or pulsed fields higher than 100 T will constitute an enormous financial and technological challenge. It will be necessary to combine all global experience and financial clout in this field to succeed. Encouraging international collaboration as much as possible will help to ensure that the conditions needed to meet these challenges are in place.
To produce even higher fields than are now available will be very costly. Fields around 30 T that are produced by all-superconducting magnets should become available in the coming decade. Such magnets will cost around $10 million and will require a specialized staff and environment to operate them. Such magnets probably will be installed in existing facilities and possibly in some new regional facilities. It is not realistic to expect that such magnets will become affordable for many smaller research groups, in contrast to the case when the 20 T superconducting magnets became commercially available.
At present, purely resistive dc magnets typically use around 24 MW of power at maximum field. Increasing the power will only marginally increase the maximum attainable field, so this type of magnet is becoming economically unattractive. The highest dc fields will therefore be produced with hybrid magnets. The operation of hybrid magnets requires the same power supply and cooling as purely resistive dc magnets, but they are operated in combination with a superconducting outer coil. The record for the highest field produced using such a magnet (as of the time of this report) is 45 T using 28 MW of power at the NHMFL; a 45 T magnet expected to require 22 MW of power is being built at Nijmegen. Higher-field hybrid magnets capable of producing fields at 50 T or even 60 T could easily cost more than $100 million. This is a very rough guess, since no realistic design with cost estimates has been produced to date. It is clear that such magnets will be very large (a minimum of several meters in all dimensions) and will require enormous amounts of materials. The size of such a project presumably will require global cooperation among the large magnet facilities. Consequently, the highest dc magnetic fields will be available at only a few dedicated facilities. It is expected that while these facilities work on the development of even better performing magnets, they will run a guest program for external users providing both the field and the necessary infrastructure and will maintain their own research program in order to stay at the forefront of science. This last point is essential to guarantee the availability of the most advanced instrumentation and the scientific excellence of the work done at the facility.
Regional centers with lower fields, possibly with new high-Tc magnets in the 30 T range, may also be created, since these magnets are too costly and cumbersome to become a normal laboratory commodity but could still be provided in dispersed facilities.