On March 31, 2023, Oskari Timgren successfully defended the thesis “Progress towards a measurement of time-reversal symmetry violation in thallium fluoride” (advisor: Steve Lamoreaux).
Timgren explained, “One of the big mysteries of the universe is how matter came to dominate over antimatter. We don’t know the exact mechanism, but we do know that the same underlying physics that is required to explain this matter-antimatter asymmetry would also produce electric dipole moments (EDMs) for fundamental particles. Precision measurements of electric dipole moments can give us hints of the underlying physics and constrain the parameter space for extensions to the Standard Model of particle physics. My thesis work describes work on building the Cold molecule Nuclear Time-Reversal Experiment, which is aiming to measure the Schiff moment (an EDM-like electric moment of a nucleus) of the thallium nucleus inside the thallium fluoride molecule. My work focused primarily on the state preparation for the experiment – essentially getting the molecules into the correct rotational state.”
Timgren is currently working as a Sales Support Data Scientist at SentiLink.
The observed matter-antimatter asymmetry of the universe is widely considered to be an indication of the existence of beyond the Standard Model time-reversal symmetry violating physics. This dissertation describes work on a new molecular beam experiment (CeNTREX) to search for T-violating physics in the hyperfine structure of the diatomic molecule thallium-205 fluoride (TlF). This thesis presents progress on various modules of the experiment. Experimental results from characterizing the TlF cryogenic buffer gas beam source are presented. We also report an improved measurement of the gain in useful signal due to the rotational cooling scheme of the experiment. Rotational state preparation using microwave driven adiabatic passage in a spatially-varying electric field is discussed, and experimental results are presented. The design of an electrostatic lens to guide the trajectories of molecules emerging from the beam source is also presented.