WP10.2 – status Reported by L. Bottura and C. Senatore Meeting at CERN, February 2 nd, 2014

Overview of cable options

Result of the discussion on tape/cables Roebel – Mechanical properties and response to loading – Manufacturing process for long length, compact cable geometry – Windability (difficult axis direction and matching the transposition to the curvature radius) Stacks – Transposition, need and effect of lack of transposition – Effect of transverse forces on the twisting region All – Impregnation and insulation effects on tapes (delamination, stress distribution) – Protection and need of copper – Striation (how much do we need ?) – Dummies for winding tests – Parallel/transverse field effects and interaction with magnet design

BSCCO Rutherford Strand parameters – Strand diameter: 0.8 (mm) – Engineering current density (15 T, 4.2 K): 675 (A/mm2) – BSCCO current density (15 T, 4.2 K): 1930 (A/mm 2 ) – Critical current (15 T, 4.2 K): 340 (A) Cable proposal: – Number of strands: 22 – Cable width: 9.5 (mm) – Cable average thickness: 1.45 (mm) – Keystone angle: 0.6 (degrees) – Thin edge: (mm) – Thick edge: (mm) – Transposition pitch: 65 (mm) Cable critical current: 6700 (A)

REBCO Roebel – tape Target Tape parameters – Tape width: 12 (mm) – Tape thickness: 0.1 … 0.15 (mm) – Engineering current density (15 T, 4.2 K): 450 (A/mm 2 ) – Critical current (15 T, 4.2 K): 800 A – SC layer: 1…2 m (TBD) – Cu layer: 30…50 m (TBD) – Homogeneity and defects TBD to assess the effect of punching – Bonding strength (delamination issue)

Cut tape geometry Optimal geometry defined by KIT t g p Status at KIT: t= 5.5 mm g= 1 mm α = 30 ° p=126, 226, 426 mm R = 1-2 mm to reduce stresses, see C. Barth, et al. Supercond. Sci. Technol. 25 (2012) By courtesy of A. Karlo, ITEP KIT

REBCO Roebel – wide (block coil) Number of tapes (-)15 Cable width (mm) 12 Cable thickness (mm)1.2 Transposition pitch (mm)226 Critical current (B perp ) (kA)5

REBCO Roebel – KIT stock Transposition 226 mm – 15 tapes (only SC) cable thickness: 1.1 mm critical current with 10% degradation: 5030 A Transposition 426 mm – 28 tapes (only sc) cable thickness: 2.1 mm critical current with 10% degradation: 9390 A – 27 superconducting tapes and 27*0.15 mm Cu cable thickness: 4.2 mm critical current with 10% degradation: 9054 A – 14 superconducting tapes (loose cable) critical current with 10% degradation: 5350 A By courtesy of A. Kario, ITEP KIT

REBCO Roebel – narrow (cos- coil) Number of tapes (-)8 15 Cable width (mm) Cable thickness (mm) Transposition pitch (mm) Critical current (perp) (kA)1.73