Next generation electric dipole moment experiments require precise knowledge of the local magnetic fields in the experimental volume. Hyperpolarized xenon-129 has been proposed as a comagnetometer gas to be used in the neutron electric dipole moment experiment planned for TRIUMF. A flow through xenon polarizer was constructed and tested, and the hyperpolarized Xe-129 produced was transported to and characterized using a new AFP-NMR spectrometer. The polarization measured in the external AFP-NMR spectrometer was (12 ± 4)%. The longitudinal spin relaxation time T1 was found to be (77 ± 24) s in the experimental NMR volume, limited by leaks and field inhomogeneity. This represents good progress towards the eventual system for nEDM experiments where polarizations greater than 50% and T1, T2 relaxation times greater than 1000 s are expected.

Next generation electric dipole moment experiments require precise knowledge of the local magnetic fields in the experimental volume. Hyperpolarized xenon-129 has been proposed as a comagnetometer gas to be used in the neutron electric dipole moment experiment planned for TRIUMF. A flow through xenon polarizer was constructed and tested, and the hyperpolarized Xe-129 produced was transported to and characterized using a new AFP-NMR spectrometer. The polarization measured in the external AFP-NMR spectrometer was (12 ± 4)%. The longitudinal spin relaxation time T1 was found to be (77 ± 24) s in the experimental NMR volume, limited by leaks and field inhomogeneity. This represents good progress towards the eventual system for nEDM experiments where polarizations greater than 50% and T1, T2 relaxation times greater than 1000 s are expected.

Active magnetic shielding has been proposed to provide low-frequency magnetic field stability in the neutron electric dipole moment (nEDM) experiment planned for TRIUMF. A prototype active magnetic shielding system was constructed and tested at the University of Winnipeg. The system is capable of providing RMS shielding factors > 1000 for magnetic field perturbation frequencies ≤ 20 mHz, and > 100 for frequencies ≤ 0.5 Hz, and can reduce magnetic field variations on the order of tens of μT to the level of tens of nT. The achievable shielding factor was limited by the fi eld sampling rate limit of 400 Hz, and by the background fi eld noise floor of the laboratory. This represents good progress towards the eventual system for nEDM experiments, where low-frequency field drifts on the order of 100 nT require active shielding to the order of 1 nT.

The existence of the matter in the universe is still an unsolved puzzle. After the Big Bang, both matter and antimatter should have been created in equal amounts, and subsequently annihilated. The leading theories to explain the existence of matter require an imbalance in the production of matter and antimatter in the early universe. This in turn requires CP violation, an asymmetry of the laws of physics between matter and antimatter. cryoEDM is designed to explore the total amount of CP violation and resolve this issue. cryoEDM is a next-generation neutron electric dipole moment search in a commissioning phase of development at the Institut Laue-Langevin, Grenoble. A critical requirement of EDM searches is knowledge of the magnetic environment. This work is concerned with the development, implementation, and performance of the currently operating magnetometry system based on SQUID magnetometers. An analysis scheme to provide magnetometry data over the volume occupied by the neutrons, from measurements using the available magnetometers, is developed. An updated method to calibrate the magnetometers using internal sources of magnetic fields is presented, and found to give good agreement with independent measurements. A new method of calibration using the neutrons as a reference is discussed, and tests on an example arrangement are shown to be promising. Algorithms for detecting and correcting for hardware induced artefacts in the data are produced, and demonstrated to reconstruct the field with good agreement in all but the noisiest environments. A software framework is developed to combine these into a real-time analysis that provides feedback and diagnostics to the experiment. Using this new system the resolution of the magnetometers installed in cryoEDM is found to be limited by the environmental noise, and would give a false EDM signal that is greater than the statistical uncertainty in neutron counting. However, the resolution has been somewhat artificially limited to reduce the susceptibility to the RF interference present. This still allows the magnetometry to act as a useful diagnostic tool on any issues in the current magnetic environment, even if in a sub-optimal configuration. For example, investigation of the magnetic shielding of the experiment finds a reduction in the shielding relative to the design, a situation which is being addressed with the design of additional shielding. Once this shielding is installed the resolution of the magnetometers will improve as well as the slew rate of the SQUIDs, which is found to be lower than the $47,mu extup{Ts}^{-1}$ required to measure AC fields applied during a measurement. The current system can also determine sources of magnetic perturbations created within the experiment, which will require addressing before a full EDM run can be performed. For example, cryogenic effects are observed to occur approximately hourly causing large shifts in the magnetic field. Also operation of valves controlling the flow of neutrons around the experiment are found to produce both AC magnetic fields from the driving motors, and shifts in the field from their movement. Situations which can be resolved by reexamination of installation and operational procedures.

abstract: Seeking an upper limit of the Neutron Electric Dipole Moment (nEDM) is a test of charge-parity (CP) violation beyond the Standard Model. The present experimentally tested nEDM upper limit is 3x10^(26) e cm. An experiment to be performed at the Oak Ridge National Lab Spallation Neutron Source (SNS) facility seeks to reach the 3x10^(28) e cm limit. The experiment is designed to probe for a dependence of the neutron's Larmor precession frequency on an applied electric eld. The experiment will use polarized helium-3 (3He) as a comagnetometer, polarization analyzer, and detector. Systematic influences on the nEDM measurement investigated in this thesis include (a) room temperature measurements on polarized 3He in a measurement cell made from the same materials as the nEDM experiment, (b) research and development of the Superconducting QUantum Interference Devices (SQUID) which will be used in the nEDM experiment, (c) design contributions for an experiment with nearly all the same conditions as will be present in the nEDM experiment, and (d) scintillation studies in superfluid helium II generated from alpha particles which are fundamentally similar to the nEDM scintillation process. The result of this work are steps toward achievement of a new upper limit for the nEDM experiment at the SNS facility. / Dissertation/Thesis / Doctoral Dissertation Physics 2019

The observed imbalance of matter and anti-matter in the universe is one of physics' most fundamental unresolved questions. The leading theories to explain this imbalance require CP violation, and the neutron electric dipole moment (nEDM) is a sensitive parameter in its determination. Many new theories of physics beyond the standard model can be constrained or ruled-out by setting limits on the nEDM. Many next generation nEDM experiments require Ultra Cold Neutrons (UCN), produced in superfluid helium. One such experiment is cryoEDM. This thesis explores various types of UCN detection technologies applicable to cryoEDM or any high-density high-efficiency cryogenic nEDM experiment. Cryogenic Phonon Scintillation detectors (CPSD) are modified for this application by operating at 500 mK, and by using a titanium transition edge sensor for phonon signal readout. A CPSD is stabilised in the transition using a novel infra-red light feedback system which reduced the response time to O</m>(100 &mu;s). The detector is characterised and calibrated using an ²⁴¹Am &alpha; source. It was found to operate reliably at this elevated temperature and measure an alpha spectrum with 11% resolution at 5.5 MeV. Scintillators are identified as a promising technology for UCN detection at low temperature. Suitable materials that are bright with fast decay times and low &gamma; sensitivity are studied in the temperature range 300 - 6 K. Their light yield to alpha excitation, their decay time characteristics and spectroscopic properties under VUV excitation are investigated. This study includes the first comprehensive investigation of the luminescence properties of plastic scintillators and of ⁶LiF/ZnS(Ag) down to 6 K. It is found that there is no degradation of the luminescence or kinetic properties of these materials across the whole temperature range, revealing them as suitable cryogenic detector materials. Using a plastic scintillator, a prototype UCN detector for operation in liquid helium is designed, manufactured and tested. It is read out using WLS optical fibres to a room temperature photomultiplier. The detector is successfully tested with cold neutrons at the ISIS neutron science facility and found to effectively measure neutrons, with a signal that is clear from background. Recommendations are made for its integration into a cryogenic neutron EDM experiment. This low-cost detector offers a promising method for the passive detection of UCN in a challenging cryogenic environment, with minimal electric interference and low background sensitivity. This technology offers the potential for improved UCN detection efficiency and thus improved sensitivity of the measurement of the neutron EDM.

A new measurement of the neutron electric dipole moment (nEDM) is being developed at TRIUMF, where a high density source of ultra cold neutrons (UCN) is currently under construction. A fast, high-efficiency UCN detector is needed for the experiment, and a 6-Li doped glass scintillation detector is being explored for this purpose. In this work, simulations and test measurements were carried out to optimize the light guide design for the new UCN detector. Acrylic and air-core light guides, the latter with two different reflecting surfaces, were considered. Three prototype light guides were constructed and tested, and results were compared with simulations. The best solution was found to be an acrylic guide, wrapped with mylar foil. For a guide 12 cm in length as required by the experimental layout, a lower limit of approximately 25 photoelectrons per neutron capture was established for the proposed geometry and photomultiplier configuration. / May 2016