Student Number : 9807515F - MSc Dissertation - School of Computational and Applied Mathematics - Faculty of Science / Statistical and algebraic techniques of subspace tracking were tested for filtering the earth’s response from airborne magnetic field gradients in order to discriminate the relatively small response (dipole) of objects on the earth’s surface, such as UXO. Filtering the data was not very effective with these methods but a subspace was found in the data for the magnitude of the magnetic moment of the dipole. This subspace is easily obtained using the singular value decomposition and can be used for an approximate location, without depth estimation, as well as the relative size of the dipole.

<p>Neuronal current MRI (ncMRI) is a field of study to directly map electrical activity in the brain using MRI, which has many benefits over functional MRI. One potential ncMRI method, Lorentz effect imaging (LEI), has shown promise but needs a better theoretical understanding to improve its use.</p><p>We develop three computational models to simulate the LEI experiments of an electrolyte filled phantom subject to a current dipole based on: ion flow, particle drift, and electromagnetohydrodynamics (EMHD). With comparative experimental results, we use the EMHD model to better understand the Lorentz effect over a range of current strengths. We also quantify the LEI experimental images and assess ways to measure the underlying current strength, which would greatly benefit comparative brain mapping.</p><p>EMHD is a good predictor of LEI signal loss. We can measure the underlying current strength and polarity in the phantom using LEI images. We can also use trends from the EMHD model results to predict the required current density for signal detection in future LEI experiments. We can also infer the electric field strength, flow velocity, displacement, and pressure from the predicted current magnitude in an LEI experiment.</p><p>The EMHD model provides information that greatly improves the utility and understanding of LEI. Future study with our EMHD model should be performed using shorter dipole lengths, higher density and lower strength of current sources, and varying current source frequencies to understand LEI in the setting of mapping brain activity.</p> / Dissertation

A new neutron Electric Dipole Moment (nEDM) experiment was proposed to be commissioned at the Fundamental Neutron Physics Beamline at the Spallation Neutron Source (SNS) of the Oak Ridge National Laboratory (ORNL). The underlying theme of this experiment (first conceived by Golub and Lamoreaux in 1994) is the search for new physics beyond the Standard Model of particle physics. The discovery of a non-zero nEDM would be of revolutionary importance to physics, with the discovery of such providing for evidence for new-beyond-the-Standard-Model physics required for a resolution to the unresolved puzzle of why the universe is dominated by matter, as opposed to anti-matter. A first demonstration of a new magnetic field monitoring system for a neutron electric dipole moment experiment is presented. The system is designed to reconstruct the vector components of the magnetic field in the interior measurement region solely from exterior measurements. The results highlight the potential for the implementation of an improved system in an upcoming neutron electric dipole moment experiment to be carried out at the Spallation Neutron Source at Oak Ridge National Laboratory.