Superconducting R&D – Now Strand and Cable R&D FERMILAB Magnet Systems Department – Now SC Materials Department (TD) HTS Insert Coil Test in External Solenoid Field Emanuela Barzi All Experimenters’ Meeting, July 11,

Motivation of R&D High Temperature Superconductors (HTS) are of interest for Muon Collider and/or Neutrino Factory accelerator magnets The muons initially occupy a large 6D phase space, which must be cooled by a factor O(10 6 ). In the muon ionization cooling channel designs, the muons are confined within a lattice of high-field solenoids. The square-root of the final transverse emittance that is achievable is inversely proportional to the solenoid field at the end of the channel. The achievable luminosity in the collider is therefore proportional to this solenoid field, up to fields of about 50 T, beyond which the beam- beam tune shift is expected to limit the luminosity. 2

“Study of HTS Wires at High Magnetic Fields”, D. Turrioni, E. Barzi, M. J. Lamm, R. Yamada, A. V. Zlobin, A. Kikuchi. IEEE Trans. On Appl. Superconductivity 19, No 3, Part 3, (2009). Why HTS? “Angular Measurements of HTS Critical Current for High Field Solenoids”, D. Turrioni et al.. Advances in Cryogenic Engineering, V. 54, AIP, V. 986, pp (2008).

1. Magnet design studies - Since 2007, A. Zlobin, V. V. Kashikhin, E. Barzi, E. Terzini “Study of High Field Superconducting Solenoids for Muon Beam Cooling”, V. V. Kashikhin et al.. IEEE Trans. Appl. Sup., V. 18, No. 2, p. 928 (2008). “Towards 50T Solenoids”, E. Barzi - Analytical Study of Stress State in HTS Solenoids – Stress distribution in a solenoid was studied for various constraint configurations, max. stresses were produced as a function of coil self-field, and results compared with Finite Element Models. E Terzini, E. Barzi, FERMILAB-TM-2448-TD. 2. HTS Conductor R&D – Ongoing since 2005, E. Barzi, L. Del Frate, V. Lombardo, D. Turrioni Conductor characterization – Studies of J e as a function of B, T, angle, and bending, longitudinal and transverse strains. BSCCO-2212 cable development. YBCO Roebel cable. 3.Insert Coil Development – Since 2008, E. Barzi, G. Norcia, A. Bartalesi, A. Cattabiani, G. Gallo, V. Lombardo Winding methods and tooling, impregnation techniques, splicing procedures, R&D on thermally conductive insulation. Development of modular test setup. Magnetic models for insert and background field were developed to calculate short sample limits of insert coils. Co-wound and impregnated YBCO coil were represented by meso-mechanic models. A. Bartalesi, FERMILAB-MASTERS Insert Coil Test – Since 2009, D. Turrioni, P. Vicini, V. Lombardo Development of instrumentation, DAQ, quench protection and detection systems for insert coil tests. Test pancake assemblies in 14 T/77 mm bore existing magnet and provide feedback to coil technology development. HTS Work Directions

ConductorSuperPower SCS4050-i Ic (A) A Ic (A) A Ic Standard Deviation2.7% Turn to Turn InsulationSpiral Wrapped Kapton Coil GeometryDouble Pancake – no inner splice Coil ID19 mm Coil OD62 mm Conductor Thickness0.1 mm Conductor + Insulation Thickness 0.2 mm Packing Factor50% Turns per Single Coil108 Conductor length per Coil13.9 m Overall Conductor Length27.8 m Coil 300K2.87 Ohm Coil mH Double-Pancake Units 5

Modular Insert Test Setup 14 T solenoid with 77 mm bore Modular Insert Test Facility 6 Coil1 Coil2 Coil3 Coil4 Modular Test Facility for HTS Insert Coils”, V. Lombardo, A. Bartalesi, E. Barzi, M. Lamm, D. Turrioni and A.V. Zlobin”. IEEE Trans. Appl. Sup., V. 20, No. 3, p. 587 (2010).

7 Result T with 14 T Bkg. Field YBCO Insert Coil External Magnet Max Current Reached335 A SSL92% Peak Field on Conductor 21.5 T Peak Axial Field21.2 T

What Next? This insert coil produced 7.5 T in a 14 T background field (about 9 T at self-field). This is an intermediate result with respect to our final goal. To develop a technology for 35 T+ solenoid, we need to double (~15 T) the field of the HTS insert in a background field of ~ 20 T provided by Nb 3 Sn/ NbTi hybrid coils.