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  • 1
    Electronic Resource
    Electronic Resource
    High-resolution deposition rate monitor (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 247-249 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 16-MHz piezoelectric quartz resonator has been used to build up a high-resolution deposition rate monitor. A direct counting allows a resolution of 1 ng/cm2 at a rate of one reading per second. Direct computer interface and increase in the voltage excitation above the plasma noise level have been successfully used to monitor the deposition rate in a dc sputtering apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144445
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  • 2
    Electronic Resource
    Electronic Resource
    Multichannel far-infrared polarimeter-interferometer system on the MST reversed field pinch : Papers from the thirteenth topical conference on high temperature plasma diagnostics (2001)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 72 (2001), S. 1077-1080 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The multichannel far-infrared (FIR) heterodyne polarimeter-interferometer system on the Madison Symmetric Torus (MST) is now operational. The combined system consists of 11 channels with variable radial and toroidal spacing. Poloidal magnetic field is determined by measuring the Faraday rotation of the FIR laser beam after propagation through the plasma by use of a phase technique. The polarimeter has 3 mrad rms noise level and 1 ms temporal resolution while the interferometer resolution is nedl=1×1012 cm−2 with time response of 1 μs. Absolute calibration of the polarimeter system is achieved by use of a rotating quartz half-wave plate. The first 11-channel polarimeter measurements from MST indicate a Faraday rotation profile in good agreement with expectations from the MSTFIT equilibrium code. Future plans to reduce the polarimeter time response from 1 ms to 10 μs will allow direct measurement of magnetic fluctuations associated with global resistive tearing modes on MST. The effect of these modes on density is already clearly resolved and provides insight into the dynamics of these structures. Improving the time response will also result in lower phase noise for both the polarimeter and interferometer. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1321744
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  • 3
    Electronic Resource
    Electronic Resource
    Horizontal-view interferometer on TEXT-Upgrade : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 852-854 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The first experimental results from the horizontal-view, multichannel, heterodyne FIR interferometer system on TEXT-Upgrade are reported. The initial system employs parabolic beam-expansion optics and a 15 cm array with minimum channel spacing of 1.5 cm. Profiles of the plasma electron density will be presented. In addition, small-amplitude density perturbations resulting from sawteeth and tearing modes are examined. Due to the double pass of the laser beam through the plasma and the large distance of the detector array (2.5 m) from the plasma, refractive effects can be important. A ray tracing code is developed to correct the measured profiles. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146249
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  • 4
    Electronic Resource
    Electronic Resource
    Inversion of chord-integrated data from noncircular tokamak plasmas (abstract)a) : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 460-460 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The superior performance of diverted and elongated plasmas in tokamaks motivates improvements of inversion techniques for chord integrated data (from interferometry, spectroscopy, bolometry, etc.) from such noncircular plasmas. We present a technique planned for TEXT-U. First, flux-surface contours are calculated using EFIT or a filament code. A computer subroutine is provided which then computes, for a given chord, the length of the chord segment enclosed within the flux surface ψ, as a function of ψ from the tangent surface ψtan outward. Using the length functions, the inversions may be performed using the technique of Park or by least-squares fitting. Inversions of FIR interferometer data are presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146382
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  • 5
    Electronic Resource
    Electronic Resource
    The elastic and piezoelectric properties of a lithium triborate single crystal (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2462-2464 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: From the velocity of sound measurements, obtained using Brillouin scattering and ultrasound techniques, the elastic and piezoelectric coefficients of lithium triborate (LiB3O5; LBO) single crystals have been determined. Based upon the sound propagation equations and above results, the slowness curves in (100), (010), and (001) crystalline planes are calculated and presented. Some properties of sound propagation and electromechanical coupling in the crystal are also discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114608
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  • 6
    Electronic Resource
    Electronic Resource
    The Auger recombination rate is larger in a GaSb quantum well than in bulk GaSb (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 836-840 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The band-to-band Auger recombination rate in bulk GaSb and in a GaSb quantum well is calculated. It turns out to be larger in the quantum well because the threshold of the Auger process is located at the band edge where the density of states is larger in the quantum well than in bulk. A simple picture is developed to illustrate the physics of the Auger processes in bulk and quantum-well direct-band-gap semiconductors. With this picture, we propose that the composition-disorder-induced band mixing should be considered in order to explain the unusual behavior of the Auger process in an InGaAsP quantum-well structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347318
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  • 7
    Electronic Resource
    Electronic Resource
    Auger recombination in HgCdTe quantum wires and quantum boxes (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3394-3398 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Quantum-wire and quantum-box structures for narrow-gap materials with small effective masses, such as HgCdTe, can readily be fabricated using current lithographic techniques. In this article, we calculate the Auger-recombination carrier lifetimes in HgCdTe quantum-wire and quantum-box structures, with band gaps in the 2–5 μm wavelength range. Quantum confinement is generally believed to increase the carrier lifetimes. However, we find the Auger recombination lifetime in a HgCdTe quantum wire is shorter than that in a quantum well, and it decreases as the wire width decreases because of the corresponding increase in the density of states. On the other hand, band-to-band Auger recombination is zero in a quantum box because the overlap functions vanish and because of the discrete nature of the energy levels. Therefore, within the confines of our model, we can expect improved temperature performance from long-wavelength quantum-box lasers but not from quantum-wire lasers. Furthermore, these conclusions are applicable for all types of band-to-band Auger processes and semiconductor materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350935
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  • 8
    Electronic Resource
    Electronic Resource
    Enhanced exciton absorption and saturation limit in strained InGaAs/InP quantum wells (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 769-772 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new approach for enhancing the exciton absorption and increasing the saturation limit in quantum wells (QWs), using tensile strain, is proposed. Because of the valence-band mixing in a strained QW, the in-plane hole mass can become very large or negative. This leads to a heavy electron-hole reduced mass (exciton mass), and therefore to a small exciton radius. Exciton absorption is substantially increased because of the increased electron-hole overlap probability in these small-radius excitons. The effects of saturation are also substantially reduced because of decreased charge-screening effects for small-radius excitons and because the rapid dispersal of the photon-generated excitons reduces the Pauli exclusion effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.351341
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  • 9
    Electronic Resource
    Electronic Resource
    Carrier lifetimes and threshold currents in HgCdTe double heterostructure and multi-quantum-well lasers (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6869-6875 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Auger and radiative combination carrier lifetimes in HgCdTe bulk and quantum-well structures, with band gaps in the wavelength range 2–5 μm, are calculated. The Auger recombination rate in a HgCdTe quantum well (QW) is shown to be significantly smaller than that in bulk material. Threshold current densities of HgCdTe double-heterostructure (DH) and multiquantum-well (MQW) lasers are calculated. In a HgCdTe DH laser, Auger recombination dominates the carrier loss at threshold. In a HgCdTe MQW laser, on the other hand, radiative recombination dominates the carrier loss. MQW lasers shown improved temperature performance over conventional DH lasers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347676
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  • 10
    Electronic Resource
    Electronic Resource
    Improved performance of an optically pumped FIR laser using metallic waveguide : Proceedings of the 9th topical conference on high temperature plasma diagnostics (1992)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4672-4674 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to improve the overall output characteristics of far-infrared (FIR) lasers, recent development at UCLA has concentrated on the use of a metallic overmoded waveguide (smooth bore and corrugated) instead of a conventional smooth-bore dielectric waveguide. The metallic waveguide has substantially lower propagation losses, especially at frequencies below 500 GHz, and also supports the desired HE11 mode. Laboratory results show a substantial increase in output power using a corrugated metallic waveguide, with 37 mW being obtained at 1.22 mm using 13CH3F (isotopic methyl fluoride) while maintaining the same mode quality and polarization. This represents an improvement of 100% over a smooth-bore dielectric waveguide. Comparison of far-infrared output using the three types of waveguide will be made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1143659
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