Design of Large Size, Force Flow Superconductors for DEMO TF Coils

Results and analysis of the hot-spot temperature experiment for a cable-in-conduit conductor with thick conduit

“…The current is driven by a 10 kA power supply with maximum voltage of 2 V. The aim of the experiment was to initiate a quench in the center of the thick-conduit sample, and to keep the current passing through the sample until it reaches the temperature of 150 K. Three measures were done in order to provoke the quench in the required position: (1) 1 h to 450°C, in order to degrade its critical temperature in the central location; (2) a 40 mm long NbTi coil was wound around the central conductor location, which allowed us to set a field of up to 1.5 T in cable center; (3) an electric heater was installed on the helium inlet, heating up just a short part of the cable, as illustrated in Fig. 1.…”

“…This is an opportunity to revise the superconducting cable design used in fusion magnets in past decades, and to come up with an up-to-date conductor solution. One promising option is to use a flat Nb 3 Sn cable based on the react-and-wind technology, as proposed in [1] for the European DEMO toroidal field (TF) magnet. This cable is designed with a thick steel conduit, the main purpose of which is the mechanical support against huge electromagnetic forces acting on the coil.…”

Modeling electro-magnetic and thermal Stability of Cable-in-Conduit Superconductors for Fusion Magnets

“…In parallel to the conceptual design and dimensioning of the LTS TF coils, High Temperature Superconductor (HTS) R&D activities were pursued, in continuity with the former program [20]. WP1, proposed by Swiss Plasma Center, follows the design basis of [21], i.e., high aspect ratio rectangular section, react & wind manufacturing route and a graded layer to layer winding approach. The WP2 design, proposed by ENEA, Italy, is also described in [21] but relies on wind & react manufacturing.…”

“…WP1, proposed by Swiss Plasma Center, follows the design basis of [21], i.e., high aspect ratio rectangular section, react & wind manufacturing route and a graded layer to layer winding approach. The WP2 design, proposed by ENEA, Italy, is also described in [21] but relies on wind & react manufacturing. WP3, proposed by "Commissariat à l'énergie atomique et aux énergies alternatives", CEA, France [22], has a square cross section, a wind & react manufacturing route and is based on pancake winding technology.…”

“…In the TF WP designs proposed for DEMO, the rectangular Cable-in-Conduit Conductors (CICCs) are wound in eight double layers (DL). The layer winding allows the use of a graded superconductor (Nb 3 Sn or NbTi, for the different layers) cross section depending on the peak field in the DL, saving about half of the superconductor cost [21]. The different designs are studied to investigate advantages and disadvantages regarding integration in the DEMO machine, e.g., savings on material amount (superconductor, steel) and thus on machine cost, or affect certain manufacturing steps (electrical junctions, winding tolerances) and thus risks in either fabrication or exploitation phases.…”