After the successful construction of two first-generation prototypes of the main quadrupoles for the LHC, three series-design prototypes have been further manufactured at CEA-Saclay. Together with the sextupole-dipole corrector magnets and tuning quadrupoles, these twin-aperture main quadrupoles are assembled into the cold masses of the so-called short straight sections. Already during their fabrication, the collared coils and later the completed cold masses undergo warm magnetic measurements. Two of the main quadrupole cold masses have been mounted into their definitive machine cryostats and submitted to training and magnetic measurements. This paper presents the results of these cold tests by describing the quench behaviour, the transfer function in each of the apertures and the multipole components found at different levels of excitation. The field quality results, in cold conditions, will be compared to those measured at room temperatur

Billan, J

Bottura, L

Peyrot, M

Remondino, Vittorio

Rifflet, J M

Siemko, A

Simon, F

Tortschanoff, Theodor

CERN Document Server

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHEuropean Laboratory for Particle PhysicsPERFORMANCE OF SERIES-DESIGN PROTOTYPE MAIN QUADRUPOLESFOR THE LHCJ. Billan1, L. Bottura1, M. Peyrot2, V. Remondino1, J.M. Rifflet2,A. Siemko1, F. Simon2  and T. Tortschanoff1After the successful construction of two first-generation prototypes of the main quadrupoles for theLHC, three series-design prototypes have been further manufactured at CEA-Saclay. Together with thesextupole-dipole corrector magnets and tuning quadrupoles, these twin-aperture main quadrupoles areassembled into the cold masses of the so-called short straight sections. Already during their fabrication,the collared coils and later the completed cold masses undergo warm magnetic measurements. Two ofthe main quadrupole cold masses have been mounted into their definitive machine cryostats andsubmitted to training and magnetic measurements. This paper presents the results of these cold tests bydescribing the quench behaviour, the transfer function in each of the apertures and the multipolecomponents found at different levels of excitation. The field quality results, in cold conditions, will becompared to those measured at room temperature1 CERN, LHC Division, Geneva, Switzerland2 CEA, Saclay, France. Member of the CERN-CEA-IN2P3 Collaboration to the LHC Project.Presented at the Seventh European Particle Accelerator Conference  (EPAC 2000)26-30 June 2000, Vienna, AustriaGeneva, Large Hadron Collider ProjectAdministrative SecretariatLHC DivisionCERNCH - 1211 Geneva 23SwitzerlandLHC Project Report 428Abstract23 September 20001PERFORMANCE OF SERIES-DESIGN PROTOTYPE MAINQUADRUPOLES FOR THE LHCT. Tortschanoff, J. Billan, L. Bottura, V. Remondino, A. Siemko,CERN, Geneva, SwitzerlandM. Peyrot, J.M. Rifflet, F. Simon, CEA, Saclay, FranceAbstractAfter the successful construction of two first-generation prototypes of the main quadrupoles for theLHC, three series-design prototypes have been furthermanufactured at CEA-Saclay. Together with thesextupole-dipole corrector magnets and tuningquadrupoles, these twin-aperture main quadrupoles areassembled into the cold masses of the so-called shortstraight sections. Already during their fabrication, thecollared coils and later the completed cold massesundergo warm magnetic measurements. Two of the mainquadrupole cold masses have been mounted into theirdefinitive machine cryostats and submitted to trainingand magnetic measurements. This paper presents theresults of these cold tests by describing the quenchbehaviour, the transfer function in each of the aperturesand the multipole components found at different levelsof excitation. The field quality results, in coldconditions, will be compared to those measured at roomtemperature.1  INTRODUCTIONThe main quadrupole magnets for the arc of LHChave been described in earlier publications [1], [2]. Thedesign and the construction of these twin aperturemagnets is the result of a close collaboration betweenCERN and the CEA-Saclay laboratory in France. Thequadrupole magnets are housed in a cold mass togetherwith the arc corrector magnets. On one end are mountedthe dipole-sextupole correctors on the other end, theconnection end, the octupole, respectively the tuning orskew quadrupole correctors. The cold mass functions asthe stiffening element of the assembly and at the sametime as the liquid helium pressure vessel. The mountingof the quadrupoles into their cryostats was executed in acollaboration between CERN and the CNRS laboratoryof Orsay in France [3]. Table 1 shows the mainparameters of these magnets. Up to now three of the newmagnets have been constructed in Saclay, named SSS3,SSS4 and SSS5. They were submitted to warm magneticmeasurements at Saclay and the first one of them, SSS3,has undergone cold tests and magnetic measurements atCERN. SSS4 was has also undergone warmmeasurements at CERN and is presently prepared forcold magnetic measurements at CERN. SSS5 will betested during the second halve of the year 2000 at thetest cryogenic test station in Saclay.Table 1: Main parameters and characteristics of theLHC quadrupole magnet and cold massValue UnitInjection field gradient (0.45 TeV beamenergy)14.5 T/mNominal field gradient (7 TeV beamenergy)223 T/mNominal current 11’870 AOperating temperature 1.9 KMagnetic length at 1.9 K 3.1 mStored energy (both apertures) at 7 TeV 0.79 MJUltimate operational field gradient 241 T/mGradient at short sample field limit 278 T/mDistance between aperture axis at 1.9 K 194.00 mmInner coil diameter at 293 K 56.00 mmOuter coil diameter at 293 K 118.60 mmNumber of conductor blocks / pole 4Electromagnetic forces / coil octant atnominal fieldRadial force (inner and outer layer)Azimuthal force (inner and outer layer)0.54-0.73MN/mMN/mCold mass length at 293 K, between endcovers5355 mmCold mass overall length with ancillaries 6.63 mCold mass weight 6.5 T2  WARM MAGNETIC MEASUREMENTSWarm magnetic measurements were made at CEA-Saclay for the prototypes at several steps of the theirfabrication. The first measurements are done once acollared coil assembly is finished. This allows to detect afaulty coil assembly and to eliminate it before it ismounted into the yoke. Once two collared coilassemblies are mounted into their common yoke andinserted into their cold mass together with the correctormagnets on each end, the warm magnetic measurementsare repeated. The magnetic field is measured by therotating coil technique.A measuring coil of 0.75 m length placed at fivepositions inside each aperture. The magnet is poweredwith 12.5 A. The field quality is expressed in terms ofrelative multipole field errors with a reference radius at17 mm. Table 1 summarises the results of the integratedmultipole components for the three prototypequadrupoles after the completion of their cold masses.2Table 1: Multipole components measured under roomtemperature in the apertures of three quadrupoleprototypes, SSS3, SSS4 and SSS5. The bn values denotethe normal components, the an the skew ones.SSS3 SSS4 SSS5Multipole Left Right Left Right Left Rightb3 3.195 -0.417 -0.440 0.039 0.431 0.364b4 0.182 -0.060 -0.249 0.048-0.196 -0.106b5 -0.757 -0.353 0.101 -0.062-0.171 -0.004b6 5.595 6.252 5.667 5.342 5.008 4.805b7 0.021 -0.064 -0.076 -0.050 0.044 0.168b8 -0.074 0.001 0.010 0.011-0.053 -0.005b9 -0.005 -0.002 0.018 -0.004-0.036 -0.026b10 -0.117 -0.117 -0.160 -0.191-0.158 -0.141b11 -0.021 -0.007 0.001 0.004-0.005 -0.007b12 -0.009 -0.011 -0.007 -0.003-0.008 -0.009b13 -0.008 -0.002 0.005 0.002 0.003 0.007b14 -0.131 -0.132 -0.140 -0.135-0.136 -0.137b15 -0.001 -0.001 0.000 0.000-0.001 -0.001a3 3.204 -1.872 1.629 -1.556 2.656 -1.516a4 -2.418 -0.890 -0.110 2.153-0.790 -2.486a5 0.664 0.436 0.003 -0.080 0.533 -0.214a6 0.609 0.577 0.167 0.024 0.060 -0.056a7 -0.002 -0.183 0.067 -0.094 0.070 -0.029a8 -0.012 0.034 -0.058 0.102-0.038 -0.145a9 0.016 0.007 0.003 -0.002 0.069 0.019a10 0.034 0.006 0.077 0.063 0.049 0.079a11 -0.005 -0.018 0.002 0.001 0.015 0.001a12 0.006 0.002 -0.004 0.011-0.004 0.001a13 0.052 0.046 0.034 0.029 0.051 0.033a14 -0.014 -0.014 0.012 0.009 0.011 0.009a15 -0.002 -0.001 0.000 0.001 0.001 -0.002  The results of these warm measurements are in goodagreement with those for the single collared apertures. Adetailed analysis of the sources of the non-allowedcomponents is given in ref. [4]. The distribution over thelength of a typical aperture, here the right one of SSS5 isshown in Figure 1. Fig. 1 Distribution of some multipole components overthe length of the left SSS5 quadrupole aperture. Lengthof measuring coil is 0.75 m, magnetic length 3.115 m.  Once the cold masses of SSS3 and SSS4 were closed,pressure and leak tested as well as measured, they wereshipped to CERN. There they were mounted into theirhorizontal cryostat before being attached to thecryogenic test station. The warm magnetic measurements have been repeatedat CERN for both apertures of the quadrupole in the coldmass of SSS4. The technique used for thesemeasurements was the same as used in CEA. Theequipment, however, was a separately constructed one.The multipole components found agree well with thosemeasures at CEA which presents a reassuringconfirmation of the results.3  PREPARATION FOR COLD TESTS For the cold magnetic measurements the fullyequipped short straight sections were attached to one ofthe newly constructed test stations at CERN. Beingprototypes, they were equipped with moreinstrumentation than foreseen for the series unit to gointo the LHC machine. Most of this instrumentationconcerns voltage taps allowing the localisation ofquenches inside the coils. The powering of bothapertures is made by means of one power supply whichrequires that both apertures are connected in series.Thus, not only the connection between the apertures hadto be made, also a return connection on the secondaperture was provided. This is different from thepowering scheme in the machine where separate circuitsexist for the focusing and de-focusing quadrupoles of thelattice. Figure 2 shows SSS3 in its cryostat together withreturn box, mounted to the CERN measuring station. During the testing at the test station no beam screen aswell as no Beam Position Monitor must be mounted tothe cold masses, both for the prototypes and the seriesmagnets. They would not allow the positioning of thequench antennas which permit the longitudinal locationof quench origins. Further, the aperture needed for therotating measuring coil for the multipole componentmeasurements would not be free. The beam screen withthe Beam Position Monitor monitors attached to themwill be inserted in the frame of the last preparatoryoperations for installing the quadrupole units into themachine.4  TRAINING The training of the SSS3 quadrupole was short sincethere was only one quench registered below the nominaloperational value of 11870 A or 223 T/m. This despitethe fact that in this magnet the ends of the quadrupolecoils were not STYCASTTM impregnated, as is done forall LHC dipoles and later for the quadrupole prototypesof SSS4 and SSS5. Figure 3 shows the training curve.After only three quenches the magnet could be poweredto 13’000A (242 T/m) which was set as the upperexcitation limit (corresponding to more that 9 T in theLHC main dipoles). When stabilising the current at 13’000A, the magnetquenched, however, after a few minutes. This was tracedback to the clamped high current joints between the-2.0.2.4.6.8.10.12.14.16.Position 1 Position 2 Position 3 Position 4 Position 5Multipoles (units) b3a3b6a6b10a103 Figure 2: The SSS3 Short Straight Section mounted tocryogenic test station at CERN.  apertures. There about 100 nano-Ohm were measured,instead of the nominal 0.5 nano-Ohm. For repairing thisconnection by soft soldering it, the magnet had to bewarmed up which provided a thermal cycling, anywayforeseen in the test programme. After the new cool-downthe magnet was ramped up to 13’000A again withoutany quench. Figure 3: Training of SSS3 quadrupole including thermalcycle after which no quench occurred.5 COLD MAGNETIC MEASUREMENTSTable 2 shows the multipole components as measuredfor excitation at injection at an intermediate level and atthe nominal operational level. The values at theintermediate level confirm the good correlation betweenwarm and cold measurements. (Compare 5000A resultsto warm measurement results of SSS3 (bold) in Table 1.)The b6, the dodeca-pole component, is about 2.6 unitsabove its nominal 3.9 units. This will be easily correctedfor the series fabrication by reducing the coil pole shimsby a few hundreds of millimetre. All the non-allowednormal and skew components can be explained bytolerance considerations, which will be difficult toimprove.Table 2: Integrated multipole components measuredcold for the SSS3 quadrupole at different excitations.    SSS3 730A SSS3 5000A SSS3 11750AMultipol Left Right Left Right Left Rightb3 3.853 -0.580 4.071 -0.926 4.406 -1.117b4 0.105 -0.134 -0.026 -0.012 -0.043 -0.017b5 -0.888 -0.898 -0.794 -0.975 -0.753 -1.023b6 3.106 4.598 6.594 7.344 6.674 7.374b7 -0.040 -0.215 -0.039 -0.096 -0.039 -0.093b8 -0.048 -0.013 -0.049 0.018 -0.034 0.007b9 0.025 0.005 -0.010 0.017 -0.007 0.017b10 -0.089 -0.151 -0.130 -0.116 -0.124 -0.112b11 -0.022 0.016 -0.026 -0.014 -0.018 -0.010b12 0.018 0.029 -0.002 -0.006 0.004 0.001b13 -0.019 0.061 -0.014 0.030 -0.023 0.022b14 -0.189 -0.212 -0.172 -0.166 -0.163 -0.163b15 0.006 0.008 -0.002 -0.003 0.002 -0.001a3 3.974 -2.669 3.835 -2.707 3.899 -2.604a4 -2.917 -0.927 -2.886 -1.325 -2.920 -1.363a5 0.609 0.729 0.408 0.722 0.319 0.751a6 0.407 0.403 0.335 0.289 0.313 0.276a7 0.038 -0.226 0.042 -0.246 0.041 -0.256a8 -0.068 -0.033 -0.031 0.014 -0.023 0.017a9 0.044 -0.031 0.031 -0.017 0.033 -0.014a10 0.046 0.001 0.063 0.029 0.051 0.029a11 -0.016 -0.024 -0.001 -0.015 -0.003 -0.018a12 0.010 -0.006 0.010 0.002 0.009 0.006a13 0.030 -0.019 0.030 -0.005 0.033 -0.001a14 -0.016 0.000 0.004 -0.001 -0.008 -0.006a15 0.002 -0.006 0.001 -0.001 -0.001 -0.003REFERENCES[1] T. Tortschanoff et al., "The Short StraightSections for the LHC",  Proc. PAC97 Conference,Vancouver, Canada. 1997.[2] M. Peyrot, J.M. Rifflet, F. Simon,T. Tortschanoff, P. Vedrine, “Construction of the NewPrototype of Main Quadrupole Cold Masses for theArc Short Straight Sections of LHC”, Proc. MT-16,Ponte Vedra Beach, Florida, USA, 1999.[3] L. Nielsen, V. Parma, T. Renaglia, P. RohmigT. Tortschanoff, J.-B. Bergot, Ph. Dambre, E. Roy,D. Vincent, M. Peyrot, J.-M. Rifflet, F. Simon,“A Modular Design for the 56 Variants of the ShortStraight Section in the Arcs of the Large HadronCollider (LHC)”, Proc. EPAC-2000, Vienna, 2000.[4] S. Redaelli, V. Remondino, W. Scandale,E. Todesco, T. Tortschanoff, M. Peyrot, F. Simon,J.M. Rifflet, “Analysis of the Warm MagneticMeasurements of the First Series-design Prototypes ofthe LHC Main Quadrupoles”, Proc. EPAC 2000,Vienna, 2000No quenchThermal Cycle2002052102152202252302352402452500 2 4 6 8 10Quench NumberMagnetic Gradient at Quench [Tesla/m]7580859095100Deposited Energy [%]Nominal Gradient = 223 T/m Ultimate Gradient Dissipated Energy [%]

Performance of Series-Design Prototype Main Quadrupoles for the LHC

Performance of Series-Design Prototype Main Quadrupoles for the LHC

Abstract

Similar works

Full text

Available Versions

CERN Document Server