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  • 1
    Publication Date: 2020-11-17
    Language: English
    Type: conferenceobject , doc-type:conferenceObject
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  • 2
  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 9 (2002), S. 1422-1430 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The azimuthally invariant cold-fluid equilibrium is obtained for a periodic, strongly bunched charged annular beam with an arbitrary radial density profile inside of a perfectly conducting cylinder and an externally applied uniform magnetic field. The self-electric and self-magnetic fields, which are utilized in the equilibrium solution, are computed self-consistently using an electrostatic Green's function technique and a Lorentz transformation to the longitudinal rest frame of the beam. An upper bound on the maximum value of an effective self-field parameter for the existence of a bunched annular beam equilibrium is obtained. As an application of the bunched annular beam equilibrium theory, it is shown that the Los Alamos National Laboratory relativistic klystron amplifier experiment is operating slightly above the effective self-field parameter limit, and a discussion of why this may be the cause for their observed beam loss and microwave pulse shortening is presented. The existence of bunched annular beam equilibria is also demonstrated for two other high-power microwave (HPM) experiments, the relativistic klystron oscillator experiment at Air Force Research Laboratory and the backward wave oscillator experiment at the University of New Mexico. In general, the results of the equilibrium analysis will be useful in the determination of the stability properties of strongly bunched annular beams in HPM devices. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 5206-5213 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nonrelativistic motion is analyzed for a highly bunched beam propagating through a perfectly conducting cylindrical pipe confined radially by a constant magnetic field parallel to the conductor axis. In the present analysis, the beam is treated as either a thin rod distribution representing a continuous (unbunched) beam or periodic collinear point charges representing a highly bunched beam. Use is made of a Green's function to compute the electrostatic force on the beam due to the induced surface charge in the conductor wall. By analyzing the Hamiltonian dynamics, a criterion is derived for the confinement of unbunched and bunched beams. It is shown that for the confinement of beams with the same charge per unit length, the maximum value of the effective self-field parameter is 2ωp2/ωc2≅2a/L for a highly bunched beam with a(very-much-less-than)L. This value is significantly lower than the Brillouin density limit for an unbunched beam 2ωp2/ωc2=1. Here, a is the radius of the conducting cylinder, and L is the periodic spacing of the bunches. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 6536-6538 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The kinetics for the replacement process of hydrogen by deuterium at the (100)Si/SiO2 interface is studied. Metal–oxide–semiconductor devices were initially annealed in hydrogen and then reannealed in deuterium at various temperatures for various durations. The deuterium concentration CD, defined as the percentage of interface defects passivated by deuterium, was then determined by a technique that is solely based on electrical measurements. From fundamental kinetics, activation energy E for replacing hydrogen by deuterium at the (100)Si/SiO2 interface is determined to be 1.84 eV. This result suggests that the replacement of hydrogen by deuterium involves a process of the dissociation of molecular deuterium at the interface. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5090-5096 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Elastic surface pulses or surface acoustic wave (SAW) pulses were launched at the surface by confining pulsed laser radiation with single-mode fibers and tapered fiber tips, produced by the focused ion beam technique, in near-field configuration. The propagation of the elastic surface pulses was studied in a point-source point-probe experiment. The transient surface displacements of the propagating SAW pulses were detected by an actively stabilized Michelson interferometer with sub-angstrom resolution. For tip aperture sizes in the micrometer range confinement effects could be observed, extending the frequency spectrum of the launched SAW pulses to approximately 800 MHz. The actual frequency spectrum was limited by the applied detection method. An inverse square root dependence of the SAW amplitude with propagation distance was confirmed experimentally, as expected for the excitation geometry employed. Results are presented for layered systems with dispersion of the ultrasonic surface pulses. The relevance of the frequency spectrum of the SAW pulse for the determination of elastic and mechanical film properties in dispersive media is discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3505-3510 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonlinear transient laser gratings were excited by crossing two 180 ps Nd:YAG laser pulses (355 nm) at the silicon surface. The launched counterpropagating surface acoustic wave trains were detected outside the source with a cw laser probe-beam-deflection setup. Phase transitions occurring within the Gaussian fluence distribution of the grating induced characteristic changes in the amplitude of the corresponding grating oscillations involved and higher harmonics were found in the frequency spectrum. In the molten surface region, the amplitude decreased compared to the thermoelastic excitation, and second-harmonic generation was observed, whereas ablation generated an asymmetric profile with higher amplitudes and even the third harmonic could be detected. An accurate method is introduced to determine the ablation threshold (340 mJ/cm2 for silicon) from the transition of linear to nonlinear behavior in the distorted non-Gaussian amplitude distribution. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6945-6947 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study size quantization effects on the conduction band dispersion in GaAs/AlAs quantum wells using a semiempirical tight-binding method. For GaAs well thicknesses between 3 and 11 nm, we find a significant increase of the conduction band mass of up to 50% compared with bulk GaAs. Concomitantly, the confinement reduces the highest achievable group velocities for electrons in the Γ conduction valley of the well by up to 30%. We discuss some of the consequences for quantum-well-based devices. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 73 (2002), S. 1775-1778 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple interference filter spectrometer, together with a modulated neutral diagnostic beam is used on the Tore Supra tokamak for the measurement of carbon impurity profiles by charge exchange spectroscopy. A temporal resolution of 8 ms with a good signal to noise ratio is obtained with a neutral hydrogen beam of about 1 A equivalent neutral current at the plasma edge at 45 kV. Experimental results with ion cyclotron heating show that fast changes of the heating power are followed by transient modifications of the carbon impurity profile. The evolution of the C6+ profile from peaked to hollow and back to normal can be followed step by step and a typical diffusion time of about 30 ms is measured. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1524-4741
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract:  Axillary lymph node dissection (ALND) is the standard of care for nodal staging of patients with invasive breast cancer. Due to significant somatic and psychological side effects, replacement of ALND with less invasive techniques is desirable. The goal of this study was to evaluate the clinical usefulness of axillary lymph node (ALN) staging by means of positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in breast cancer patients qualifying for sentinel lymph node biopsy (SLNB). FDG-PET was performed within 1 week before surgery in 24 clinically node-negative breast cancer patients with tumors smaller than 3 cm. Sentinel lymph nodes (SLNs) were identified by preoperative lymphoscintigraphy following peritumoral technetium 99m-labeled colloid albumin injection, and by intraoperative gamma detector and blue dye localization. Following SLNB, a standard ALND was performed. Serial sectioning and immunohistochemistry of the SLN as well as standard histologic examination of the non-SLN was performed. FDG-PET detected all primary breast cancers. Staging of ALNs by PET was accurate in 15 of 24 patients (62.5%), whereas PET staging was false negative in 8 of 10 node-positive patients and false-positive in 1 patient. The sensitivity, specificity, positive predictive value, and negative predictive value of FDG-PET for nodal status was 20%, 93%, 67%, and 62%, respectively. The mean diameter of false-negative ALN metastases was 7.5 mm (range 1–15 mm). Lymph node staging using FDG-PET is not accurate enough in clinically node-negative patients with breast cancer qualifying for SLNB and should not be used for this purpose. 
    Type of Medium: Electronic Resource
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