A magnet coil system (2) which is at least partially superconducting at a cryogenic temperature, comprising at least two partial coils (3, 4, 5) which are connected in series and are each bridged by a superconducting switch (6, 7, 8), such that the partial coils form independent electric loops (11, 12, 13) when the superconducting switches (6, 7, 8) are closed, is characterized in that two electric loops (11, 12) have a common section and a flux pump (10) is provided which is circuited in the common section (14) of the electric loops (11, 12) of two partial coils (3, 4), wherein the sum of the currents of the two partial coils (3, 4) flows through the flux pump (10) in the operating state. In this fashion, the drifts of two independent electric loops can be compensated for with a few devices.