Mechanical Coil Structure of the FAIR SIS 100 Magnets

The SIS 100 magnets of the Nuclotron-type are fast- pulsed superferric cold iron magnets. The dipole coil is a double layer saddle-shaped coil with 16 turns. The cable is a hollow tube NbTi composite cable of about 7.2 mm outer diameter, cooled with two phase helium flow at 4.5 K. A 2D structural analysis of the dipole cross section has been performed to determine the stress levels in the components of the coil package and to suggest an appropriate support structure for the conductor. Different design proposals with the focus on limiting stress in the CuNi cooling tubes and on feasibility of industrial manufacturing procedures have been conceived and analysed. The chosen coil support structure (substrate or "comb"), together with new insulation and modification of the winding scheme, seems to be an appropriate way to stabilize the coil better and offers important advantages like precise positioning of the conductor, more uniform distribution of loads on the CuNi tubes, an easier winding process on a guiding support, and simplified production procedures. Samples of the new coil structure were produced and tested. The obtained results are presented and discussed.