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Title: A new measurement of the electron electric dipole moment using ytterbium fluoride
Author: Smallman, Ian Joseph
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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This thesis describes a new measurement of the electron electric dipole moment (eEDM, de) made using a pulsed beam of ytterbium fluoride (YbF) molecules. YbF molecules are used as they greatly enhance the eEDM interaction with an applied electric field. In addition they suppress interactions with magnetic fields in the plane perpendicular to the applied electric field. This is hugely beneficial for suppressing the systematic effect that limited previous atomic eEDM searches. We measure the eEDM by performing a type of separated oscillating field interferometry, wherein the direction of applied electric and magnetic fields are reversed in between pulses of the molecular beam. From a dataset of 6194 individual eEDM measurements we find de = (-2.4 ± 5.7stat ± 1.5syst) x 10[superscript -28] e cm. This result is consistent with zero, so we set a new upper limit of |de| < 10.6 x 10[superscript -28] e cm at the 90% confidence level. A complete analysis of the dataset is given, with a thorough account of all the supplementary tests that were performed to check for systematic error. After publishing this world leading result we proceeded to upgrade the experiment to improve eEDM sensitivity and reduce certain systematic effects. This involved improving the rf polarisation along the parallel plate transmission line, shortening the rf pulse length and improving the magnetic shielding. A detailed discussion of the development and testing of the upgrades is given, including new measurements of the systematic uncertainties which will limit our next eEDM measurement.
Supervisor: Hudson, Jony ; Sauer, Ben Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral