Engineering and cryogenic aspects of the Nijmegen 25 Tesla hybrid magnet

The High Field Magnet Laboratory at the Faculty of Science of the University of Nijmegen has been operational since 1976. It has 6 MW of DC power available to energize (the resistive part of) the magnets. The purpose of the laboratory is to provide high continuous magnetic fields (at present up to 25 T) for scientific and technological research. The laboratory has a number of 15 T Bitter magnets and a 25 T hybrid magnet which has been in operation since 1978. In general a hybrid magnet consists of a combination of resistive and superconducting coils. In this case two concentric resistive coils are surrounded by a large superconducting coil. A description of this system is given. Cryogenic requirements, cooldown-, check-out-and operating-procedures will be discussed.