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  • 1
    Electronic Resource
    Electronic Resource
    A dynamic local bump system for producing synchrotron radiation with an alternating elliptical polarization (1998)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 5 (1998), S. 398-400 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: To facilitate high-sensitivity soft X-ray magnetic circular dichroism experiments, a dynamic local bump system has been developed at the SRRC storage ring. This system was devised to vary dynamically the vertical slope of the electron beam in a bending magnet, producing, in the electron orbit plane, soft X-rays with an alternating elliptical polarization. The local bump was created by using two pairs of vertical correctors located on each side of the bending magnet. The bump strength coefficient was obtained both from calculated estimation and from measured beam-response matrices. Control electronics for proper bump strength settings were designed to incorporate the existing orbit-corrector function. A corresponding graphic user interface was implemented so that the bump amplitude could be easily adjusted. The performance of this system is presented. Disturbance on the stored electron beam orbit was observed while flipping the corrector polarity during EPBM (elliptical polarization from bending magnets) operation. A local feedback loop, developed to eliminate such disturbance on other beamlines, is also described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049597013149
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  • 2
    Electronic Resource
    Electronic Resource
    A high-performance wide-range beamline for elliptically polarized undulator source (1998)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 5 (1998), S. 551-553 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A high-performance wide-range beamline has been designed for monochromatizing circularly polarized photons with energies from 10 to 1400 eV. A grazing SGM-based beamline with two entrance slits has been employed to optimize the performance. The degree of the circular polarization affected by the beamline optics has been analysed. The horizontal and vertical refocusing mirrors have been specially arranged to improve greatly the polarization degree in the low-energy region. By connecting this beamline to a high-efficiency elliptically polarized undulator, this beamline should be able to provide, in the entire energy range, intensive and high-resolution photons of a high degree of circular polarization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049597015409
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  • 3
    Electronic Resource
    Electronic Resource
    A unique high-performance wide-range (10–1500 eV) spherical grating monochromator beamline (1998)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 5 (1998), S. 723-725 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A wide-spectral-range high-performance 6 m-spherical grating monochromator (6 m-SGM) beamline has been designed and is under construction at SRRC. Two different entrance slits, instead of additional mirrors, are used to optimize the overall performance. Six gratings are used to cover photon energies from 10 to 1500 eV. Movable entrance slits and bendable vertical focusing mirrors are used to enhance further the beamline performance. A bendable horizontal focusing mirror is used to improve the resolution and to focus the photon beam at the experimental station immediately after the exit slit. Several end-stations can be installed at the same time to utilize the beam time fully. The expected energy-resolving power, with both slit openings set at 10 µm, is up to 15 000 and 40 000 for the high- and low-energy branches, respectively. A photon flux of 1 × 1011 photons s−1 can be obtained with an energy-resolving power of 20 000.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S090904959701282X
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced cervical MRI in identifying intracranial dural arteriovenous fistulae with spinal perimedullary venous drainage (1998)
    Springer
    Neuroradiology 40 (1998), S. 393-397 
    Details
    ISSN: 1432-1920
    Keywords: Key words Brain diseases ; Arteriovenous fistula ; Myelopathy ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Diagnosis of an intracranial dural arteriovenous fistula (DAVF) with spinal perimedullary venous drainage is challenging because the presenting symptoms are usually related to dysfunction of the spine, not of the brain. Repeated spinal angiograms are usually performed before the diagnosis is finally made by cerebral angiography. We report two cases of intracranial DAVFs with spinal perimedullary venous drainage. In both cases contrast-enhanced cervical MRI demonstrated dilated lower brainstem and upper spinal veins, which, we believe, is a good indicator of the existence of such drainage. We suggest that, in cases with perimedullary serpentine enhancement on thoracic or lumbar MR images, additional Gd-enhanced cervical spinal MR imaging should be performed. The simple process of tracing the veins upwards may avoid a lot of unnecessary examinations and delay in the diagnosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002340050609
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  • 5
    Electronic Resource
    Electronic Resource
    Stability properties of coherently gyrating relativistic electron beams (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 3416-3439 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An investigation is made of the effects of nongyrotropic equilibrium distributions in the phase angle of p⊥ on the stability properties of a relativistic electron beam propagating along and gyrating about an applied uniform magnetic field. Perturbations are assumed to vary spatially only in the direction of the applied magnetic field, so that generated electromagnetic and longitudinal electric fields propagate parallel to the applied field. The two equilibrium distributions considered are the time-dependent distribution f0(p⊥,pz,ξ) with ξ=φ−Ωct/γ and the axial-dependent distribution f0(p⊥,pz,ζ) with ζ=φ−mΩcz/pz. A Vlasov-Maxwell analysis leads to integral equations relating the field Fourier components. These equations reduce to algebraic equations when no spread in γ is present in the time-dependent equilibrium distribution and when no spread in pz is present in the axial-dependent distribution. Numerical computations for these special cases show that a rich variety of stability properties are obtained by changing the distributions in ξ and ζ. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873056
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  • 6
    Electronic Resource
    Electronic Resource
    Fabrication of high-temperature superconducting Josephson junctions on substrates patterned by focused ion beam (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1730-1732 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High aspect ratio trenches were patterned on (100) LaAlO3 substrates by focused ion-beam milling prior to film deposition. Subsequent YBCO films deposited by pulsed laser deposition were found to break naturally across these trenches. In situ Au was then deposited to connect the separated YBCO electrodes. Junctions were then patterned across the trenches to form a superconductor/normal/superconductor configuration. The resistively shunted junctions exhibited supercurrents up to 86 K. Under microwave irradiation, the junctions exhibited a number of clear Shapiro steps in the I–V characteristics. The transverse magnetic-field diffraction pattern indicted uniform current distribution across the junction. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122259
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  • 7
    Electronic Resource
    Electronic Resource
    Observation of persistent photoluminescence in porous silicon: Evidence of surface emission (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1605-1607 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the observation of persistent photoluminescence (PPL) in oxidized porous silicon. The PPL decay can be well described by a stretched-exponential function, and its decay rate is not sensitive to the change of temperature. We point out that the PPL behavior can be interpreted in terms of the picture that the emission arises from the excited surface complexes, which is produced by capture of photocarriers tunneling from the nearest shallow trap in the nanocrystalline silicon. To explore the microscopic origin of the surface compounds, we performed infrared absorption, and found that the PPL intensity correlates well with Si–OH vibration mode. Further evidence is provided by the recent theoretical calculation showing that the Si–OH complex can emit the photon energy in the range observed here. We thus provide concrete evidence to support the fact that the PL signal of porous silicon does contain surface emission. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121128
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  • 8
    Electronic Resource
    Electronic Resource
    Two-color corrugated quantum-well infrared photodetector for remote temperature sensing (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 7-9 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A quantum-well infrared photodetector (QWIP) based on the corrugated light-coupling scheme has been fabricated and tested for remote temperature sensing. The QWIP consists of two stacks of multiple quantum wells (MQWs), each sensitive in one of the atmospheric infrared transmission windows and each with a separate readout circuit. High optical coupling efficiency is obtained in both wavelength ranges, demonstrating the use of the corrugated structure for two-color detection. By monitoring the ratio of the photocurrent generated simultaneously in each MQW stack, the temperature of the object emitting the radiation can be determined, regardless of its emissivity and the geometrical factors. This temperature sensing ability is tested by using a blackbody radiator with precision temperature control as the target. The agreement between the measured and the preset temperatures indicates that the corrugated QWIP is capable of precision thermometric measurements. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120629
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  • 9
    Electronic Resource
    Electronic Resource
    Sm2(Co,Fe,Cu,Zr)17 magnets for use at temperature ≥400 °C : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6706-6708 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sintered Sm2(Co,Fe,Cu,Zr)17 magnets with improved high temperature performance have been obtained by reducing the iron content in the magnet alloys. A record intrinsic coercive force, IHC, of 8.3 kOe at 400 °C was obtained when the iron content was decreased to 7 wt%. At 400–600 °C, 2:17 magnets with low iron content have demonstrated lower irreversible loss of magnetic flux, higher maximum energy product, and lower temperature coefficient of IHC. A temperature coefficient of IHC=−0.12%/°C (20–400 °C) was obtained for the low Fe magnets, compared to −0.23%/°C for commercial 2:17. Reducing iron content increases both Curie temperature and anisotropy field. Therefore, it is anticipated that new 2:17 magnet materials capable of operating at 400 °C or higher temperatures can be developed by reducing or eliminating the iron content and making other adjustments in composition and heat treatment. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367937
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  • 10
    Electronic Resource
    Electronic Resource
    Developments on the KSU-CRYEBIS, a user facility for low energy, highly charged ions : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 665-667 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The KSU-CRYEBIS, a CRYogenic electron beam ion source, supplies experiments with low-energy, highly charged ions of numerous species. The supplied charge states cover the range from 1+ to 52+, with typical beam currents of a nA for low charge states and a few pA for the highest charge states. The ion energies cover the range from 0.3 to 165 keV per charge. This is an unusually broad range of final ion energies and hence requires an unusual dynamic ion transport system. This paper presents advances made with respect to the CRYEBIS ion beam transport, diagnostics, and identification. In addition, an update on the developments of ion beams with very high duty cycles is given. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148464
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