Biological effects of high strength electric fields. Second interim progress report, September 1976--March 1977

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, R.D.; Kaune, W.T.


    This report describes progress made on the Project during the period of September 9, 1976 to March 31, 1977 towards the determination of the biological effects of high strength electric fields on small laboratory animals. The efforts to date can be divided into five categories: (1) the design, construction, and testing of a prototype and special studies exposure system; (2) the design and construction of exposure systems for rats and mice; (3) dosimetry; (4) experiments to determine the maximum field strength which does not produce corona discharge, ozone formation, shocks to the animal, hair stimulation, or a behavioral preference by rats to avoid exposure to the field; and (5) preparations for the biological screening experiments.

  11. The Analog-Method: Reconstruction of highly resolved Atmospheric Forcing Fields (United States)

    Schenk, Frederik; Zorita, Eduardo


    In this study we test and apply a new method to reconstruct highly resolved atmospheric forcing fields for Northern Europe since 1850 AD. As a simple statistical upscaling method, the analog-method is used to find best fitting atmospheric fields (predictand) to a given variable from long historical station measurements (predictor). The atmospheric fields are taken from a regional climate simulation and serve as a pool of analogs to match the local climate information of station measurements. An important advantage of this non-linear approach is the conservation of full variability in the reconstruction which is generally underestimated by linear regression methods by more than a factor of two. In a first step, the analog method is tested within the model domain serving as surrogate climate. Atmospheric fields (0.25° x 0.25°) of SLP, wind components, temperature, relative humidity, total cloud cover and precipitation are reconstructed by the analog-method using different amounts of grid points (5-25) as synthetic stations. Within the regional model, reconstructions of atmospheric forcing fields for the variables SLP and wind components show excellent skills (r ~ 0.8) when being reconstructed by daily SLP as predictor. For temperature, rel. humidity, total cloud cover and precipitation, SLP is a weak physical predictor leading to lower skills but significantly better than their climatological mean. Using daily air temperature as predictor instead of SLP, temperature fields are reconstructed with very good skills (r > 0.5 for summer and >0.7 in winter). In a second step, the same approach is repeated with real daily SLP data from 23 stations as predictor spanning the period from 1850 to 2009. Limited by the length of the model simulations, 25 years (1958-1982, 1983-2007) are used as calibration and validation periods. The forcing fields for SLP and wind (u,v) show correlations >0.7 for the validation periods. Although the physical link between SLP and relative

  12. Implicit Solution of the Four-field Extended-magnetohydroynamic Equations using High-order High-continuity Finite Elements

    Energy Technology Data Exchange (ETDEWEB)

    S.C. Jardin; J.A. Breslau


    Here we describe a technique for solving the four-field extended-magnetohydrodynamic (MHD) equations in two dimensions. The introduction of triangular high-order finite elements with continuous first derivatives (C{sup 1} continuity) leads to a compact representation compatible with direct inversion of the associated sparse matrices. The split semi-implicit method is introduced and used to integrate the equations in time, yielding unconditional stability for arbitrary time step. The method is applied to the cylindrical tilt mode problem with the result that a non-zero value of the collisionless ion skin depth will increase the growth rate of that mode. The effect of this parameter on the reconnection rate and geometry of a Harris equilibrium and on the Taylor reconnection problem is also demonstrated. This method forms the basis for a generalization to a full extended-MHD description of the plasma with six, eight, or more scalar fields.

  13. Flow field analysis of high-speed helium turboexpander for cryogenic refrigeration and liquefaction cycles (United States)

    Sam, Ashish Alex; Ghosh, Parthasarathi


    Turboexpander constitutes one of the vital components of Claude cycle based helium refrigerators and liquefiers that are gaining increasing technological importance. These turboexpanders which are of radial inflow in configuration are generally high-speed micro turbines, due to the low molecular weight and density of helium. Any improvement in efficiency of these machines requires a detailed understanding of the flow field. Computational Fluid Dynamics analysis (CFD) has emerged as a necessary tool for the determination of the flow fields in cryogenic turboexpanders, which is often not possible through experiments. In the present work three-dimensional transient flow analysis of a cryogenic turboexpander for helium refrigeration and liquefaction cycles were performed using Ansys CFX®, to understand the flow field of a high-speed helium turboexpander, which in turn will help in taking appropriate decisions regarding modifications of established design methodology for improved efficiency of these machines. The turboexpander is designed based on Balje's nsds diagram and the inverse design blade profile generation formalism prescribed by Hasselgruber and Balje. The analyses include the study of several losses, their origins, the increase in entropy due to these losses, quantification of losses and the effects of various geometrical parameters on these losses. Through the flow field analysis it was observed that in the nozzle, flow separation at the nozzle blade suction side and trailing edge vortices resulted in loss generation, which calls for better nozzle blade profile. The turbine wheel flow field analysis revealed that the significant geometrical parameters of the turbine wheel blade like blade inlet angle, blade profile, tip clearance height and trailing edge thickness need to be optimised for improved performance of the turboexpander. The detailed flow field analysis in this paper can be used to improve the mean line design methodology for turboexpanders used

  14. Effect of high-hydrostatic pressure and moderate-intensity pulsed electric field on plum. (United States)

    García-Parra, J; González-Cebrino, F; Delgado-Adámez, J; Cava, R; Martín-Belloso, O; Élez-Martínez, P; Ramírez, R


    Moderate intensity pulse electric fields were applied in plum with the aim to increase bioactive compounds content of the fruit, while high-hydrostatic pressure was applied to preserve the purées. High-hydrostatic pressure treatment was compared with an equivalent thermal treatment. The addition of ascorbic acid during purée manufacture was also evaluated. The main objective of this study was to assess the effects on microorganisms, polyphenoloxidase, color and bioactive compounds of high-hydrostatic pressure, or thermal-processed plum purées made of moderate intensity pulse electric field-treated or no-moderate intensity pulse electric field-treated plums, after processing during storage. The application of moderate intensity pulse electric field to plums slightly increased the levels of anthocyanins and the antioxidant activity of purées. The application of Hydrostatic-high pressure (HHP) increased the levels of bioactive compounds in purées, while the thermal treatment preserved better the color during storage. The addition of ascorbic acid during the manufacture of plum purée was an important factor for the final quality of purées. The color and the bioactive compounds content were better preserved in purées with ascorbic acid. The no inactivation of polyphenoloxidase enzyme with treatments applied in this study affected the stability purées. Probably more intense treatments conditions (high-hydrostatic pressure and thermal treatment) would be necessary to reach better quality and shelf life during storage.

  15. Visual field loss morphology in high- and normal-tension glaucoma. (United States)

    Iester, Michele; De Feo, Fabio; Douglas, Gordon R


    Purpose. To determine whether the patterns of visual field damage between high-tension glaucoma (HTG) and normal-tension glaucoma (NTG) are equivalent. Methods. In this retrospective cross-sectional study, fifty-one NTG and 57 HTG patients were recruited. For each recruited patient only the left eye was chosen. Glaucomatous patients had abnormal visual fields and/or glaucomatous changes at the optic nerve head. They were classified as HTG or NTG on the basis of intraocular pressure (IOP) measurements. Patients' visual fields were analyzed by using Humphrey Field Analyzer (HFA), program 30-2, full threshold. The visual field sensitivity values and the pattern deviation map values of the 72 tested points were considered. Then a pointwise analysis and an area analysis, based on the Glaucoma Hemifield test criteria, were performed, and a comparison between the two subgroups was made by Student's t test. Results. Between NTG and HTG, no significant difference was found pointwise for almost all the visual field points, except for two locations. One was under the blind spot, and the other was in the inferior hemifield around the twenty-degree position. When area analysis was considered, three areas showed a significantly different sensitivity between HTG and NTG. Conclusions. These data suggested that there was no relevant difference in the pointwise analysis between NTG and HTG; however, when visual field areas were compared, no difference in paracentral areas was found between NTG and HTG, but superior nasal step and inferior and superior scotomata showed to be deeper in HTG than in NTG.

  16. A study of high field quantum electrodynamics in the collision of high energy electrons with a terawatt laser

    Energy Technology Data Exchange (ETDEWEB)

    Horton-Smith, G.A.


    An experiment is described which studied quantum electrodynamic interactions under conditions of extremely high fields, along with a review of the relevant theory. The high fields were created by an intense, tightly-focused pulse of laser light at green or infrared wavelengths, into which was sent an ultra-relativistic electron beam of 46.6-GeV energy. The relevant theory is that of an electron in an electromagnetic wave so intense that the electron's mass is effectively shifted by the transverse momentum imparted to it by the wave, and the electron encounters field strengths comparable to the Schwinger critical field strength of 511 kV per Compton wavelength. An electron in the intense wave may radiate a photon and balance 4-momentum by absorbing multiple photons from the laser, which can lead to real photons with energies above the kinematic limit for conventional Compton scattering. All particles have significant probability of scattering multiple times while in the focus of the laser, including the photons radiated by the electrons, which may convert into electron-positron pairs, again with absorption of multiple photons from the laser. This experiment was able to measure the rates and spectra of positrons, electrons, and photons emerging from the interaction region. Results from both experiment and theoretical simulations are presented and compared. The results from the electron and positron measurements are compatible with the accepted theory, within experimental uncertainties due mainly to the laser intensity measurement. The photon spectrum shows the correct shape, but the ratio of rates in the linear and two-absorbed-photon portions of the spectrum does not vary as expected with the laser intensity, suggesting a disagreement with the accepted theory, with a significance of roughly two standard deviations. A follow-up experiment would be in order.

  17. Optimised, low cost, low field dedicated extremity MRI is highly specific and sensitive for synovitis and bone erosions in rheumatoid arthritis wrist and finger joints: comparison with conventional high field MRI and radiography

    DEFF Research Database (Denmark)

    Ejbjerg, B.J; Narvestad, E; Jacobsen, S


    were performed. In an initial low field MRI 'sequence selection phase', based on a subset of 10 patients and 10 controls, sequences for comparison with high field MRI were selected. RESULTS: With high field, spin echo MRI considered as the reference method, the sensitivity, specificity, and accuracy...... of low field 3D gradient echo MRI for erosions were 94%, 93%, 94%, while the corresponding values for x ray examination were 33%, 98%, and 83%. Sensitivity, specificity, and accuracy of low field MRI for synovitis were 90%, 96%, and 94%, and for bone marrow oedema 39%, 99%, and 95%. Intraclass......, specificity is high, but sensitivity only moderate. Low cost, patient compliant, low field dedicated extremity MRI provides similar information on bone erosions and synovitis as expensive high field MRI units...

  18. Effects of high-gradient magnetic fields on living cell machinery (United States)

    Zablotskii, V.; Lunov, O.; Kubinova, S.; Polyakova, T.; Sykova, E.; Dejneka, A.


    A general interest in biomagnetic effects is related to fundamental studies of the influence of magnetic fields on living objects on the cellular and whole organism levels. Emerging technologies offer new directions for the use of high-gradient magnetic fields to control cell machinery and to understand the intracellular biological processes of the emerging field of nanomedicine. In this review we aim at highlighting recent advances made in identifying fundamental mechanisms by which magnetic gradient forces act on cell fate specification and cell differentiation. The review also provides an analysis of the currently available magnetic systems capable of generating magnetic fields with spatial gradients of up to 10 MT m-1, with the focus on their suitability for use in cell therapy. Relationships between experimental factors and underlying biophysical mechanisms and assumptions that would ultimately lead to a deeper understanding of cell machinery and the development of more predictive models for the evaluation of the effects of magnetic fields on cells, tissue and organisms are comprehensively discussed.

  19. Acoustic characterization of high intensity focused ultrasound fields generated from a transmitter with a large aperture

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tao; Fan, Tingbo [Institute of Acoustics, Key Laboratory of Modern Acoustics, MOE, Nanjing University, Nanjing 210093 (China); Jiangsu Province Institute for Medical Equipment Testing, Nanjing 210012 (China); Zhang, Wei [Jiangsu Province Institute for Medical Equipment Testing, Nanjing 210012 (China); Qiu, Yuanyuan [Department of electronic information, Nantong University, Nantong 226019 (China); Tu, Juan, E-mail:, E-mail:; Guo, Xiasheng [Institute of Acoustics, Key Laboratory of Modern Acoustics, MOE, Nanjing University, Nanjing 210093 (China); Zhang, Dong, E-mail:, E-mail: [Institute of Acoustics, Key Laboratory of Modern Acoustics, MOE, Nanjing University, Nanjing 210093 (China); Institute of Acoustics, State Key Laboratory of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China)


    Prediction and measurement of the acoustic field emitted from a high intensity focused ultrasound (HIFU) is essential for the accurate ultrasonic treatment. In this study, the acoustic field generated from a strongly focused HIFU transmitter was characterized by a combined experiment and simulation method. The spheroidal beam equation (SBE) was utilized to describe the nonlinear sound propagation. The curve of the source pressure amplitude versus voltage excitation was determined by fitting the measured ratio of the second harmonic to the fundamental component of the focal waveform to the simulation result; finally, the acoustic pressure field generated by the strongly focused HIFU transmitter was predicted by using the SBE model. A commercial fiber optic probe hydrophone was utilized to measure the acoustic pressure field generated from a 1.1 MHz HIFU transmitter with a large half aperture angle of 30°. The maximum measured peak-to-peak pressure was up to 72 MPa. The validity of this combined approach was confirmed by the comparison between the measured results and the calculated ones. The results indicate that the current approach might be useful to describe the HIFU field. The results also suggest that this method is not valid for low excitations owing to low sensitivity of the second harmonic.

  20. High resistance to sulfur poisoning of Ni with copper skin under electric field

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xiaopei; Zhang, Yanxing [College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007 (China); Yang, Zongxian, E-mail: [College of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007 (China); Collaborative Innovation Center of Nano Functional Materials and Applications, Kaifeng, Henan Province (China)


    The effects of sulfur poisoning on the (1 0 0), (1 1 0) and (1 1 1) surfaces of pure Ni and Cu/Ni alloy are studied in consideration of the effect of electric field. The effects of Cu dopants on the S poisoning characteristics are analyzed by the means of the density functional theory results in combination with thermodynamics data using the ab initio atomistic thermodynamic method. When the Cu concentration increases to 50% on the surface layer of the Cu/Ni alloy, the (1 1 0) surface becomes the most vulnerable to the sulfur poisoning. Ni with a copper skin can mostly decrease the sulfur poisoning effect. Especially under the electric field of 1.0 V/Å, the sulfur adsorption and phase transition temperature can be further reduced. We therefore propose that Ni surfaces with copper skin can be very effective to improve the resistance to sulfur poisoning of the Ni anode under high electric field. - Highlights: • The electric field and Cu dopant effects on S poisoning feature of Ni are analyzed. • The present of large electric field can enhance S tolerance. • Cu dopant concentration affect the surface electronic structure of Ni. • 100% Cu doping on surface Ni layer can mostly decrease the sulfur poison.