The RFX toroidal field winding design

The RFX toroidal field winding consists of 48 coils, which can be connected in many series/parallel configurations according to the toroidal field programming required for plasma operation. For ease of maintenance each coil consists of two identical half-coils connected at the equatorial plane of the machine. To be in alignment, the half coils are placed into grooves machined in an aluminum shell, which also has the function of withstanding the overturning moment caused by to the interaction between the current and the poloidal field. Stainless-steel clamping belts are provided around the coils to withstand their electromagnetic expansion forces and to keep them in the grooves. Thermal expansion of the half coils takes place freely along the grooves, due to thin layers of low-friction material placed on the coil surfaces. The demountable joints which connect the conductors of the half coils are designed to allow thermal expansion. Two basic alternative solutions considered for the electric contacts are discussed: the first based on a multicontact plug-in system, the second on bolted joints.