A cold atoms gravimeter for use in absolute gravity comparisons

• Main Author: Zhu, Lingziao
• Published: University of Birmingham 2018
• Subjects: 500; QC Physics
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.742657

This thesis describes the construction of high precision absolute gravimeter, aiming at realising a comparison with a state-of-the-art gravimeter. The instrument is based on performing Raman atom interferometry on ensembles of laser-cooled 87Rb atoms in an atomic fountain. The highlight of this work is the demonstration of an IQ modulator based optical single-sideband (OSSB) laser system providing a highly coherent light source. The advantage this brings to atom interferometry is the suppression of the unwanted sidebands, eliminating interference effects, especially the spatially dependent Rabi frequency and the interferometric phase shift. Recently 5x106 atoms were launched at a rate of 0.5 Hz with a temperature of 10 �K. After improving the vibration isolation, we have observed interference fringes with a sensitivity of 225 �Gal/pHz. The preliminary accuracy is estimated to be 218 �Gal. A study of systematic noise and bias sources has been undertaken, �finding that the limitation of the above performance is the vibration noise and Coriolis effect, respectively. The apparatus has been transported to NERC Space Geodesy Facility in Herstmonceux, where a comparison campaign is in preparation.