Development of a Uniform Magnetic Field Generator for Magnetic Resonance Applications

In this thesis work, we have investigated possible structures for generating uniform magnetic fields. As an introduction, we gave an overall picture of the uniform magnetic field generation literature. In the second part, we worked on several different candidate structures for uniform magnetic field generation, and we have concluded that spheroidal surfaces – which have been revealed in theoretical analysis, and later confirmed by FEA results – are very promising for practical applications. For making use of the advantages of spheroidal surfaces, firstly a constant ampere per turn ratio along the major axis of a spheroid was studied for uniform magnetic field generation therein. Later, a continuous winding structure, which is easier to realize in practice – a spheroidal helical coil – have been proposed and modelled by FEA calculations. Our results suggest that, uniformity of at least 20 ppm within 75% of a whole spheroidal volume and 50 ppm uniformity within 90% of it are in fact achievable. In the final part of the thesis, we have focused on the production of such a coil and a method has been proposed, applied and experimental measurements were conducted on the prototype. For that, a computer aided design (CAD) of an air-cored spheroidal coil was performed a priori, using the formulation; and a coil template was produced, employing a commercial off the shelf, affordable, 3D desktop printer; inasmuch as it is virtually impossible via conventional production techniques. The coil has been finalized using this template, and the magnetic field created inside employing a current source was measured by a Hall probe through holes that have been intentionally left on the template. Our measurements agree with the finite element results and show a good magnetic field uniformity therein. We have achieved a field uniformity of around 1% experimentally, although numerical analysis pointed out the possibility of 20 ppm uniformity. Thus, the developed spheroidal surface coil can be improved by following a more accurate manufacturing process