151 research outputs found
Generating Schr\"{o}dinger-cat states in momentum and internal-state space from Bose-Einstein condensates with repulsive interactions
Resonant Raman coupling between internal levels induced by continuous
illumination of non-collinear laser beams can create double-well momentum-space
potentials for multi-level ``periodically-dressed'' atoms. We develop an
approximate many-body formalism for a weakly interacting, trapped
periodically-dressed Bose gas which illustrates how a tunable exchange
interaction yields correlated many-body ground states. In contrast to the case
of a position-space double well, the ground state of stable
periodically-dressed Bose gases with repulsive interactions tends toward a
Schr\"{o}dinger cat state in the regime where interactions dominate the
momentum-space tunnelling induced by the external trapping potential. The
dependence of the momentum-space tunnelling and exchange interaction on
experimental parameters is derived. We discuss how real-time control of
experimental parameters can be used to create Schr\"{o}dinger cat states either
between momentum or internal states, and how these states could be dynamically
controlled towards highly sensitive interferometry and frequency metrology.Comment: 7 pages, 3 figures. Submitted to PR
A gamma ray monitor for the OSO-7 spacecraft
A 3 in. x 3 in. NaI(Tl) gamma ray (0.3 to 10 MeV) spectrometer with a CsI(Na) charged particle and anti-Compton shield has been developed for the Orbiting Solar Observatory (OSO-7) which was launched September 30, 1971. The instrument, designed for a rotating wheel compartment, utilizes a 377 channel quadratic PHA with accumulation times of 3, 1, or 0.5 minutes. Quick look and calibration data obtained via a direct data link to a minicomputer allows near real time monitoring and control of the experiment. Various commands changing the operating mode can be executed. The functions which can be commanded include: rotation of the quadrants in which data is collected by 90 deg; gain adjustment of the central detector over a 6:1 range; manual or automatic sequencing of calibrations; variations of accumulation times by telemetering selected channels; and selection of reference directions. A small X-ray detector covering the range 7.5 to 120 keV is also included
Frodo and Childe Roland
Suggests Browning’s poem as a source for Frodo’s quest in The Lord of the Rings. Sees echoes of the former in both the main plot and many details of The Lord of the Rings
Coherence-enhanced imaging of a degenerate Bose gas
We present coherence-enhanced imaging, an in situ technique that uses Raman
superradiance to probe the spatial coherence properties of an ultracold gas.
Applying this method, we obtain a spatially resolved measurement of the
condensate number and more generally, of the first-order spatial correlation
function in a gas of Rb atoms. We observe the enhanced decay of
propagating spin gratings in high density regions of a Bose condensate, a decay
we ascribe to collective, non-linear atom-atom scattering. Further, we directly
observe spatial inhomogeneities that arise generally in the course of extended
sample superradiance.Comment: 4 pages, 4 figure
Large periodic time variations of termination shock particles between ~0.5-20 mev and 6-14 mev electrons measured by the crs experiment on Voyager 2 as it crossed into the heliosheath in 2007: An example of freshly accelerated cosmic rays?
We have examined features in the structure of the heliosheath using the fine scale time variations of termination shock particles (TSP) between ~0.5 - 20 MeV and electrons between 2.5-14 MeV measured by the CRS instrument as the V2 spacecraft crossed the heliospheric termination shock in 2007. The very disturbed heliosheath at V2 is particularly noteworthy for strong periodic intensity variations of the TSP just after V2 crossed the termination shock (2007.66) reaching a maximum between 2007.75 and 2008.0. A series of 42/21 day periodicities was observed at V2 along with spectral changes of low energy TSP and the acceleration of 6-14 MeV electrons. Evidence is presented for the acceleration of TSP and electrons at the times of the 42/21 day periodicities just after V2 crossed the HTS. Spectra for TSP between 2-20 MeV and electrons between 2.5-14 MeV are derived for three time periods including the time of the HTS crossing. The energy spectra of TSP and electrons at these times of intensity peaks are very similar above ~3 MeV, with exponents of a power law spectrum between -3.0 and -3.6. The ratio of TSP intensities to electron intensities at the same energy is ~500. The electron intensity peaks and minima are generally out of phase with those of nuclei by ~1/2 of a 42 day cycle. These charge dependent intensity differences and the large periodic intensity changes could provide new clues as to a possible acceleration mechanism
Development of an Advanced Recycle Filter Tank Assembly for the ISS Urine Processor Assembly
Recovering water from urine is a process that is critical to supporting larger crews for extended missions aboard the International Space Station. Urine is collected, preserved, and stored for processing into water and a concentrated brine solution that is highly toxic and must be contained to avoid exposure to the crew. The brine solution is collected in an accumulator tank, called a Recycle Filter Tank Assembly (RFTA) that must be replaced monthly and disposed in order to continue urine processing operations. In order to reduce resupply requirements, a new accumulator tank is being developed that can be emptied on orbit into existing ISS waste tanks. The new tank, called the Advanced Recycle Filter Tank Assembly (ARFTA) is a metal bellows tank that is designed to collect concentrated brine solution and empty by applying pressure to the bellows. This paper discusses the requirements and design of the ARFTA as well as integration into the urine processor assembly
High-Resolution Magnetometry with a Spinor Bose-Einstein Condensate
We demonstrate a precision magnetic microscope based on direct imaging of the
Larmor precession of a Rb spinor Bose-Einstein condensate. This
magnetometer attains a field sensitivity of 8.3 pT/Hz over a
measurement area of 120 m, an improvement over the low-frequency field
sensitivity of modern SQUID magnetometers. The corresponding atom shot-noise
limited sensitivity is estimated to be 0.15 pT/Hz for unity duty cycle
measurement. The achieved phase sensitivity is close to the atom shot-noise
limit suggesting possibilities of spatially resolved spin-squeezed
magnetometry. This magnetometer marks a significant application of degenerate
atomic gases to metrology
Direct, Non-Destructive Imaging of Magnetization in a Spin-1 Bose Gas
Polarization-dependent phase-contrast imaging is used to spatially resolve
the magnetization of an optically trapped ultracold gas. This probe is applied
to Larmor precession of degenerate and nondegenerate spin-1 Rb gases.
Transverse magnetization of the Bose-Einstein condensate persists for the
condensate lifetime, with a spatial response to magnetic field inhomogeneities
consistent with a mean-field model of interactions. Rotational symmetry implies
that the Larmor frequency of a spinor condensate be density-independent, and
thus suitable for precise magnetometry with high spatial resolution. In
comparison, the magnetization of the noncondensed gas decoheres rapidly.Comment: 4 pages, 4 figure
Small-sized dichroic atomic vapor laser lock
Two, lightweight diode laser frequency stabilization systems designed for
experiments in the field are described. A significant reduction in size and
weight in both models supports the further miniaturization of measurement
devices in the field. Similar to a previous design, magnetic-field lines are
contained within a magnetic shield enclosing permanent magnets and a Rb cell,
so that these DAVLL systems may be used for magnetically sensitive instruments.
The Mini-DAVLL system (49 mm long) uses a vapor cell (20 mm long), and does not
require cell heaters. An even smaller Micro-DAVLL system (9mm long) uses a
micro-fabricated cell (3 mm square), and requires heaters. These new systems
show no degradation in performance with regard to previous designs, while
considerably reducing dimensions.Comment: 13 pages, 11 figures, published versio
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