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  • 1
    Electronic Resource
    Electronic Resource
    Stark effect and Stark-ladder effect in Al0.4Ga0.6As/GaAs asymmetric coupled multiple quantum wells (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2486-2494 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) measurements at 10 K were performed in order to investigate the influence of electric fields on the exciton states in Al0.4Ga0.6As/GaAs asymmetric coupled multiple quantum wells (ACMQW) grown by molecular-beam epitaxy. The coupling of the electronic energy levels in the wells led to an enhancement of the quantum-confined Stark effect. The PL intensity decreased as the electric field increased. Calculated values of the intersubband transition energies were in good agreement with the experimental values for the ACMQW, and these values showed a similar behavior as those for the step quantum well. When the external applied field was very strong, Stark-ladder transitions were observed, and the measured dependence of the field-induced energy shifts of the Stark-ladder transitions for the ACMQW agreed with theory. These results indicate that the Stark effect and the Stark-ladder transitions in a unique ACMQW based on the AlxGa1−xAs/GaAs structure were observed simultaneously. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358777
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  • 2
    Electronic Resource
    Electronic Resource
    Carrier lifetimes in dielectric cap disordered GaAs/AlGaAs multiple quantum well with SiN capping layers (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 3438-3440 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Time resolved photoluminescence (PL) characteristics of a SiN cap disordered GaAs/AlGaAs multiple quantum well (MQW) structure exhibit a decrease in carrier lifetime in conjunction with an increase in quantum well disordering (QWD) as the SiN capping layer thickness is increased. The decrease in carrier lifetime is attributed to enhanced carrier trapping due to the defects introduced during dielectric cap quantum well disordering and the relaxation of the momentum conservation during radiative recombination by QWD. Potential applications of these effects on high speed optical devices such as laser diodes (LD's) and optical modulators are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115272
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  • 3
    Electronic Resource
    Electronic Resource
    Numerical study on the dynamics of Z-pinch carbon plasma (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 1340-1347 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamics of Z-pinch carbon plasma has been investigated using one-dimensional Lagrangian code. This code calculates the single-fluid, two-temperature magnetohydrodynamic (MHD) equations coupled with an ionization balance equation. The motion of plasma column and shock front is studied in comparison with the analytical models such as the snowplow and the slug model. The energy flow during the pinch is also studied. During the pinch phase, the temperature increases due to shock heating and adiabatic heating. After the pinch the plasma is cooled down rapidly due to adiabatic expansion which can lead to an adequate condition for recombination Extreme-Ultra-Violet (XUV) lasers. The effect of the radiative trapping of resonance line on hydrodynamics and population kinetics is also investigated. The calculation shows that there can exist a high gain on hydrogen-like C VI Balmer-α line (18.2 nm). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871787
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  • 4
    Electronic Resource
    Electronic Resource
    Inductively coupled plasma heating in a weakly magnetized plasma (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 2926-2935 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A one-dimensional analysis of electron heating process in a weakly magnetized, inductively coupled plasma (MICP) is presented. It is found that the main difference in the heating process of a MICP from that of a usual unmagnetized ICP is in that circularly polarized wave modes can exist in the plasma. The right handed circularly polarized wave (R-wave) can propagate into the plasma and its amplitude can be enhanced by cavity resonance effect at an appropriate chamber length and external magnetic field strength. The enhanced R-wave amplitude can raise the heating efficiency significantly. It is also found that a bounce cyclotron-resonance effect can exist, which, however, is not as significant as the cavity resonance effect. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873250
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  • 5
    Electronic Resource
    Electronic Resource
    Electron temperature control with grid bias in inductively coupled argon plasma (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1017-1028 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The mechanism of controlling electron temperature with grid-biased voltage is studied experimentally and the relevant physics is discussed in an inductively coupled Ar discharge. To obtain the electron density and electron temperature, the electron energy distribution functions (EEDFs) are measured with a Langmuir probe. As the grid voltage decreases negatively, the effective electron temperature is controlled from 2.0 to 0.6 eV and the electron density changes from 3×1010 to 2×1010 cm−3 in the diffusion region, while the effective electron temperature and electron density are not changed in the source region. The dependence of such various parameters, as electron density, electron temperature, plasma potential in each region, and so on, on the applied voltage, is presented. The functional relations between the measured physical quantities are well explained based on a global particle and energy balance relations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873342
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  • 6
    Electronic Resource
    Electronic Resource
    Investigation of low-frequency beam motion at the Advanced Photon Source : The 9th National conference on synchrotron radiation instrumentation (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 3371-3371 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The storage ring of the Advanced Photon Source has relatively tight tolerance requirements for beam stability. The tolerances of the rms beam motion in the insertion device straight sections are set to be less than 4.4 μm and 17 μm in the vertical and horizontal planes, respectively, in a bandwidth of 4–50 Hz. Sources of beam motions have been investigated for mechanical vibrations of the magnets and vacuum chambers induced by ground motion and water systems and for power supply ripple. Horizontal beam motions in a bandwidth of 9–12 Hz have been significantly reduced by inserting viscoelastic damping pads between the girder supports and pedestals, and by welding the magnet cooling headers to the ceiling of the storage ring tunnel. Current ripple of S1A sextupoles has been identified as a source of beam motion in a bandwidth of 5–8 Hz. The eddy current induced by the ripple field in the sextupole produced a vertical dipole field to drive the beam horizontally. After modification of the sextupole power supplies, the beam stability requirements have now been met even without activating the feedback system. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147333
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  • 7
    Electronic Resource
    Electronic Resource
    A novel rectilinear ion source for direct metal ion beam deposition (abstract) : Proceedings on the 6th international conference on ion sources (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 908-908 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel rectilinear ion beam disposition technique has been developed for the direct metal ion beam deposition over a large area. The technology is based on the patent pending solid-state cesium ion beam technology. This technique has several unique advantages: (1) Due to the rectilinear shape of the ion beam, the ion beam length is expandable to any size up to several meters; (2) The technique uses no carrier gas or gas medium to generate the ion beams, thus, it is very compact and economical; (3) It is capable of producing various negative metal ion beams such as C, Si, Au, Ni, Fe, Mo, W, etc.; (4) The ion source is operating in a low energy range (10–500 eV) and it is ideal for the direct ion beam disposition. The prototype of the ion source has produced superior quality amorphous diamond films which exhibited superior hardness ((approximately-greater-than)60 GPa), low wear rate (〈108 mm3/Nm), low friction coefficient (〈0.1) and high transparency. Furthermore the coatings contain no hydrocarbon impurities, and exhibit atomically smooth surfaces (〈1 nm Ra) on the as-grown materials. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147254
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  • 8
    Electronic Resource
    Electronic Resource
    A simple current mode preamplifier for electron multipliers with high voltage biased anode (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 4120-4123 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We developed a simple current mode preamplifier for the microchannel plate (MCP) with the anode biased to high voltage. It uses a capacitor to block dc high voltage and measures the MCP current through the capacitor. Then it compensates exactly the distortion caused by the capacitor so the amplifier can measure any length of signals without distortion. It is much less expensive and simpler than using the phosphor screen system to isolate the dc high voltage. We derived a formula for that compensation and implemented it by using an op-amp's circuit. It gives an approximate time resolution of 10 μs which is restricted by the op-amp's characteristics. So, it may be improved by using fast op-amp's. This can also be used for channeltron and other electron multipliers. For the test of the preamplifier, we measured the photoelectron currents induced by the soft x rays radiated from the KT-1 tokamak of which the pulse length was 20 ms. The data revealed well, without distortion, the time evolution of the line radiation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147557
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  • 9
    Electronic Resource
    Electronic Resource
    A beamline for macromolecular crystallography at the Advanced Light Source : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1738-1740 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A beamline for macromolecular crystallography has been designed for the ALS. The source will be a 37-pole wiggler with a 2-T on-axis peak field. The wiggler will illuminate three beamlines, each accepting 3 mrad of horizontal aperture. The central beamline will primarily be used for multiple-wavelength anomalous dispersion measurements in the wavelength range from 4 to 0.9 A(ring). The beamline optics will comprise a double-crystal monochromator with a collimating premirror and a double-focusing mirror after the monochromator. The two side stations will be used for fixed-wavelength experiments within the wavelength range from 1.5 to 0.95 A(ring). The optics will consist of a conventional vertically focusing cylindrical mirror followed by an asymmetrically cut curved-crystal monochromator. This paper presents details of the optimization of the wiggler source for crystallography, gives a description of the beamline configuration, and discusses the reasons for the choices made. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145835
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  • 10
    Electronic Resource
    Electronic Resource
    An evaluation of errors in determining the refractive index and thickness of thin SiO2 films using a rotating analyzer ellipsometer (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 5277-5281 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Errors are examined in determining the refractive index and thickness of very thin SiO2 films on c-Si substrates as measured with the commonly used rotating analyzer ellipsometer. Systematic errors in the ellipsometric parameters Δ, ψ, δΔ, and δψ are calculated from the experimental hardware errors. Random errors are measured. The propagation of errors from δΔ and δψ to errors in refractive index (n) and film thickness (d), δn and δd, are calculated for oxide thicknesses from 30 to 200 A(ring). It is verified that the thinner the oxide is and the lower the photon energy where c-Si becomes less absorbing, the larger the errors become. A minimum error of δn and δd is observed at the spectral region of 3.6–4.0 eV and around 5.2 eV. From the reported results for a high precision ellipsometer, judgments are made about the value of the extracted parameters for thin films, and recommendations are offered to minimize the errors. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146521
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