Evaporative cooling of a guided rubidium atomic beam

Lahaye, Thierry; Wang, Z.; Reinaudi, Gaël; Rath, Steffen Patrick; Dalibard, Jean; Guéry-Odelin, David

doi:10.1103/physreva.72.033411

Cited by 29 publications

(35 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We monitor the maximum of this absorption spectrum with a sample-and-hold electronic circuit, which generates a data point for the absorption every 15 ms. This technique reveals to be remarkably insensitive to the inhomogeneity of the magnetic field in the probe region, leading to a reliable and robust signal proportional to the local atomic density [7].…”

Section: Methodsmentioning

confidence: 99%

A moving magnetic mirror to slow down a bunch of atoms

et al. 2006

Self Cite

View full text Add to dashboard Cite

show abstract

Section: Methodsmentioning

confidence: 99%

A moving magnetic mirror to slow down a bunch of atoms

et al. 2006

Self Cite

View full text Add to dashboard Cite

show abstract

“…The temperature of the guided beam is deduced from a radio-frequency (rf) spectroscopy technique [5]. This technique allows for the determination of the temperature with an accuracy of typically 3% [4]. For our parameters, we find T = 640 µK.…”

mentioning

confidence: 93%

“…In recent experiments, evaporative cooling of a beam has been implemented by driving transitions to an untrapped state with radio-frequency [5] or/and microwave [4] fields. The drawback of these two methods lies in the range over which a radio-frequency antenna or a microwave horn effectively acts.…”

mentioning

confidence: 99%

“…The currents run are chosen with opposite sign for adjacent tubes in order to generate a two-dimensional quadrupole magnetic field configuration characterized by a transverse gradient b = 800 G/cm, with a current of 320 A per tube. In addition we superimpose a longitudinal bias field B 0 = 1 G to avoid Majorana spin-flips losses [4]. The resulting semi-linear confining potential reads:…”

mentioning

confidence: 99%

See 1 more Smart Citation

Evaporation of an atomic beam on a material surface

et al. 2006

Self Cite

View full text Add to dashboard Cite

We report on the implementation of evaporative cooling of a magnetically guided beam by adsorption on a ceramic surface. We use a transverse magnetic field to shift locally the beam towards the surface, where atoms are selectively evaporated. With a 5 mm long ceramic piece, we gain a factor 1.5 ± 0.2 on the phase space density. Our results are consistent with a 100% efficiency of this evaporation process. The flexible implementation that we have demonstrated, combined with the very local action of the evaporation zone, makes this method particularly suited for the evaporative cooling of a beam.PACS numbers: 32.80. Pj, 03.75.Pp Since its first demonstration for magnetically trapped atomic hydrogen [1], evaporative cooling has proven to be a powerful technique to increase the phase-space density of trapped gases. It was used, in the case of alkali vapors, to reach the Bose-Einstein condensation (BEC) threshold [2]. This cooling technique plays a central role in the rapidly expanding field of ultracold quantum degenerate gases. Evaporative cooling occurs when energetic atoms are removed from the cloud as a result of elastic collisions. Since these atoms belong to the high energy tail of the thermal distribution, the remaining trapped atoms collisionally equilibrate to a lower temperature.As initially proposed and studied theoretically in Ref.[3], if a non-degenerate, but already slow and cold beam of particles, is injected into a magnetic guide where transverse evaporation takes place, quantum degeneracy can be achieved at the exit of the guide. Such a scheme transposes in the space domain what is usually done for trapped atoms in time, so that all operations leading to condensation are performed in parallel, resulting in a much larger expected output flux.In recent experiments, evaporative cooling of a beam has been implemented by driving transitions to an untrapped state with radio-frequency [5] or/and microwave [4] fields. The drawback of these two methods lies in the range over which a radio-frequency antenna or a microwave horn effectively acts. On our experimental setup, atoms are affected by the field on a zone whose length is at least 20 cm. Such a range limits the number of evaporation zones that can be practically implemented. In addition, it turns out that it is quite difficult to ensure a 100% efficiency of the evaporation with those two methods, which strongly affects the possible gains on the phase space density and on the collision rate.In this article we report on a much more local evaporation technique -the evaporation zone is 5 mm long. It relies on the elimination of atoms on a surface. This technique has been used in Ref.[6] to evaporatively cool atoms to Bose Einstein Condensation with a dielectric surface. We demonstrate here a possible implementation of this technique to a magnetically guided atomic beam, and discuss its prospects.The experimental setup, described in detail in Refs.[4, 5], allows for the generation of an intense and continuous beam of cold 87 Rb atoms polarized in the |F =...

show abstract

“…A continuous * p.vanderstraten@uu.nl atom laser can be achieved by cooling an atomic beam down to degeneracy, leading to a "truly" continuous beam of coherent atoms, which can be used for interferometry and atom optics [14]. Intensive research has been performed in this field [15][16][17][18][19][20][21][22][23][24]. To achieve a continuous atom laser, evaporative cooling is performed on a beam propagating through a magnetic guide.…”

Section: Introductionmentioning

confidence: 99%

Rate of runaway evaporative cooling

2011

View full text Add to dashboard Cite

Evaporative cooling is a process that is essential in creating Bose-Einstein condensates in dilute atomic gasses. This process has often been simulated based on a model using a truncated Boltzmann distribution. This model assumes that the energy distribution up to the threshold energy can still be described by a Boltzmann distribution: it assumes detailed balance up to the threshold energy. However, the evolution of the distribution function in time is not taken into account. Here we solve the kinetic Boltzmann equation for a gas undergoing evaporative cooling in a harmonic and linear trap in order to determine the evolution of the energy distribution. The magnitude of the discrepancy with the truncated Boltzmannmodel is calculated by including a polynomial expansion of the distribution function. We find that up to 35% fewer particles are found in the high-energy tail of the distribution with respect to the truncated Boltzmann distribution and up to 15% more collisions are needed to reach quantum degeneracy. Supported by a detailed investigation of the particle loss rate at different energies, we conclude that the limited occupation of high-energy states during the evaporation process causes the lowering of the evaporation speed and efficiency.

show abstract

Evaporative cooling of a guided rubidium atomic beam

Cited by 29 publications

References 30 publications

A moving magnetic mirror to slow down a bunch of atoms

A moving magnetic mirror to slow down a bunch of atoms

Evaporation of an atomic beam on a material surface

Rate of runaway evaporative cooling

Contact Info

Product

Resources

About