A cryogen free conduction cooled NbTi superconducting magnet for a X-band klystron was designed,fabricated, and tested successfully. The magnet has a room temperature bore of 190 mm. The rated field distribution, the NbTi coil is separated to three parts and a return yoke is set. The coil is cooled by a twostage Gifford-McMahon cycle refrigerator. The refrigeration capacity is 1.1 W at 6 K and 30 W at 40 K for each stage. Current leads are made of 2223 Bi-based oxide superconductor. The coil was cooled down to superconducting state from temperature in 85 hours. The ultimate temperature of the coil was below power. The magnet was tested successfully and no problem at all is 0.7 T. In order to meet the requested magnetic field fl . MAGNET DESIGN
A. NbTi superconducting coilThe solenoid consists of three coils which are wound in series on a stainless steel bobbin. The cold head of the refrigerator is thermally connect-4K, and the coil was energized without quench to 18.5 A ed to each coil bv a coolling: busbar. The magnet " " has a iron yoke to fit the magnetic field distribuwhich was 105% of rated current. The power consumption of 6 kW is 118 of the normal conducting magnet. The thermal leak of 0.2 W into the coil was measured, tion required for the klystron. Figure 1 shows a which was the same value of the design.
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