2,560 research outputs found
Divertor Heat Load in ASDEX Upgrade L-Mode in Presence of External Magnetic Perturbation
Power exhaust is one of the major challenges for a future fusion device.
Applying a non-axisymmetric external magnetic perturbation is one technique
that is studied in order to mitigate or suppress large edge localized modes
which accompany the high confinement regime in tokamaks. The external magnetic
perturbation brakes the axisymmetry of a tokamak and leads to a 2D heat flux
pattern on the divertor target. The 2D heat flux pattern at the outer divertor
target is studied on ASDEX Upgrade in stationary L-Mode discharges. The
amplitude of the 2D characteristic of the heat flux depends on the alignment
between the field lines at the edge and the vacuum response of the applied
magnetic perturbation spectrum. The 2D characteristic reduces with increasing
density. The increasing divertor broadening with increasing density is
proposed as the main actuator. This is supported by a generic model using field
line tracing and the vacuum field approach that is in quantitative agreement
with the measured heat flux. The perturbed heat flux, averaged over a full
toroidal rotation of the magnetic perturbation, is identical to the
non-perturbed heat flux without magnetic perturbation. The transport
qualifiers, power fall-off length and divertor broadening , are
the same within the uncertainty compared to the unperturbed reference. No
additional cross field transport is observed.Comment: 23 pages, 28 figures. This is an author-created, un-copyedited
version of an article submitted for publication in Plasma Physics and
Controlled Fusion. IoP Publishing Ltd is not responsible for any errors or
omissions in this version of the manuscript or any version derived from i
Edge channel confinement in a bilayer graphene -- quantum dot
We combine electrostatic and magnetic confinement to define a quantum dot in
bilayer graphene. The employed geometry couples -doped reservoirs to a
-doped dot. At magnetic field values around T, Coulomb blockade is
observed. This demonstrates that the coupling of the co-propagating modes at
the - interface is weak enough to form a tunnel barrier, facilitating
transport of single charge carriers onto the dot. This result may be of use for
quantum Hall interferometry experiments
Interactions and magnetotransport through spin-valley coupled Landau levels in monolayer MoS
The strong spin-orbit coupling and the broken inversion symmetry in monolayer
transition metal dichalcogenides (TMDs) results in spin-valley coupled band
structures. Such a band structure leads to novel applications in the fields of
electronics and optoelectronics. Density functional theory calculations as well
as optical experiments have focused on spin-valley coupling in the valence
band. Here we present magnetotransport experiments on high-quality n-type
monolayer molybdenum disulphide (MoS) samples, displaying highly resolved
Shubnikov-de Haas oscillations at magnetic fields as low as . We find the
effective mass , about twice as large as theoretically predicted and
almost independent of magnetic field and carrier density. We further detect the
occupation of the second spin-orbit split band at an energy of about ,
i.e. about a factor larger than predicted. In addition, we demonstrate an
intricate Landau level spectrum arising from a complex interplay between a
density-dependent Zeeman splitting and spin and valley-split Landau levels.
These observations, enabled by the high electronic quality of our samples,
testify to the importance of interaction effects in the conduction band of
monolayer MoS.Comment: Phys.Rev.Lett. (2018
Environmental description
Environmental description is the description of general, physical, personal and social
space and action, where visual, auditory and other sensory information is shared with
the receiver in spoken, written or sign language, either vocally, i.e. producing sounds
or in another form (pointing, touching, drawing). It can be divided into the expression
of basic characteristics, basic description, precise and extended description, and it can
be carried out physically on the spot (close description) or far away from the target
(distant description). Description can be carried out spontaneously in real time, in joint
action systematically i.e. pre-prepared description or it can be recorded beforehand as
a text format, or as consecutive i.e. a postponed description after the event. The target
group may be one person or a group. In addition to verbal description, environmental
description can be produced with various sounds, such as vocalization without words or
other sources of sounds e.g. musical instruments. Interaction in a situation between the
describer and the receiver may be a one-way description or a dialogue. It can further be
divided into functional dialogue, reciprocal description supporting sensory perceptions,
telling and pointing in front of the target, reciprocal description by drawing or through
movements and the exploration of objects. In detailed descriptions the main subjects are
followed by details. Description can be classified according to the size of the space that is
extensive, large, in a room or nearby
Reproduktionsmedizin bei Muslimen: säkulare und religiöse Ethiken im Widerstreit?
Fragen der Reproduktionsmedizin bei Muslimen werden anhand der Fallbeispiele Indien, Ägypten und Mali vorgestellt. Zusätzlich wird die Frage diskutiert, ob bioethische Debatten sich mit einer Einteilung in säkulare vs. religiöse Lager sinnvoll analysieren lassen
Incommensurate magnetic structure of CrAs at low temperatures and high pressures
The magnetic structure of chromium arsenide CrAs is studied with neutron powder diffraction at ambient pressure in the temperature range 1.5–300 K as well as with neutron single-crystal diffraction at 2 K and 0.12 GPa. The material undergoes an anti-isostructural phase transition at TN = 267 K and atmospheric conditions, in which both orthorhombic phases have the same space-group symmetry (Pnma, Z = 4) but different distortions of the parent hexagonal structure of the NiAs type (P63/mmc, Z = 2). The magnetic structure below TN is incommensurate with the propagation vector k = (0, 0, kc). At ambient pressure, the component kc decreases from kc = 0.3807 (7) at 260 K to kc = 0.3531 (6) at 50 K. Below this temperature, it is basically constant. With increasing pressure at 2 K, kc is also constant within standard uncertainties [kc = 0.353 (2)]. For the analysis of the magnetic structure, a group-theoretical approach based on the space group of the nuclear structure and its subgroups is used. To avoid falling into false minima in the refinements, a random search for magnetic moments in the models is implemented. In the literature, the magnetic structure has been determined on the basis of powder diffraction data as a double helix propagating along the c axis. Although this double-helical model leads to satisfactory agreement factors for our powder data, it does not reproduce the intensities of the magnetic satellite reflections measured on single-crystal data in a satisfactory way and can therefore be discarded. Instead, several other models are found that lead to better agreement. Each of them is spiral-like with directional components in all three directions and with no spin-density wave character that would cause a non-constant magnetic moment. In all these models, the ordering of the spins is neither a pure helix nor a pure cycloid. Instead, the unit vectors of the spin rotation planes make an angle α, 0° < α < 90°, with respect to the c* direction. The model in superspace group P21.1′(α0γ)0s yields the best agreement factors in the refinements of the neutron single-crystal and powder diffraction data. This model is unique as it is the only one in which all the magnetic moments rotate with the same chirality
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