1. FuturE circular collider MAGNETS TECHNOLOGIES
Wound Conductor Test Facilities (TASK 2)
Status
F. Lackner, D. Tommasini, C. Scheuerlein, D. Schoerling, T. Koettig, D. Pulikowski,
P. Ebermann, F. Wolf, J. Fleiter, S. Luzieux, F. Meuter.
MSC-LMF, MSC-MNC, MSC-SCD, CRG-CI
9th, May 2017

2. F. Lackner, overview wound conductor tests
Who ?
The current team:
D. Pulikowski, PhD student, West Pomeranian University of Technology, Szczecin, Poland
P. Ebermann, PhD student, Vienna University of Technology, Atominstitut, Austria
F. Wolf, PhD student, Bergakademie Freiberg, Germany
M. Michels, Senior-Fellow, MSC-LMF
C. Scheuerlein, MSC-LMF
D. Schörling, MSC-MNC
F. Lackner, MSC-LMF
Collaboration with SCD (J. Fleiter), CRL (T. Koettig)
Weekly meeting on Friday afternoon to monitor the progress and to discuss the technical challenges
F. Lackner, overview wound conductor tests

3. F. Lackner, overview wound conductor tests
Characterization of Nb3Sn wound conductor
Introduction: Mechanical coil characterization by measurement and simulation
What can we measure directly in the coils/coil assembly ?
Shell shrinkage, axial stress
Strain on collar nose
Coil geometry after impregnation (ideally state free, no ext. stress)
Fuji paper can provide information on pole and midplane stress and its distripution
What can we not measure currently ?
Conductor stress-strain state during production, cooling, operation
Axial stress/strain in the coil during production, cooling, operation
What do we currently estimate from simulations ?
Stress-distribution in the coil cross-section (mainly by 2D analysis)
Shimming of coils to achieve and keep pre-stress during different operation conditions (cooling – operation) is presently based on measured coil geometry and stress estimates from FEA simulations using 10-stack stiffness results.
An average azimuthal coil stress of 60 MPa should be achieved after the shell welding, to avoid losing the compression when operating at ultimate current (12.8kA/12T)
F. Lackner, overview wound conductor tests

4. Characterization of Nb3Sn wound conductor
Irreversible degradation
Quantify irreversible degradation of the conductor during the mechanical loading at RT (RRP, PIT)
Develop knowledge about stress distribution on Rutherford cable stack due to the transversal load
Measurement of Ic degradation as a function of transverse compressive stress applied at RT (Rutherford cable at FRESCA, wire at Cryolab)
Windability
Improving knowledge on cable windability
Development of winding test setup to determine the Rutherford cable instabilities during the winding process
Development of adequate scanning method to quantify strand displacements during the winding process
Develop a “windability factor” allowing comparison between different cable types
Material characterization
Improving knowledge of magnet material parameters for refined FE modelling
Improved FE meshing using tomographic coil characterization
Nb3Sn strain state development during the coil reaction heat treatment
Coil volume changes during the reaction heat treatment
Lateral shim
Coil size top
Arc length
Coil size bottom
Collar-Yoke shim
Collar nose shim
F. Lackner, overview wound conductor tests

5. Ic degradation after transversal pressure at RT
The dominating load case in accelerator magnets is transverse compressive.
Coils are loaded during the assembly, cooling, powering, quenching, thermal cycles.
Experimental results about the room temperature (RT) stress limits of Nb3Sn wires, cables and coils at which irreversible conductor degradation occurs are lacking.
The proposed experiment aims to determine the critical RT transverse compressive stress limits of cured, reacted and impregnated Nb3Sn coil components.
The degradation will be quantified in terms of critical current and n-value.
The experiment should allow to measure several RRP coil segments after loading to different stress levels.
F. Lackner, overview wound conductor tests

6. Ic degradation after transversal pressure at RT
Analysis of electrical degradation of reacted Nb3Sn conductors based on an Ic measurement after transversal stress at room temperature (RT)
Sample preparation
The transversal stress on cable resp. strand is carried out on a hydraulic press in LMF, S. Luzieux, F. Meuter and F. Wolf.
Ic degradation measurement in collaboration with SCD in the FRESCA test facility (bldg. 163), J. Fleiter (CERN-TE-MSC-SCD)
Strand with adapted setup in CryoLab (bldg. 165), T. Koettig (CERN-TE-CRG-CI) and C. Scheuerlein
Hydraulic setup bldg.180
Improved knowledge on stress-distribution
F. Lackner, overview wound conductor tests

7. F. Lackner, overview wound conductor tests
Windability study
Improving knowledge on cable windability
Measure and model the geometrical evolution of cables during winding
Identification of the parameters dominating this process to possibly provide feedback for cabling & winding
Set-up a standard to quantify a “windability factor” or similar
New slide from Davide.
Showing that conductor development is launched at international level, Russia, Japan, (Korea and Europe in preparation)
Underline importance of that development as main cost driver for the hadron collider machine.
Envelope
Protrusion
Pop-out
Definition of observed instabilities and their quantification
Proposal and definition of a “windability factor” allowing to compare results of different cable geometries
F. Lackner, overview wound conductor tests

8. Material characterization
From: C. Scheuerlein, F. Lackner, F. Savary, B. Rehmer, M. Finn, P. Uhlemann, “Mechanical properties of the HL-LHC 11 Tesla Nb3Sn magnet constituent materials”, IEEE Trans. Appl. Supercond., 27(4), (2017), , DOI /TASC
Tomographic characterisation of Nb3Sn cables and coils
Tribology (friction coefficients, effect of coatings)
Nb3Sn strain state distribution in 11 T coils
Thermomechanical properties of magnet materials
Temperature dependent elastic properties (0 to 1000 K)
Thermal expansion ( K)
Non-linear stress-strain behaviour
Anisotropic mechanical properties
11T dipole cross-section
Technical Seminar - MSC