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R. Bonomi R. Kleindienst J. Munilla Lopez M. Chaibi E. Rogez

CASE STUDY 1: Group 1C. Nb 3 Sn Quadrupole Magnet. R. Bonomi R. Kleindienst J. Munilla Lopez M. Chaibi E. Rogez. CERN Accelerator School, Erice 2013. GOAL. LHC upgrade requires quadrupole magnets with larger apperture .

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R. Bonomi R. Kleindienst J. Munilla Lopez M. Chaibi E. Rogez

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  1. CASE STUDY 1: Group 1C Nb3SnQuadrupole Magnet R. Bonomi R. Kleindienst J. Munilla Lopez M. Chaibi E. Rogez CERN Accelerator School, Erice 2013

  2. GOAL • LHC upgrade requires quadrupole magnets with larger apperture. • Design proposal for Nb3Sn superconducting quadrupole with 150 mm aperture for operation at 1.9 K. • Study includes coil design, magnetic and mechanical properties. CERN Accelerator School, Erice 2013

  3. COIL WIDTH • The magneticgradientdepends on thewidthofthecoil • Adding additional coilwidthleadstodiminishingrewards • A relativelythin design was chosenas a compromisebetweencostandgradient -> 2 coils of 10 mm width • Twolayerschosentoallowmorepossibilities in design forminimizingfielderrors 3 CERN Accelerator School, Erice 2013

  4. CABLE PARAMETERS t w 4 CERN Accelerator School, Erice 2013

  5. LOAD LINE • Loadline plottedforourconfiguration • Short sample and operational parameterscomputed • Higher fieldgradientpossiblewith(118 T/m vs. 83 T/m) • Temperaturestabilitymarginhigherby~3K CERN Accelerator School, Erice 2013

  6. COIL LAYOUT • Coil layout used to compensate higher order multipoles • Each sector used to cancel out next non-forbiddenorder CERN Accelerator School, Erice 2013

  7. MECHANICAL DESIGN • Mechanical Design shouldavoidtensile stress • Thinshellapproximationused(26%) • Forces computedusingformula: • Iron yokesupporting 90% ofIss • Collarthickness 20 mm for a maximum stress of 70 MPa • Thicknessofshrinkingcylinder12 mm forupto 100 MPa -> Useof Aluminium possible CERN Accelerator School, Erice 2013

  8. ISSUES

  9. ISSUES: YBCO vs. Bi2212 • Both are cuprites, the SC isconfinedtotheCuO plane, mechanism not fullyunderstood • In bothcases high criticalcurrentin singlecrystals, howeverseverlyloweredby grain boundries! • Bi2212, unlike YBCO canbeformedtoroundwiresusing power in tubeprocess • Compactionandheatinghave large impact on SC-properties, large parameterspacetooptimize CERN Accelerator School, Erice 2013

  10. ISSUES: SC COIL DESIGN • The block-coil geometry naturally suppresses extrinsic losses, which typically constitute ~half of all ac losses, which are reduced in the block-coil geometry by the aspect ratio of the cable, typically 10:1 • The simple equivalent block-coil design requires 20% less superconductor than the cosθ design of the same aperture and field strength. • Furthermore, one of the characteristics of the block-coil model is its scalability. After having studied the basic characteristics of a small aperture block coil magnets, an attempt could be made to design a large aperture magnet in a fast and efficient way by scaling up both the dimension of the aperture and the number of the blocks. CERN Accelerator School, Erice 2013

  11. ISSUES: ASSEMBLY PROCEDURE • Pre-stress isneededtobesurethatnotensilestresses will beapplied on thecoil • Pre-stress isusuallyloweredwhenthemagnetiscooled down • Enoughamountofpre-stress toremainatcompressivestateofstressesateveryoperationconditionisneeded. • As a generalrule, pre-stress shouldbeassmallasneededtoaccomplishthiscondition, plus somesafetymarginofsomeMpaastypicalvalue (0-30 MPa) CERN Accelerator School, Erice 2013

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