NHMFL, USA – magnet test facility

Helium refrigerator for the Florida State University and its Series Connected High Field Magnet SCH.

The first SCH with a field strength of 25 Tesla and the horizontal bore is designed for the Helmholtz Centre Berlin (HZB) in Germany and will be used for neutron scattering experiments. The second SCH with a field strength of 35 Tesla and the vertical bore is designed for the National High Magnetic Field Laboratory (NHMFL) itself. Both SCH Magnets combine a set of resistive Bitter coils with a superconducting outset coil constructed of the cable-in-conduit conductor (CICC). The two SCH magnets are designed for various operating scenarios including those with multiple ramp cycles at various rates.

Both of the superconducting magnets are forced flow cooled using supercritical helium at 4.5 K. A Linde refrigerator with a capacity of about 150 – 200 W at 4.5 K is used to supply the cooling power and the forced mass flow rate. The cryogenic system of the SCH magnet consists of a helium refrigerator, a valve box with a sub-cooler, a magnet cryostat, and cryo-lines.

The cryogenic system is also used to produce and distribute liquid helium (LHe) to other magnet systems and users at the NHMFL. The cryogenic system will replace an existing piston expander refrigerator which has been in operation for more than 15 years.