Abstract
This paper describes an innovative solution for the power supply of a fast field cycling (FFC) nuclear magnetic resonance (NMR) spectrometer considering its low power consumption, portability and low cost. In FFC cores, the magnetic flux density must be controlled in order to perform magnetic flux density cycles with short transients, while maintaining the magnetic flux density levels with high accuracy and homogeneity. Typical solutions in the FFC NMR literature use current control to get the required magnetic flux density cycles, which correspond to an indirect magnetic flux density control. The main feature of this new relaxometer is the direct control of the magnetic flux density instead of the magnet current, in contrast with other equipment available in the market. This feature is a great progress because it improves the performance. With this solution it is possible to compensate magnetic field disturbances and parasitic magnetic fields guaranteeing, among other possibilities, a field control below the earth magnetic field. Experimental results validating the developed solution and illustrating the real operation of this type of equipment are shown.
Highlights
A fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometer [1] is a very versatile equipment that has been increasingly used to study molecular dynamics in different types of materials, such as those found, in oil industry, food sector, medical or materials sciences [2].This type of equipment includes a set of subsystems as typically represented in Figure 1 [3]
Despite the circuit natural time constant is maintained, one can increase the current rise rate by adjusting the auxiliary supply voltage (Uaux ), so that iM can be reached after time ∆tr, in order to fulfill the dynamic requirements of the application
As expected, when use of an auxiliary power supply (Uaux) is disabled, the transient lasts near 150 ms, which is too high for a generalized use of the FFC NMR technique
Summary
A fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometer [1] is a very versatile equipment that has been increasingly used to study molecular dynamics in different types of materials, such as those found, in oil industry, food sector, medical or materials sciences [2]. Figure is presented a power supply withislow power consumption, In this work, aassolution a new approach, thebased poweronsupply of the magnet designed to portability, and low This power supply,cycles when connected to by an optimized iron core magnet [9,10], control directly the cost. Since, until now, this technique has been owned by research core magnets, due to its intrinsic nonlinear magnetic characteristic, require featuring the control loop groups, this prototype can contribute to diversify use magnetic of FFC relaxometry, mainly by technicians in with increased complexity, i.e., a direct control the of the flux density, as described in this industrial paper. Developed solutions under the FFC requirements are shown; in Section 5 conclusions are presented
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