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

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 an effective source temperature T¿=¿(3¿±¿2) mK and the corresponding transversal reduced emittance er¿=¿1.4¿×¿10-8 m rad are determined. Space charge effects that may affect the measurement are also discusse