Large bore high field magnets

Abstract The National High Magnetic Field Laboratory (NHMFL) is, as part of its charter with the National Science Foundation (NSF), building several state-of-the-art magnets which exploit the technological limits in field strength and useful volume. Four magnets are of special interest in this context: a 20 T, 200 mm bore resistive magnet, a persistent 21.1 T, 144 mm bore superconducting NMR magnet, a 15 T, 620 mm bore powered superconducting magnet, and a 50 T, 200 mm bore pulse magnet, built in cooperation with LANL. A condensed overview of the NHMFL and a description of its activities in magnet research is given. The path to a magnet optimized for the detection of axions is explored. To this end, the large bore magnets in use or construction at the NHMFL and their different technologies are compared. Design issues of superconducting magnets for reliable operation, an optimization example and a demonstration of the cost constraints follow.