From cold to ultracold: development of the next-generation eedm apparatus for ybf molecules
File(s)
Author(s)
Collings, Frederick
Type
Thesis
Abstract
Searching for electric dipole moments (EDMs) of fundamental particles provides key insight into physics beyond the Standard Model. The existence of EDMs of fundamental particles would violate both parity and time reversal symmetries, which, if found, would
hint towards explanations of unknowns in physics, such as the matter-antimatter imbalance in the universe.
Imperial’s search for the electron’s electric dipole moment (eEDM) uses an unpaired electron of a heavy polar molecule, YbF. By using spin interferometry on a cold beam of these molecules, a spin precession phase can measure a subtle shift in energy due to an eEDM interaction. The next generation of this experiment uses two-dimensional transverse laser cooling to reduce the thermal expansion of the beam to ultracold temperatures. This will allow for a longer spin precession time with more molecules, vastly improving precision in the measurement. We detect 2×10^5 molecules in our ultracold beam, which, together with a spin precession time of 5 ms, allows for a shot noise limited sensitivity of 1.5×10^−29 e cm/√Nday of measurement, already an order of magnitude more sensitive than the previous generation.
Whilst the spin precession time is longer, the magnetic field noise must be reduced to capitalise on this improved sensitivity. In this thesis, I present the progress towards developing the next-generation apparatus that meets the strict requirements for controlling
the electric and magnetic fields. I detail the characterisation of the apparatus, including a four-layer magnetic shield and a low magnetic field noise electric field setup. I measure magnetic field noise as low as 50 fT/√Hz, allowing for a magnetic field limited sensitivity in the experiment of 4.6×10^−30 e cm/√Nday. When the shot noise limited sensitivity of the experiment can achieve this level of precision, we can expect to make a new measurement of the eEDM with world-leading precision.
hint towards explanations of unknowns in physics, such as the matter-antimatter imbalance in the universe.
Imperial’s search for the electron’s electric dipole moment (eEDM) uses an unpaired electron of a heavy polar molecule, YbF. By using spin interferometry on a cold beam of these molecules, a spin precession phase can measure a subtle shift in energy due to an eEDM interaction. The next generation of this experiment uses two-dimensional transverse laser cooling to reduce the thermal expansion of the beam to ultracold temperatures. This will allow for a longer spin precession time with more molecules, vastly improving precision in the measurement. We detect 2×10^5 molecules in our ultracold beam, which, together with a spin precession time of 5 ms, allows for a shot noise limited sensitivity of 1.5×10^−29 e cm/√Nday of measurement, already an order of magnitude more sensitive than the previous generation.
Whilst the spin precession time is longer, the magnetic field noise must be reduced to capitalise on this improved sensitivity. In this thesis, I present the progress towards developing the next-generation apparatus that meets the strict requirements for controlling
the electric and magnetic fields. I detail the characterisation of the apparatus, including a four-layer magnetic shield and a low magnetic field noise electric field setup. I measure magnetic field noise as low as 50 fT/√Hz, allowing for a magnetic field limited sensitivity in the experiment of 4.6×10^−30 e cm/√Nday. When the shot noise limited sensitivity of the experiment can achieve this level of precision, we can expect to make a new measurement of the eEDM with world-leading precision.
Version
Open Access
Date Issued
2024-03-24
Date Awarded
01/12/2024
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Tarbutt, Michael
Sauer, Benjamin
Lim, Jongseok
Fitch, Noah
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)