J Fleiter A Bonasia B Bordini and A Ballarino 17 th January 2017 US EuroCirCol cable meeting Outline Accelerator magnets cable design Nb 3 Sn cable geometry HLLHC Cables specs 1 ID: 1025010
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1. Rutherford cable design approach and experience at CERNJ. Fleiter, A. Bonasia, B. Bordini and A. Ballarino 17th January 2017US-EuroCirCol cable meeting
2. OutlineAccelerator magnets cable designNb3Sn cable geometryHL-LHC Cables specs 1st generationPIT cable Ic degradation vs. thin edge compactionHL-LHC Cables specs final geometryFRESCA2 and ERMC cablesTheoretical Nb3Sn cable width Nb3Sn facet dimensionCable ProductionSummary
3. Accelerator Magnets Cable DesignNb-Ti cables: LHC cables, LHC cored cable, MCBX and MQXF bus barNb3Sn cables: HL-LHC,FRESCA2 and SMC (next slides)
4. HL-LHC Wires Technical SpecsSeries conductor:11 T RRP 108/127MQXF RRP 108/127 and PIT 192
5. HL-LHC cables Specs: 1st Generation 5Performances of 1st generation cable geometry:RRP: Ic degradation lower than 5% and RRR of extr. strands>100PIT (old layout): Ic degradation of 6-10%, with RRR down to 60 for 11T
6. PIT Cable Ic degradation vs. cable thicknessTo enhance the Ic and RRR retention of the PIT conductor after cabling, a second iteration on cable geometry was launched.PIT wire Ic reduction measured to be lower than 5% if rolling compaction less than 15% (t=1-t/2d)Production of cables (mainly PIT) with different Keystone angles and mid thicknesses, resulting in thin edge compaction in the range 12.5-18%. Compaction at cable thick edge was not reduced to avoid cable instability during winding. 6
7. PIT Ic degradation vs. cable thicknessPIT Cable Ic degradation less than 5%, if cable thin edge compaction less than 15.9% RRP cables are not sensitive to cable thin edge compaction (in the range 14-18%)Reduction of thin edge compaction is beneficial to the RRR of RRP and PIT cables Cable degradation also depends on width compaction and pitch angle (shear stress)7
8. HL-LHC: Final Cable GeometryMQXF cables: same geometry for PIT and RRP => Keystone of 0.4°11 T RRP cables with the 1st generation geometry=>Keystone of 0.79°11 T PIT cables with reduced Keystone angle of =>Keystone of 0.5°8
9. FRESCA2 Nb3Sn Cable40 strands cable made from 1 mm diam. PIT 192 or RRP 132/169 wiresERMC cable => Fresca2 cable with a core: RRP 120/127 or 150/169=>FRESCA 2 cable performances:RRP cables: Ic degradation <3% with RRR> 200PIT cables: Ic degradation >5% with RRR>1009
10. Cable Width DesignThe target cable width is empirically [1] found to be described by:HL-LHC cable width better described with 0.24 coefficient:10[1] D.R. Dietderich and A. Godeke, Cryogenics 48 (2008) 331–3400.72d 0.24d
11. Facet dimensionsRegular and moderate aspect ratio of facet are required to achieve low Ic and low RRR degradation. yx D.R. Dietderich et al., Cryogenics 48 (2008) 331–340
12. Facet of Nb3Sn cablesPITFRESCA2RRPMQXF PITthick edgethin edgeMQXF RRPthick edgethin edge11 T RRPthin edgethick edge
13. CERN Rutherford Cabling machine40 spools cabling machine with active regulation of strand tension (~20-70N)Preventive maintenance was performed in 2016 in order to improve the regulation of the strands mechanical tension. Motors, drivers and force transducers ( 40 of each) were replaced. Upgrade of the strand tension monitoring system: Record at 50 Hz instead of 2.5 Hz
14. Cable production plan established in accordance with strand delivery and requirements for coils winding Strategic stock of HL-LHC cables: buffer of 4 fully qualified cables – to compensate for unforeseen stop of production (cabling machine, QC equipment, delay in measurements…)Cabling of multiple unit length during same cabling run possible by using:Long piece length of conductors (e.g. 2 UL)Mechanical junction, developed by Angelo Bonasia (e.g. 2-4 UL)14Cable Production
15. Control of cable geometry along full UL is crucial to achieve good performances. Relative changes of cable dimensions are monitored on line with the production:Cable dimensions: thickness, width and Keystone measured and monitored online with the Cable Measuring Machine (CMM) (see next slides)Cable Faces Inspection System (CFIS): detect crossovers, abnormal flattening of wires or deviation from its nominal shape and inclusions. Same system as for LHCCable Edges Inspection System (CEIS): measure facets dimension, New system, implemented on production line by A. Gharib and A. Bonasia in 2016. (see next slides)Strand Tension Monitoring System: monitoring and recording of mechanical tension applied on each individual strand. New system, (see next slides)15Cable Homogeneity
16. Cable Dimensions Cable thickness, width and keystone angle measured online with the CMM: stringent control on cable dimensions.Same system used as for LHC A 10 stack measurement is performed at the beginning of each cabling run, to determinate the absolute value of the cable mid-thickness.
17. Facet Dimensions Dimensions of each facets (at thin and thick edges) over full cable length are measured since mid 2016. Measurement performed by Keyence CV-X vision system equipped with camerasThreshold of acceptable facet dimensionsSave photograph of facets with non conformity for off line analysis
18. Facet Dimensions Limited oscillation (<0.15 mm PP) of facet dimension during productionArtefact spikes in facet dimensions due to brightness difference on the facet or on light reflexionNon conformity determined by operator based on photographs and visual inspection if needed
19. Mechanical Tension on single strandsGood strand regulation is crucial to produce good quality cablesA new system recording at 50 Hz the mechanical tension applied on each single strands in operation since 2016Useful tool for the commissioning of the machine after maintenance Useful tool to detect abnormal strand tensionSystematic recording of data during cable production
20. Large variety of cable design (in both Nb3Sn and Nb-Ti) developed and produced at CERNA correlation between the Rutherford cable thin edge compaction and the strand Ic degradation was established for PIT conductorsTo maintain the Ic degradation to less than 5%, the QXF and the 11 T cable thin edge compaction made of PIT conductors shall be lower than respectively 15.5% and 15.9%. Based on these results, new baseline geometries for the Rutherford cables of 11 T and QXF magnets have been proposed.Reduction of cable thin edge compaction is beneficial to the RRR of both RRP and PIT cables. Cable design should account for conductor sensitivity to strain and shear stress.Cable design is an iterative process between strand development and magnet design.20Summary
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