1,373 research outputs found
New ion trap for atomic frequency standard applications
A novel linear ion trap that permits storage of a large number of ions with reduced susceptibility to the second-order Doppler effect caused by the radio frequency (RF) confining fields has been designed and built. This new trap should store about 20 times the number of ions a conventional RF trap stores with no corresponding increase in second-order Doppler shift from the confining field. In addition, the sensitivity of this shift to trapping parameters, i.e., RF voltage, RF frequency, and trap size, is greatly reduced
Spinor Dynamics-Driven Formation of a Dual-Beam Atom Laser
We demonstrate a novel dual-beam atom laser formed by outcoupling oppositely
polarized components of an F=1 spinor Bose-Einstein condensate whose Zeeman
sublevel populations have been coherently evolved through spin dynamics. The
condensate is formed through all-optical means using a single-beam running-wave
dipole trap. We create a condensate in the field-insensitive state, and
drive coherent spin-mixing evolution through adiabatic compression of the
initially weak trap. Such dual beams, number-correlated through the angular
momentum-conserving reaction , have been
proposed as tools to explore entanglement and squeezing in Bose-Einstein
condensates, and have potential use in precision phase measurements.Comment: 4 pages, 4 figure
Simple analytic potentials for linear ion traps
A simple analytical model was developed for the electric and ponderomotive (trapping) potentials in linear ion traps. This model was used to calculate the required voltage drive to a mercury trap, and the result compares well with experiments. The model gives a detailed picture of the geometric shape of the trapping potenital and allows an accurate calculation of the well depth. The simplicity of the model allowed an investigation of related, more exotic trap designs which may have advantages in light-collection efficiency
Atomic frequency standards for ultra-high-frequency stability
The general features of the Hg-199(+) trapped-ion frequency standard are outlined and compared to other atomic frequency standards, especially the hydrogen maser. The points discussed are those which make the trapped Hg-199(+) standard attractive: high line Q, reduced sensitivity to external magnetic fields, and simplicity of state selection, among others
The JPL trapped mercury ion frequency standard
In order to provide frequency standards for the Deep Space Network (DSN) which are more stable than present-day hydrogen masers, a research task was established under the Advanced Systems Program of the TDA to develop a Hg-199(+) trapped ion frequency standard. The first closed-loop operation of this kind is described. Mercury-199 ions are confined in an RF trap and are state-selected through the use of optical pumping with 194 nm UV light from a Hg-202 discharge lamp. Absorption of microwave radiation at the hyperfine frequency (40.5 GHz) is signaled by atomic fluorescence of the UV light. The frequency of a 40.5 GHz oscillator is locked to a 1.6 Hz wide atomic absorption line of the trapped ions. The measured Allan variance of this locked oscillator is currently gamma sub y (pi) = 4.4 x 10 to the minus 12th/square root of pi for 20 is less than pi is less than 320 seconds, which is better stability than the best commercial cesium standards by almost a factor of 2. This initial result was achieved without magnetic shielding and without regulation of ion number
Janssen effect and the stability of quasi 2-D sandpiles
We present the results of three dimensional molecular dynamics study of
global normal stresses in quasi two dimensional sandpiles formed by pouring
mono dispersed cohesionless spherical grains into a vertical granular Hele-Shaw
cell. We observe Janssen effect which is the phenomenon of pressure saturation
at the bottom of the container. Simulation of cells with different thicknesses
shows that the Janssen coefficient is a function of the cell
thickness. Dependence of global normal stresses as well as on the
friction coefficients between the grains () and with walls () are
also studied. The results show that in the range of our simulations
usually increases with wall-grain friction coefficient. Meanwhile by increasing
while the other system parameters are fixed, we witness a gradual
increase in to a parameter dependent maximal value
Passively mode locked Raman laser
We report on the observation of a novel mode locked optical comb generated at
the Raman offset (Raman comb) in an optically pumped crystalline whispering
gallery mode resonator. Mode locking is confirmed via measurement of the
radio-frequency beat note produced by the optical comb on a fast photodiode.
Neither the conventional Kerr comb nor hyper-parametric oscillation is observed
when the Raman comb is present
Computer simulations of ions in radio-frequency traps
The motion of ions in a trapped-ion frequency standard affects the stability of the standard. In order to study the motion and structures of large ion clouds in a radio-frequency (RF) trap, a computer simulation of the system that incorporates the effect of thermal excitation of the ions was developed. Results are presented from the simulation for cloud sizes up to 512 ions, emphasizing cloud structures in the low-temperature regime
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