NMR DETECTION AT 8.9 mT WITH A GMR BASED SENSOR COUPLED TO A SUPERCONDUCTING Nb FLUX TRANSFORMER

Raffaele Sinibaldi (1) , Cinzia de Luca (1) , Jaakko O. Nieminen (1) , Angelo Galante (2) , Vittorio Pizzella (1) , Piero Sebastiani (3) , Myriam Pannetier-Lecoeur (4) , Antonietta Manna (5) , Piero Chiacchiaretta (1) , Gabriella Tamburro (1) , Antonello Sotgiu (2) , Claude Fermon (4) , Gian Luca Romani (1) , Stefania Della Penna (1)

1 Department of Clinic Sciences and Bioimaging, University G. d'Annunzio Chieti-Pescara
2 UNIVAQ - Università degli Studi dell'Aquila = University of L'Aquila
3 ITA S.r.l., L’Aquila, Italy
4 LNO - Laboratoire Nano-Magnétisme et Oxydes
5 Department of Oncology

—This study presents NMR signal detection by means of a superconducting channel consisting of a Nb surface detection coil inductively coupled to a YBCO mixed sensor. The NMR system operates at a low-field (8.9 mT) in a magnetically shielded room suitable for magnetoencephalographic (MEG) recordings. The main field is generated by a compact solenoid and the geometry of the pickup coil has been optimized to provide high spatial sensitivity * Corresponding author: Raffaele Sinibaldi ([e-mail]). 390 Sinibaldi et al. in the NMR field of view. The Nb detection coil is coupled to the mixed sensor through a Nb input coil. The mixed sensor consists of a superconducting YBCO loop with 2-µm constriction above which two Giant MagnetoResistance sensors are placed in a half-bridge configuration to detect changes of the bridge voltage as a function of the flux through the YBCO loop. The sensitivity of the receiving channel is calibrated experimentally. The measured spatial sensitivity is in agreement with the simulations and is ∼10 times better than that of the stand-alone mixed sensor. A NMR echo at 375 kHz shows a SNR only a factor 4 smaller than a tuned room temperature coil tightly wound around the sample, with a noise level which is a factor 3 better than for the volume coil. Our results suggest that mixed sensors are suitable for the integration of low-field MRI and MEG in a hybrid apparatus, where MEG and MRI would be recorded by SQUIDs and mixed sensors, respectively.

Domaines: Physique [physics]

Raffaele Sinibaldi, Cinzia de Luca, Jaakko O. Nieminen, Angelo Galante, Vittorio Pizzella, et al.. NMR DETECTION AT 8.9 mT WITH A GMR BASED SENSOR COUPLED TO A SUPERCONDUCTING Nb FLUX TRANSFORMER. Progress In Electromagnetics Research, 2013, 142, pp.389 - 408. ⟨10.2528/PIER13070404⟩. ⟨cea-01481107⟩