774,493 research outputs found
Intrinsic rotation in tokamaks: theory
Self-consistent equations for intrinsic rotation in tokamaks with small
poloidal magnetic field compared to the total magnetic field are
derived. The model gives the momentum redistribution due to turbulence,
collisional transport and energy injection. Intrinsic rotation is determined by
the balance between the momentum redistribution and the turbulent diffusion and
convection. Two different turbulence regimes are considered: turbulence with
characteristic perpendicular lengths of the order of the ion gyroradius,
, and turbulence with characteristic lengths of the order of the
poloidal gyroradius, . Intrinsic rotation driven by gyroradius
scale turbulence is mainly due to the effect of neoclassical corrections and of
finite orbit widths on turbulent momentum transport, whereas for the intrinsic
rotation driven by poloidal gyroradius scale turbulence, the slow variation of
turbulence characteristics in the radial and poloidal directions and the
turbulent particle acceleration can be become as important as the neoclassical
and finite orbit width effects. The magnetic drift is shown to be indispensable
for the intrinsic rotation driven by the slow variation of turbulence
characteristics and the turbulent particle acceleration. The equations are
written in a form conducive to implementation in a flux tube code, and the
effect of the radial variation of the turbulence is included in a novel way
that does not require a global gyrokinetic formalism.Comment: 88 pages, 4 figure
Progress on tilted axis cranking covariant density functional theory for nuclear magnetic and antimagnetic rotation
Magnetic rotation and antimagnetic rotation are exotic rotational phenomena
observed in weakly deformed or near-spherical nuclei, which are
respectivelyinterpreted in terms of the shears mecha-nism and two shearslike
mechanism. Since their observations, magnetic rotation and antimagnetic
rotation phenomena have been mainly investigated in the framework of tilted
axis cranking based on the pairing plus quadrupole model. For the last decades,
the covariant density functional theory and its extension have been proved to
be successful in describing series of nuclear ground-states and excited states
properties, including the binding energies, radii, single-particle spectra,
resonance states, halo phenomena, magnetic moments, magnetic rotation,
low-lying excitations, shape phase transitions, collective rotation and
vibrations, etc. This review will mainly focus on the tilted axis cranking
covariant density functional theory and its application for the magnetic
rotation and antimagnetic rotation phenomena.Comment: 53 pages, 19 figure
The axial breathing mode in rapidly rotating Bose-Einstein condensates and uncertainty of the rotation velocity
Experiments on the axial breathing mode in a rapidly rotating Bose-Einstein
condensate are examined. Assuming a cold cloud without thermal component, we
show that errors due to defocus of an imaging camera in addition to an
inclination of the rotational axis can lead to a significant underestimate of
the rotation rate in the fast rotation limit; within these uncertainties, our
theoretical prediction agrees with the experimental data. We also show that, in
the fast rotation regime, the Thomas-Fermi theory, which is inapplicable there,
underestimates the rotation rate. Underestimate of the rotation rate due to
these effects would also partly explain a discrepancy between theory and
experiment for the Tkachenko mode frequency in the fast rotation regime.Comment: 5 pages, 2 figures; this paper is related to cond-mat/0506331;
accepted for publication in Phys. Rev. A Rapid Communication
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