Introduction
Microgravity has multiple beneficial implications for atom optics experiments which cannot be reproduced in a ground based setup. The atoms do not experience any gravitational sag during the preparation phase and when the atoms are trapped, and stay at rest with respect to the experimental apparatus after release. In principle, suspension techniques can be utilized to counteract gravity, but they would disturb the atomic ensembles themselves, which is not the case in microgravity.
The gravitational sag depends on the mass of the atoms and the trapping potential. In the experiment, it manifests as a displacement with respect to the trapping center which can lead to systematics, depending on the type of experiment performed. Moreover, it prevents trapping frequencies below a certain threshold, since they will be insufficient to suspend the atoms against gravity. Consequently, this regime can only be explored in microgravity. A second implication of reduced gravitational sag is a well-defined release from the trap when lowering the trap depth.
After release, the atoms will not move with respect to the trapping potential. Consequently, any experiment which require switching-on the potential again for recapturing, delta-kick collimation or similar purposes will greatly benefit. This is especially relevant for producing ensembles with very low residual expansion rates. It unlocks extended free evolution times beyond several seconds and is additionally relevant for subsequent atom interferometry experiments for high beam splitting efficiencies and reduction of systematics biases.
The motivation for extended free evolution times in atom interferometry can be found in the sensitivity of the interferometric phase which scales quadratically with the free evolution time. Differential acceleration measurements for testing the universality of free fall or measuring gravity gradients reproduce the same dependence. Finally, gravitational wave detection based on atom interferometry benefits from an extended free evolution time, as it enables tracking of lower frequencies.
MAIUS - 1
The MAIUS 1 (Matter-Wave Interferometry in Microgravity) experiment could be described as one of the most complex experiment ever flown on a sounding rocket. MAIUS 1 was launched at 03:30 Central European Time (CET) on 23 January 2017 on board a sounding rocket from the Esrange Space Center near Kiruna in northern Sweden. During the approximately six-minute microgravity phase of the flight, German scientists succeeded in producing a Bose-Einstein condensate (BEC) in space for the first time and performing atom interferometry experiments with them. "Bose-Einstein condensates are produced when a gas is cooled down to close to absolute zero," explains Rainer Forke from the Space Administration at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). "We are delighted to be able to demonstrate that the MAIUS 1 system works perfectly in space. During the microgravity phase, around 100 individual experiments were carried out on different aspects of matter-wave interferometry."
The MAIUS 1 project is under the scientific supervision of the Leibniz University of Hannover in collaboration with the Humboldt University and the Ferdinand Braun Institute in Berlin, ZARM of the University of Bremen, the Johannes Gutenberg University of Mainz, the University of Hamburg, the University of Ulm and the Technical University of Darmstadt. The DLR Institute of Space Systems in Bremen, the DLR 'Simulation and Software Technology' facility in Braunschweig and the DLR Mobile Rocket Base (MORABA), which also carries out the launch campaign, are also part of the research group.
30167 Hannover
MAIUS - 2/3
Within the upcoming sounding rocket mission MAIUS-2 and -3, a second atomic species K-41 is added to the experimental setup. With these two species, an atom interferometer based on Raman double diffraction will be realized.
In the last step the experiment will perform a measurement of the differential accelerations of K-41 and Rb-87 in free fall.
The new system has been commissioned and qualified on ground and first results on ground-based cooling of alkaline atoms have been achieved. The next steps towards the second launch are the creation and observation of BECs of Rb-87 and K-41.
We offer Bachelor and Master projects to various interesting topics. Don''t hesitate to contact us!
If you are interested, please contact Jonas Böhm or Baptist Piest.
We offer an interesting experimental Hiwi position in our project. Please contact Baptist Piest to learn more.
30167 Hannover
BECCAL
BECCAL (Bose-Einstein Condensate and Cold Atom Laboratory) is a bi-lateral project of NASA and DLR (Deutsches Zentrum für Luft- und Raumfahrt) for experiments on atom optics at the International Space Station (ISS). The continuous microgravity environment enables experiments at significantly extended timescales than or even not possible on ground. The anticipated scienfitic topics cover a broad spectrum from fundamental physics to studies for applications in earth observation. They include atom optics, atom interferometry, physics of degenerate quantum gases, and their mixtures.
BECCAL builds on the heritage of the droptower experiments (QUANTUS) and the sounding rocket missions (MAIUS), both financially supported by DLR, and benefits from the experience of the Cold Atom Lab (CAL), financed by NASA. Significant improvements will enable BECCAL to provide more complex trap geometries for atoms, generation of ensembles with higher numbers of atoms, and light-puls atom interferometry at extended time scales.
