Number Of Trapped Atoms Research Articles

Magneto-optic trap using a reversible, solid-state alkali-metal source.

We demonstrate a novel way to form and deplete a vapor-cell magneto-optic trap (MOT) using a reversible, solid-state alkali-metal source via an applied polarized voltage. Using ∼100 mW of electrical power, a trapped-atom number of 5×106 has been achieved, starting from near zero and the timescales of the MOT formation and depletion of ∼1 s. This fast, reversible, and low-power alkali-atom source is desirable in both tabletop and portable cold-atom systems. The core technology of this device should translate readily to other alkali and alkaline-earth elements that could find a wide range of uses in cold-atom systems and instruments.

Simulating the Three-Dimensional Image of Cold Atomic Cloud.

We propose a scheme for accurately simulating of the three-dimensional image of cold atomic cloud, which is more intuitive and stereoscopic than former two-dimensional image by probe laser. We have realized simulating of cold atomic cloud. The number of trapped atoms is about 10(8). The atomic cloud is about the geometric three-dimensional shape. Tri-axial ellipsoid with distinct semi-axis lengths Ｒ(x)＝1.06 mm, R(y)＝1.06 mm, R(z)＝0.57 mm, and the three-dimensional image of cold atomic cloud was simulated for the first time.

Drift-Compensated Low-Noise Frequency Synthesis Based on a cryoCSO for the KRISS-F1

In this paper, we report on the implementation and stability analysis of a drift-compensated frequency synthesizer from a cryogenic sapphire oscillator (CSO) designed for a Cs/Rb atomic fountain clock. The synthesizer has two microwave outputs of 7 and 9 GHz for Rb and Cs atom interrogation, respectively. The short-term stability of these microwave signals, measured using an optical frequency comb locked to an ultrastable laser, is better than $5 \times 10^{-15}$ at an averaging time of 1 s. We demonstrate that the short-term stability of the synthesizer is lower than the quantum projection noise limit of the Cs fountain clock, KRISS-F1(Cs) by measuring the short-term stability of the fountain with varying trapped atom number. The stability of the atomic fountain at 1 s averaging time reaches $2.5 \times 10^{-14}$ at the highest atom number in the experiment when the synthesizer is used as an interrogation oscillator of the fountain. In order to compensate the frequency drift of the CSO, the output frequency of a waveform generator, in the synthesis chain, is ramped linearly. By doing this, the frequency stability of the synthesizer at an average time of one hour reaches a level of $10^{-16}$ , which is measured with the fountain clock.

Light-induced atomic desorption in a compact system for ultracold atoms

In recent years, light-induced atomic desorption (LIAD) of alkali atoms from the inner surface of a vacuum chamber has been employed in cold atom experiments for the purpose of modulating the alkali background vapour. This is beneficial because larger trapped atom samples can be loaded from vapour at higher pressure, after which the pressure is reduced to increase the lifetime of the sample. We present an analysis, based on the case of rubidium atoms adsorbed on pyrex, of various aspects of LIAD that are useful for this application. Firstly, we study the intensity dependence of LIAD by fitting the experimental data with a rate-equation model, from which we extract a correct prediction for the increase in trapped atom number. Following this, we quantify a figure of merit for the utility of LIAD in cold atom experiments and we show how it can be optimised for realistic experimental parameters.

Light desorption from an yttrium neutralizer for Rb and Fr magneto-optical trap loading.

We present here the first evidence of photodesorption induced by low-intensity non-resonant light from an yttrium thin foil, which works as a neutralizer for Rb and Fr ions beam. Neutral atoms are suddenly ejected from the metal surface in a pulsed regime upon illumination with a broadband flash light and then released in the free volume of a pyrex cells. Here atoms are captured by a Magneto-Optical Trap (MOT), which is effectively loaded by the photodesorption. Loading times of the order of the flash rise time are measured. Desorption is also obtained in the continuous regime, by exploiting CW visible illumination of the metallic neutralizer surface. We demonstrate that at lower CW light intensities vacuum conditions are not perturbed by the photodesorption and hence the MOT dynamics remains unaffected, while the trap population increases thanks to the incoming desorbed atoms flux. Even with the Y foil at room temperature and hence with no trapped atoms, upon visible illumination, the number of trapped atoms reaches 10(5). The experimental data are then analyzed by means of an analytical rate equation model, which allows the analysis of this phenomenon and its dynamics and allows the determination of critical experimental parameters and the test of the procedure in the framework of radioactive Francium trapping. In this view, together with an extensive investigation of the phenomenon with (85)Rb, the first demonstration of the photodesorption-aided loading of a (210)Fr MOT is shown.

Zeeman slowing and magneto-optically trapping of lithium atoms in atomic interferometry experiments

To prepare cold lithium atoms for atomic interferometry experiments, we have carried out experimental researches on Zeeman deceleration and magneto-optical trap (MOT) of lithium atoms. We have also designed and implemented a compact adjustable Zeeman slower with an inner water cooling chamber, to decelerate the velocity of the 7Li atom beam from 600 m/s down to 60 m/s, and load them into the MOT. The loading rate is 5108 /s, the total trapped atom number is 1109 , and the lowest temperature of the atom cloud is 220 30 K. Then we investigate the dependence of lifetime of 7Li atoms in optical molasses on the detuning of trapping laser beams. The above results lay a foundation for further sub-Doppler cooling, optical trap based on evaporative cooling, and atomic interferometry experiments.

Detection of excited level population transfer in an MOT through the measurement of trapped atom number

We study the rubidium magneto-optical trap (MOT) population changes induced by a laser beam interacting with the trapped atoms and resonant with different transitions from both the ground and the excited trap levels. Laser excitation outside the cooling scheme induces losses in the MOT population, while the laser increases the trap population when tuned to transitions linked to the trapping cycle. The experiment is performed with a small number of trapped atoms (100 to 10 000). A discussion of our ability in manipulating the atomic population of different hyperfine states is reported.

Light-induced atomic desorption for loading a sodium magneto-optical trap

We report studies of photon-stimulated desorption, also known as light-induced atomic desorption, of sodium atoms from a vacuum-cell glass surface used for loading a magneto-optical trap (MOT). Fluorescence detection was used to record the trapped atom number and the desorption rate. We observed a steep wavelength dependence of the desorption process above $2.6 \mathrm{eV}$ photon energy, a result significant for estimations of sodium vapor density in the lunar atmosphere. Our data fit well to a simple model for the loading of the MOT dependent only on the sodium desorption rate and residual gas density. Up to $3.7\ifmmode\times\else\texttimes\fi{}{10}^{7}$ Na atoms were confined under ultrahigh-vacuum conditions, creating promising loading conditions for a vapor-cell-based atomic Bose-Einstein condensate of sodium.

Corrected Sum Rule, Generalized Virial Identity and Elementary Excitation Spectrum of Bose-Einstein Condensates at any Trapped Atom Number

Using a corrected sum rule and a generalized virial identity, we study the analytical expression for entire modes of the collective elementary excitation spectrum in a trapped Bose–Einstein condensate at any atom number. Explicit analytical formulas for the spectrum are obtained for the harmonic traps with both spherical symmetry and axial symmetry using the gaussian approximation for the N-body ground-state wave function of the condensate. These formulas give the simple dependence of all energy levels on the atom numbers, their interaction strength and trap geometry parameters.

Time Dependence of the Atomic Density in a Magneto-optical Trap

We have studied the evolution of the atomic density in magneto-optical traps. We have observed that the density increases according to (1-e-t/ τn ), where the characteristic time τn may differ only slightly from the trap lifetime. We discuss the implications this has on the constant density approximation and solve the rate equation for trapped atom number in the case of a time-dependent density.