Workshop Accelerator magnet superconductors, design and optimization

208 Pages·2009·17.9 MB·English

CERN–2009–01
CARE–Conf–08–029–HHH
19January2009
ORGANISATION EUROP(cid:131)ENNE POUR LA RECHERCHE NUCL(cid:131)AIRE
CERN
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH
WAMSDO Workshop
Accelerator magnet superconductors,
design and optimization
CERN, Geneva, Switzerland, 19–23 May 2008
Proceedings
Editor: E. Todesco
GENEVA
2009
CERN–300copiesprinted–January2009
Abstract
This report contains the proceedings of the CARE-HHH-AMT Workshop on Accelerator Magnet Supercon-
ductors,DesignandOptimization(WAMSDO)heldatCERNfrom19to23May2008. Theneedsintermsof
superconducting magnets for the accelerator projects were discussed, mainly for the LHC interaction regions
andinjectorupgrades, andfortheGSIFAIRcomplex. Thefirstpartoftheworkshopfocusedonthedevelop-
mentofsuperconductorandcables,i.e.,low-lossNb-Ticables,Nb Snandhigh-temperaturesuperconductors.
3
An industry session summarized the actual plans and status of the activities in the main European industries.
Then, a worldwide status of the high field magnets programme was presented. A special session was devoted
to fast cycled magnets, including FAIR facilities and LHC injector upgrades. A final session focused on the
optimizationmethodsandnumericaltoolsformagnetdesign.
iii

Preface
Thescience(or, asmany wouldsay, theart)ofsuperconductingmagnetsfor accelerators reliesonknowl-
edgeofseveraldifferentfields,suchaselectromagnetism,mechanicsandmaterialscience. Thisisthethirdand
last of the workshops on magnet design organized in the framework of the European Programme FP6 by the
CARE-HHHnetwork. Thefirstworkshop,WAMS,wasmorefocusedonsuperconductors,andthesecondone,
WAMDO, rather on magnet design and optimization. In this third workshop we include aspects concerning
both magnet design and superconductor development, to describe the present status and to draw perspectives
forfutureR&Dactivities.
Magnetrequirements
The opening session of the workshop was devoted to the magnet requirements coming from current or future
projects. The possibilities for a LHC luminosity upgrade have been studied for several years, requiring the
difficult task of identifying the LHC luminosity bottlenecks before having the first collisions. The unanimous
opinion is that the present 70 mm aperture of the interaction region quadrupoles is too small, and that larger-
aperturequadrupolesareneeded. Theupgradehasrecentlybeensplitintotwophases: thefirstone,scheduled
for2013,requires120mmaperture10-m-longquadrupolesinNb-Ti(seethecontributionofR.Ostojic,p. 1).
Thisfirstphaseaimsatanincreaseofafactor2.5withrespecttonominalluminosity,i.e.,2.5 1034cm 2s 1.
− −
×
Half of this increase would come from the stronger focusing (β = 0.25 m instead of 0.55 m) allowed by the
∗
larger-aperturequadrupoles,andtheotherhalffromanincreaseofthebunchintensity. Asecondphasewould
pushthefocusingtothelimitgivenbytheNb Sntechnology,i.e.,β = 0.15m,throughquadrupoleswithan
3 ∗
even larger aperture of 130–150 mm. This quadrupole aperture is somewhat larger than the original proposal
made by the U.S. LHC Accelerator Research Program (LARP), which considered 90 mm aperture magnets.
Today several 90 mm aperture models are being built, successfully validating the technology, and a 120 mm
aperturequadrupole,whichcouldbeusedasaspareforPhaseI,isinthedesignphase.
The upgrade of the chain of the LHC injectors has also been the object of a long series of studies: today,
LINAC4hasjuststartedthecivilengineeringworksandaconceptualdesignforthePSupgrade(PS2)isbeing
finalized. EventhoughthepresentbaselineforthePS2considersnormalconductingmagnets,asuperferricop-
tionisstillonthetable. ThisoptioncouldalsobeinterestingforafutureupgradeoftheSPS.Thisrequirement
ofrelativelylowfield(2–4T),fastcyclingmagnetsalsocomesfromtheconstructionofSIS100andSIS300
inGSI,Darmstadt. Bothasuperferricoptionandastandardcosθ designwithlowlossesarebeingconsidered.
These magnets could offer a reliable and more environmentally friendly alternative to the normal conducting
technology.
Inordertotestcablesusedforsuperconductingmagnets, oneneedsabackgroundmagneticfieldwhichis
usually generated by solenoids and/or dipoles. These magnets used in test facilities need a large aperture to
house the samples. At CERN, a replacement of the FRESCA facility with a 100 mm aperture dipole in the
rangeof13–15T,makinguseoftheNEDcable,isunderstudy.
For a linear collider such as the ILC or CLIC, a large set of superconducting magnets is foreseen (see the
slidesofM.Tartagliaavailableontheconferencewebsitehttp://indico.cern.ch/conferenceDisplay.
py?confId=28832): forexample,theforeseenILChardwarezooincludesquadrupoles,steeringdipoles,wig-
glers and undulators; in most cases the chosen option is the superferric one. Future projects such as muon
collidersorneutrinofactoriespresentthechallengingfeatureofhavingalargeradiationloadinthebeammid-
plane: thiscouldrequireinnovativesolutionsforthemagnetdesignsuchastheopenmid-planeoption,strongly
supported by R. Gupta in recent years. The Farthest Energy Frontier (FEF) which is conceivable today with
presenttechnology,infrastructureandcostslimitationsistheLHCdoubler(seetheslidesofL.Evansavailable
v
ontheconferencewebsitehttp://indico.cern.ch/conferenceDisplay.py?confId=28832). Thisnew
machine,makinguseofmostoftheLHCinfrastructure,wouldrequire15TdipolesinNb Snwithanaperture
3
ofabout40mm. TheLBNLmodelHD2,recentlytested,hasparameterswhichfallinthisrange.
ThefirstresultsfromLHCphysicswillbeanextremelyimportantpieceofinformationtohelpunderstand
wheretogo.
Materials,strandsandcables
The research on superconductors is focused on several issues. For the Nb-Ti, which has been the workhorse
for accelerator magnets for 30 years, the main research line aims at low-loss cables for fast cycling magnets.
Thetopicoflossesinsuperconductingfastcyclingmagnetsisstillfarfrombeingclosed,boththeoreticallyand
from a manufacturing point of view. The main challenge is to find a strand layout that can minimize losses,
achievethenecessaryJ ,andthatcanbemanufactured. Gettingastrandwiththinnerandthinnerfilamentsize
c
is not the only issue: considerations about the transverse resistivity, the geometry of the cable, and the design
ofthewholemagnetarealsorelevant(seethecontributionsbyM.N.Wilson,G.Volpini,U.Gambardella,and
V.Pantsyrny,pp. 8–23). Anextensionoftheworkonlow-losscablestoNb SnwaspresentedbyT.Collings,
3
p. 42.
Nb SnhasforalongtimebeenconsideredasthenaturalsuccessorofNb-Ti,allowingtoroughlydoublethe
3
fieldfrom8–10Tto15–20T,inthesamerangeoftemperatures(1.9–4.2K).Theprogressinthedevelopment
of Nb Sn cables towards larger critical currents has been impressive: in the past ten years the current density
3
inthenon-copperparthasdoubled(seetheA.GodekeandT.Boutboulcontributions,pp. 24–29). Atthesame
time, recent analyses show that very large critical current densities can produce self-field instabilities limiting
theperformances(seethecontributionbyB.Bordini,p. 51);thisanalysisaccountsforthereducedperformance
of LARP quadrupoles at 1.9 K. This could be the sign that the quest for larger and larger current densities at
12–15Thasreacheditsnaturallimit,orthat,ifonewantstostillpursuethisdirection,newparametershaveto
betakenintoaccountinthecabledesign.
One of the main issues of Nb Sn is its sensitivity to strain. Several techniques can be used to study this
3
complex issue and many other characteristics, related both to the strand layout and to the magnet design and
optimization. Metallographic techniques, calorimetric analysis, synchrotron radiation, and measurements of
critical current under strain have been used for Nb Sn strands for the ITER and for the NED projects (see
3
contributionsbyM.Jewell,C.Scheuerlein,andB.Seeberpp. 30–41).
A special cable layout used for fusion projects such as ITER is the so-called cable-in-conduit, aiming at
higher current and having a more efficient cooling with respect to the Rutherford cable used for accelerator
magnets. AfullreviewoftheperformanceofbothNb-TiandNb Sncable-in-conduitusedinITERisgivenin
3
thecontributionofR.Wesche,p. 68.
For accelerator magnets, and even more for fusion magnets, the issue of radiation resistance is critical.
A complete overview of the radiation resistance of Nb-Ti and Nb Sn, focused on a particle spectrum relative
3
to the debris of the collision in the LHC upgrade, can be found in the contribution by R. Flu¨kiger, p. 55.
With the present knowledge of radiation loads, both Nb-Ti and Nb Sn should not suffer from a degradation
3
of performance over the expected lifetime of the magnets. The limitation to the magnet lifetime would rather
comefromothermaterialssuchastheplasticusedforendspacersortheepoxyusedforNb Snimpregnation.
3
Newsuperconductorsarediscoveredeveryyear,andsomematerialshaveshownimpressiveprogress. This
isthecaseofMgB ,amaterialwhichwasdiscoveredin2001,whosefieldrangeis2–4Tat20Kand5–10T
2
at 4.2 K. The current industrial developments aiming at having long cables with large current densities are
described in the contributions of G. Grasso and G. Giunchi, pp. 78–88. High-temperature superconductors
have been used for power lines and current leads in the LHC. The current state-of-the-art of HTS materials,
mainlyBi-2212andYBaCuO,andtheirapplications,isgiveninthecontributionsofP.TixadorandofM.Noe,
pp.89–97.
vi
High-fieldmagnets
The results on high-field magnets constitute the core of these proceedings. The present design for the Nb-Ti
upgradeoftheLHCinteractionquadrupolesispresentedbyP.Fessia,p. 101. Threedifferentprojectsaimingat
constructingaccelerator-qualityNb SnmagnetsareunderwayintheU.S.TheLARPcollaborationisbuilding
3
large-aperture quadrupoles for the LHC interaction region upgrade, including several short models to test two
mechanical structures, and a 3.4-m-long model, see the contributions of P. Ferracin, P. Wanderer, S. Caspi,
and H. Felice, pp. 105–122. FNAL is developing high-field long dipoles, and LBNL has built and tested a
short dipole based on a block coil and a bladder and keys structure, reaching a bore field of 13.5 T, see the
contributionofP.Ferracin,p.105.
Europe, mainly busy during the past ten years with LHC construction, started the NED programme in
2004 to develop a Nb Sn conductor within European industry. The programme is now successfully ending:
3
a new initiative has been financed by the EU to build a large-aperture dipole of 13 T with a large aperture to
upgradethecableteststationatCERN,seethecontributionofG.DeRijk,p. 128. InCEA-Saclay,theNb Sn
3
programmeaimingatbuildinganLHC-likequadrupolewithNb Sncoilsisslowlybutsteadilyprogressing: the
3
finalmagnettestshouldbecarriedoutin2008(seethecontributionofJ.M.Rifflet,p. 131). Japanisexploring
the possibility of building accelerator magnets with Nb Al, a conductor whose critical surface is not far from
3
Nb Snbutwhichhasanegligibledegradationduetostrain(seethecontributionofK.Sasaki,p. 132).
3
Othermagnetprojects
To break the barrier of 20 T one needs to go to high-temperature superconductors. Today, these materials
have been used to construct high-field solenoids; the present state-of-the-art is given in the contribution by
D.Larbalestier,p.136.
A recent project which is in the final stage, and will be commissioned in the next months, is the JPARC
facilityforneutrinophysics. Itmakesuseofcombined-functionsuperconductingmagnets,whichareafirstin
termsofmagnetdesign. Thisoptionisofgreatinterestforallmachineswherecompactnessisarelevantissue.
Fastcycledmagnets
In the past, low-energy machines have always made use of normal conducting magnets. Indeed, during the
past years the GSI laboratory has chosen a superconductive technology for a low-energy machine, and su-
perferric or superconductive options are being considered for several machines, including the LHC injectors.
Thepossibilityofhavingbeamtransferlinesmadewithsuperferricmagnetsisexploredinthecontributionof
H.Piekarz,p.142,includingboththeLTSandtheHTSoptions. Thesuperferricmagnetsthatwillbeusedfor
theSIS100arepresentedbyE.Fischer,p. 147. TheDiscorapproject,aimingatbuildingalow-losscosθcurved
dipoleinthe4TrangefortheSIS300facilityispresentedinthecontributionsbyP.FabbricatoreandM.Sorbi,
pp.157–162.
Magnetdesignoptimizationandtest
Magnet design relies on the use of several codes for computing and optimizing the electromagnetic layout,
mechanicalstructure, losses, andprotection. TheRoxiecode, whichhastakenanimportantplaceinthecom-
munityofacceleratormagnetdesigners,hasrecentlyincludedquenchanalysis. Anoutlineofthenewfeatures
andofthefuturedevelopmentsisgivenbyB.Auchmann,p. 163. Ontheotherhand,inthephaseofconceptual
designitcanbeusefultohavealsoanalyticalorsemi-analyticalapproachesforafastexplorationoftheparam-
eterspace. Asummaryofsemi-analyticalestimatesfortheshortsamplelimit, Lorentzstresses, andmagnetic
energy as a function of the main coil parameters is given by E. Todesco, p. 168. The state-of-the-art of the
magneticmeasurementsatCERNisgivenbyM.Buzio, p.172. ThetwofinalpapersbySchnizeraredevoted
tothemeasurementsofSIS100andSIS300magnets,andtotheiroptimization.
Furtherinformationontheworkshopcanbeaccessedfromitshomewebsite,
http://indico.cern.ch/conferenceDisplay.py?confId=28832.
vii
Conferenceorganizingcommittee: L.Bottura,G.DeRijk,J.Kerby,L.Rossi,E.Todesco
Theseproceedingshavebeenpublishedinpaperandelectronicform. Thepapercopyisinblackandwhite;
theelectronicversioncontainscolourpictures. Electroniccopiescanberetrievedthrough:
http://care-hhh.web.cern.ch/CARE-HHH/LUMI-06/Proceedings/proceedings_lumi06.htm
Thecompilationoftheseproceedingswouldnothavebeenpossiblewithoutthehelpoftheconvenersand
speakers. TheorganizationalsupportbytheworkshopsecretaryClaudineBosteelsisalsogratefullyacknowl-
edged. In particular, we would like to thank all the participants for their stimulating contributions and lively
discussions.
TheWAMSDOworkshopwassponsoredandsupportedbytheEuropeanCommunity-ResearchInfrastruc-
ture Activity under the FP6 “Structuring the European Research Area” programme (CARE, contract number
RII3-CT-2003-506395).
Geneva,15December2008
E.Todesco
viii
Contents
Preface ........................................................................................... v
RequirementsformagnetR&D
(convener: P.Lebrun)
UpgradescenariofortheLHCcomplex1 L.Evans
LHCinteractionregionupgrade-phaseI R.Ostojic ................................................1
MagnetsforLinacs1 M.Tartaglia
Magnetsforneutrinoandmuonphysics1 A.Blondel
MagnetR&DformuoncollidersatFermilab1 M.Lamm
Low-temperaturesuperconductors
(conveners: R.Flu¨kiger,L.Bottura,T.Nakamoto)
Advancesinlow-lossNb-Tistrandandcable M.Wilson ............................................8
Low-losswiredesignfortheDiSCoRaPdipole G.Volpini .........................................13
MagnetizationmeasurementsandanalysesonthinfilamentNb-TiwiresforSIS300synchrotron
superconductingdipoles U.Gambardella ........................................................16
AdvancesinITER-relevantNb-TiandNb Snstrandsandlow-lossNb-TistrandsinRF V.Pantsyrny ...19
3
AdvancesinNb Snperformance A.Godeke ......................................................24
3
OptimizationoftheheattreatmentforNEDPITNb Snstrand T.Boutboul ..........................28
3
MetallographicinvestigationoffracturebehaviorinITER-styleNb Snsuperconductingstrands
3
M.Jewell .......................................................................................30
DevelopmentofhighcurrentNb SnRutherfordcables1 A.Godeke
3
SynchrotronradiationtechniquesforthecharacterizationofNb Snsuperconductors C.Scheuerlein ....33
3
ElectromechanicalbehaviourofPITNb SnwiresforNED B.Seeber ...............................37
3
InterstrandcouplingandmagnetizationinNb SnRutherfordcables T.Collings ......................42
3
StabilityinNb Sn1 M.Sumption
3
Self-fieldinstabilitiesinhigh-J Nb Snstrands: theeffectofcopperRRR B.Bordini .................51
c 3
Axialandtransversestress-straincharacterizationofRRPNb Snstrand2 A.Nijhuis
3
IrradiationeffectsinlowT superconductors R.Flu¨kiger ..........................................55
c
ResultsofconductortestinginSULTAN:areview R.Wesche ......................................68
CablestabilityforGSIlikemagnets1 G.Willering
1Apaperwasnotsubmittedtotheproceedings.However,theslidespresentedareavailableinelectronicformathttp://indico.
cern.ch/conferenceDisplay.py?confId=28832.
2PaperpublishedasA.Nijhuis,Y.Ilyin,W.Abbas,‘Axialandtransversestress-straincharacterisationoftheEUdipolehighcurrent
densityNb3Snstrand’,Supercond.Sci.Technol.21(2008)065001.
ix
High-temperaturesuperconductors
(conveners: A.BallarinoandA.Siemko)
CurrentMgB wireperformanceandtheirindustrialdevelopment G.Grasso ........................78
2
ThereactiveMg-liquidinfiltrationtoobtainlongsuperconductingMgB cables G.Giunchi ...........83
2
AdvancesinHTSmaterials P.Tixador ...........................................................89
HTSapplications M.Noe .......................................................................94
Wind-and-reactBi-2212acceleratormagnettechnology1 G.Sabbi
Industrysession
(convener: H.TenKate)
LuvataCompanyPresentation1 A.Baldini
EAScompanypresentation1 M.Thoener
StatusandperspectivesatBabcockNoell W.Walter ...............................................98
ManufacturingofthefirstSIS100fullsize-model1 G.Sikler
ASGcompany1 R.Penco
High-fieldmagnets
(conveners: E.TodescoandG.L.Sabbi)
MagnetsforthephaseILHCupgrade P.Fessia ................................................. 101
Nb SnacceleratormagnetandsuperconductorR&DatFermilab1 A.Zlobin
3
TestresultsofHD2,ahighfieldNb Sndipolewitha36mmbore P.Ferracin ......................105
3
Nb SnmagnetdevelopmentforLHCluminosityupgrade P.Wanderer .............................108
3
Shell-basedsupportstructuresforNb Snacceleratorquadrupolemagnets P.Ferracin ...............114
3
TestsresultsofNb Snquadrupolemagnetsusingashell-basedsupportstructure S.Caspi ........... 117
3
Nb SnquadrupoledesignsfortheLHCupgrades H.Felice .......................................120
3
15Tandbeyond-Dipolesandquadrupoles G.Sabbi ............................................123
ThehighfieldmagnetprograminEurope G.DeRijk ............................................ 128
Nb SnquadrupoledevelopmentatCEA/Saclay J.M.Rifflet ......................................131
3
Nb AlhighfieldacceleratormagnetR&D K.Sasaki .............................................132
3
Othermagnetprojects
(convener: J.Kerby)
Fusionvsaccelerator(ITERandDAprograms)1 A.Vostner
TheBi-2212conductorandmagnetprogramattheNationalHighMagneticFieldLaboratory
D.Larbalestier ................................................................................136
StatusofthesuperconductingmagnetsystemfortheJ-PARCneutrinobeamline T.Nakamoto .......139
1Apaperwasnotsubmittedtotheproceedings.However,theslidespresentedareavailableinelectronicformathttp://indico.
cern.ch/conferenceDisplay.py?confId=28832.
x