An intense, slow and cold beam of metastable Ne(3s) 3 P 2 atoms

Abstract

An intense, slow and cold beam of metastable Ne(3s) 3 P 2 atoms. (February 8, 2018) We employ laser cooling to intensify and cool an atomic beam of metastable Ne(3s) atoms. Using several collimators, a slower and a compressor we achieve a 20 Ne * flux of 6 × 10 10 atoms/s in an 0.7 mm diameter beam traveling at 100 m/s, and having longitudinal and transverse temperatures of 25mK and 300µK, respectively. This constitutes the highest flux in a concentrated beam achieved to date with metastable rare gas atoms. We characterize the action of the various cooling stages in terms of their influence on the flux, diameter and divergence of the atomic beam. I. BRIGHTENING RARE-GAS ATOMIC BEAMSThe efficiency with which metastable rare gas atoms can be produced in gas discharge sources is notoriously low, usually only on the order of 10 −5 with the highest reported value being 10 −3 for helium [1]. Traditionally, therefore, metastable rare gas atomic beams have shown much smaller flux and density than alkali-metal beams. In recent years, several groups [2-17] have tried to bridge this gap by employing laser cooling techniques [18] to intensify rare gas beams. At the same time, atomic beams could be made slow and monochromatic.The principle of beam intensification using laser manipulation of atomic trajectories was illustrated by Sheehy et al in a 1990 paper [19]. The essential element in any such scheme is a laser collimator, whose purpose is to increase the solid angle under which atoms can leave the source and still contribute to the beam flux further downstream. This is achieved by cooling the velocity component transverse to the atomic beam axis. The collimator completely determines the maximum gain in beam flux that can be obtained with laser cooling. Without collimation, the flux of atoms through a constant area decreases geometrically with its distance from the source; with collimation, this flux is essentially constant. Collimators for rare gas atomic beams have been employed by several groups [2][3][4][5][11][12][13][14][15]17].Since transverse cooling takes a certain time and thus a certain transverse distance, laser collimation inevitably leads to large-diameter atomic beams whose density may be rather low despite the increased beam flux. The solution to this, according to Ref. [19], is to focus the beam and re-collimate it at the focal point. This idea was implemented in its purest form by Hoogerland et al [2] who used a separate magneto-optical lens (MOL) followed by a second collimator. Scholz et al [6], Nellissen et al [7] and Schiffer et al [8] developed a magneto-optical compressor (MOC) in which both focusing and collimation occur within the same device. The mayor difference between a MOL and a MOC is the time spent within the device interacting with the laser fields: a compressor is basically a lens with a focal length shorter than the length of the interaction region. In order for the length of the MOC to stay within reasonable limits, laser slowing of the atomic beam [18,20] between collimator and...

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