8 T Cryogen Free Magnet With a Variable Temperature Insert Using a Heat Switch

The paper presents design and test results for a conduction cooled 8 T superconducting magnetic system with a variable temperature insert for electrical measurements. The system is based on one Pulse Tube cryocooler. The helium gas gap heat switch is used as controllable thermal link between variable temperature chamber and the 4 K stage to avoid overheating of the magnet at high temperatures of the insert. The superconducting magnet is manufactured from NbTi wire and impregnated with epoxy resin by ¿wet¿ technology. The clear diameter of variable temperature chamber is 20 mm. The system provides sample temperature range of 5.4-300 K. The maximum operating magnetic field depends on the temperature of the insert and belongs to the range of 7.1-8.2 T. The cool down time of the magnet from room temperature to 3.6 K is 6 hours.