The 18 Tesla-100 mm 4.2 K free bore solenoid for LASA-Milan

The high-field facility SOLEMI is under construction at the LASA laboratory. This multiple solenoid starts with an outer NbTi coil in an independent cryostat, which provides 8 T in a 540-mm room-temperature bore. The high magnetic field will be obtained by inserting a cryostat in which two (NbTa)₃Sn coils are located. The inner coil is demountable, allowing access to fields of 15 T in a 240-mm bore and 18 T in a 100-mm bore. The authors present progress on the design of the 15-T coil and the results of an extensive campaign of measurements on the superconducting cable, which is of the Rutherford type with superconducting and copper (tantalum-sheathed) strands and whose characteristics vs. temperature and time of heat treatment have been carefully investigated. The experience obtained in winding a small coil model with superconducting dummy cable is also reported. Finally, the cable and the basic coil design of the 18-T insert are described