Superconducting RF coil assembly and method of setting up the same

An NMR spectrometer is offered which can have a high filling factor if an NMR detection coil using a superconducting material is employed. Also, a method of setting up this spectrometer is offered. For these purposes, the following three steps are performed. (1) An external magnetic field is set to H 0 + ”H (where ”H > 0). When the detection coil made of the superconducting material is still in a normal state, a magnetic field stronger than the ultimate target static magnetic field strength H 0 by ”H is applied to the detection coil. (2) The detection coil made of the superconducting material is cooled down to To lower than its critical temperature T c to bring the coil into a superconducting state while the external magnetic field H 0 + ”H is applied to the detection coil. (3) The external magnetic field is lowered from H 0 + ”H to H 0 such that the applied external magnetic field is decreased by ”H while the detection coil is kept in the superconducting state.