Browsing by Author "Sousa, D. M."
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- Fast-Field Cycling Nuclear Magnetic Resonance relaxometer's electromagnet with optimized homogeneity and reduced volumePublication . Videira, P.; Sebastião, P.; Roque, A.; Sousa, D. M.; Margato, ElmanoIn this article a Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) electromagnet with low power consumption (less than 200 W), high field homogeneity and reduced volume is projected and described. The electromagnet is iron and copper based, possessing a high permeability and allowing for good magnetic field homogeneity in the operating range of 0 to 0.33 T. With this solution, it is possible to increase 65% the maximum magnetic field keeping the magnetic field homogeneity in comparison with former similar FFC relaxometers. Electromagnet's experimental and simulation results evaluating the generated magnetic field, field homogeneity, heating effects and cooling requirements are also presented. In addition, some technical aspects of the required coupled systems such as the cooling, sample heating are assessed.
- Simulation of the Magnetic Induction Vector of a Magnetic Core to be Used in FFC NMR RelaxometryPublication . Roque, António; Ramos, S.; Barão, J.; Machado, M.; Sousa, D. M.; Margato, Elmano; Maia, J.This paper is a contribution for the assessment and comparison of magnet properties based on magnetic field characteristics particularly concerning the magnetic induction uniformity in the air gaps. For this aim, a solver was developed and implemented to determine the magnetic field of a magnetic core to be used in Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometry. The electromagnetic field computation is based on a 2D finite-element method (FEM) using both the scalar and the vector potential formulation. Results for the magnetic field lines and the magnetic induction vector in the air gap are presented. The target magnetic induction is 0.2 T, which is a typical requirement of the FFC NMR technique, which can be achieved with a magnetic core based on permanent magnets or coils. In addition, this application requires high magnetic induction uniformity. To achieve this goal, a solution including superconducting pieces is analyzed. Results are compared with a different FEM program.
- Temperature distribution of a Fast-Field Cycling Nuclear Magnetic Resonance relaxometer's electromagnet with reduced volumePublication . Videira, P.; Sebastião, P.; Roque, A.; Sousa, D. M.; Fernandes, A.; Margato, ElmanoThe temperature distribution of a Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) electromagnet plays an important role in the operation of this type of apparatus. The designed electromagnet presents a reduced volume and is iron and copper based, fulfilling the technical requirements for the magnetic field. With this solution, it is possible to increase the overall performance in comparison with former similar FFC relaxometers. Electromagnet's simulation results evaluating the temperature distribution, heating effects and cooling requirements are presented.