Speaker
Description
Roebel cables from HTS coated conductors are used in the first real application, in dipole insert magnets for particle accelerators, performed in a work package of the EU-project Eucard2 of CERN. Following-up the first sub-size dipole magnet demonstrator, future full-size magnets require cable designs with significantly enhanced operation currents for favorable magnet impedance, for accelerator magnets as well as for TF-magnets of the future fusion reactor DEMO. The Roebel geometry is quite flexible to enhance the number of strands, either using stacks or increasing the transposition pitch. Both methods however have disadvantages for the application in coils and may lead to higher stress load depending on the coil details.
A proposed new concept extends the existing Roebel cable design by adding an additional Roebel shaped layer of strands around the standard cable resulting in the so-called double core (DOCO) cable. By keeping the strands width constant, the cable cross-section will double in width (12 to 24 mm) and increase in thickness by two layers of coated conductors. The favorable properties of the Roebel cable as full strand transposition and excellent bending ability are nearly completely preserved. An enhancement of the current by more than a factor of 2 is achieved. We demonstrate the feasibility of the concept with a 1.3 kA sub-size cable with experiment and modeling. The effects of parallel and crossed orientation of the two cable parts is investigated. The material for a full width DOCO-cable is under development at industrial partners and the status of the efforts for a full size cable will be reported. The future current carrying potential of the DOCO-approach will be discussed on basis of prototypes and the latest improvements of the industrial coated conductors.