A PULSED SUPERCONDUCTING MAGNET FOR A STATIC MAGNETIC REFRIGERATOR OPERATING BETWEEN 1.8 K AND 4.5 K

Superfluid helium is increasingly used as a technical cooling medium i n large-scale research projects involving high-field superconducting m agnets, such as the CERN Large Hadron Collider (LHC). For refrigeratio n cycles operating below the normal boiling point of helium, a potenti ally interesting alternative to vapour compression is magnetic refrige ration, pioneered decades ago. In the framework of development for an industrial-size 1.8 K magnetic refrigerator using a static active mate rial, we have designed, built and tested a pulsed superconducting magn et producing up to 3 T at a ramping rate of 6.5 T/s. The solenoid-type coil, wound with low-loss superconducting wire (small-filament NbTi i n a composite Cu/Cu-Ni matrix), is internally cooled by normal boiling helium, and installed inside a toroidal yoke, made of tapered laminat ions of commercially pure iron. After describing design and constructi on of the magnet, we present test results and measurements of performa nce, field quality and pulsed-operation losses.