Evaporative cooling of an atomic beam

TL;DR

This paper provides a theoretical analysis of evaporative cooling in an atomic beam within a magnetic guide, demonstrating significant phase-space density increase and estimating the length needed for quantum degeneracy.

Contribution

It introduces two validated methods to analyze evaporative cooling in atomic beams and predicts the conditions for reaching quantum degeneracy.

Findings

Phase-space density increases significantly along the guide.

Two methods (analytical and Monte-Carlo) agree well in their domain.

Estimated length needed to reach quantum degeneracy.

Abstract

We present a theoretical analysis of the evaporative cooling of an atomic beam propagating in a magnetic guide. Cooling is provided by transverse evaporation. The atomic dynamics inside the guide is analyzed by solving the Boltzmann equation with two different approaches: an approximate analytical ansatz and a Monte-Carlo simulation. Within their domain of validity, these two methods are found to be in very good agreement with each other. They allow us to determine how the phase-space density and the flux of the beam vary along its direction of propagation. We find a significant increase for the phase-space density along the guide for realistic experimental parameters. By extrapolation, we estimate the length of the beam needed to reach quantum degeneracy.