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Development of a torsion balance facility and a search for temporal variations in the Newtonian gravitational constant

Panjwani, Hasnain (2012)
Ph.D. thesis, University of Birmingham.

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Abstract

The torsion balance is one of the key pieces of apparatus used in experimental searches for weak forces. In the search for an understanding of a Unified Theory, physicists have suggested a number of signatures that are detectable in laboratory measurements. This thesis describes the development of a new torsion balance facility, relocated from the BIPM (Bureau International des Poids et Mesures) [1], which has excellent environmental stability and benefits from a new compact interferometric readout for measuring angular motion which has been characterised and installed onto the torsion balance. The interferometer has sensitivities of 5 \( \times\) 10\(^{-11}\) radians\(\char{cmti10}{0x2f}\)\(\sqrt{Hz}\) between 10\(^{-1}\) Hz and 10 Hz, an angular range of over \(\pm\)1\(^ \circ\) and significantly reduces sensitivity to ground tilt. With the new facility the first experiment searching for temporal variations in the Newtonian gravitational constant has been undertaken with a null result for \( \delta\)\(\char{cmti10}{0x47}\)\(\char{cmti10}{0x2f}\)\(\char{cmti10}{0x47}\)\(_0\) for both sidereal and half sidereal signals at magnitudes greater than 5\( \times\)10\(^{-6}\). These results have been used to set an upper limit on some of the parameters within the Standard Model Extension framework [2]. The thesis also reports on the design and manufacture of prototype test masses with a high electron-spin density of approximately 10\(^{24}\) and negligible external magnetic field \( \leq\) 10\(^{-4}\)\(\char{cmr10}{0x54}\). These test masses can be used within the facility to potentially make it sensitive enough to conduct future spin-coupling experiments.

Type of Work:Ph.D. thesis.
Supervisor(s):Speake, Clive C.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:Astrophysics and Space Research Group, School of Physics and Astronomy
Subjects:QB Astronomy
QC Physics
TS Manufactures
Institution:University of Birmingham
ID Code:3758
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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