Patent ID: 6987436

Claim:
A method for charging an actively shielded magnet coil arrangement which is superconductingly short-circuited via a superconducting main switch, in particular of an NMR magnet, wherein the magnet coil arrangement comprises at least one first and one second partial region, wherein the first partial region can be separately superconductingly short-circuited via an additional superconducting switch and the second partial region cannot be short circuited by that additional switch, and during operation, the first and the second partial regions generate magnetic fields whose respective magnetic dipole moments D (1) and D (2) have opposite signs, the method comprising the steps of: a) opening the main switch and the additional switch using a power supply unit; b) charging, following step a), the magnet coil arrangement to a first current strength value I 1 ; c) measuring a fringe field B* at a predetermined fringe field position; d) calculating a difference ΔB* between theoretical and measured magnetic field values at the fringe field position to determine a fringe field deviation; e) calculating an additional dipole moment D* associated with the fringe field deviation ΔB* measured in step d); f) determining additional currents ΔI (1) and ΔI (2) in the first and second partial regions, wherein the additional currents ΔI (1) and ΔI (2) are selected to generate an additional magnetic field with a dipole moment −D*; g) calculating a second current strength value I 2 through the magnet coil arrangement at which the additional switch is to be closed, and calculating a third current strength value I 3 of the second partial region at which the main switch is to be closed, such that, taking into consideration a mutual inductance between the first and second partial regions and after reaching I 3 in the second partial region, a respective current distribution in said first and said second partial regions is given by I (1) =I 2 +ΔI (1) and I (2) =I 3 =I 2 +ΔI (2) wherein a targeted magnetic field B is also present; h) continuing charging the magnet coil arrangement after the additional switch has been closed when I 2 has been reached; and i) closing the main switch when I 3 has been reached, wherein I 2 is reached before I 3 .