The US-LHC Magnet Database is designed for production-magnet quality assurance, field and alignment error impact analysis, cryostat assembly assistance, and ring installation assistance. The database consists of tables designed to store magnet field and alignment measurements data and quench data. This information will also be essential for future machine operations including local IR corrections. (7 refs)

Bottura, L

Jain, A

MacKay, W W

McChesney, D

Peggs, S

Pilat, F

Sabbi, G L

Wei, J

CERN Document Server

US-LHC MAGNET DATABASE AND CONVENTIONSJ. Weiy , D. McChesney, A. Jain, S. Peggs, F. Pilat, BNL, Upton, NY 11973, USAL. Bottura, CERN, 1211 Geneva 23, SwitzerlandG. Sabbi, Fermi Lab, P. O. Box 500, Batavia, IL 60134, USAAbstractThe US-LHC Magnet Database is designed for production-magnet quality assurance, field and alignment error impactanalysis, cryostat assembly assistance, and ring installa-tion assistance. The database consists of tables designed tostore magnet field and alignment measurements data andquench data. This information will also be essential for fu-ture machine operations including local IR corrections.1 INTRODUCTIONThe US part of the Large Hadron Collider (US-LHC) ac-celerator program is responsible for manufacturing super-conducting magnets for the Insertion Region (IR) innertriplet and RF Region dipoles. Dipoles built at BrookhavenNational Laboratory, quadrupoles built at Fermi Lab andJapan’s KEK, and correctors built in Europe will be mea-sured and assembled in cryostats in the US and thenshipped to CERN for installation. In a multi-laboratorycollaboration like this, it is necessary to unify the mea-surement and application conventions, and to establish adatabase structure commonly accepted by CERN and othercollaborating laboratories. The US-LHC Magnet Database[1] is designed for production-magnet quality assurance,field and alignment error impact analysis, cryostat assem-bly assistance, ring installation assistance. The databaseconsists of tables designed to store magnet field and align-ment measurements data and quench data. This informa-tion will also be essential for future machine operations in-cluding local IR corrections.The design of US-LHC Magnet Database is based onthe existing structure used for the Relativistic Heavy IonCollider (RHIC). Analysis and monitoring software forfield quality [2] and alignment quality [3] have also beenadapted for US-LHC magnet use.2 DATABASE FUNCTIONS ANDDATAFLOWFig. 1 shows the function of Magnet Database during theproduction stage, at installation, and after operation. Afterindividual magnet elements (coldmasses) are constructedand measured, quench data, field quality data (integraltransfer function, center offset and field angle relative tomechanical fiducials, field harmonics, etc.) and alignmentdata (fiducial positions, magnetic center, etc.) are collected.After processing (analyzing measurement conditions andstatistics, correcting calibration and other systematic er-rors, etc.), a minimum set of representative data is trans-Work performed under the auspices of the US Department of Energy.y Email: wei1@bnl.govstrengthCorrectorsettingcoldmassquenchsurveycenter pos.field angleopticalfiducialsmagnetI.T.F.targetscryostatassemblyorientationcenter &assemblyacceptanceInstallationassistanceAssemblyanalysisdeliverycenter dev.field anglemultipoleAssemblyassistancedipoles (BNL)quads (FNAL, KEK)correctors (European)coldmassassemblyImpactacceptanceFigure 1: Dataflow for US-LHC magnet field and align-ment quality analysis.fered to the US-LHC Magnet Database. Based on thesestored data, computer tracking and simulation is performedto assess the impact of errors; statistical and trend analysisis performed to monitor field quality and to assist in mag-net coldmass acceptance; information of magnetic centerand field angle can be used for alignment sorting [4] be-fore cryostat assembly; and multipoles with signs definedaccording to the convention are used for future machineoperation including IR correction [5].During cryostat assembly, survey and alignment data areextracted and stored in the database. Sufficient informationis contained to provide the center and field angle of theassembly relative to the cryostat fiducials. Along with thecompleted assembly, this information will be delivered toCERN to assist in ring installation.3 MEASUREMENT AND ANALYSISCONVENTIONS3.1 Measurement ConventionConventions are established among BNL, CERN andFNAL defining the reference measurement coordinates.Magnetic multipoles are defined in the reference system[6, 7] illustrated in Fig. 2. The description is 2-dimensional0-7803-5573-3/99/$10.00@1999 IEEE. 3179Proceedings of the 1999 Particle Accelerator Conference, New York, 1999XYZ Lead End(Connection End)Return EndFigure 2: Reference frame for the measurement of mag-netic multipoles.LE LE LELEofAssembly Combined Element AssemblyFigure 3: Lead end of a combined element assembly.with x y axes chosen such that the skew (or normal) com-ponent in the main field of a normal (or skew) magnet iszero.If the measurement is performed on a single magnet el-ement (coldmass), the reference frame is defined with re-spect to the lead end of the element. If the measurement isperformed on a magnet element contained in a combinedelement assembly, the reference frame is defined with re-spect to the lead end of the assembly (which may be oppo-site to that of the individual element), as shown in Fig. 33.2 Multipole Sign ConventionBoth the magnitude and sign of measured multipole errorsare important for error analysis and for IR local correction[5]. For example, the systematic a2from the lead endsof the triplet quadrupole is significant. Since IR magnetsat opposite side of the interaction point (IP) are orientedsymmetrically towards the IP, the actual sign of a2seen bythe beam changes accordingly.Fig. 4 shows the change of magnet multipole sign fromtheir measured value for a beam circulating counterclock-wise. In general, rules for multipole transformation under180 rotation around vertical (y) axis (orientation flip), lon-gitudinal (z) axis (upside-down change) and radial (x) axisare summarized in Tab. 1.4 DATABASE STRUCTUREPresently, the database contains 17 tables as listed in Tab. 2.The first 13 tables are intended for quench and field quality     quadrupole:  b   =>  (-)      b   ;      a   =>  (-)      aii iLHC-BCMSiALICE beamMultipole transformation for ‘‘opposite’’ orientation magnets:ATLASn ndefault oppositelead endnn+1 nn+1n nn nndipole:          b   =>  (-)      b   ;      a   =>  (-)      anFigure 4: Change of the sign of magnet multipoles fromtheir reference measurement value for a beam circulatingcounterclockwise.of individual magnet coldmass, while the last 4 tables areintended for survey and alignment data.The Integral table contains the integral harmonics andtransfer function information. In the case of short magnets,this information may be obtained from a single measure-ment with a suitably long measuring coil. For long mag-nets, e.g. the RF dipoles, the integral harmonics will beobtained from a sum of several measurements (a Z-Scan).In the case of a Z-Scan, one can also extract the harmonicsaveraged over the straight section as well as the integratedcontributions from the two ends. If available, these resultswill be stored in the BodyHarmAvg and EndsHarm tablesTable 1: Transformation rule for magnet multipoles. It isassumed that the magnet polarity is adjusted, if necessary,so that the fundamental term remains positive. N = 2 is forquadrupole magnet, while n = 2 is for quadrupole order.Item Normal magnet Skew magnetof order N of order NOrientation:bn( )n+Nbn( )n+N+1bnan( )n+N+1an( )n+NanUpside-down:bn( )n+Nbn( )n+Nbnan( )n+Nan( )n+Nan180 about x:bnbn bnan anan3180Proceedings of the 1999 Particle Accelerator Conference, New York, 1999Table 2: Summary of US-LHC Magnet Database tables.Name ContentMagnets magnet name, ID, summary info.Assembly combined element assembly info.Quench quench performanceIntegral int. geometric multipoleLocalHarm multipoles measured at one positionBodyHarmAvg average body multipoleEndsHarm lead and return end multipoleIntField integral field strengthMagz magnetization multipoleEddy Eddy current multipoleTDecay time decay multipoleCenters magnetic centering offsetsWarmCold ITF & multipole warm/cold conversionFidMagInfo survey information summaryFidOpt fiducial position from optical surveyCentMag mag. center wrt external referenceAngle mag. field angle wrt external referencerespectively. In addition, each individual measurement in aZ-Scan will be recorded in the table LocalHarm. The en-tries for various positions in the LocalHarm table can beused to identify any location which may be unusual fromthe field quality point of view. Such spots of concern aregenerally difficult to identify from the integral or the aver-age body harmonics, and the information can be essential inestablishing models for study of, e.g. magnet fringe field.Tables Integral, BodyHarmAvg, EndsHarm containtransfer function, multipoles and field angle data of indi-vidual magnet coldmass. Both normal and skew Multipolesup to order 15 are recorded in accordance with the conven-tion. Both the body and the ends harmonics are normalizedto the value of the main field component in the straight sec-tion, whereas the integral harmonics are normalized to theintegrated main field component. Thus both the body andintegral harmonics are expressed in units. Since the endsharmonics are integrated values over a certain length of themagnet, these are expressed in unitm rather than units.The integral transfer function obtained by summing sev-eral measurements in a Z-Scan may not be very accuratedue to small errors in positioning of the measuring coil. Ifthis be the case, an independent measurement of integraltransfer function is needed, for example with a long non-rotating coil, as was done for RHIC. With this in mind, aseparate table (IntField) is created to store the most accu-rate measurements of integral transfer function.For measurements in the superconducting state, mea-surements during the upward and the downward sweeps ofcurrent reveal contribution to harmonics due to supercon-ductor magnetization. The difference between the up rampmeasurements and the average of up and down ramp mea-surements will be stored in the table Magz. Similarly, ifharmonic measurements are made while the magnet cur-rent is still ramping, then such harmonics will include anycontributions from eddy currents generated in the super-conductor. These harmonics will be stored in the Eddy ta-ble. Another superconductor related table is Tdecay, whichwill contain the time dependence of various harmonics at afixed current (most important is the injection current) soonafter a ramp.Table Centers will contain the centering offsets and fieldangles from the magnetic measurements. These values aremeaningful only when the measuring coil is well centeredin the magnet yoke. In such cases, one can use this infor-mation, for example, to better align various elements in acombined element magnet.Table WarmCold will contain the systematic values ofwarm to cold offsets based on data from all the magnets ofa particular type for which both types of data exist. Thistable is only of academic interest if all magnets are mea-sured cold. However, the table can be used to obtain thebest estimates of cold harmonics if some magnets are onlymeasured warm.Tables CentMag and Angle contain information of as-sembly center offset and orientation relative to the externalfiducials. This, together with Tables FidMagInfo and Fi-dOpt containing information of fiducial positions, providesguidance to final ring installation of the magnet assembly.5 SUMMARYAlong with the magnet assembly delivered for installa-tion at CERN, magnet measurement data containing tablesof quench performance, field quality, alignment and sur-vey data will be transferred to CERN. This informationis essential both for ring installation and for future ma-chine operation including IR corrections. US-LHC Mag-net Database has been designed to fulfill such tasks, andit will also benefit production stage quality assurance, errorimpact analysis, and assembly assistance including sorting.We thank participants of the 1998 US-LHC MagnetDatabase Workshop for contributing to the establishmentof the database structure.6 REFERENCES[1] J. Wei, D. McChesney, et al. Summary on US-LHC MagnetDatabase Workshop, RHIC/AP Note 160 (1998).[2] J. Wei, R. C. Gupta, A. Jain, S. G. Peggs, C. G. Trahern,D. Trbojevic, P. Wanderer, Field Quality Evaluation of theSuperconducting Magnets for the Relativistic Heavy Ion Col-lider PAC95, (1995) 461.[3] J. Wei, G. Ganetis, R. Gupta, M. Harrison, M. Hemmer,A. Jain, F. Karl, S. Peggs, S. Tepikian, P.A. Thompson, D.Trbojevic, P. Wanderer, Misalignment Evaluation of Super-conducting Magnets in the Relativistic Heavy Ion ColliderEPAC96, Sitges (1996) 2222.[4] J. Wei, et al., Real-World Sorting of RHIC SuperconductingMagnets, PAC99 (1999).[5] J. Wei, W. Fischer, V. Ptitsin, R. Ostojic, J. Strait, IR LocalCorrection for the LHC, these proceedings.[6] A. Jain, et al., RHIC Magnetic Measurements: Definitionsand Conventions, RHIC/AP/95 (1996).[7] R. Wolf, Field Error Naming Conventions for LHC Magnets,LHC-MMS/ES/01 (1998).3181Proceedings of the 1999 Particle Accelerator Conference, New York, 1999

US-LHC Magnet Database and conventions

US-LHC Magnet Database and conventions

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