International Conference on Atomic Physics (ICAP)

Ionization in a Bose-Einstein condensate of metastable Helium: a quantitative monitoring tool

Alain Aspect, O. Sirjean, Signe Louise Seidelin, J. Viana Gomes, Denis Boiron, Christoph Ira Westbrook

Published Apr 1, 2003• 0 citations

Abstract

Residual ionization in a BEC of 2 3 S1 metastable Helium (He*), can be used to monitor in real time the evolution of a single sample of condensate. We use this method, combined to Time Of Flight measurements, to study the decay of the condensate. It has also allowed us to measure 2-body and 3-body ionizing collisions rate constants. This method should allow for the study of the growth of a condensate, in particular in the hydrodynamic regime. We point out the importance of quantum depletion in He * BEC’s. 1

DOI: 10.1142/9789812705099_0005

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International Conference on Atomic Physics (ICAP)

Ionization in a Bose-Einstein condensate of metastable Helium: a quantitative monitoring tool

Alain Aspect, O. Sirjean, Signe Louise Seidelin, J. Viana Gomes, Denis Boiron, Christoph Ira Westbrook

Published Apr 1, 2003• 0 citations

Publisher

Abstract

DOI: 10.1142/9789812705099_0005

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We have observed a Bose-Einstein condensate in a dilute gas of

{}^{4}\mathrm{He}

in the

^{3}2S_{1}

metastable state. We find a critical temperature of $(4.7\ifmmode\pm\else\textpm\fi{}0.5)\ensuremath{\mu}\mathrm{K}$ and a typical number of atoms at the threshold of $8\ifmmode\times\else\texttimes\fi{}{10}^{6}$. The maximum number of atoms in our condensate is about $5\ifmmode\times\else\texttimes\fi{}{10}^{5}$. An approximate value for the scattering length $a\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}(16\ifmmode\pm\else\textpm\fi{}8)\mathrm{nm}$ is measured. The mean elastic collision rate at threshold is then estimated to be about $2\ifmmode\times\else\texttimes\fi{}{10}^{4}{\mathrm{s}}^{\ensuremath{-}1}$, indicating that we are deeply in the hydrodynamic regime. The typical decay time of the condensate is

2\mathrm{s}

, which places an upper bound on the rate constants for two-body and three-body inelastic collisions.

We have produced a Bose-Einstein condensate of metastable helium

(^{4}\mathrm{He}^{*})

containing over $1.5\ifmmode\times\else\texttimes\fi{}{10}^{7}$ atoms, which is a factor of 25 higher than previously achieved. The improved starting conditions for evaporative cooling are obtained by applying one-dimensional Doppler cooling inside a magnetic trap. The same technique is successfully used to cool the spin-polarized fermionic isotope

(^{3}\mathrm{He}^{*})

, for which thermalizing collisions are highly suppressed. Our detection techniques include absorption imaging, time-of-flight measurements on a microchannel plate detector, and ion counting to monitor the formation and decay of the condensate.