Cold atom sources
Two identical atomic sources emit Rubidium 87 atoms pulsed in time on flat parabolic trajectories into the interferometer. Each source consists of a two-dimensional magneto-optical trap (2D-MOT) loading a subsequent 3D-MOT with a high flux of several 109 at/s. Using the moving molasses technique 108 atoms with a temperature of 8 µK are launched in each interferometry cycle. To realize an optimal spatial overlap of both interferometers and a precise control of the enclosed area the forward drift velocity vat can be tuned independently between 2.5-5 m/s with a relative uncertainty of < 3×10-4.
In a next step the atoms are state- and velocity-selectively transferred into one of the two interferometer states via a multi-stage preparation using precisely controllable laser manipulation. The velocity filtering as one of the preparation steps is performed with a Raman-π-pulse, resulting in a velocity distribution in the direction of the Raman-beams which corresponds to a temperature of about 1 µK.