Measurement of the temperature of an ultracold ion source using time-dependent electric fields

TL;DR

This paper measures the temperature of an ultracold rubidium ion source using a pulsed-field technique, achieving a temperature estimate of about 1 mK, with implications for ion beam quality.

Contribution

It introduces a method to determine the temperature of an ultracold ion source through time-dependent electric fields and particle-tracking simulations.

Findings

Measured source temperature T = (1 ± 2) mK

Determined transversal reduced emittance of 7.9 x 10^{-9} m rad √eV

Results likely limited by space charge effects

Abstract

We report on a measurement of the characteristic temperature of an ultracold rubidium ion source, in which a cloud of laser-cooled atoms is converted to ions by photo-ionization. Extracted ion pulses are focused on a detector with a pulsed-field technique. The resulting experimental spot sizes are compared to particle-tracking simulations, from which a source temperature $T = (1 \pm 2)$ mK and the corresponding transversal reduced emittance $\epsilon_r = 7.9 X 10^{-9}$ m rad $\sqrt{\rm{eV}}$ are determined. We find that this result is likely limited by space charge forces even though the average number of ions per bunch is 0.022.