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  • American Physical Society  (163)
  • American Institute of Physics (AIP)  (38)
  • 1
    Electronic Resource
    Electronic Resource
    Die-upset rare-earth iron-boron ingot: Coercivity dependence on composition and heat treatment : The 5th Joint MMM−Intermag Conference (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6474-6476 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rapid solidification (melt spinning) and powder metallurgy (sintering) methods have been successfully developed to fabricate excellent permanent magnets from RE2Fe14B-based alloys (RE=rare earth). Hot deformation of a chill-cast ingot is a potentially simpler and less costly method. However, development of this method will require better understanding of the coercivity mechanisms in this form of the magnet material. Toward this end, this paper reports results of a study of the dependence of the room-temperature demagnetization of a die-upset chill-cast ingot on composition and postpress heat treatment. Substitution of Pr for Nd and Cu for Fe results in smaller 2:14:1 grain size which leads to improved magnetic alignment and higher coercivity in a die-upset ingot. Postpress heat treatment produces a reversible order of magnitude coercivity change from a low-coercivity state (quench from 1000 °C) to a high-coercivity state (quench from 600 °C). This large effect is discussed in the light of electron probe analyses of the grain boundaries. A contributor to coercivity in these materials appears to be the REFe2 component of the eutectic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349935
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of surfactant Sb on carrier lifetime in GaInP epilayers (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 199-203 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Samples of Ga0.52In0.48P grown on (001) GaAs with small amounts of surfactant Sb were investigated using time-resolved photoluminescence. All samples show a luminescence that may be fit to a two-stage exponential decay with a fast and a slow lifetime. For growth without Sb (Sb/III(v)=0), the sample shows a strong CuPtB ordering and a fast component lifetime of 7 ns. As the Sb concentration is increased, the degree of order is reduced, with a consequent increase in band gap energy. In the highest band gap material, produced at Sb/III(v)=0.016, the fast lifetime is 2.9 ns, an order of magnitude larger than published values for GaInP disordered by misorienting the substrate. Increasing the Sb further causes the band gap energy to decrease due to the onset of composition modulation. At Sb/III(v)=0.064, the fast component lifetime decreases to 0.79 ns. Samples grown with Sb/III(v)〉0.016 show a lifetime that depends on energy and is fit well by a model of localized excitons. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1423396
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  • 3
    Electronic Resource
    Electronic Resource
    Surfactant controlled growth of GaInP by organometallic vapor phase epitaxy (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 3730-3735 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of the surfactant Sb has been studied for GaInP semiconductor alloys grown by organometallic vapor phase epitaxy. Dramatic changes in the optical and electrical properties of GaInP with CuPt ordering have been observed. A small concentration of triethylantimony (TESb) in the vapor is found to cause Sb to accumulate at the surface. In situ surface photoabsorption analysis indicates that Sb changes the surface bonding by replacing the [1¯10] P dimers that are responsible for the formation of the CuPt structure during growth with [1¯10] Sb dimers. As a result, the degree of order for the GaInP layers is decreased, as shown by transmission electron diffraction studies. The 20 K photoluminescence spectra show a 131 meV peak energy increase for GaInP layers grown on vicinal substrates when a small amount of Sb [Sb/P(v)=4×10−4] is added to the system during growth. The use of surfactants to control specific properties of materials is expected to be a powerful tool for producing complex structures. In this article, the growth of heterostructures by modulating the Sb concentration in the vapor is demonstrated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372408
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  • 4
    Electronic Resource
    Electronic Resource
    Disruption mitigation studies in DIII-D : The 40th annual meeting of the division of plasma physics of the american physical society (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1872-1879 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data on the discharge behavior, thermal loads, halo currents, and runaway electrons have been obtained in disruptions on the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 2A 441 (1985)]. These experiments have also evaluated techniques to mitigate the disruptions while minimizing runaway electron production. Experiments injecting cryogenic impurity "killer" pellets of neon and argon and massive amounts of helium gas have successfully reduced these disruption effects. The halo current generation, scaling, and mitigation are understood and are in good agreement with predictions of a semianalytic model. Results from "killer" pellet injection have been used to benchmark theoretical models of the pellet ablation and energy loss. Runaway electrons are often generated by the pellets and new runaway generation mechanisms, modifications of the standard Dreicer process, have been found to explain the runaways. Experiments with the massive helium gas puff have also effectively mitigated disruptions without the formation of runaway electrons that can occur with "killer" pellets. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873445
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  • 5
    Electronic Resource
    Electronic Resource
    Imaging of laser-irradiated targets at a wavelength of 33.8 A(ring) using a normal-incidence multilayer mirror (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1997-2002 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The morphology of the 33.8 A(ring) emission from laser-irradiated targets was studied using a concave mirror with a W/B4C multilayer coating. The mirror had peak normal-incidence reflectance of 1.8% at a wavelength of 33.8 A(ring). The emissions from a variety of targets were imaged on film with a spatial resolution of 30 μm in the target plane. Radiatively heated, low-density plastic and silica foams, x-ray laser targets, and a gas-filled enclosure were imaged. Several targets were simultaneously imaged at wavelengths of 33.8 and 130 A(ring) using two normal-incidence microscopes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870655
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  • 6
    Electronic Resource
    Electronic Resource
    High Z x-ray spectroscopy of laser-imploded capsules : Eight topical conference on high-temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2774-2776 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: X-ray spectroscopy is a valuable tool for diagnosing laser-imploded capsules. Using a compact spectrometer/streak camera, which fits down a 6-in.-diam tube, we routinely perform time-resolved measurements of deuterium-filled capsules, seeded with Ar, on implosions driven by the NOVA laser. Future high performance targets will preclude the use of Ar as a diagnostic; we are pursuing spectral diagnostics at higher proton energy (Ne-like Xe) and have performed a series of direct drive implosions of capsules filled with Xe, and with Kr, to help validate line broadening models for Ne-like ions. We will discuss the details of the instrument and these experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141827
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  • 7
    Electronic Resource
    Electronic Resource
    Line broadening of Ne-like xenon as a diagnostic for high-density implosion experiments : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2780-2782 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The broadening of x-ray spectral lines has become an established diagnostic of Ne in high-density plasmas, particularly those of interest in inertial confinement fusion (ICF). Work to date has concentrated mostly on the broadening of K-shell lines in moderate Z (Z∼10–20) ions in plasmas with electron densities up to 1024 cm−3. In this paper we report on calculations of line broadening for Ne-like Xe (Xe44+) appropriate for diagnosis of higher density plasmas with Ne∼1025 cm−3. These calculations have been performed with a recently developed state of the art computer code which treats the ion and electron broadening in the quasi-static and impact approximations, respectively. In this paper, we summarize recent work examining the behavior of the width of the Ne-like Xe 3–2 and 4–2 transitions with electron density. The broadening of the 1s–3p line in H-like Ar and the 1s2–1s3p transition in He-like Ar is also studied in order to benchmark the code used in the calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141829
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  • 8
    Electronic Resource
    Electronic Resource
    Hot electron production and heating by hot electrons in fast ignitor research : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1966-1972 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In an experimental study of the physics of fast ignition, the characteristics of the hot electron source at laser intensities up to 1020 W cm−2 have been measured and a diagnosis of the heating at depth by hot electrons has been initiated. Generation of hot electrons with more than 30% efficiency has been observed. Preliminary heating data suggest temperatures kT in the range 300–800 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872867
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  • 9
    Electronic Resource
    Electronic Resource
    Time-resolved x-ray imaging of high-power laser-irradiated underdense silica aerogels and agar foams (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3820-3831 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article presents the results of experiments in which a high-power laser was used to irradiate low density (4–9 mg/cm3) silica aerogel and agar foam targets. The laser–solid interaction and energy transport through the material were monitored with time-resolved imaging diagnostics, and the data show the production and propagation of an x-ray emission front in the plasma. The emission-front trajectory data are found to be in significant disagreement with detailed simulations, which predict a much more rapid heating of the cold material, and the data suggest that this discrepancy is not explainable by target inhomogeneities. Evidence suggests that energy transport into the cold material may be dominated by thermal conduction; however, no completely satisfactory explanation for the discrepancies is identified, and further experimental and theoretical research is necessary in order to resolve this important problem in laser–plasma interaction physics. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871081
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  • 10
    Electronic Resource
    Electronic Resource
    Spectroscopic study of surfactant enhanced organometallic vapor phase epitaxy growth of GaInP (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 1040-1046 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Samples of GaxIn1−xP grown by organometallic vapor phase epitaxy on (001) GaAs substrates by addition of TESb demonstrating a lateral superlattice compositional modulation (CM) have been studied by low temperature polarized photoluminescence (PL), power dependent PL, and photoluminescence excitation (PLE) spectroscopy. Strong polarization is observed in the low temperature PL and PLE spectra at Sb concentrations below that where CuPtB ordering is removed and triple period ordering is produced. Low temperature polarized PL is shown to be the most sensitive optical technique for detecting the presence of CM. The radiative recombination mechanism at low temperature is excitonic, originating from the exponential tail of band gap states observed in the PLE spectra. From the measured band gaps, a continuum model of the band structure allows an estimate of an upper limit of the percent modulation present in the samples. Above Sb/III(v)=0.01, compositional modulation is the dominant factor determining the low temperature optical properties. The percent fluctuation of composition increases monotonically with increasing Sb during growth. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1378060
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