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  • 1
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    Linear chirped slope profile for spatial calibration in slope measuring deflectometry (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-05-25
    Description: Slope measuring deflectometry is commonly used by the X-ray optics community to measure the long-spatial-wavelength surface figure error of optical components dedicated to guide and focus X-rays under grazing incidence condition at synchrotron and free electron laser beamlines. The best performing instruments of this kind are capable of absolute accuracy on the level of 30-50 nrad. However, the exact bandwidth of the measurements, determined at the higher spatial frequencies by the instrument’s spatial resolution, or more generally by the instrument’s modulation transfer function (MTF) is hard to determine. An MTF calibration method based on application of a test surface with a one-dimensional (1D) chirped height profile of constant amplitude was suggested in the past. In this work, we propose a new approach to designing the test surfaces with a 2D-chirped topography, specially optimized for MTF characterization of slope measuring instruments. The design of the developed MTF test samples based on the proposed linear chirped slope profiles (LCSPs) is free of the major drawback of the 1D chirped height profiles, where in the slope domain, the amplitude strongly increases with the local spatial frequency of the profile. We provide the details of fabrication of the LCSP samples. The results of first application of the developed test samples to measure the spatial resolution of the BESSY-NOM at different experimental arrangements are also presented and discussed.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
    Electronic Resource
    Electronic Resource
    New powder diffractometer at HASYLAB/DESY : International conference on synchrotron radiation instrumentation (SRI−88) (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 2380-2381 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The new powder diffractometer installed on the beamline B2 at HASYLAB/DESY is described. It features a new design with a blocked double circle plus a third single circle which can be translated towards one another. The wide space between the two circle units conveniently holds complicated and spacious attachments and makes the instrument especially suitable for measurements under controlled environment conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140725
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of low confinement mode transport simulations using the mixed Bohm/gyro-Bohm and the Multi-Mode-95 transport model (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 975-985 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Predictive transport simulations using the mixed Bohm/gyro-Bohm (JET) transport model [M. Erba et al., Plasma Phys. Controlled Fusion 39, 261 (1997)] are compared with simulations using the Multi-Mode-95 (MMM95) transport model [G. Bateman et al., Phys. Plasmas 5, 1793 (1998)]. Temperature and density profiles from these simulations are compared with experimental data for 13 low confinement mode (L-mode) discharges from the Doublet III-D Tokamak (DIII-D) [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)] and the Tokamak Fusion Test Reactor (TFTR) [D. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)]. The selected discharges include systematic scans over gyro-radius, plasma power, current, and density. It is found that simulations using the two models match experimental data equally well, in spite of the fact that the JET model has predominantly Bohm scaling (proportional to gyro-radius) while the MMM95 model has a purely gyro-Bohm scaling (proportional to gyro-radius squared). © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1344195
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  • 4
    Electronic Resource
    Electronic Resource
    Multi-Mode transport modeling of the International Thermonuclear Experimental Reactor (ITER) (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2355-2362 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Predictions are made for the performance of the International Thermonuclear Experimental Reactor (ITER) [R. Aymar, V. Chuyanov, M. Huguet, R. Parker, and Y. Shimomura, in Proceedings of the Sixteenth International Atomic Energy Agency Fusion Energy Conference, Montréal, Canada 1996 (International Atomic Energy Agency, Vienna, 1997), Paper IAEA-CN-64/01-1] design using the Multi-Mode model in the time-dependent one- and one-half-dimensional (1-1/2-D) BALDUR [C. E. Singer et al., Comput. Phys. Commun. 49, 275 (1988)] transport code. This model predicts the temperature and density profiles observed in present-day tokamak experiments more closely on the average than other models currently available. Simulations using the Multi-Mode transport model, with its inherent gyro-Bohm scaling, indicate that ITER will ignite, even with edge temperatures as low as 0.25 keV (L-mode, or low-confinement mode, boundary conditions) or with volume averaged density as low as 0.775×1020 m−3 (just below the Greenwald density limit, when Tedge=0.75 keV). The ignition is found to be thermally stable, and the fusion power production is easily controlled by varying plasma density, impurity content, or edge temperatures. The nonequilibrium impurity radiation model used in these simulations predicts that a significant fraction of the fusion power is radiated when conditions are close to marginal ignition. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872909
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  • 5
    Electronic Resource
    Electronic Resource
    Predictive simulations of tokamak plasmas with a model for ion-temperature-gradient-driven turbulence (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 1369-1379 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A drift wave transport model, recently developed by Ottaviani, Horton and Erba (OHE) [Ottaviani et al., Plasma Phys. Controlled Fusion 39, 1461 (1997)], has been implemented and tested in a time-dependent predictive transport code. This OHE model assumes that anomalous transport is due to turbulence driven by ion temperature gradients and that the fully developed turbulence will extend into linearly stable regions, as described in the reference cited above. A multiplicative elongation factor is introduced in the OHE model and simulations are carried out for 12 discharges from major tokamak experiments, including both L- and H-modes (low- and high-confinement modes) and both circular and elongated discharges. Good agreement is found between the OHE model predictions and experiment. This OHE model is also used to describe the performance of the International Thermonuclear Experimental Reactor (ITER) [Putvinski et al., in Proceedings of the 16th IAEA Fusion Energy Conference, Montréal, Canada, 1996 (International Atomic Energy Agency, Vienna, 1997), Vol. 2, p. 737.] A second version of the OHE model, in which the turbulent transport is not allowed to penetrate into linearly stable regions, has also been implemented and tested. In simulations utilizing this version of the model, the linear stability of the plasma core eliminates the anomalous thermal transport near the magnetic axis, resulting in an increase in the core temperatures to well above the experimental values. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872797
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  • 6
    Electronic Resource
    Electronic Resource
    Sensitivity of predictive tokamak plasma transport simulations (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2207-2214 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sensitivity of our time-dependent simulations of low confinement (L-mode) discharges to variations in initial profiles and time-dependent boundary conditions has been explored. These time-dependent tokamak plasma simulations were performed using a theory-based Multi-mode transport model that includes ion temperature gradient (ITG) and trapped electron modes (TEM), kinetic and resistive ballooning modes and neoclassical modes. The density and temperature profiles predicted in our simulations of L-mode discharges are found to be robust, even with significant variations in the initial or boundary conditions. Although transport associated with a single mode can be strongly affected by local changes in plasma parameters resulting from changes in the boundary conditions, the total transport remains largely unchanged because of compensation by other transport modes. The sensitivity of the predicted temperature and density profiles to a variation in the Multi-mode model is also examined. When the Dominguez-Waltz theory of transport driven by ITG and TEM modes is replaced in the Multi-mode model by the Weiland description, we find that the predictions of the Weiland model more closely match the experimental data. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872384
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of isotope mass on transport simulations of Joint European Torus high-mode plasmas with Edge Localized Modes (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 4607-4614 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of isotopic mass on heat and particle transport in Joint European Torus (JET) [P.-H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] plasma discharges is studied using the Multi-Mode model in the BALDUR predictive transport code [Bateman et al., Phys. Plasmas 5, 1793 (1998)]. Temperature and density profiles from these simulations generally agree with the experimentally measured profiles for high-mode JET discharges with Edge Localized Modes in hydrogen, deuterium, and tritium discharges. It is surprising that a purely gyro-Bohm transport model, used in these simulations, correctly predicts the experimentally observed improvement in confinement as the isotope mass is increased—given the fact that gyro-Bohm diffusion coefficients increase with isotope mass when the shapes of all the plasma profiles are held fixed. However, in the JET experiment, it was found that the electron and ion temperature at the top of the edge pedestal increases systematically as the isotope mass in increased (J. G. Cordey et al., Report No. JET-P (98)53, 1998). The numerical simulations reported here show that this increase in the edge temperatures and subsequent broadening of the temperature profiles account for the improvement in confinement as the isotope mass is increased. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873724
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  • 8
    Electronic Resource
    Electronic Resource
    Predicting temperature and density profiles in tokamaks : 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. 1793-1799 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A fixed combination of theory-based transport models, called the Multi-Mode Model, is used in the BALDUR [C. E. Singer et al., Comput. Phys. Commun. 49, 275 (1988)] transport simulation code to predict the temperature and density profiles in tokamaks. The choice of the Multi-Mode Model has been guided by the philosophy of using the best transport theories available for the various modes of turbulence that dominate in different parts of the plasma. The Multi-Mode model has been found to provide a better match to temperature and density profiles than any of the other theory-based models currently available. A description and partial derivation of the Multi-Mode Model is presented, together with three new examples of simulations of the Tokamak Fusion Test Reactor (TFTR) [K. M. McGuire et al., Phys. Plasmas 2, 2176 (1995)]. The first simulation shows the strong effect of recycling on the ion temperature profile in TFTR supershot simulations. The second simulation explores the effect of a plasma current ramp—where the plasma energy content changes slowly on the energy confinement time scale. The third simulation shows that the Multi-Mode Model reproduces the experimentally measured profiles when tritium is used as the hydrogenic isotope in L-mode (low confinement mode) plasmas. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872848
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  • 9
    Electronic Resource
    Electronic Resource
    Comparison of two resistive ballooning mode models in transport simulations (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 561-570 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Predictive transport simulations of the temperature and density profiles have been carried out for Tokamak Fusion Test Reactor (TFTR) [K. Young et al., Plasma Phys. Controlled Fusion 26, 11 (1984)] current, density, and heating power scans. Two competing resistive ballooning mode theories are considered in order to examine their intrinsic magnetic-q dependence. The theoretically derived transport model employed in this study includes drift wave contributions from the Weiland theory of trapped electron and ion temperature gradient modes, the Kwon–Biglari–Diamond neoclassical magnetohydrodynamic (MHD) theory, the Tang–Rewoldt kinetic ballooning mode theory, and either the previously used Carreras–Diamond or the recently developed Guzdar–Drake resistive ballooning mode theories. It is found that the Guzdar–Drake theory provides the correct scaling with plasma current while maintaining a scaling with density and auxiliary heating power that is consistent with experimental data from TFTR low confinement (L-mode) plasmas. A statistical analysis of the profile results for the current scan is included to give quantitative measures of how well simulations that include either the Guzdar–Drake or the Carreras–Diamond theory compare with the experimental data. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871883
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  • 10
    Electronic Resource
    Electronic Resource
    Drift mode growth rates and associated transport (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 1162-1167 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Drift mode linear growth rates and quasilinear transport are investigated using the FULL kinetic stability code [Rewoldt et al., Phys. Plasmas 5, 1815 (1998)] and a version of the Weiland transport model [Strand et al., Nucl. Fusion 38, 545 (1998)]. It is shown that the drift mode growth rates (as well as the marginal stability temperature gradient) obtained using the FULL code are dependent on the accuracy of the equilibrium employed. In particular, when an approximate equilibrium model is utilized by the FULL code, the results can differ significantly from those obtained using a more accurate numerical equilibrium. Also investigated are the effects of including full electron physics. It is shown, using both the FULL code and the Weiland model, that the nonadiabatic (e.g., trapped) electron response produces a significant increase in the linear growth rate of the ion-temperature-gradient (ITG) driven branch of the drift instability. Other consequences of the nonadiabatic electron response include a reduction in the marginal temperature gradient for the onset of the ITG mode and an additional contribution to transport due to the excitation of the Trapped Electron Mode (TEM). Physical explanations are given for the sensitivity of the mode growth rates to the equilibrium and the nonadiabatic electron response. Finally, linear growth rates for the ITG mode computed using the FULL code are compared with growth rates obtained using the Weiland model. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873360
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