High-T/sub c/ SQUIDs for low-field NMR and MRI of room temperature samples

摘要

We have constructed a high-T/sub c/ SQUID spectrometer to detect NMR signals from samples at room temperature in magnetic fields up to 3 mT. The multiloop SQUID magnetometer has a system noise of about 30 fT/Hz/sup 1/2/ at the relevant frequencies of 2 to 100 kHz. The magnetometer is operated in vacuum at 77 K, and is separated from the sample, which Is less than 1.5 mm away, by a sapphire window. In a magnetic field of 2 mT we can detect the proton spin echo at 86 kHz without signal averaging. This sensitivity enables us to obtain one-dimensional images. In addition, we present data on hyperpolarized /sup 129/Xe, which has an optically pumped polarization of several percent.