The precision of atom interferometers, targeted for example in the Hannover Very
Long Baseline Atom Interferometer (VLBAI) facility, imposes stringent requirements
in several respects. They concern the control of center-of-mass motion and expansion
of the wave packets by the matter-wave source as well as the number of atoms.
By reducing the expansion, systematic errors, appearing e.g. through wavefront
aberrations, can be lowered. These requirements can be matched by employing
ultracold quantum gases or even quantum degenerate gases. A promising method
to create those ensembles is evaporative cooling in a spatially modulated optical
dipole trap. Here, the utilization of time-averaged potentials enables the fast creation
of ultracold atomic ensembles with large number of atoms. Both, the higher
number of atoms and the increased repetition rate, enhance the performance of the
interferometer due to a lower quantum projection noise, which scales with 1/sqrt(N),
and a larger bandwidth of the sensor due to faster sampling. The shaping of the
matter-waves by techniques such as matter-wave lensing or Delta-Kick collimation
is also feasible due to the dynamic control of the trapping potential.
In this thesis the implementation and application of dynamic time-averaged optical
potentials created via center position modulation of dipole trap beams is
demonstrated. By evaporative cooling in these potentials, 1.9(0.4) x 10^5 condensed
atoms with an expansion temperature of 29.2(1.3) nK were achieved after 3 s of
evaporation. Up to 4.2(0.1) x 10^5 condensed atoms could be observed with slower
evaporation of 5 s. Subsequent matter-wave lensing is carried out yielding expansion
rates as low as 553(49) μms^-1 resulting in an effective temperature of 3.2(0.6) nK in
two dimensions. This lens can be applied at any stage of evaporative cooling, thus
short-cutting the generation of ultracold effective temperatures. In this thesis the
limitations of optical matter-wave lensing in the current setup are revealed and
ways to improve the performance are discussed.
The fast generation of ultracold atomic ensembles will enhance the performance of
the dual-species atom interferometer, which represents the experiment apparatus
for this thesis and strives for a test of the Universality of Free Fall with an uncertainty
on the order of 10^-9. The results of this thesis were used to test numerical
simulations which were utilized to show the perspective of generating up to 10^6
collimated condensed atoms within 1 s of cycle time in the rubidium source system
of Hannover’s VLBAI.
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