Achievement of Quantum Degeneracy in a Na-QUIC trap in Brazil: an in situ observation

TL;DR

This paper reports the in situ observation of Bose-Einstein Condensation in sodium atoms using a QUIC trap, demonstrating the phase transition through direct imaging and phase space density analysis.

Contribution

First in situ detection of Bose-Einstein Condensation in a Na-QUIC trap with phase space density measurements and analysis of evaporation efficiency.

Findings

Crossed the critical phase space density at 1.65 MHz evaporation frequency

Ideal gas model explains the observations due to low atom number

In situ detection allows measurement of harmonic gas pressure during condensation

Abstract

Using a system composed of a Quadrupole and Ioffe Configuration (QUIC) trap loaded from a slowed atomic beam, we have performed experiments to observe the Bose-Einstein Condensation of Na atoms. In order to obtain the atomic distribution in the trap, we use an in situ out of resonance absorption image through a probe beam, to determine temperature and density. The phase space density (D) is calculated using the density profile and the temperature. We have followed D as a function of the final evaporation frequency. The results show that at 1.65 MHz we crossed the value for D expected to correspond to the critical point to start de Bose-Condensation of the sample. Due to the low number of atoms remaining in the trap at the critical point, the interaction produces minor effects and therefore an ideal gas model explains well the observations. We analyze the obtained low number in terms of efficiency of evaporation. The utility of an in situ detection is illustrated by measuring the harmonic gas pressure of the trapped gas in the route to condensation.