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  • 1
    Electronic Resource
    Electronic Resource
    Identification of Alfvén mode location via multichannel interferometer measurements (abstract) : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 698-698 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Quasicoherent magnetohydrodynamics modes with an Alfvén frequency scaling are seen routinely in TFTR neutral beam heated plasmas as well as some Ohmic plasmas. So far, they are only observed in external magnetic fluctuation measurement (Mirnov coils). A close correlation is observed between the changes in the mode frequency and electron density measured by the multichannel infrared interferometer. This correlation allows us to determine the location of the Alfvén modes. The result shows that they are near the plasma edge, r/a〉0.85. This method is also used to identify the location of the toroidicity-induced Alfvén eigenmode driven by fast ions in a radiowave heating experiment. The result is consistent with the location determined by the reflectometer measurement.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147925
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  • 2
    Electronic Resource
    Electronic Resource
    Far infrared tangential interferometry/polarimetry on the National Spherical Tokamak Experiment : Proceedings of the 12th topical conference on high temperature plasma diagnostics (1999)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 710-713 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Measurement of the core BT(r,t) value is essential in the National Spherical Tokamak Experiment (NSTX), since the effects of paramagnetism and diamagnetism in the NSTX are expected to be considerably greater than that in higher aspect ratio tokamaks. Therefore, without independent BT(r,t) measurement, plasma parameters dependent upon BT such as the q profile and local β value cannot be evaluated. Tangential interferometer/polarimeter systems (eight channels) [H. Park, L. Guttadora, C. Domier, W. R. Geck, and N. C. Luhman, Jr., First and Second NSTX Research Forums, Princeton, NJ, 1997 (unpublished)] for the NSTX will provide temporally and radially resolved toroidal field profile [BT(r,t)] and two-dimensional electron density profile [ne(r,t)] data. The outcome of the proposed system is extremely important to the study of confinement, heating, and stability of the NSTX plasmas. The research task is largely based on utilizing existing hardware from the TFTR multichannel infrared interferometer system [D. K. Mansfield, H. K. Park, L. C. Johnson, H. Anderson, S. Foote, B. Clifton, and C. H. Ma, Appl. Opt. 26, 4469 (1987) and H. K. Park, D. K. Mansfield, and C. L. Johnson, Proceedings of the 3rd International Symposium on Laser-Aided Plasma Diagnostic, Los Angeles, CA, 28–30 Oct. 1987 (unpublished), pp. 96–104] which will be reconfigured into a tangential system for NSTX, and to develop the additional hardware required to complete the system. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149364
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  • 3
    Electronic Resource
    Electronic Resource
    Application of microwave reflectometry to the measurement of fast magnetosonic waves in the Tokamak Fusion Test Reactor : Proceedings of the eleventh topical conference on high temperature plasma diagnostics (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 450-453 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The application of microwave reflectometry to the study of fast magnetosonic waves in the Tokamak Fusion Test Reactor (TFTR) is investigated. Assuming the validity of geometric optics for reflectometer measurements, it is shown that linearity to the fast wave amplitude is restricted to very small density fluctuation levels (ñ/n〈10−3). Beyond this level, both phase and amplitude ambiguities occur that makes interpretation difficult. Measurements of 30 MHz fast magnetosonic waves in the core of TFTR plasmas are presented. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147604
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  • 4
    Electronic Resource
    Electronic Resource
    Alpha-driven magnetohydrodynamics (MHD) and MHD-induced alpha loss in the Tokamak Fusion Test Reactor : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1610-1616 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Alpha-driven toroidal Alfvén eigenmodes (TAEs) are observed as predicted by theory in the post-neutral beam phase in high central q (safety factor) deuterium–tritium (D–T) plasmas in the Tokamak Fusion Test Reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)]. The mode location, poloidal structure, and the importance of q profile for TAE instability are discussed. So far no alpha particle loss due to these modes was detected due to the small mode amplitude. However, alpha loss induced by kinetic ballooning modes (KBMs) was observed in high-confinement D–T discharges. Particle orbit simulation demonstrates that the wave–particle resonant interaction can explain the observed correlation between the increase in alpha loss and appearance of multiple high-n (n≥6, n is the toroidal mode number) modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872363
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  • 5
    Electronic Resource
    Electronic Resource
    The role of the neutral beam fueling profile in the performance of the Tokamak Fusion Test Reactor and other tokamak plasmas : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1699-1706 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Scalings for the stored energy and neutron yield, determined from experimental data, are applied to both deuterium-only and deuterium–tritium plasmas in different neutral-beam-heated operational domains in the Tokamak Fusion Test Reactor [Nucl. Fusion 25, 1167 (1985)]. The domain of the data considered includes the Supershot, high poloidal beta, low-mode, and limiter high-mode operational regimes, as well as discharges with a reversed magnetic shear configuration. The new important parameter in the present scaling is the peakedness of the heating beam fueling profile shape. Ion energy confinement and neutron production are relatively insensitive to other plasma parameters compared to the beam fueling peakedness parameter and the heating beam power when considering plasmas that are stable to magnetohydrodynamic modes. However, the stored energy of the electrons is independent of the beam fueling peakedness. The implication of the scalings based on this parameter is related to theoretical transport models such as radial electric field shear and ion temperature gradient marginality models. Similar physics interpretation is provided for beam heated discharges on other major tokamaks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872272
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  • 6
    Electronic Resource
    Electronic Resource
    Local transport barrier formation and relaxation in reverse-shear plasmas on the Tokamak Fusion Test Reactor : The 38th annual meeting of the Division of Plasma Physics (DPP) of the American Physical Society (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 1736-1744 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The roles of turbulence stabilization by sheared E×B flow and Shafranov shift gradients are examined for Tokamak Fusion Test Reactor [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)] enhanced reverse-shear (ERS) plasmas. Both effects in combination provide the basis of a positive-feedback model that predicts reinforced turbulence suppression with increasing pressure gradient. Local fluctuation behavior at the onset of ERS confinement is consistent with this framework. The power required for transitions into the ERS regime are lower when high power neutral beams are applied earlier in the current profile evolution, consistent with the suggestion that both effects play a role. Separation of the roles of E×B and Shafranov shift effects was performed by varying the E×B shear through changes in the toroidal velocity with nearly steady-state pressure profiles. Transport and fluctuation levels increase only when E×B shearing rates are driven below a critical value that is comparable to the fastest linear growth rates of the dominant instabilities. While a turbulence suppression criterion that involves the ratio of shearing to linear growth rates is in accord with many of these results, the existence of hidden dependencies of the criterion is suggested in experiments where the toroidal field was varied. The forward transition into the ERS regime has also been examined in strongly rotating plasmas. The power threshold is higher with unidirectional injection than with balance injection. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872275
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  • 7
    Electronic Resource
    Electronic Resource
    Tests of local transport theory and reduced wall impurity influx with highly radiative plasmas in the Tokamak Fusion Test Reactor (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 877-884 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron temperature (Te) profile in neutral beam-heated supershot plasmas (Te0∼6–7 keV ion temperature Ti0∼15–20 keV, beam power Pb∼16 MW) was remarkably invariant when radiative losses were increased significantly through gas puffing of krypton and xenon in the Tokamak Fusion Test Reactor [McGuire et al., Phys. Plasmas 2, 2176 (1995)]. Trace impurity concentrations (nz/ne∼10−3) generated almost flat and centrally peaked radiation profiles, respectively, and increased the radiative losses to 45%–90% of the input power (from the normal ∼25%). Energy confinement was not degraded at radiated power fractions up to 80%. A 20%–30% increase in Ti, in spite of an increase in ion–electron power loss, implies a factor of ∼3 drop in the local ion thermal diffusivity. These experiments form the basis for a nearly ideal test of transport theory, since the change in the beam heating power profile is modest, while the distribution of power flow between (1) radiation and (2) conduction plus convection changes radically and is locally measurable. The decrease in Te was significantly less than predicted by two transport models and may provide important tests of more complete transport models. At input power levels of 30 MW, the increased radiation eliminated the catastrophic carbon influx (carbon "bloom") and performance (energy confinement and neutron production) was improved significantly relative to that of matched shots without impurity gas puffing. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873327
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  • 8
    Electronic Resource
    Electronic Resource
    Concentration dependent photoluminescence of Te-doped In0.5Ga0.5P layers grown by liquid phase epitaxy (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4024-4027 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) of Te-doped In0.5Ga0.5P epilayers grown by the liquid phase epitaxy technique has been investigated as a function of carrier concentration. The PL results are interpreted using a model taking into account nonparabolicity of the conduction band. Both the band filling as well as band tailing due to the Coulomb interaction of free carriers with ionized impurities and band shrinkage due to the exchange interaction between free carriers are considered in order to properly portray the observed features of the PL spectra. The theoretical calculations are in satisfactory agreement with the observed PL results. The PL line shape is well explained by a direct transition with a simple k-selection rule up to a carrier concentration of 2.0 ×1018 cm−3. Above the carrier concentration of 2.0 ×1018 cm−3, on the other hand, it is properly interpreted in terms of non-k-conserving transitions that arise from the indirect recombination of electrons in a highly filled conduction band. It was found that a concentration dependent gap shrinkage due to the exchange interaction in Te-doped In0.5Ga0.5P at 17 K is described by the relation Ece=2.34×10−8 n1/3 (eV). The concentration dependent effective mass has also been calculated using Kane's three band model. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365754
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  • 9
    Electronic Resource
    Electronic Resource
    Rubbing-free, vertically aligned nematic liquid crystal display controlled by in-plane field (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2851-2853 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We fabricated a homeotropically aligned nematic liquid crystal display with positive dielectric anisotropy, whose on and off states are controlled by in-plane field. The rubbing-free device, dark in voltage-off state, reveals bright uniformity in all directions due to the dual domainlike director configuration in the voltage-on state. The electro-optic characteristics of one prototype with excellent viewing angles are reported herein. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120153
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  • 10
    Electronic Resource
    Electronic Resource
    Prognostic factors for toluene diisocyanate-induced occupational asthma after removal from exposure (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical & experimental allergy 27 (1997), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background The outcome of isocyanatc-induced occupational asthma remains to be further defined. There have been few studies on the role of specific antibodies in prognosis of toluene diisocyanate (TDI) induced occupational asthma. Moreover, to the best of our knowledge, there have been no studies on the improvement pattern of airway hyper-responsiveness (AH). We analysed the prognostic factors that affected the outcome of 35 toluene diisocyanate-induced occupational asthma.Objectives To define clinical and laboratory parameters predicting favourable prognosis for TDI-induced occupational asthma.Methods and results After confirmation of bronchial sensitivity by TDI hronchoprovocation test (BPT), 35 patients were recommended to avoid exposure to TDI; they were also given anti-asthmatic medications including inhaled steroids and monitored for 2 years. Seventeen (49%) recovered completely with disappearance of airway hyperresponsiveness (AH) to methacholine during the follow-up period (mean duration: 12 months, range of 3–30 months). Eleven (31%) showed a significant improvement in AH for first year, which improvement stabihzed in the next year with mild symptoms. Seven (20%) patients did not show any evidence of improvement in AH and had persistent symptoms. Favourable prognosis was associated with a short duration of asthmatic symptoms before diagnosis (P 〈 0.05), immediate cessation of exposure after diagnosis (P 〈 0.05), milder degree of AH at diagnosis (P 〈 0.05), and the presence of specific IgE antibodies to TDI-human serum albumin conjugate (0.05 〈 P 〈 0.1). No association was found with atopic and smoking status, age, exposure duration, or length of latent period (P 〉 0.05).Conclusion These data suggest that early detection of TDI-induced asthma and immediate cessation of exposure are important factors for a favourable prognosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.1997.tb01151.x
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