Superconducting hexapole/solenoid for SERSE

We review the design, fabrication, and test of the coldmass of the superconducting hexapole/solenoid for the source SERSE (superconducting electron cyclotron resonance source) built in a joint venture between INFN, Catania, and CEA/DRFMC, Grenoble. Following the magnetic field specifications we did the optimization of coil shape and positioning to keep the induction in the coil heads at the necessary minimum. The forces acting on the coil heads due to the combined hexapole/solenoid field nevertheless are of highly complex structure. Therefore special attention was given to the structural analysis including 3D coil head simulations. According to ACCEL’s experience with s.c. wigglers and wavelength shifters the 700 mm long racetrack coils were imbedded into a stainless steel structure being completed by a set of structural wedges and shrink rings. After assembling of the quench protection diodes the magnet has been cold tested in a temporary cryostat and after a reasonable number of quenches it achieved all levels of performance for the axial profiles and the hexapolar field specified by INFN. Subsequently the training was continued to the exceptional maximum field of 1.54 T at the position of the plasma chamber wall (radius 65 mm), which is 10% above specification. The completed coldmass has been integrated into its final cryostat and is being tested at CEA.