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.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:560853 |
| Date | January 2012 |
| Creators | Panjwani, Hasnain |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.bham.ac.uk//id/eprint/3758/ |
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