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Digitale Medien

Effect of rotation on H-mode transport in DIII–D via changes in the E×B velocity shear (2002)

Petty, C. C. ; Wade, M. R. ; Kinsey, J. E. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 9 (2002), S. 128-136

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The effect of rotation on the heat and particle transport is measured in the DIII–D tokamak [Fusion Technol. 8, 441 (1985)] for high-confinement mode (H-mode) plasmas with edge localized modes. In a novel experiment, transport is compared for nearly identical scans of the relative gyroradius in co- and counter-rotating plasmas. Since the plasma profiles are the same, the difference in the transport scaling can be attributed to changes in the sheared E×B flow caused by the shift in the toroidal plasma velocity. The ion heat and particle transport are found to be sensitive to the change in the rotation direction and magnitude whereas the electron heat transport is not. Simulations using a gyroLandau-fluid drift wave transport model show that the variation in the ion heat transport for co/counter rotation is due to changes in the E×B shear stabilization, but the electrons appear to be governed by a different transport mechanism. © 2002 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1421077

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Digitale Medien

Sustained rotational stabilization of DIII-D plasmas above the no-wall beta limit : Review,Tutorial and Invited Papers from the 43rd Annual Meeting of the APS Division of Plasma Physics (2002)

Garofalo, A. M. ; Jensen, T. H. ; Johnson, L. C. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 9 (2002), S. 1997-2005

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ISSN: 1089-7674

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Sustained stabilization of the n=1 kink mode by plasma rotation at beta approaching twice the stability limit calculated without a wall has been achieved in DIII-D by a combination of error field reduction and sufficient rotation drive. Previous experiments have transiently exceeded the no-wall beta limit. However, demonstration of sustained rotational stabilization has remained elusive because the rotation has been found to decay whenever the plasma is wall stabilized. Recent theory [Boozer, Phys. Rev. Lett. 86, 5059 (2001)] predicts a resonant response to error fields in a plasma approaching marginal stability to a low-n kink mode. Enhancement of magnetic nonaxisymmetry in the plasma leads to strong damping of the toroidal rotation, precisely in the high-beta regime where it is needed for stabilization. This resonant response, or "error field amplification" is demonstrated in DIII-D experiments: applied n=1 radial fields cause enhanced plasma response and strong rotation damping at beta above the no wall limit but have little effect at lower beta. The discovery of an error field amplification has led to sustained operation above the no-wall limit through improved magnetic field symmetrization using an external coil set. The required symmetrization is determined both by optimizing the external currents with respect to the plasma rotation and by use of feedback to detect and minimize the plasma response to nonaxisymmetric fields as beta increases. Ideal stability analysis and rotation braking experiments at different beta values show that beta is maintained 50% higher than the no wall stability limit for durations greater than 1 s, and approaches beta twice the no-wall limit in several cases, with steady-state rotation levels. The results suggest that improved magnetic-field symmetry could allow plasmas to be maintained well above no-wall beta limit for as long as sufficient torque is provided. © 2002 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1446036

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Digitale Medien

Method for repairing Mo/Si multilayer thin film phase defects in reticles for extreme ultraviolet lithography (2002)

Mirkarimi, P. B. ; Stearns, D. G. ; Baker, S. L. ; [weitere]

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 91 (2002), S. 81-89

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The development of a nearly defect-free reticle blank is an important challenge facing extreme ultraviolet lithography (EUVL). The core element of an EUVL reticle blank is the reflective Mo/Si multilayer film, and deposition of Mo/Si on very small substrate defects can result in critical Mo/Si phase defects. In this article we present a method for repairing Mo/Si multilayer film phase defects in EUVL reticle blanks. An electron beam is used to deposit energy in the immediate vicinity of the defect, producing a small local contraction of the layer thicknesses due to silicide formation at the Mo/Si interfaces. We show in simulations that this contraction can significantly reduce the original structural deformation. We also present experimental results showing that it is possible to use an electron beam to controllably produce depressions in Mo/Si with nanometer-scale depths, and that this can be achieved without significantly impairing the reflective properties of the Mo/Si multilayer films. © 2002 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1419265

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Digitale Medien

Assessment of the Handy–Cohen optimized exchange density functional for organic reactions (2002)

Baker, Jon ; Pulay, Peter

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 117 (2002), S. 1441-1449

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ISSN: 1089-7690

Quelle: AIP Digital Archive

Thema: Physik , Chemie und Pharmazie

Notizen: We have investigated the performance of the new optimized exchange functional (OPTX) developed by Handy and Cohen [Mol. Phys. 99, 403 (2001)] for predicting geometries, heats of reaction, and barrier heights for twelve organic reactions (six closed-shell and six radical). OPTX has been used in conjunction with, among others, the well-known Lee–Yang–Parr (LYP) correlational functional to form two new functionals, OLYP and O3LYP. These are similar to the well-established BLYP and B3LYP functionals, respectively, with OPTX replacing the standard Becke exchange functional, B88. Our results strongly support claims made by their developers that OLYP is superior to BLYP, and essentially renders it obsolete. The computed OLYP heats of reaction, barrier heights, and even molecular geometries (with larger basis sets), are comparable with, if not better than, the corresponding B3LYP values. The O3LYP functional is overall better than B3LYP, albeit not by much. Both OLYP and O3LYP are among the best functionals currently available; the performance of OLYP in particular is noteworthy given that this functional includes no exact exchange. © 2002 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1485723

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