Modeling He-II cryostat performance and characterization of spin manipulation components for a neutron electric dipole moment experiment at TRIUMF

Abstract

This thesis chronicles measurements of ultracold neutrons (UCN) performed at TRIUMF in fall 2018 and fall 2019. Heat response data of the UCN source bottle was taken by measuring its temperature using the vapour pressure of the 4He. The time-dependence of the He-II bottle temperature is well-described by a model where heat transport is limited by quantum turbulence in the He-II. In addition, measurements of UCN spin manipulation components showed that the adiabatic fast-passage device had a spin flipping efficiency of 0.977 ± 0.008 and 1.007 ± 0.008, and the spin analyzers had a measured polarizing power of 0.650 ± 0.003 and 0.630 ± 0.003. Simulations show that the low spin analyzer efficiency is most likely due to a lower than expected magnetization in the foils, and additional sources of depolarization around the spin-analyzers. The simulations of the analyzer show that the single pass polarizing power of the foil is 0.78 ± 0.08. Under the assumption of no transmission of the wrong spin state through the superconducting magnet, the polarizing power was measured as 0.57 ± 0.05. Simulations reveal that the bore was responsible for some reduction in polarizing power, however better magnetic field gradient control for the spin flipper gradient is required to rule out the possibility of inefficient spin flippers as the cause of the depolarization.