Magnetic field stabilizer for NMR imaging systems with resistive magnets

The NMR stabilizer has been constructed for the purpose of magnetic field stabilization. The error signal for field correction is derived from the 1H resonance of pure H2O. A NMR transducer, operating in the pulse mode with time multiplexing, is connected to the transmit–receive radio frequency stage and yields information about the magnetic induction changes in the frequency form which is compared with the reference frequency. The frequency deviation is evaluated as a voltage that controls the power supply of the electromagnet coil. The stability achieved was slightly better than ±1 ppm.