Cryocooled Bi-2212/Ag solenoid magnet system generating 8 T in 50 mm room temperature bore; design and preliminary test

The combination of Bi-2212/Ag conductors and cryocooler is becoming a promising candidate for cryogen free magnet systems because of the rapid progress in conductor fabrication and cryocooler engineering. We started a new project to develop a cryocooled Bi-2212 magnet system generating 8 T in 50 mm room temperature bore. In this project, the system is designed to be composed of two magnets of solenoid winding by using ROSAT (Rotation-Symmetric Arranged Tape-in-tube) wires and to be operated at 10 K with 30 W refrigeration capacity (two GM cryocoolers of 15 W at 10 K). Inner and outer magnets are designed to generate 3.8 T and 4.2 T at 10 K with operating coil current density of 80 and 100 A/mm/sup 2/, respectively. The dimensions of the inner and the outer magnets are 80 mm (bore)/spl times/169 mm (outer diameter)/spl times/203 mm (height) (total conductor length, 0.8 km) and 178 mm/spl times/260 mm/spl times/230 mm (total conductor length, 2.3 km), respectively. We finished the fabrication and a preliminary test of the inner magnet. The whole system and a full operation test will be completed in near future. In this paper, we report the details of system design and the test results of the inner magnet.