After a number of years of operation at nominal parameters, the LHC will be upgraded to a higher luminosity. This paper discusses the possibility of using a limited number of Nb{sub 3}Sn quadrupoles for hybrid optics layouts for the LHC Phase I luminosity upgrades with both NbTi and Nb{sub 3}Sn quadrupoles. Magnet parameters and issues related to using Nb{sub 3}Sn quadrupoles including aperture, gradient, magnetic length, field quality, operation margin, et cetera are discussed

De Maria, R.

Johnstone, J. A.

Kashikhin, V. V.

Mokhov, N. V.

Peggs, S.

Rakhno, I. L.

Robert-Demolaize, G.

Wanderer, P.

Zlobin, A. V.

UNT Digital Library

1  Fermilab-Conf-08-204-APC-TD   June 2008Nb3Sn QUADRUPOLES IN THE LHC IR PHASE I UPGRADE*†A.V. Zlobin, J.A. Johnstone, V.V. Kashikhin, N.V. Mokhov, I.L. RakhnoFNAL, Batavia, IL 60510, U.S.A.R. de Maria, S. Peggs, G. Robert-Demolaize, P. WandererBNL, Upton, NY 11973, U.S.A.AbstractAfter a number of years of operation at nominal parameters, the LHC will be upgraded to a higher luminosity. Thispaper discusses the possibility of using a limited number of Nb3Sn quadrupoles for hybrid optics layouts for the LHCPhase  I  luminosity  upgrades  with  both  NbTi  and Nb3Sn quadrupoles. Magnet parameters and issues related to usingNb3Sn quadrupoles including aperture, gradient, magnetic length, field quality, operation margin, et cetera arediscussed.*Work supported by Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359 with the U.S.Department of Energy.†Presented paper at the 11th European Particle Accelerator Conference, Genoa, Italy, June 23-27, 2008.2_________________________________________* This work was supported by the U.S. Department of Energy.†zlobin@fnal.govNb3Sn QUADRUPOLES IN THE LHC IR PHASE I UPGRADE*       A.V. Zlobin†,  J.A. Johnstone, V.V. Kashikhin, N.V. Mokhov, I.L. Rakhno, FNAL, USA,       R.de Maria, S. Peggs, G. Robert-Demolaize, P. Wanderer, BNL, USA.AbstractAfter a number of years of operation at nominalparameters, the LHC will be upgraded for higherluminosity. This paper discusses the possibility of using alimited number of Nb3Sn quadrupoles for hybrid opticslayouts for the LHC Phase I luminosity upgrades withboth  NbTi  and  Nb3Sn quadrupoles. Magnet parametersand issues related to using Nb3Sn quadrupoles includingaperture, gradient, magnetic length, field quality,operation margin, et cetera are discussed.INTRODUCTIONCERN is planning to upgrade two LHC IRs in twophases with a target luminosity for Phase I of ~2.5·1034cm-2s-1 and up to 1035 cm-2s-1 for Phase II [1]. In Phase Ithe baseline 70-mm NbTi low-beta quadrupoles willnominally be replaced with larger aperture NbTi magnetsand in Phase II with higher performance Nb3Sn magnets.U.S.-LARP  is  working  on  the  development  of  largeaperture high-performance Nb3Sn quadrupoles for theLHC Phase II upgrade [2]. Recent progress with Nb3Snmagnets suggests the possibility of using Nb3Snquadrupoles in the Phase I upgrade, improving theluminosity through an early demonstration of Nb3Snmagnet technology in a real accelerator environment.The final version of Phase I optics and magnetparameters have not been chosen yet. Two preferableoptics layouts, Lowbetamax (LBM) and Symmetric(SYM), based on large aperture NbTi quadrupoles arebeing studied at CERN [3]. LARP is participating in theoptimization and study of Phase I upgrade scenariosexploring the advantages and feasibility of using Nb3Snquadrupoles  to  replace  either  the  Q1  or  Q3  NbTiquadrupoles. The study includes optics, magnetparameters, operating margins and tracking. The results ofLBM and SYM optics and radiation heat depositionanalysis  are  reported  in  [4].  The  main  NbTi  quadrupoleparameters required for these two cases are shown inTable 1. This paper discusses the parameters of Nb3Snmagnets for hybrid optics layouts for the Phase I upgrade.Table 1: NbTi quadrupole parameters for LowBetaMax(LBM) and Symmetric (SYM) Phase I optics.LBM SYMCoilID, mmLmag,mGnom,T/mCoilID, mmLmag,mGnom,T/mQ1 90 7.060 167.21 130 9.200 121.86Q2a 130 7.787 -121.37 130 7.800 -121.86Q2b 130 7.787 -121.37 130 7.800 -121.86Q3 130 8.711 121.37 130 9.200 121.86Nb3Sn QUADRUPOLES FOR PHASE ITo  replace  NbTi  magnets  in  Phase  I  optics  withoutimpact on the triplet optical functions and other systems,Nb3Sn magnets should be completely compatible withtriplet vacuum, cryogenics, power and quench protectionsystems.  In particular, Nb3Sn magnets should provide thesame focusing strength as the relevant NbTi quadrupolesat the same operation current (~12.5 kA for NbTiquadrupoles based on LHC cables [5]).  The operationmargin of Nb3Sn quadrupoles has to be increased withrespect to the baseline NbTi quadrupoles to compensatefor the earlier state of this new technology.Magnet aperture and parametersDesign studies were performed for Nb3Sn quadrupoleswith apertures ranging from 90 to 134 mm and maximumfield gradients at least 20% above the nominal gradient inthe NbTi magnets presented in Table 1. Magnetparameters are summarized in Table 2.Table 2: Basic parameters of Nb3Sn IR quadrupoles for LHC Phase I upgrade.TQC-90 IRQ-90 IRQ-110 IRQ-110 IRQ-130 HQ-134Coil cross-sectionCoil ID, mm 90 110 130 134Strand OD, mm 0.7 0.7 0.7 0.8 0.7 0.8Cable width,mm 10.05 15.14 15.10 15.15 15.10 15.15Bmax(1.9K), T 12.9 13.8 14.4 14.5 14.5 15.0Gmax(1.9K), T/m 248 268 229 229 193 193Gnom(12.5kA) 208.3 185.6 179.7 168.0 155.9 144.5Gmax/Gnom 1.19 1.44 1.28 1.37 1.24 1.34W(12.5kA),kJ/m 358 384 674 595 923 857Jcu, A/mm2 2407 1546 1585 1345 1585 13453Design options were limited by two-layer coils basedon a 15-mm wide Nb3Sn cable (comparable with the LHCNbTi cables). The magnet maximum field and fieldgradient were calculated for the Nb3Sn strands withJc(12T,4.2K)=2.5 kA/mm2. The parameters in Table 2characterize the relative complexity of different magnetdesigns and their operation at the nominal current. Thestored energy (and Lorentz forces) increases with magnetaperture, which complicates the magnet mechanicalstructure and the magnet quench protection.For comparison, the design parameters of the LARPtechnology quadrupoles of the TQ series [6]-[7] based on10-mm  wide  cable  are  also  presented.  Ten  1-m  longmodels of the TQS and TQC series have been fabricatedand tested. The maximum field gradient reached in thosemodels was on the level of 200-220 T/m, which is ~15-20% lower that the design values for these magnets at 1.9K. While the causes of magnet degradation are beinginvestigated, the present level of degradation has to beadded to the magnet operation margin. One can see thatIRQ-90, IRQ-110 and HQ-134 provide sufficientoperation margins required for Nb3Sn quadrupoles at thepresent time.Magnet lengthThe Nb3Sn magnet length is currently limited to 4meters. This limitation comes from the limited experiencewith long Nb3Sn coils which includes two 3.5-m longracetrack coils tested in a common coil configuration [8]and 2-m and 4-m long cos-theta coils tested in a mirrorconfiguration [9]. LARP is working on a 4-m longquadrupole  of  LQ  series  to  demonstrate  the  Nb3Sntechnology scale up for large aperture quadrupoles [10].Thus, the 8-9 m long NbTi Q1 or Q3 quadrupoles in bothPhase I optics layouts have to be replaced by two ~4-mlong or shorter Nb3Sn magnets with appropriate gradient.To study the magnetic coupling between two closelyplaced coils, the magnet end gradient and field harmonicswere calculated for two values of coil-to-coil gap. The gapof 50 mm corresponds to the minimal distance betweenthe coils installed in the same iron yoke. The gap of 250mm corresponds to the case of two independent coldmasses placed in the same cryostat.Fig. 1 shows the relative coil end position with a coil-to-coil gap of 50 mm. Figs. 2 and 3 show the variation ofmagnet gradient and b6 between magnets with coil-to-coilFigure 1: Coil end position with coil-to-coil gap of 50mm.gaps  of  50  and  250  mm.  As  can  be  seen,  in  both  casesthere is no magnetic coupling between the two coils.Thus, they should be considered as independent magnetsin optics and tracking analysis.0501001502002500 100 200 300 400 500 600 700Z (mm)G (T/m)50mm gap250mm gapFigure 2: Longitudinal variation of field gradient betweenmagnets.-50-40-30-20-1001020304050600 100 200 300 400 500 600 700Z (mm)b650mm gap250mm gapFigure 3: Longitudinal variation of b6 between magnets.Field qualityField quality and its reproducibility for Nb3Sn IRquadrupoles was estimated based on magneticmeasurements of five LARP TQ short models [11]. Thesystematic low-order harmonics and their RMS spread atthe reference radius equal to half of the coil aperture arereported in Table 3.Table 3: Systematic field harmonics and their RMSspread at Rref = 22.5 mm.Systematic RMSn bn an bn an3 -0.40 0.43 1.87 2.464 0.51 -1.56 1.10 3.425 0.81 3.81 3.55 3.746 -6.70 -0.27 0.35 0.707 0.02 -0.22 0.12 0.198 -0.02 -0.16 0.16 0.329 0.07 -0.14 0.11 0.1310 0.14 0.00 0.08 0.054The  harmonics  RMS  spread  in  Nb3Sn 90-mm TQmodels and NbTi 70-mm LHC IR quadrupoles of theHGQ series  [12]  are  plotted  in  Fig.  4.   A comparison ofTQ  and  HGQ  data  shows  that  the  RMS  spread  ofgeometrical harmonics in Nb3Sn quadrupoles is a factor of3 larger then the harmonics spread in NbTi quadrupoles.This is also consistent with the observation in Nb3Sndipole models [13].0.010.11102 4 6 8 10Harmonic numberSt. deviation, 10-4HGQ, anHGQ, bnTQ, anTQ, bnFigure  4:  Normal  bn and  skew  an random errors in 5Nb3Sn TQ and 8 NbTi HGQ models.Analysis of field quality in Nb3Sn model magnets (bothdipoles and quadrupoles) shows that they have quite largepersistent current effects in low-order allowed harmonicsdue to the large effective filament size in the state-of-the-art high-Jc Nb3Sn  strands.  However,  it  was  shown  thatthis effect can be reduced by reducing the Deff orcompensated using relatively simple passive correction[13]. The eddy current effects in present Nb3Sn modelsare also quite large and vary from magnet to magnet,which is likely due to inter-strand contact resistancevariations in the cable. This effect can be reduced byusing a stainless steel core inside the cable. The long-termdecay and snap-back effects were not observed in eitherof the Nb3Sn TQ models. This is different from the resultsof NbTi HGQ and MQXB magnets which exhibitedprominent decay and snap-back effects. However, it isconsistent with the absence of snap-back in other Nb3Snmagnets made of similar conductors [14].CONCLUSIONSDesigns and parameters of Nb3Sn quadrupoles withapertures from 90 mm up to 134 mm were studied.Quadrupoles with 90, 110 and 130 mm with largeoperation  margin  of  ~40%  were  used  in  optics  andoperation margin studies. The field quality of Nb3Snquadrupoles was estimated based on the data for five 90-mm LARP TQ models. Studies of the effects of fieldquality in Nb3Sn quadrupoles are in progress.The experience with TQ models suggests that the 90-mm design is most ready for use in the Phase I upgrade asQ1 in both LBM and SYM optics. Quadrupoles with 110-130 mm aperture can provide a larger aperture margin andcould be used as Q1 or Q3 in LBM or SYM optics.  The130-mm quadrupoles are the most complicated magnetswith the most challenging performance parameters. It isunlikely that they could be ready for installation in PhaseI on time. The 110-mm quadrupoles have sufficientaperture and operation margin, and more realisticoperation parameters. They have the greatest flexibilityfor installation in Phase I and would pave the way towardIR quadrupoles for the Phase II upgrade.REFERENCES[1] R. Ostojic, “Phased Approach to the LHC InsertionUpgrade and Magnet Challenges”, IR’07 mini-workshop, CARE-HHH-AMT, Frascati (Italy), 2007.[2] S. A. Gourlay et al.,  “Magnet R&D for the US LHCAccelerator Research Program”, IEEE Trans. onApplied Supercond., V. 16,  N2,  June 2006, p. 324.[3] R.  de  Maria,  “The  summary  of  optics  study  for  theLHC Phase I upgrade”, IR’07 mini-workshop,CARE-HHH-AMT, Frascati (Italy), 7-9 Nov 2007.[4] J.A. Johnstone et al., “Optics Implications ofImplementing Nb3Sn Magnets in the LHC Phase IUpgrade”, EPAC2008, Genoa (Italy), June 2008.[5] E. Todesco, “Magnet design issues for a 130 mmtriplet”, IR’07 mini-workshop, CARE-HHH-AMT,Frascati  (Italy), 7-9 Nov 2007.[6] R.C. Bossert et al.,  “Development and Test of LARPTechnological Quadrupole Models of TQC Series”,IEEE Trans. on Applied Supercond., V. 18, N2, June2008, p.175.[7] S. Caspi et al.,  “Test and Analysis of TechnologyQuadrupole Shell (TQS) Magnet Models for LARP”,IEEE Trans. on Applied Supercond., V. 18, N2, June2008, p.179.[8] P. Wanderer et al., “Construction and Test of 3.6 mNb3Sn Racetrack Coils for LARP”, IEEE Trans. onApplied Supercond., V. 18, N2, June 2008, p. 171.[9] F. Nobrega et al, “Nb3Sn Accelerator MagnetTechnology Scale-up using Cos-theta Dipole Coils”,IEEE Trans. on Applied Supercond., V. 18, N2, June2008, p. 273.[10]G. Ambrosio et al.,  “LARP Long Nb3Sn QuadrupoleDesign”, IEEE Trans. on Applied Supercond., V.18, N2, June 2008, p. 268.[11]G.V. Velev et al., “Field Quality Measurements andAnalysis of the LARP Technology QuadrupoleModels of TQC Series”, IEEE Trans. on AppliedSupercond., V. 18, N2, June 2008, p. 184.[12]N. Andreev et al., “Field Quality in Fermilab-builtModels of Quadrupole Magnets for the LHCInteraction Region”, IEEE Trans. on AppliedSupercond., V. 11, N1, March 2001, p. 1566.[13]V.V. Kashikhin et al., “Passive Correction of thePersistent Current Effect in Nb3Sn AcceleratorMagnets”, IEEE Trans. on Applied  Supercond.,V.13, N 2, June 2003, p.1270.[14]A.V. Zlobin et al., “Nb3Sn Accelerator MagnetTechnology R&D at Fermilab”, Proc. of PAC 2007,Albuquerque, NM, June 2007, pp. 482-484.

Nb3Sn quadrupoles in the LHC IR Phase I upgrade

After a number of years of operation at nominal parameters, the LHC will be upgraded for higher luminosity. This paper discusses the possibility of using a limited number of Nb{sub 3}Sn quadrupoles for hybrid optics layouts for the LHC Phase I luminosity upgrades with both NbTi and Nb{sub 3}Sn quadrupoles. Magnet parameters and issues related to using Nb{sub 3}Sn quadrupoles including aperture, gradient, magnetic length, field quality, operation margin, et cetera are discussed

Zlobin,A.

Johnstone, J.

Kashikhin, V.

Mokhov, N.

Rakhno, I.

deMaria, R.

Robert-Demolaize, F.

   BNL-81377-2008-CP     Nb3Sn Quadrupoles in the LHC IR Phase I Upgrade   A. Zlobin, J. Johnstone, V. Kashikhin, N. Mokhov, I. Rakhno (Fermilab)  R. Demaria, S. Peggs, F. Robert-Demolaize, P. Wanderer (BNL)   Presented at  11th European Particle Accelerator Conference (EPAC) Genoa, Italy June 23-27, 2008  July 30, 2008    Superconducting Magnet Division  Brookhaven National Laboratory P.O. Box 5000 Upton, NY 11973-5000 www.bnl.gov       Notice: This manuscript has been authored by employees of Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The publisher by accepting the manuscript for publication acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.   This preprint is intended for publication in a journal or proceedings.  Since changes may be made before publication, it may not be cited or reproduced without the author’s permission.                                   DISCLAIMER  This report was prepared as an account of work sponsored by an agency of the United States Government.  Neither the United States Government nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or any third party’s use or the results of such use of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof or its contractors or subcontractors.  The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.      2_________________________________________* This work was supported by the U.S. Department of Energy.†zlobin@fnal.govNb3Sn QUADRUPOLES IN THE LHC IR PHASE I UPGRADE*       A.V. Zlobin†,  J.A. Johnstone, V.V. Kashikhin, N.V. Mokhov, I.L. Rakhno, FNAL, USA,       R.de Maria, S. Peggs, G. Robert-Demolaize, P. Wanderer, BNL, USA.AbstractAfter a number of years of operation at nominalparameters, the LHC will be upgraded for higherluminosity. This paper discusses the possibility of using alimited number of Nb3Sn quadrupoles for hybrid opticslayouts for the LHC Phase I luminosity upgrades withboth  NbTi  and  Nb3Sn quadrupoles. Magnet parametersand issues related to using Nb3Sn quadrupoles includingaperture, gradient, magnetic length, field quality,operation margin, et cetera are discussed.INTRODUCTIONCERN is planning to upgrade two LHC IRs in twophases with a target luminosity for Phase I of ~2.5·1034cm-2s-1 and up to 1035 cm-2s-1 for Phase II [1]. In Phase Ithe baseline 70-mm NbTi low-beta quadrupoles willnominally be replaced with larger aperture NbTi magnetsand in Phase II with higher performance Nb3Sn magnets.U.S.-LARP  is  working  on  the  development  of  largeaperture high-performance Nb3Sn quadrupoles for theLHC Phase II upgrade [2]. Recent progress with Nb3Snmagnets suggests the possibility of using Nb3Snquadrupoles in the Phase I upgrade, improving theluminosity through an early demonstration of Nb3Snmagnet technology in a real accelerator environment.The final version of Phase I optics and magnetparameters have not been chosen yet. Two preferableoptics layouts, Lowbetamax (LBM) and Symmetric(SYM), based on large aperture NbTi quadrupoles arebeing studied at CERN [3]. LARP is participating in theoptimization and study of Phase I upgrade scenariosexploring the advantages and feasibility of using Nb3Snquadrupoles  to  replace  either  the  Q1  or  Q3  NbTiquadrupoles. The study includes optics, magnetparameters, operating margins and tracking. The results ofLBM and SYM optics and radiation heat depositionanalysis  are  reported  in  [4].  The  main  NbTi  quadrupoleparameters required for these two cases are shown inTable 1. This paper discusses the parameters of Nb3Snmagnets for hybrid optics layouts for the Phase I upgrade.Table 1: NbTi quadrupole parameters for LowBetaMax(LBM) and Symmetric (SYM) Phase I optics.LBM SYMCoilID, mmLmag,mGnom,T/mCoilID, mmLmag,mGnom,T/mQ1 90 7.060 167.21 130 9.200 121.86Q2a 130 7.787 -121.37 130 7.800 -121.86Q2b 130 7.787 -121.37 130 7.800 -121.86Q3 130 8.711 121.37 130 9.200 121.86Nb3Sn QUADRUPOLES FOR PHASE ITo  replace  NbTi  magnets  in  Phase  I  optics  withoutimpact on the triplet optical functions and other systems,Nb3Sn magnets should be completely compatible withtriplet vacuum, cryogenics, power and quench protectionsystems.  In particular, Nb3Sn magnets should provide thesame focusing strength as the relevant NbTi quadrupolesat the same operation current (~12.5 kA for NbTiquadrupoles based on LHC cables [5]).  The operationmargin of Nb3Sn quadrupoles has to be increased withrespect to the baseline NbTi quadrupoles to compensatefor the earlier state of this new technology.Magnet aperture and parametersDesign studies were performed for Nb3Sn quadrupoleswith apertures ranging from 90 to 134 mm and maximumfield gradients at least 20% above the nominal gradient inthe NbTi magnets presented in Table 1. Magnetparameters are summarized in Table 2.Table 2: Basic parameters of Nb3Sn IR quadrupoles for LHC Phase I upgrade.TQC-90 IRQ-90 IRQ-110 IRQ-110 IRQ-130 HQ-134Coil cross-sectionCoil ID, mm 90 110 130 134Strand OD, mm 0.7 0.7 0.7 0.8 0.7 0.8Cable width,mm 10.05 15.14 15.10 15.15 15.10 15.15Bmax(1.9K), T 12.9 13.8 14.4 14.5 14.5 15.0Gmax(1.9K), T/m 248 268 229 229 193 193Gnom(12.5kA) 208.3 185.6 179.7 168.0 155.9 144.5Gmax/Gnom 1.19 1.44 1.28 1.37 1.24 1.34W(12.5kA),kJ/m 358 384 674 595 923 857Jcu, A/mm2 2407 1546 1585 1345 1585 13453Design options were limited by two-layer coils basedon a 15-mm wide Nb3Sn cable (comparable with the LHCNbTi cables). The magnet maximum field and fieldgradient were calculated for the Nb3Sn strands withJc(12T,4.2K)=2.5 kA/mm2. The parameters in Table 2characterize the relative complexity of different magnetdesigns and their operation at the nominal current. Thestored energy (and Lorentz forces) increases with magnetaperture, which complicates the magnet mechanicalstructure and the magnet quench protection.For comparison, the design parameters of the LARPtechnology quadrupoles of the TQ series [6]-[7] based on10-mm  wide  cable  are  also  presented.  Ten  1-m  longmodels of the TQS and TQC series have been fabricatedand tested. The maximum field gradient reached in thosemodels was on the level of 200-220 T/m, which is ~15-20% lower that the design values for these magnets at 1.9K. While the causes of magnet degradation are beinginvestigated, the present level of degradation has to beadded to the magnet operation margin. One can see thatIRQ-90, IRQ-110 and HQ-134 provide sufficientoperation margins required for Nb3Sn quadrupoles at thepresent time.Magnet lengthThe Nb3Sn magnet length is currently limited to 4meters. This limitation comes from the limited experiencewith long Nb3Sn coils which includes two 3.5-m longracetrack coils tested in a common coil configuration [8]and 2-m and 4-m long cos-theta coils tested in a mirrorconfiguration [9]. LARP is working on a 4-m longquadrupole  of  LQ  series  to  demonstrate  the  Nb3Sntechnology scale up for large aperture quadrupoles [10].Thus, the 8-9 m long NbTi Q1 or Q3 quadrupoles in bothPhase I optics layouts have to be replaced by two ~4-mlong or shorter Nb3Sn magnets with appropriate gradient.To study the magnetic coupling between two closelyplaced coils, the magnet end gradient and field harmonicswere calculated for two values of coil-to-coil gap. The gapof 50 mm corresponds to the minimal distance betweenthe coils installed in the same iron yoke. The gap of 250mm corresponds to the case of two independent coldmasses placed in the same cryostat.Fig. 1 shows the relative coil end position with a coil-to-coil gap of 50 mm. Figs. 2 and 3 show the variation ofmagnet gradient and b6 between magnets with coil-to-coilFigure 1: Coil end position with coil-to-coil gap of 50mm.gaps  of  50  and  250  mm.  As  can  be  seen,  in  both  casesthere is no magnetic coupling between the two coils.Thus, they should be considered as independent magnetsin optics and tracking analysis.0501001502002500 100 200 300 400 500 600 700Z (mm)G (T/m)50mm gap250mm gapFigure 2: Longitudinal variation of field gradient betweenmagnets.-50-40-30-20-1001020304050600 100 200 300 400 500 600 700Z (mm)b650mm gap250mm gapFigure 3: Longitudinal variation of b6 between magnets.Field qualityField quality and its reproducibility for Nb3Sn IRquadrupoles was estimated based on magneticmeasurements of five LARP TQ short models [11]. Thesystematic low-order harmonics and their RMS spread atthe reference radius equal to half of the coil aperture arereported in Table 3.Table 3: Systematic field harmonics and their RMSspread at Rref = 22.5 mm.Systematic RMSn bn an bn an3 -0.40 0.43 1.87 2.464 0.51 -1.56 1.10 3.425 0.81 3.81 3.55 3.746 -6.70 -0.27 0.35 0.707 0.02 -0.22 0.12 0.198 -0.02 -0.16 0.16 0.329 0.07 -0.14 0.11 0.1310 0.14 0.00 0.08 0.054The  harmonics  RMS  spread  in  Nb3Sn 90-mm TQmodels and NbTi 70-mm LHC IR quadrupoles of theHGQ series  [12]  are  plotted  in  Fig.  4.   A comparison ofTQ  and  HGQ  data  shows  that  the  RMS  spread  ofgeometrical harmonics in Nb3Sn quadrupoles is a factor of3 larger then the harmonics spread in NbTi quadrupoles.This is also consistent with the observation in Nb3Sndipole models [13].0.010.11102 4 6 8 10Harmonic numberSt. deviation, 10-4HGQ, anHGQ, bnTQ, anTQ, bnFigure  4:  Normal  bn and  skew  an random errors in 5Nb3Sn TQ and 8 NbTi HGQ models.Analysis of field quality in Nb3Sn model magnets (bothdipoles and quadrupoles) shows that they have quite largepersistent current effects in low-order allowed harmonicsdue to the large effective filament size in the state-of-the-art high-Jc Nb3Sn  strands.  However,  it  was  shown  thatthis effect can be reduced by reducing the Deff orcompensated using relatively simple passive correction[13]. The eddy current effects in present Nb3Sn modelsare also quite large and vary from magnet to magnet,which is likely due to inter-strand contact resistancevariations in the cable. This effect can be reduced byusing a stainless steel core inside the cable. The long-termdecay and snap-back effects were not observed in eitherof the Nb3Sn TQ models. This is different from the resultsof NbTi HGQ and MQXB magnets which exhibitedprominent decay and snap-back effects. However, it isconsistent with the absence of snap-back in other Nb3Snmagnets made of similar conductors [14].CONCLUSIONSDesigns and parameters of Nb3Sn quadrupoles withapertures from 90 mm up to 134 mm were studied.Quadrupoles with 90, 110 and 130 mm with largeoperation  margin  of  ~40%  were  used  in  optics  andoperation margin studies. The field quality of Nb3Snquadrupoles was estimated based on the data for five 90-mm LARP TQ models. Studies of the effects of fieldquality in Nb3Sn quadrupoles are in progress.The experience with TQ models suggests that the 90-mm design is most ready for use in the Phase I upgrade asQ1 in both LBM and SYM optics. Quadrupoles with 110-130 mm aperture can provide a larger aperture margin andcould be used as Q1 or Q3 in LBM or SYM optics.  The130-mm quadrupoles are the most complicated magnetswith the most challenging performance parameters. It isunlikely that they could be ready for installation in PhaseI on time. The 110-mm quadrupoles have sufficientaperture and operation margin, and more realisticoperation parameters. They have the greatest flexibilityfor installation in Phase I and would pave the way towardIR quadrupoles for the Phase II upgrade.REFERENCES[1] R. Ostojic, “Phased Approach to the LHC InsertionUpgrade and Magnet Challenges”, IR’07 mini-workshop, CARE-HHH-AMT, Frascati (Italy), 2007.[2] S. A. Gourlay et al.,  “Magnet R&D for the US LHCAccelerator Research Program”, IEEE Trans. onApplied Supercond., V. 16,  N2,  June 2006, p. 324.[3] R.  de  Maria,  “The  summary  of  optics  study  for  theLHC Phase I upgrade”, IR’07 mini-workshop,CARE-HHH-AMT, Frascati (Italy), 7-9 Nov 2007.[4] J.A. Johnstone et al., “Optics Implications ofImplementing Nb3Sn Magnets in the LHC Phase IUpgrade”, EPAC2008, Genoa (Italy), June 2008.[5] E. Todesco, “Magnet design issues for a 130 mmtriplet”, IR’07 mini-workshop, CARE-HHH-AMT,Frascati  (Italy), 7-9 Nov 2007.[6] R.C. Bossert et al.,  “Development and Test of LARPTechnological Quadrupole Models of TQC Series”,IEEE Trans. on Applied Supercond., V. 18, N2, June2008, p.175.[7] S. Caspi et al.,  “Test and Analysis of TechnologyQuadrupole Shell (TQS) Magnet Models for LARP”,IEEE Trans. on Applied Supercond., V. 18, N2, June2008, p.179.[8] P. Wanderer et al., “Construction and Test of 3.6 mNb3Sn Racetrack Coils for LARP”, IEEE Trans. onApplied Supercond., V. 18, N2, June 2008, p. 171.[9] F. Nobrega et al, “Nb3Sn Accelerator MagnetTechnology Scale-up using Cos-theta Dipole Coils”,IEEE Trans. on Applied Supercond., V. 18, N2, June2008, p. 273.[10]G. Ambrosio et al.,  “LARP Long Nb3Sn QuadrupoleDesign”, IEEE Trans. on Applied Supercond., V.18, N2, June 2008, p. 268.[11]G.V. Velev et al., “Field Quality Measurements andAnalysis of the LARP Technology QuadrupoleModels of TQC Series”, IEEE Trans. on AppliedSupercond., V. 18, N2, June 2008, p. 184.[12]N. Andreev et al., “Field Quality in Fermilab-builtModels of Quadrupole Magnets for the LHCInteraction Region”, IEEE Trans. on AppliedSupercond., V. 11, N1, March 2001, p. 1566.[13]V.V. Kashikhin et al., “Passive Correction of thePersistent Current Effect in Nb3Sn AcceleratorMagnets”, IEEE Trans. on Applied  Supercond.,V.13, N 2, June 2003, p.1270.[14]A.V. Zlobin et al., “Nb3Sn Accelerator MagnetTechnology R&D at Fermilab”, Proc. of PAC 2007,Albuquerque, NM, June 2007, pp. 482-484.

Nb3Sn Quadrupoles in the LHC IR Phase I Upgrade

https://digital.library.unt.edu/ark:/67531/metadc897255/m2/1/high_res_d/935791.pdf

Nb3Sn quadrupoles in the LHC IR Phase I upgrade

Abstract

Similar works

Full text

Available Versions

UNT Digital Library

UNT Digital Library