Optimisation and realisation of a portable NMR apparatus and micro antenna for NMR

This paper is focused on two designs and realizations. The first one concerns a prototype of a portable NMR (nuclear magnetic resonance) apparatus. The second one concerns NMR micro antenna realization. For the first part, our goal is the NMR magnetic field homogeneity and the signal-to-noise ratio (SNR) improvement. Since de the volume of the sample to analyse is around 1 cm³, the design is optimized to obtain a good SNR Particularly, the magnet is chosen to obtain a high magnetic field with limited inhomogeneities. The receiver antenna is designed and optimized to have high feeling factor and then more sensitivity. A mixer and a low-pass filter are used in order to limit the bandwidth and reduce the thermal noise. The FID is digitized and addressed to a FPGA which averages successive acquisitions in order to increase the SNR. The final acquisition is processed for determining the FID spectrum. In the second part, a new concept of micro coil is presented in order to measure the small volumes and small concentrations samples by NMR spectroscopy at 4.7 T (200 MHz proton frequency resonance). This micro sensor would offer the possibility of new investigation techniques based on micro coils´ implantation used for in vivo study of local cerebral metabolites of animals models.