Magnetic trapping for an atom-chip-based gravimeter

Downloadstatistik des Dokuments (Auswertung nach COUNTER):

Matthias, Jonas: Magnetic trapping for an atom-chip-based gravimeter. Hannover : Gottfried Wilhelm Leibniz Universität, Diss., 2020, III, 95 S. DOI: https://doi.org/10.15488/10196

Zeitraum, für den die Download-Zahlen angezeigt werden:

Jahr: 
Monat: 

Summe der Downloads: 640




Kleine Vorschau
Zusammenfassung: 
In the past century, the development of gravimeters with low uncertainty and long-term stability has led to new fields of research in geodesy and geoscience. Decreasing the instrumental measurement uncertainty further will enable observations of previously inaccessible phenomena, for instance, mass transport in hydrology and volcanology. During the last decades, quantum sensors based on the interference of cold atoms have been developed. Using a cold atomic gas as test mass, the accuracy of these sensors is not limited by mechanical properties but by effects caused by the thermal expansion of the atomic ensemble. The application of ultra-cold atomic ensembles with lower expansion rates in atom interferometer gravimeters is projected to reduce the leading order uncertainties by more than an order of magnitude. At the same time, atom chip technology makes it possible to prepare ultra-cold atomic ensembles at a high repetition rate and to miniaturise the sensor size. These advancements promise the realisation of an absolute gravimeter with unprecedented accuracy.This thesis describes the design considerations and the assembly of the transportable Quantum Gravimeter (QG-1) based on light-pulse atom interferometry of Bose-Einstein condensates (BEC) prepared on an atom chip. It is estimated, that the two leading order uncertainties of systematic biases governing the instrumental measurement uncertainty of current generation cold atom gravimeters are reduced to less than 1 nm/s² in the QG-1 apparatus. The established design of an atom-chip-based BEC source pioneered in the Quantus collaboration is modified to meet the requirements of QG-1. A free optical aperture of 18 mm for the interferometry laser beam is realised by changing the orientation of the atom-chip-based BEC source. Therefore, a new layout of the mesoscopic wire structure of the atom chip is required. The design described in this thesis enables atom interferometry with a free falling test mass with a baseline of 330 mm. The retro-reflection mirror is placed inside the vacuum chamber to eliminate optical elements in the atom interferometer beam path. It is mounted on a custom designed tip/tilt-stage with compact size and a large dynamic range of up to a hundredfold of the Earth's rotation rate for characterisation. Furthermore, a compact, robust and transportable fibre based laser system with modular electronics and a computer control system are set up.The key result of this thesis is the reliable operation of the ultra-cold atomic source on the atom chip. After optimisation of the trap loading procedure for a high atom number and low excitation of oscillations, it was shown that the necessary design change of the atom chip allows for efficient operation. The compressed magnetic trap has a geometrically averaged trap frequency of 2π · 256 Hz and the trapped ensemble has a lifetime of 3.2 s. The evaporative cooling procedure starts with 3.3 · 10⁷ atoms at a temperature of 166 μK. Within 1.3 s, or 2.3 s for the complete sequence, 3000 atoms are prepared at a temperature of 160 nK close to the critical temperature for Bose-Einstein condensation.
Lizenzbestimmungen: CC BY 3.0 DE
Publikationstyp: DoctoralThesis
Publikationsstatus: publishedVersion
Erstveröffentlichung: 2020
Die Publikation erscheint in Sammlung(en):Dissertationen
QUEST-Leibniz-Forschungsschule

Verteilung der Downloads über den gewählten Zeitraum:

Herkunft der Downloads nach Ländern:

Pos. Land Downloads
Anzahl Proz.
1 image of flag of Germany Germany 283 44,22%
2 image of flag of China China 141 22,03%
3 image of flag of United States United States 59 9,22%
4 image of flag of United Kingdom United Kingdom 18 2,81%
5 image of flag of Russian Federation Russian Federation 15 2,34%
6 image of flag of India India 15 2,34%
7 image of flag of France France 10 1,56%
8 image of flag of Australia Australia 8 1,25%
9 image of flag of No geo information available No geo information available 7 1,09%
10 image of flag of Singapore Singapore 7 1,09%
    andere 77 12,03%

Weitere Download-Zahlen und Ranglisten:


Hinweis

Zur Erhebung der Downloadstatistiken kommen entsprechend dem „COUNTER Code of Practice for e-Resources“ international anerkannte Regeln und Normen zur Anwendung. COUNTER ist eine internationale Non-Profit-Organisation, in der Bibliotheksverbände, Datenbankanbieter und Verlage gemeinsam an Standards zur Erhebung, Speicherung und Verarbeitung von Nutzungsdaten elektronischer Ressourcen arbeiten, welche so Objektivität und Vergleichbarkeit gewährleisten sollen. Es werden hierbei ausschließlich Zugriffe auf die entsprechenden Volltexte ausgewertet, keine Aufrufe der Website an sich.