Ageing studies of TPB in noble gas detectors for dark matter and neutrinoless ββ decay searches 2017 N. Yahlali.pdf

该【Ageing studies of TPB in noble gas detectors for dark matter and neutrinoless ββ decay searches 2017 N. Yahlali 】是由【探春文档】上传分享，文档一共【6】页，该文档可以免费在线阅读，需要了解更多关于【Ageing studies of TPB in noble gas detectors for dark matter and neutrinoless ββ decay searches 2017 N. 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】的内容，可以使用淘豆网的站内搜索功能，选择自己适合的文档，以下文字是截取该文章内的部分文字，如需要获得完整电子版，请下载此文档到您的设备，方便您编辑和打印。SAA-14388;NoofPages6SpectrochimicaActaPartA:MolecularandBiomolecularSpectroscopyxxx(2016)xxx–xxxContentslistsavailableatScienceDirectSpectrochimicaActaPartA:MolecularandBiomolecularSpectroscopyjournalhomepage:ate/,?,,íaza,,ísicaCorpuscular(IFIC),CSIC&UniversitatdeValència,CatedráticoJoséBeltrán2,46980Paterna,Valencia,SpainbInstitutodeCienciaMolecular(ICMOL),UniversitatdeValència,CatedráticoJoséBeltrán2,46980Paterna,Valencia,SpaincLIBPhys,DepartmentofPhysics,UniversityofCoimbra,3004-516Coimbra,PortugalarticleinfoabstractArticlehistory:Noblegases(Xe,Ar,Kr)areveryattractiveasdetectormediainDarkMattersearchandneutrinolessdouble-,thedetectionoftheirscintillationlight(intheVUVspectralregion)requiresReceivedinrevisedform3March2016shiftingtheVUVlighttovisiblelight,wherestandardphotosensorsaremoreef?(TPB)iswidelyusedaswavelengthshifter,absorbingtheVUVlightandre-emittingintheblueregionAvailableonlinexxxx(~430nm).,wepresentTPBageingstudiesduetoexposuretoVUVlight,aimingatquantifyingKeywords:?Neutrinolessdouble-betadecaythereductionoftheabsoluteuorescenceyieldofTPBcoatingsofseveralthicknesses(130nm,260nm,390nm,Highpressurexenongas1600nm),exposedtovariousdosesofVUVlightat170nm(similartotheXescintillation).Inoursetup,theVUVTimeprojectionchamber(TPC)-100experimentforWavelengthshifterneutrinolessdouble-betadecaysearch.?,toourknowl-edge,thephoto-degradationofTPBcoatingshasnotbeenquanti?edHeavynoblegases(argon,krypton,xenon)haveoutstandingspec-parabletothatobtainedinatroscopicpropertiesthatmakethemveryattractiveasdetectormedianoblegasdetector,operatedintheconditionsofanundergroundinDarkMattersearchandneutrinolessdouble-beta(ββ)decayexperi-[1].However,theirscintillationlight,whichisinthevacuumul-Inthispaper,wepresentastudyofTPBageingduetoexposuretotraviolet(VUV)spectralregion,isdif?culttodetectbymoststandardVUVlightaround170nm(xenonscintillationpeak),aimingatquanti-photodetectors,especiallysiliconphotomultipliers(SiPM),whicharefyingthereductionoftheabsolute?uorescenceyield(orconversionef-mostlyef??ciency)-lightusingawavelength-?uoringsofdifferentthicknesses(130nm,260nm,390nm,1600nm)weretetraphenylbutadiene(TPB)of≥99%puritygrade[2]absorbslightindepositedbyvacuumevaporationonquartzsubstrates,followingthetheVUV-UVspectralregionandreemitsintheblueregion,aroundprotocoldescribedin[6].EachsamplewasexposedtocontrolledVUV430nm,,whichsimulatestheexposureconditionsingasdetectors(NEXT[3],ArDM[4])duetotheshortscintillationwave-thegaseousXeelectroluminescentTPC,calledNEW,usedintheNEXTlengthsofthenoblegases(128nmforAr,172nmforXe).Itisusedasexperiment[3].ThisTPCispresentlybeinginstalledintheCanfrancUn-acoatingfortheactivesurfaceofthephotosensorsandtheinternaldergroundLaboratory(LSC)[7]formeasuringthetwo-(ββ2ν)-(mostlyhumidityandoxygen)andtointensephoto-degradationoftheTPBresultingfromthisVUVexposureisana-lightlevels,bymeansoffree-radicalmediatedphoto-oxidationre-[5].Thisdegradationresultsinareductionofthe?uores-?×10×1mmE-mailaddress:Nadia.******@i?().wereusedforthevacuumdepositionofTPBlayersofdifferenthttp://dx./.-1425/?:,etal.,AgeingstudiesofTPBinnoblegasdetectorsfordarkmatterandneutrinolessββdecaysearches,SpectrochimicaActaPartA:MolecularandBiomolecularSpectroscopy(2016),http://dx./../SpectrochimicaActaPartA:MolecularandBiomolecularSpectroscopyxxx(2016)xxx–xxxisobtainedusingaprimarypumpinserieswithtwoturbo-molecularpumps,(ThorlabsDGUV10–220)isusedattheVMCoutputtoprovideauniformillumina-tionoftheTPB-,ata?xeddistance,wherethelightintensityisprevious-lymeasuredbyacalibratedphotomultipliertube(PMT)operatedwith-outgain,??uxatthechosenlongitudinaldistancefromtheVMCoutput,?xedtoamovablevacuumfeed-throughthatallowsthecorrectadjust-mentofthePMT/(at170±3nm)beingsimilarinboththeXeTPC()andthetestsetup(),fromEq.(1)(redcurve)obtainedexcitingaTPBlayer,depositedonainthetestsetup:quartzsubstrate,withUVlightat250nm(blackcurve)(black)isobtainedusingareferencequartzsubstratewithoutTPB.(Forinterpretationofthereferencestocolorinthis?gurelegend,thereaderisreferredto???eT1T12T22thewebversionofthisarticle.)thicknesses:130nm,260nm,-InEq.(2),?1and?2arethephoton?uxes(numberofphotonspertumyield(or?uorescenceef?ciency)ofthesecoatingswasmeasuredunitoftimeandperunitofarea)impingingintheTPB-coatedsurfacesimmediatelyafterthecoatingprocessandafterexposuretoVUVlightfortheTPCandthetestsetup,respectively;-,whennotexposedtoVUVlight,werestoredindarkandinnitro-heVUVlightexposureintheTPB-coatedsur-genatmospheretoavoidhydrationandoxidationthatmaybiasourfacesoftheNEXTTPCpresentlybeinginstalledatLSC(NEW),weas-photo--?eldof2kV/cm/barintheTPCELregion,whichcor-respondstoanopticalgainofabout2000photonsperprimaryelectronThephoto-degradationofTPBcoatingsandthesubsequentreduc-[9].Theaverageenergyrequiredtoproduceanelectron-ionpairintionofthe?uorescenceresultingfromexposuretolightisastochasticxenonbeingW=,thenumberofprimaryelectronsproducedprocessthatdependsonthelightintensityI,itsfrequencyoreventpereventof1MeVis106/=,=×?ux,?=Iν/?,where?-he?uxofphotonsintheTPB-coatedsurfacessureEcanthenbede?nedbyEq.(1).oftheNEWTPC,?eldcagewithalengthL=508mmandaradiusE?IνT???Te1TR=,the262totalareacoveredisA1=2πR+2πRL=×?uxofInanoblegasTPC,theinteractionofaparticlewiththegasproducesphotonsintheTPBlayersisthen?1=N1ν1/A1=7967photons/s/,assuminganeventrateν1=,ampli?(EL)isanopticalampli?cationprocessoftheionizationsignal[8].eleratingtheelec-tronsinanarrowregionofhighelectric?eld,wheresecondaryscintilla-tionlightisgenerated,,withagainofabout2thousandphotonsperelectron(seepage3reference[9]).TheELyieldthusdependsontheenergyoftheincidentparticlesthatoriginatetheeleratetheelectrons,typically2to3kV/cm/,theELscintillationisemittedintheVUVspectralregion,around128nmand172nm,-coatingsinsuchaTPCoverlongperiodsoftime(atleastseveralmonths),asusuallyrequiredforundergroundexperiments,anequivalentlightexposurehastobeprovidedonsimilarTPB-coatings,usingamonochromaticVUVlightof?xedintensityandfrequency,varyingtheexposuretime,-(),VUVlightisprovidedbyadeuteriumlampcoupledtoavacuummonochromator(VMC)fortheselectionoftheir-radiationwavelengthat170±-(S2)ampli?esthe?(electrons):,etal.,AgeingstudiesofTPBinnoblegasdetectorsfordarkmatterandneutrinolessββdecaysearches,SpectrochimicaActaPartA:MolecularandBiomolecularSpectroscopy(2016),http://dx./../SpectrochimicaActaPartA:MolecularandBiomolecularSpectroscopyxxx(2016)xxx–?uorescencespectro-gramofaTPB-coatedquartzsample,thesamplewasplacedinsideanintegrationspherecoupledtoaspectrometer,withinwhichitwasex-posedtomonochromaticUV–-cludesaxenonlampfromHamamatsuPhotonics(modelE7536,150W),coupledtoamonochromator(MC)fortheselectionoftheex-citationwavelength,andaspectrometeralsofromHamamatsuPhoton-ics(MultichannelAnalyzerC10027)?ectivePTFEcoating,allowingmultiplescatteringofthelight,--coatingsamplesexposededfromtheMCtotheintegratingsphereandfromthislattertothetoVUVlightat170±3nmfromadeuteriumlampcoupledtoavacuummonochromatorspectrometerthroughquartzoptical?-he?uxofVUVlightat170nminthetestsetuplutequantumyieldoftheTPBlayeriscalculatedastheratiobetween(),weusethephotocurrentmeasuredinthePMTatthepositionthe?uorescenceyieldandtheabsorptionyield,thelatterbeingdeter-oftheTPBsamples,whichis1nA,×?,S0beingtheareaoftheincidentlightpeak,PMT(),thenumberofS1theareaofthelightpeakscatteredfromthesample,×=,theVUVphoton?uxinEq.(3).Theexcitationwavelengthsconsideredwerefrom250nm,97thePMTis?2=N2ν2/A2=×10/=×10photons/s/whichisthelowestwavelengthmeasuredbythespectrometer,?uxintheTPB-coatedsamplesisthesameastheyareplaced430nmwhichcorrespondstothe?(T1=×10s),ac-?S2eTcordingtoEq.(2)theequivalentexposuretimeinthetestsetupisT2=QY3S0àS1T1?1/?2=436s().So,irradiatingtheTPB-coatedsamplesover7mininourtestsetup,withaphoton?uxcorrespondingto1nAcurrentinthePMT,wouldcorrespondto1monthofexposuretoVUVThedura