813 research outputs found
Resonances for coupled Bose-Einstein Condensates
We study some effects arising from periodic modulation of the asymmetry and
the barrier height of a two-well potential containing a Bose-Einstein
condensate. At certain modulation frequencies the system exhibits resonances,
which may lead to enhancement of the tunneling rate between the wells and which
can be used to control the particle distribution among the wells. Some of the
effects predicted for a two-well system can be carried over to the case of a
Bose-Einstein condensate in an optical lattice
Analyzing Feshbach resonances -- A Li -Cs case study
We provide a comprehensive comparison of a coupled channels calculation, the
asymptotic bound state model (ABM), and the multichannel quantum defect theory
(MQDT). Quantitative results for Li -Cs are presented and compared
to previously measured Li -Cs Feshbach resonances (FRs) [M. Repp et
al., Phys. Rev. A 87 010701(R) (2013)]. We demonstrate how the accuracy of the
ABM can be stepwise improved by including magnetic dipole-dipole interactions
and coupling to a non-dominant virtual state. We present a MQDT calculation,
where magnetic dipole-dipole and second order spin-orbit interactions are
included. A frame transformation formalism is introduced, which allows the
assignment of measured FRs with only three parameters. All three models achieve
a total rms error of < 1G on the observed FRs. We critically compare the
different models in view of the accuracy for the description of FRs and the
required input parameters for the calculations.Comment: 16 pages, 3 figures, 1 tabl
Design and Tests of the Silicon Sensors for the ZEUS Micro Vertex Detector
To fully exploit the HERA-II upgrade,the ZEUS experiment has installed a
Micro Vertex Detector (MVD) using n-type, single-sided, silicon micro-strip
sensors with capacitive charge division. The sensors have a readout pitch of
120 micrometers, with five intermediate strips (20 micrometer strip pitch). The
designs of the silicon sensors and of the test structures used to verify the
technological parameters, are presented. Results on the electrical measurements
are discussed. A total of 1123 sensors with three different geometries have
been produced by Hamamatsu Photonics K.K. Irradiation tests with reactor
neutrons and Co-60 photons have been performed for a small sample of sensors.
The results on neutron irradiation (with a fluence of 1 x 10^{13} 1 MeV
equivalent neutrons / cm^2) are well described by empirical formulae for bulk
damage. The Co-60 photons (with doses up to 2.9 kGy) show the presence of
generation currents in the SiO_2-Si interface, a large shift of the flatband
voltage and a decrease of the hole mobility.Comment: 33 pages, 25 figures, 3 tables, accepted for publication in NIM
A high-flux 2D MOT source for cold lithium atoms
We demonstrate a novel 2D MOT beam source for cold 6Li atoms. The source is
side-loaded from an oven operated at temperatures in the range 600<T<700 K. The
performance is analyzed by loading the atoms into a 3D MOT located 220 mm
downstream from the source. The maximum recapture rate of ~10^9 /s is obtained
for T=700 K and results in a total of up to 10^10 trapped atoms. The recaptured
fraction is estimated to be 30(10)% and limited by beam divergence. The
most-probable velocity in the beam (alpha_z) is varied from 18 to 70 m/s by
increasing the intensity of a push beam. The source is quite monochromatic with
a full-width at half maximum velocity spread of 11 m/s at alpha_z=36 m/s,
demonstrating that side-loading completely eliminates beam contamination by hot
vapor from the oven. We identify depletion of the low-velocity tail of the oven
flux as the limiting loss mechanism. Our approach is suitable for other atomic
species.Comment: 13 pages,9 figures, submitted to Phys.Rev.
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