Reducing the size of Fast Field Cycling NMR spectrometers based on the use of IGBTs

The fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometry is a powerful technique that owes its advances to the use of semiconductors, materials, optimization techniques and computational tools. This type of laboratorial equipment has specific characteristics being the requirements of the magnet and the main power supply the most relevant to the performance of the spectrometer. The main power supply is, in general, a current source, which must present an adequate dynamic behavior having response times in the milliseconds range. In particular, the main power supply owes its recent advances to the use of power semiconductors. In this paper, general characteristics of three different power supplies used in three generations of Fast Field Cycling Nuclear Magnetic Resonance spectrometers are presented and compared. In order to fulfill the technique requirements, power supplies using IGBTs have been developed presenting better performances and having higher power/volume ratios. In addition to their dynamic and steady-state performances, the mechanical characteristics are also described, mainly the aspects that had been contributing to reduce the size of this type of apparatus.