5,934 research outputs found
Ultrastable CO2 Laser Trapping of Lithium Fermions
We demonstrate an ultrastable CO2 laser trap that provides tight confinement
of neutral atoms with negligible optical scattering and minimal laser-noise-
induced heating. Using this method, fermionic 6Li atoms are stored in a 0.4 mK
deep well with a 1/e trap lifetime of 300 sec, consistent with a background
pressure of 10^(-11) Torr. To our knowledge, this is the longest storage time
ever achieved with an all-optical trap, comparable to the best reported
magnetic traps.Comment: 4 pages using REVTeX, 1 eps figur
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Geohydrology of Pahute Mesa-3 test well, Nye County, Nevada
The Pahute Mesa-3 test well is on Pahute Mesa about 3 miles west of the Nevada Test Site and 20 miles northeast of Oasis Valley near Beatty, Nevada. The well was drilled for the U.S. Department of Energy Radionuclide Migration Program to monitor conditions near the western edge of the Nevada Test Site. The well was drilled with conventional rotary methods and an air-foam drilling fluid to a depth of 3,019 feet. A 10.75-inch diameter steel casing was installed to a depth of 1,473 feet. The test well penetrates thick units of non-welded to partly welded ash-flow and air-fall tuff of Tertiary age with several thin layers of densely welded tuff, rhyolite and basalt flows, and breccia. Geophysical logs indicate that fractures are significant in the Tiva Canyon Tuff of the Paintbrush Group and this was confirmed by high flow in this unit during a borehole-flow survey. The geophysical logs also show that the effective porosity in tuffaceous units ranges from 19 to 38 percent and averages 30 percent, and the total porosity ranges from 33 to 55 percent and averages 42 percent. The measured temperature gradient of 1.00 degree Celsius per 100 feet is steep, but is similar to that of other nearby wells, one of which penetrates a buried granite intrusion. Injection tests for six intervals of the well yielded transmissivities that ranged from 3.1 x 10{sup -3} to 25 feet squared per day and hydraulic conductivities that ranged from 6 x 10{sup -5} to 0.12 foot per day. The sum of the transmissivities is 28 feet squared per day and the geometric mean of hydraulic conductivity is 1.7 x 10{sup -3} foot per day. Estimates of storage coefficient range from 2.1 x 10{sup -5} to 3.8 x 10{sup -3}, indicating that the aquifer responded to the injection tests in a confined manner. An aquifer test produced a drawdown of 78 feet during 31 hours of testing at 169 gallons per minute
Motional Squashed States
We show that by using a feedback loop it is possible to reduce the
fluctuations in one quadrature of the vibrational degree of freedom of a
trapped ion below the quantum limit. The stationary state is not a proper
squeezed state, but rather a ``squashed'' state, since the uncertainty in the
orthogonal quadrature, which is larger than the standard quantum limit, is
unaffected by the feedback action.Comment: 8 pages, 2 figures, to appear in the special Issue "Quantum
Correlations and Fluctuations" of J. Opt.
Optimizing end-labeled free-solution electrophoresis by increasing the hydrodynamic friction of the drag-tag
We study the electrophoretic separation of polyelectrolytes of varying
lengths by means of end-labeled free-solution electrophoresis (ELFSE). A
coarse-grained molecular dynamics simulation model, using full electrostatic
interactions and a mesoscopic Lattice Boltzmann fluid to account for
hydrodynamic interactions, is used to characterize the drag coefficients of
different label types: linear and branched polymeric labels, as well as
transiently bound micelles.
It is specifically shown that the label's drag coefficient is determined by
its hydrodynamic size, and that the drag per label monomer is largest for
linear labels. However, the addition of side chains to a linear label offers
the possibility to increase the hydrodynamic size, and therefore the label
efficiency, without having to increase the linear length of the label, thereby
simplifying synthesis. The third class of labels investigated, transiently
bound micelles, seems very promising for the usage in ELFSE, as they provide a
significant higher hydrodynamic drag than the other label types.
The results are compared to theoretical predictions, and we investigate how
the efficiency of the ELFSE method can be improved by using smartly designed
drag-tags.Comment: 32 pages, 11 figures, submitted to Macromolecule
Double-beta decay Q values of 130Te, 128Te, and 120Te
The double-beta decay Q values of 130Te, 128Te, and 120Te have been
determined from parent-daughter mass differences measured with the Canadian
Penning Trap mass spectrometer. The 132Xe-129Xe mass difference, which is
precisely known, was also determined to confirm the accuracy of these results.
The 130Te Q value was found to be 2527.01(32) keV which is 3.3 keV lower than
the 2003 Atomic Mass Evaluation recommended value, but in agreement with the
most precise previous measurement. The uncertainty has been reduced by a factor
of 6 and is now significantly smaller than the resolution achieved or foreseen
in experimental searches for neutrinoless double-beta decay. The 128Te and
120Te Q values were found to be 865.87(131) keV and 1714.81(125) keV,
respectively. For 120Te, this reduction in uncertainty of nearly a factor of 8
opens up the possibility of using this isotope for sensitive searches for
neutrinoless double-electron capture and electron capture with positron
emission.Comment: 5 pages, 2 figures, submitted to Physical Review Letter
Fast shower simulation in the ATLAS calorimeter
The time to simulate pp collisions in the ATLAS detector is largely dominated by the showering of electromagnetic particles in the heavy parts of the detector, especially the electromagnetic barrel and endcap calorimeters. Two procedures have been developed to accelerate the processing time of electromagnetic particles in these regions: (1) a fast shower parameterisation and (2) a frozen shower library. Both work by generating the response of the calorimeter to electrons and positrons with Geant 4, and then reintroduce the response into the simulation at runtime.
In the fast shower parameterisation technique, a parameterisation is tuned to single electrons and used later by simulation. In the frozen shower technique, actual showers from low-energy particles are used in the simulation. Full Geant 4 simulation is used to develop showers down to ~1 GeV, at which point the shower is terminated by substituting a frozen shower. Judicious use of both techniques over the entire electromagnetic portion of the ATLAS calorimeter produces an important improvement of CPU time. We discuss the algorithms and their performance in this paper
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