13,692 research outputs found
Intense terahertz laser fields on a quantum dot with Rashba spin-orbit coupling
We investigate the effects of the intense terahertz laser field and the
spin-orbit coupling on single electron spin in a quantum dot. The laser field
and the spin-orbit coupling can strongly affect the electron density of states
and can excite a magnetic moment.
The direction of the magnetic moment depends on the symmetries of the system,
and its amplitude can be tuned by the strength and frequency of the laser field
as well as the spin-orbit coupling.Comment: 5 pages, 4 figures, to be published in J. Appl. Phy
The NSNS High Energy Beam Transport Line
In the National Spallation Neutron Source (NSNS) design, a 180 meter long
transport line connects the 1 GeV linac to an accumulator ring. The linac beam
has a current of 28 mA, pulse length of 1 ms, and 60 Hz rep rate. The high
energy transport line consists of sixteen 60 degrees FODO cells, and
accommodates a 90 degrees achromatic bend, an energy compressor, collimators,
part of injection system, and enough diagnostic devices to measure the beam
quality before injection. To reduce the uncontrolled beam losses, this line has
nine beam halo scrapers and very tight tolerances on both transverse and
longitudinal beam dynamics under space charge conditions. The design of this
line is presented.Comment: 3 pages, transfer line desig
Spectral Analyses of the Nearest Persistent Ultraluminous X-Ray Source M33 X-8
We provide a detailed analysis of 12 XMM observations of the nearest
persistent extragalactic ultraluminous X-ray source (ULX), M33 X-8. No
significant spectral evolution is detected between the observations, therefore
we combine the individual observations to increase the signal-to-noise ratio
for spectral fitting. The combined spectra are best fitted by the
self-consistent p-free disk plus power-law component model with p =
0.571_{-0.030}^{+0.032}, kT_{in} = 1.38_{-0.08}^{+0.09} keV, and the flux ratio
of the p-free disk component to the power-law component being 0.63:0.37 in the
0.3 -- 10 keV band. The fitting indicates that the black hole in M33 X-8 is of
\sim 10 M_{\odot} and accretes at a super-Eddington rate (\sim 1.5 L_{Edd}),
and the phase of the accretion disk is close to a slim disk (p = 0.5). We
report, for the first time, that an extra power-law component is required in
addition to the p-free disk model for ULXs. In super-Eddington cases, the
power-law component may possibly result from the optically thin inner region f
the disk or a comptonized corona similar to that of a standard thin disk.Comment: 11 pages, 1 table, 2 figures, accepted by PAS
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