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  • 1
    Electronic Resource
    Electronic Resource
    Dynamic response of detached recombining plasmas to plasma heat pulse in a divertor simulator (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2486-2494 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The experiments on the plasma heat pulse to the detached recombining helium plasma associated with the volumetric radiative and three-body recombination (EIR) have been performed in a linear divertor plasma simulator. Detailed observations of the time evolution of plasma parameters and helium Balmer series spectra show that the dynamic response of the detached recombining plasma to the heat pulse depends strongly on the heat transport through energetic electrons generated by the heat pulse. For the detached recombining plasma with a relatively low neutral pressure, it was found that the EIR is not sufficient to suppress an increase of ion flux to the target plate during the pulse. Several key characteristic time scales involved in this system are also analyzed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873520
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  • 2
    Electronic Resource
    Electronic Resource
    Excitation mechanism of standing waves produced by electron beam plasma instability (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 3582-3587 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The excitation mechanism of standing waves produced by the electron beam plasma instability is experimentally studied using a Double Plasma device. When an electron beam is injected into the target plasma, standing waves around the electron plasma frequency are excited. A test wave is propagated in an electron beam plasma system and is identified as the beam mode from the dispersion relation. The propagation direction of the beam mode is determined from the wave pattern utilizing a phase shifter. It is found that a reflected beam mode exists as well as a forward beam mode, and is generated by the reflection of the forward beam mode from a potential well produced by the injection of the electron beam. The observed standing waves are formed by superposing the beam modes propagating in opposite directions from each other. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871057
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  • 3
    Electronic Resource
    Electronic Resource
    Three-dimensional analysis of ion beam deflection by the magnetic field at H− ion sources for the negative-ion-based neutral beam injection : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1144-1146 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In negative-ion-based neutral beam injection (NBI) systems for the large helical device (LHD), beams must be transported over 13 m from the H− ion source to the injection port. In order to clarify beam deflection by the electron deflection magnets set in a beam extraction grid (EG) and to control beam transport direction, we analyzed beam trajectories. The physics of the beam deflection was studied with theoretical calculations and the deflection angle was estimated by 3D beam trajectory simulation. The evaluated deflection angle was 10 mrad in the opposite direction of the electron deflection when the maximum magnetic field on the beam axis was 480 G and the beam energy was 83.2 keV. The electrostatic lens effect on the beam deflection at the EG exit was estimated to be larger than the magnetic field effect. This deflection was reduced to 2 mrad by a 1.3 mm displacement of the grounded grid (GG) aperture, a result in agreement with experimental results of a 1/3-scale model for the LHD ion source. The maximum GG aperture displacement of the LHD ion source was designed as 3.4 mm to reduce the deflection and to focus multibeamlets using the simulation. We have developed the ion source with this design. The targeted performance is a production of H− beams of 40 A (40 mA/cm2), 180 keV. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148651
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  • 4
    Electronic Resource
    Electronic Resource
    High-density plasma production for neutralizing negative ion beam : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 980-982 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electron cyclotron resonance (ECR) plasma production method using electron cyclotron wave is presented. This method is not subjected to any cutoff-density scaling, and is capable of generating dense plasmas far beyond the critical density of an ordinary wave. It has been demonstrated that a plasma density more than 1013 cm−3 (argon) is obtained with a low frequency (2.45 GHz) and low power (11 kW) microwave. The experimental results and the application to plasma neutralizer are described. The experimental verification of superpermeability of Nb membrane in a plasma environment is in progress to develop a plasma neutralizer with Nb-membrane wall. The design parameters of Nb-membrane pump are presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148607
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  • 5
    Electronic Resource
    Electronic Resource
    Development of a microwave ion source for negative oxygen ion beam production (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 4911-4915 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A volume production type microwave negative ion source has been developed for negative ion beam processes such as ion implantation and ion beam deposition, etc. In order to increase efficiency of negative oxygen ion production, we employed a double plasma cell system in which two plasma cells were connected to each other. A high density primary plasma was generated in the first plasma cell with 2.45 GHz microwave power and negative ions were effectively generated in the second plasma cell. A filter magnetic field of about 0.1 T was applied on the second plasma cell to prevent diffusion of high energy electrons from the first plasma cell. Oxygen negative ion beams were generated by this method and the maximum oxygen (O−) ion current of 142 μA (current density: 325 μA/cm2) was extracted continuously from the ion source at an extraction voltage of 30 kV and a microwave power of 500 W. This value was three orders larger than that obtained by a single plasma cell system without the filter magnetic field. Molecular oxygen ions (O−2 and O−3) were also obtained at percentages of about 20% and 2% of the major O− ion intensity. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146173
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  • 6
    Electronic Resource
    Electronic Resource
    Development of an intense negative hydrogen ion source with an external magnetic filter (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2541-2546 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An intense negative hydrogen ion source has been developed, which has a strong external magnetic filter field in the wide area of 35 cm×62 cm produced by a pair of permanent magnet rows located at 35.4 cm separation. The filter strength is 70 G in the center and the line-integrated filter strength is 850 G cm, which keeps the low electron temperature in the extraction region. Strong cusp magnetic field, 1.8 kG on the chamber surface, is generated for improvement of the plasma confinement. These resulted in the high arc efficiency at the low operational gas pressure. 16.2 A of H− ion current with the energy of 47 keV was obtained at the arc efficiency of 0.1 A/kW at the gas pressure of 3.8 mTorr in the cesium-mode operation. The magnetic field in the extraction gap is also strong, 450 G, for the electron suppression. The ratio of the extraction current to the negative ion current was less than 2.2 at the gas pressure of 3 mTorr. The two-stage acceleration was tested, and 13.6 A of H− ion beam was accelerated to 125 keV. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145655
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  • 7
    Electronic Resource
    Electronic Resource
    X-ray scattering and absorption studies of MnAs/GaAs heterostructures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1435-1440 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic MnAs thin films grown on GaAs (001) substrates by molecular-beam epitaxy have been studied by the methods of grazing incidence x-ray scattering, x-ray diffraction, and extended x-ray-absorption fine structure. Microstructures in two films prepared with different first-layer growth conditions (template effects) are compared in terms of the interfacial roughness in the layer structure, lattice constants, epilayer thickness, local environment surrounding the Mn atoms, coordination number, and local disorder. Our results indicate that the template effects can cause significant differences in the local structures and crystallinity of the MnAs epitaxial layers. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360981
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  • 8
    Electronic Resource
    Electronic Resource
    Epitaxial ferromagnetic MnAs thin films grown on Si (001): The effect of substrate annealing : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4957-4959 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied two different types of epitaxial ferromagnetic MnAs thin films on Si (001) substrates grown by molecular beam epitaxy. When the Si substrates were annealed at a relatively high temperature (∼900 °C) and then MnAs was grown, we obtained epitaxial MnAs films with twofold crystal symmetry (type I). In contrast, when the thermal cleaning of the Si substrate was done at a lower temperature (∼600 °C), epitaxial MnAs thin films had fourfold crystal symmetry (type II). The growth plane in both types of MnAs thin films was the (1¯101) of the hexagonal MnAs. The type I MnAs films are single domain with strong magnetic anisotropy, whereas the type II MnAs films are double domain with the lack of strong magnetic anisotropy. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361602
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  • 9
    Electronic Resource
    Electronic Resource
    Galvanomagnetic properties and magnetic domain structure of epitaxial MnAs films on GaAs(001) : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 4967-4969 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial MnAs films on GaAs(001) in the thickness range 20–200 nm were studied. Using ordinary and extraordinary Hall effect data to determine the field required for perpendicular saturation and saturation magnetizations reported elsewhere, we determined the shape anisotropy constant in the basal plane of the hexagonal structure to be 3.7(0.6)×105 erg/cm3 and the surface anisotropy constant to be −1.3(0.4) erg/cm2. The negative sign indicates thin enough films will be perpendicularly magnetized. By magnetic force microscopy of a 100 nm film we found stripe domains with 180° Bloch walls, thereby avoiding the hard c axis. The widths of the domains and the walls are 4.0(0.3) μm and 95(6) nm, respectively. In magnetoresistance, we observed behavior similar to other ferromagnets, namely peaks centered around the positive and negative coercive fields, and at fields beyond the coercive field a linear dependence on magnetic field. The electrical resistance showed rapid increase with temperature beginning about 5° below the Curie temperature (40 °C) caused by the change in crystal structure from hexagonal to orthorhombic. The resistivities are, respectively, 300(24) and 375(30) μΩ cm. Comparison with bulk values indicates the large lower temperature value is partly due to the presence of some orthorhombic phase observed in x-ray studies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361605
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  • 10
    Electronic Resource
    Electronic Resource
    Room-temperature negative differential resistance in AlAs/ErAs/AlAs heterostructures grown on (001)GaAs (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 84-86 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated resonant tunneling structures having a buried ErAs semimetallic quantum well and AlAs double barriers, on (001)GaAs substrates. In order to suppress the three-dimensional island growth of GaAs and AlAs on ErAs and to obtain flat interfaces, we adopted a template approach, in which one monolayer of Mn was deposited on ErAs prior to the growth of AlAs, in molecular beam epitaxy. In the current–voltage characteristics at room temperature, negative differential resistance was clearly observed in a significant number of diodes with the ErAs thickness ranging from 2.6 to 5.0 nm. This room-temperature device operation on (001) substrates is, we believe, an important step towards the realization of semimetal/semiconductor hybrid quantum devices. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116766
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