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Authors: Stromberger, Peter
Title: Coherent matter wave manipulation in microgravity
Online publication date: 15-Sep-2021
Language: english
Abstract: A microgravity environment offers beneficial conditions for research on cold atom clouds. The trapping potentials are not distorted by gravity, the dynamic of cold atom ensembles is determined by inter-atomic interactions and interaction with controlled external fields. Moreover, the time-of-flight is not restricted by the size of the vacuum-chamber. On the other hand, new challenges arise such as expansion velocities limiting the observability of the cold atom clouds after a long time-of-flight, less controlled environmental conditions in comparison to laboratory experiments such as temperature, vibrations, external magnetic and electric fields. QUANTUS-2 is a mobile Bose-Einstein condensate (BEC) experiment used for experiments in microgravity in the drop tower in Bremen, Germany. It aims to utilize the microgravity environment of the drop tower to study coherent manipulation of rubidium and potassium ensembles. The most significant field of study will be atom interferometry, which prospectively will allow to test the universality of free fall at new levels of precision. The main objective of QUANTUS-2 is to investigate atom interferometry in microgravity. The sensitivity of atom interferometers increases quadratically with the interrogation time making microgravity an ideal environment. Utilizing a magnetic lens in combination with collective mode excitations, we were able to reduce the expansion velocity of a BEC below 80 𝜇𝑚/𝑠 in all three spatial directions and allow for observation of the BEC after evolution times greater than 2 seconds. In this thesis the combination of a magnetically lensed rubidium 87 BEC with Double-Bragg atom interferometry will be investigated. Under gravity and in microgravity the coherence length of Bose-Einstein condensates released from different magnetic traps will be investigated. In microgravity the coherence length and wavefront distortions of magnetically lensed Bose-Einstein condensates will be studied. On ground measurements with symmetric and asymmetric Mach-Zehnder geometries will be performed. Additionally, a novel method of determining the optimal collimation of a magnetic lens with a Double-Bragg Open Ramsey type interferometer will be presented. Furthermore, in microgravity it is possible to implement dressed state shell potentials and confine cold atoms in two dimensions without gravity distortion leading to partially filled shells. Studying a Bose gas on a shell surface allows to investigate topology dependent vortex behavior, new collective modes, crossovers from thick to thin shells, and self- interference effects. We realize shell potentials by radio-frequency dressing the magnetic sub states of the hyperfine ground-state F = 2 of rubidium 87. In this thesis measurements of thermal atoms in shell potentials in microgravity at varying positions from the atom chip, different detunings and Rabi frequencies will be presented. The results will be compared to simulations.
DDC: 500 Naturwissenschaften
500 Natural sciences and mathematics
530 Physik
530 Physics
Institution: Johannes Gutenberg-Universität Mainz
Department: FB 08 Physik, Mathematik u. Informatik
Place: Mainz
Version: Original work
Publication type: Dissertation
License: in Copyright
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Extent: iii, 133 Seiten
Appears in collections:JGU-Publikationen

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