Evaporative Cooling of a Guided Rubidium Atomic Beam

TL;DR

This paper demonstrates evaporative cooling of a high-flux guided rubidium atomic beam, significantly increasing phase-space density and reducing temperature, advancing the development of continuous cold atom sources.

Contribution

It presents the first implementation of evaporative cooling on a magnetically guided atomic beam, achieving notable temperature reduction and phase-space density enhancement.

Findings

Temperature reduced by a factor of ~4

Phase-space density increased tenfold

High collision rate enabled effective evaporative cooling

Abstract

We report on our recent progress in the manipulation and cooling of a magnetically guided, high flux beam of $^{87}{\rm Rb}$ atoms. Typically $7\times 10^9$ atoms per second propagate in a magnetic guide providing a transverse gradient of 800 G/cm, with a temperature $\sim550$ $\mu$K, at an initial velocity of 90 cm/s. The atoms are subsequently slowed down to $\sim 60$ cm/s using an upward slope. The relatively high collision rate (5 s$^{-1}$) allows us to start forced evaporative cooling of the beam, leading to a reduction of the beam temperature by a factor of ~4, and a ten-fold increase of the on-axis phase-space density.