Prototype of superferric quadrupole magnets for the BigRIPS separator at RIKEN

Three superferric quadrupoles with a pole-tip radius of 170 mm and a design field gradient of 14.1 T/m have been constructed for use as spectrometer elements. All three quadrupoles are assembled into a single cryostat and cooled by liquid-He bath cooling method. A small Gifford-McMahon/Joule-Thomson (GM/JT) cooler, mounted on the cryostat, liquefies He gas that evaporates in the He vessel. The high-T-c superconducting current leads and radiation shield surrounding the He-vessel, cooled by a small GM cooler, reduce the heat load of the He vessel. Both cryocoolers operate using separate water-cooled compressors and allow us a stand-alone operation of the quadrupole magnets without big cryogenic plant. Results of quench protection tests, measured heat loads and field-maps are presented.