The U.S. NHMFL 60 T long pulse magnet failure

The 60 T long pulse magnet operated by the U. S. National High Magnetic Field Laboratory at Los Alamos National Laboratory, Los Alamos, New Mexico failed catastrophically on July 28, 2000. The failure was investigated and the cause was determined to be unusually low toughness in the nitrogen strengthened manganese stainless steel (Nitronic-40) reinforcing material. The source of the reduced toughness condition was a sigma phase conversion in the microstructure. The magnet failure, failure investigation and results of the investigation are described. Plans for the construction of the successor magnet, the 60 tesla long pulse Mark II, are described