High Temperature Superconductor. Cable Concepts for Fusion Magnets. Christian Barth. \iyit Scientific. ^VI I Publishing

Transcription

1 High Temperature Superconductor Cable Concepts for Fusion Magnets by Christian Barth \iyit Scientific ^VI I Publishing

2 Contents 1 Introduction and motivation 1 2 Superconductors 5 21 Superconductivity Type I and type II superconductors Critical values Critical temperature Critical magnetic field Critical current density Operating parameters Technical superconductors Low temperature superconductors Niobium-titanium (NbTi) Niobium-tin (Nb3Sn) High temperature superconductors Bismuth-strontium-calcium-copper-oxide (BSCCO) 2223 tapes Bismuth-strontium-calcium-copper-oxide (BSCCO) 2212 round wires Rare-earth-barium-copper-oxide {REBCO) tapes Composition and manufacturing of REBCO Properties of REBCO Production of REBCO Outlook on production and performance of REBCO tapes Comparison of superconductors and their usability for fusion magnets 27 3 Superconducting fusion magnets Introduction to fusion Magnetic confinement Development of magnets for controlled fusion State-of-the-art of fusion magnet technology Cable-in-conduit conductors Challenges in fusion magnets 35 v

3 32 Main parameters of fusion power plants Conductors in fusion power plants Electrical and mechanical requirements Cooling options Nuclear activation Potential of high temperature superconductors in fusion magnets 50 4 Materials of high temperature superconductor cables Thermal expansion Experimental setup Measurement uncertainty Characterized materials Results Structural materials Insulating materials Filling materials Summary and recommendation for HTS cables Degradation free impregnation Thermal expansion Characterized materials Results Measurement uncertainties Degradation measurements on short REBCO tapes Measurement procedure Results Validating results on an HTS cable Summary Thermal conductivity Experimental setup Measurement uncertainty Characterized materials Results REBCO tapes, parallel to the tape REBCO tapes, perpendicular to the tape Structural and insulating materials Filling materials Summary and on impact HTS cables 84 VI

4 no 5 Roebel Assembled Coated Conductor (RACC) cables Introduction High temperature superconductor Roebel cables Manufacturing of HTS Roebel cables Optimizing the geometry of the meander structure Parametrization of the meander structure Influence of geometric parameters on mechanical properties Simulation method Simulation results Impact on Roebel geometry Influence of geometric parameters on current density Simulation method Simulation results Impact on Roebel geometry Summary and recommendation Optimizing the contacts of HTS Roebel cables State-of-the-art Soldering methods Coating copper with solder Coating REBCO tapes with solder Individually contacted tapes Performance of individually contacted RACC cables Summary and recommendation Ill 6 High temperature superconductor fusion magnet cable concepts Experimental setup The FBI test facility Temperature variable insert Layout Validation Assessment Roebel Assembled Coated Conductor (RACC) cable Composition Mechanical properties Field and temperature dependent measurements strand RACC - epoxy impregnation x5 RACC epoxy resin impregnation In-field tests at CERN 125

5 624 Scaling to currents relevant for fusion magnets Extrapolation with present REBCO tape performance Corresponding RACC cables Contacts Coated Conductor Rutherford Cable (CCRC) Composition In-and out-of-plane bending Current carrying capabilities of a sub-size CCRC Scaling to currents relevant for fusion magnets Contacts Conductor on Round Core (CORC) cable Composition Mechanical properties Field and temperature dependent measurements LNi characterization In-field measurements High current ramping rates Temperature distribution Scaling to currents relevant for fusion magnets Contacts Twisted Stacked-Tape Cable (TSTC) Composition Mechanical properties Field and temperature dependent measurements Critical current measurements at increasing and decreasing magnetic fields Temperature dependence at different background fields Temperature distribution Scaling to currents relevant for fusion magnets Contacts Round Strands Composed of Coated Conductor Tapes (RSCCCT) cable Composition Scaling to currents relevant for fusion magnets Contacts Comparison of HTS cable concepts HTS winding packs for fusion magnets HTS winding pack for ITER 164

6 6811 Calculation method Results Winding packs for fusion power plants Calculation method for LTS Comparison with HTS Summary Summary 175 A Annex 179 Al Anisotropic strain effect of REBCO tapes 179 A 11 Single REBCO crystals 179 A 12 REBCO tapes 179 A2 Influence of shear stress on the current carrying capabilities of HTS tapes 181 A21 Experimental setup 181 A22 Finite element method calculations 182 A23 Results 184 A3 Normalized critical currents of Nb^Sn and REBCO at different magnetic fields 185 A4 Fitting parameters of the field and temperature dependent tests of CORC cables 186 A5 Scaling behavior of CORC cables 186 A6 Fitting parameters of the field and temperature dependent tests of TSTCs 189 B Designations and abbreviations 191 C Index of symbols 195 D Bibliography 201