Superconducting solenoide in liquid helium (ca. -269 ºC) The magnet - the main component Strong static magnetic field. 1-3 T (10.000- 30.000 Gauss)
Precessing of nuclear spins in a magnetic field (Bloch & Purcell Nobel price, 1946) Spinning nuclei acts like very small bar magnets because they have a magnetic momentum due the spinning charges (magnetic dipole). When an external field is applied the population of spins splits in two: parallel and antiparallel to the applied field (the proton 1 H have spin ½ which gives two allowed energy levels).