Improving ultracold neutron density and storage: applications to neutron lifetime and electric dipole moment experiments

Abstract

This thesis presents a comprehensive study on ultracold neutron (UCN) stor- age measurements for the n2EDM experiment, which searches for a property of the neutron called "electric dipole moment", and the τSPECT experiment, which measures the free neutron lifetime. Both experiments are situated at the Paul Scherrer Institute in Villigen, Switzerland. Additionally, this thesis includes studies on the UCN source at the research reactor TRIGA Mainz, Germany, and a comparison to the UCN source at Paul Scherrer Institute in Villigen, Switzerland.

Ultracold neutron sources: An optimization of the UCN source at the research reactor TRIGA Mainz is described, achieved by increasing the temperature of the deuterium and hy- drogen crystals, which are the central component of the UCN source where neutrons are moderated and then converted to UCNs. This optimization in- creases the UCN densities available for experiments. A comparison of the UCN source at the research reactor TRIGA Mainz, Germany, and the one at the Paul Scherrer Institute is made for a storage volume mimicking the conditions of the τSPECT experiment.

τSPECT: The τSPECT experiment aims to measure the neutron lifetime by storing UCNs in a magnetic field gradient trap and counting the UCNs reaming after a storage period. The first storage curves after the relocation of the τSPECT experiment from the research reactor TRIGA Mainz, Germany, to the Paul Scherrer Institute were measured.

n2EDM: The n2EDM experiment aims to measure the neutron’s electric dipole moment. This work describes the manufacturing and characterization of the insulating rings and the first UCN storage measurements for the n2EDM experiment. Furthermore, a new method to investigate the UCN energy spectrum in the n2EDM experiment was developed.