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The AL I CE TPC U pg r ade P r o ject

The AL I CE TPC U pg r ade P r o ject. R i c ha r d M aj k a. R . M a j ka. W h a t i s a T P C and w h y i s i t us e d i n A L IC E ? *

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The AL I CE TPC U pg r ade P r o ject

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  1. TheALICETPCUpgrade Project RichardMajka 16June2017 R.Majka

  2. What isaTPC andwhyisitusedin ALICE?* • Alargecylindricalgasvolumewithelectricfieldarranged to driftionizationelectronsfromchargedparticlespassingthrough thegasto eitherend. • Amagneticfieldparallelto theelectricfieldbendstheparticlesandallowsmeasurementoftheparticlemomentum. • Bymeasuringthenumberofionizationelectronsperunitpathlength forachargedparticlethevelocityof theparticleisdeterminedandonecan determinetheparticlemass. Invented byDaveNygren,~1975http://www.slac.stanford.edu/pubs/slacreports/reports04/slac-r-190.pdf,p 126 PhysicsToday31,46(1978);http://doi.org/10.1063/1.2994775 16June2017

  3. ALICETPC PEP4TPC At lowmomentumtheionizationcrosssectionfallswithincreasingmomentum,athigher energyrelativisticcontraction/dilationof theparticle’selectricfieldcausestheionizationcrosssectionto increase. 16June2017

  4. Basicideaofgasdetectorforionizingradiation: Ionizingradiation–suchasachargedparticle– passingthroughagas(usuallyanoblegaswith“additives”)canknockelectronsoffthegasatoms. Undertheinfluenceofanelectricfieldtheelectronscandrifttoanelectrodetobedetected. But,onaverageonlyafewionizationelectrons/mmareproduced.Withmodern,lownoise,inexpensivepreamplifiersyouneed~104 electronstobecomfortablyabovethenoiselevel. Amechanismtomultiplythesignalisneeded. Efield Multiplier Collectionelectrode 16June2017

  5. Sinceitsinventionin1968byGeorges Charpak*,thebasic“workhorse”ofgasdetectorsfortrackinghigh-energychargedparticleshasbeentheMulti- WireProportionalChamberanditsderivatives. ~2kV–4kVManyM =25 -50m Microelectronicsmadepossiblereadoutfor104–105channels. Fewmm Fieldishighenoughnearwiresto accelerateelectronsto sufficientenergyso theycancreatefurtherionization 1-2mm *G. Charpak,etal.,Nucl.Intrum. andMeth.,62,262,1968. 16June2017

  6. UpgradeofLHCinjectorchain-WhatandWhen Pb-Pbinteractionrate:8kHz 50kHz 16June2017

  7. LHCUpgrade→NewPhysicsOpportunitiesforALICE • StudythethermalizationofpartonsintheQGP,withfocuson • charmandbeautyquarksatlowpT • secondaryvertices • Low-momentumcharmoniadissociation(andregeneration?)tostudydeconfinementandmediumtemperature • Productionofthermalphotonsandlow-massdileptonsemittedbyQGPtostudyinitialtemperatureandequationofstateofthe medium • exploitlowpTreach&PIDofALICE • ProcessesCannotbeselectedattriggerlevel • Movefrom1kHztriggeredrunninginALICEto50kHzPb-Pb • RecordEverything! 16June2017

  8. Why We Needto UpgradetheTPC PresentTPC: Wirechamberendplates ~ • pResolution: spT/pT< 3.5%atpT= 50GeV/candbelow1% atpT=1 GeV/c. • • • • dE/dxresolution: 5%(p-p)– 6.5%(centralPb-Pb)(158max. samples) Event rate: 1 kHzPb-Pbminimumbias Wantto beable to record50kHzPb-Pbcollisionrateand maintainthecurrent performance BUT Drifttimeforionizationelectronsfromcentral electrodeto endplateisO(100s) Drifttimeforionsfrom endplateto central electrodeisO(160ms) Buildupofpositiveionsinthe drift volume →electricfielddistortion→distortion ofthe ionizationelectrontracksas theydriftto theendplates Ionsproducedbychargedparticlestraversingthe detector areunavoidable– this isthe signal Ionsfromthegainstructure-typicallyafew thousandtimestheinitialionization- mustbepreventedfromgettingto maindriftvolume 16June2017

  9. UsualSolution Usea gatinggridbetween thegainelementandthedriftvolume MainDrift Gatinggridisnormallybiased to preventpassageof charged particles(ionizationelectronsandions) GatingGrid GroundPlane Anodewires(gain) TPCisrun intriggeredmode • Readout(padplane) • Whena triggeroccurs,gatinggridisbiased(opened)to allowpassageof chargedparticles • Thegridiskeptopenforthetimerequiredto collecttheionizationelectronsO(100s) • In thistime,noionsfromthegainelement(anodewires)canescapethegainregion • Gridthen mustbekeptclosedlongenoughto collectallionsO(300s) • Intrinsicdead time→ratelimitation~3kHz • EliminatethegatinggridbyexploitingthelowIonBackFlow(IBF)ofGasElectronMultipliers(GEMs)* • *B.Ketzeretal.,Nucl.Instrum.Meth.A732(2013)237-240 16June2017

  10. GasElectronMultipliers(GEMs) Oneofseveralmicropatterngasdetectorsdeveloped overthepast~20years. InventedbyFabioSauliat CERN SauliNIMA386(1997)531 5 m Copper 70m 50m 50mpolyimide • Typical parameters: • 50mKapton • metalcoated • Ø50-70mholes • •100-200mpitch 5 m Copper 140 m 1e-in >103e-sout Electricfieldintheholes~100kV/cm 10 16June2017

  11. Solution– TechnologyChoice • Severalyear R&Dprogramdevelopeda solutionwith4-GEMchambers • Different GEMholepatternsoneachGEMhelps to blockionbackflow • Tradeoffbetweenenergyresolution(large gaininfirstfoil)andionback flow (IBF)(smallgain infirstfoil) StandardPitch notrotated LargePitch 400V/cmdriftfield DV=270V DV=800V DV=230V 55Fepeaks/mean(%) DV=800V rotated LargePitchnotrotated StandardPitchrotated DV=288V dE/dxres.=8.5% dE/dxres.=8.0% DV=20 DV=359V DV=800V IonBackflowcurrent/AnodeCurrent(%) 90-10-5 Ne-CO2-N2 Eightvoltages(DV on4 GEMsandDVon4 gaps)makeshugeparameterspace to scan Curvesofenergyresolutionvsionbackflowshowaregionthat meets ourdesigngoalsandalargerregionthatgivesacceptableperformanceto meetthephysics goals. Calibrationmethodforcorrectingspace-chargedistortionsisalreadyin usefor thecurrentrunandhandlesvariations evenlargerthanwesee inprototypechamber. 11 16June2017

  12. ReadoutChamber DesignandConstruction ALICETPCendplatereadoutisdividedinto18 20osectorsoneachend.Eachsectorhasaninnerchamber(IROC)andouterchamber(OROC).TomaintainreasonablesizesfortheGEMfoilstheOROCsaredividedinto3sections. GEMfoilsizes ₋ 40sectors(36installed+ 4spare) ₋ 4 GEMstackspersector ₋ 4GEMfoilsperstack GEMfoilnumbers =640GEMfoils Toaccomplishthisverylargeconstructionefforttheprojecthasbeendividedamongseveralinstitutions 16June2017

  13. DivisionofEffortforROCandElectronicsConstructionandTesting 45Institutes Managingmaterial flowamongmany institutesisnota smallpart oftheproject.ForROC constructionDatabase isusedto trackmateriallocation,statusand archive QA+testdata. 16June2017

  14. Divisionofeffortand materialflowforROC constructionandtesting. Managingmaterialflow isnota smallpart oftheproject. Database isinplaceandbeingusedto trackmateriallocation,statusand archive QA+testdata. 16June2017

  15. Single FoilAdvancedQA • Twoinstituteshave optical scanners andsoftware to measureall inner (polyimide)andouter (copper)holediameters. • Wealso canmapthe gainacrosssingle foils. • Trainingneuralnet software to predict thegainbasedonopticalmeasurements. • Clear correlationis seenandthe optical scanisfasterandeasiertodo. • Everyfoilwillbe opticallyscannedandacceptance criteriaestablished. HoleDiameter(mm) RelativeGain Scan shownisfrom“flawed”foil–usefultohave largerrange ofholesizesforneuralnet training 16June2017

  16. FoilHandlingandTesting Commercialstencilstretchingframeused. Theinnerframeisused forhandlingfoilsuntiltheyareglued ontofiberglassframe. HV Testing: • Plexiglassboxcanbeflushedwithdrynitrogen. • Springpinsinlidconnectto eachofthefoilHVsegments • Multichannelfloatingpicoammeterdevelopedcanmeasureleakagecurrentsat HV downtoafewpA • FoilscheckedbeforeleavingCERN,atadvancedQAsite,beforeandafterframingandbeforemountinginchamber • Foilmountedininnerframeassoonasitcomesfrom CERN shop • Stayswithfoiluntilfoilisfinallytrimmedto finalfiberglassframe • Outer(blue)frameclampsinnerframeandappliescalibratedstretchingforce(Calibratedsprings) 16June2017

  17. FrameingluingfixtureatWayne State 16June2017

  18. Foilingluing fixture 16June2017

  19. Curingin dryatmosphere 16June2017

  20. Foiltrimmingplate Glassplatewithholematchingalignmentholeincornerof GEMfoil andframe. Dowelpinskeepfoil,frameandprotectivealuminumcoverinplaceduringtrimming 20 16June2017

  21. Alubody atYale, mountedon baseplatefortestand shippingvessel 16June2017

  22. Closeup showing highvoltageconnectorsandcoolingtubes 16June2017

  23. 16June2017

  24. For assemblywork,solderingHVleadstoGEM’sorwhennotnecessarytohaveGEMexposeditisalwayskeptcovered. 16June2017

  25. IROC foilsassembled on pad plane,alubody,testvesselbaseplate. Readyfortestvesselcover. 16June2017

  26. X-raygeneratormountedtoilluminatefullchamber 16June2017

  27. Shortingcards bringcurrentfrom allreadout padstoacurrent meter. 16June2017

  28. X-raygenerator mountedtoscanchambertomapgain andion backflow. ThinWindow X-Y Stages X-rayGenerator 16June2017

  29. Typicallivedisplaywhilescanningchambergainvsposition 16June2017

  30. AssembledChamberTestingandQA • Gastightness(monitorH20,O2ingasexitstream) • Gaincurveandgainatstandard voltages(55Fepeak) • Stability–run for2 days,monitorgain andany discharges • Spatialmapof gainand IonBackFlow(IBF)–scan chamberwithcollimatedX-ray source, measureanodeandcathodecurrentsateachlocation • “Stress”test –illuminatefullchamberwithX-ray sourceto give10nA/cm2anodecurrent(max. expectedin operationatLHC). Monitorfordischarges. Inches Inches Inches Inches *Local IBFvariation canbetoleratedif thepatternisstableintime. Testsindicatethatitis. 30 16June2017

  31. DataCompression Allthis datapouringoutofthefrontend hastobefurthercompressed,monitored, usedtofeedcalibrationsbackintocompression,… 3.2TByte/sintoPCfarm O2(OnlineOffline)SystemHardwareandsoftwaredevelopmentsongoing 50 kHz ReconstructionCompressionMonitoringCalibration Storage PEAKOUTPUT (20GB/saverage) 75 GB/s 16June2017

  32. StatusandSchedule • TwofullprototypeIROCandOROCchambershavebeenbuiltusingnearlyfinaldesignandtested • Changesmadetodesignandtoprocedures • Final-designpartsorderedfor5IROCand5OROCchambers • Gainmoreexperiencebeforestartingfullproduction • Finaldesignchamberbuiltandundertestnow. → → → → 16June2017

  33. BackupSlides 16June2017

  34. NewFrontEndCard(FEC)forTPCUpgradereadout-5x105Channels • UsesfiveALICEcustom-designed32channelASICs(SAMPA)providing preamp/shaper/ADCanddigitalsignal processing • 3276FECswillbeinstalled,eachwith160channelsusingradiationtolerantcomponents(radtolerantto 5.6kRadintegrateddose) • Systemcontinuouslydigitizessignalsat 5MHz*for0.5MTPC channels. • FECssenddigitizeddataoverfiber optic linksto ALICECommonReadoutUnits(CRU) • *Detailedsimulationsshowthat the TPC samplingratecanbeloweredfrom the present 10MHzto 5MHzwithout compromisingthephysics performance. • >> Onboardfrontendzerosuppressionnotrequired • Baselinecorrectionandzero suppressioncanbe doneina computer– mucheasiertoprogramandchangeif needed. 16June2017

  35. SAMPA– Custom ASICforTPCandMuonTrackingChambers • SAMPA= 32channelchip–mixed analogand digital–also used formuon trackerupgradeDevelopmentplanallows3cycles • Cycle1 –functionalitydividedinto 3chips,lotsoftestfeaturesincluded • Cycle2 –allfunctionsintegratedinto onechip • Deliveredandtested. Noiseperformancelooksverygood-average360electronsonthebench • Someglitchesindigitalpartfoundbutworkaroundshaveallowedfunctionalfront endcards(FEC)to bebuilt • Test • Cycle3 –allfixesincorporated • SubmitthisSpring • ExpectchipsinSummer • Workalreadyongoingforfinal FEC design • Testfullyinstrumentedchamber 16June2017

  36. TPCFrontEndCardPrototype(Rev.0a) 5cycle2SAMPAchips 4connectorsforflatjumpersto connectorson padplane Note:FinalFECwillberigid-flexwitha flex layerextendinghereto plugdirectlyinto padplaneconnectors–no jumpercablesneeded 18.4cm 18.6cm 16June2017

  37. Summary The ALICEcollaboration isbuildinga majorupgradefortheALICETPC tobeinstalledinthe LHCLongShutdown2(2019-2020) • This upgradewillallow operation inthe highluminosityin LHCruns 3and4 (50kHz Pb-Pb collisionrate)while maintainingthecurrent physics performanceofthe TPC. • The upgradeinvolves: • Replacingallreadoutwire chambers withquadruple-GEMchambers. • The GEMsare designedto minimizeionbackflow to allow continuous,ungatedanduntriggeredreadout. • Replacingthefront endelectronicswithelectronicsbasedonanewASIC (SAMPA)designedto allowcontinuousreadout • Developingsoftwareto achieve compressionofthe 3.2TB/secrawdata fromthe TPC • ThisupgradewillallowALICEto recordthe full Pb-Pbluminosityandgather veryhighstatisticsdatasetsevenforprocesseswhere a triggerisnotpossible. 16June2017

  38. Usingrollertoapplyepoxy 16June2017

  39. PressureplateandSSbricks 16June2017

  40. FEC Blockdiagram 40 16June2017

  41. WhatwillALICEdoto exploitthesenewphysicsopportunities? NextPresentation,PaoloMartinengo Thenew FastInteraction Triggerdetectorfor theALICEUpgradeWladyslawHenrykTrzaska,Poster DetectorControlSystem ofthenewMuonForwardTrackeratALICEKentaShigaki,Poster ProspectsforALICEphysicswiththeMuonSpectrometerUpgrade and thenew MuonForward Tracker AntonioUras,Poster This Presentation 16June2017

  42. Nygren,http://www.slac.stanford.edu/pubs/slacreports/reports04/slac-r-190.pdf,p126Nygren,http://www.slac.stanford.edu/pubs/slacreports/reports04/slac-r-190.pdf,p126 16June2017

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