Lifetime of HPK Square-shape MCP-PMT

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Lifetime of HPK Square-shape MCP-PMT. T. Mori ( Nagoya University) On behalf of Belle II PID group Dec. 1, 2010 Fast Timing Workshop Cracow , Poland. Belle & Belle-II Experiments. Super B-factory. Belle detector. Belle II experiment. K /π-ID is important Belle: 3σ. K /π-ID power: 4σ - PowerPoint PPT Presentation

Transcript of Lifetime of HPK Square-shape MCP-PMT

Performance Test of TOP Counter Prototype

Lifetime of HPK Square-shape MCP-PMTT. Mori (Nagoya University)On behalf of Belle II PID group

Dec. 1, 2010Fast Timing WorkshopCracow, Poland

Belle detector3.5GeV8GeVBelle & Belle-II ExperimentsK/-ID is importantBelle: 3

K/-ID power: 4ex. S/N 5 for B High background rateDec. 1, 2010Fast Timing WS, Cracow2Higher statistics Higher luminosity (~40)B-factoryHigher accuracy Belle detector upgradeSuper B-factory

2.6m1.2me- : 7GeVe+: 4GeV1.5TForwardBackwardInstall here(10cm gap of barrel part)Belle II detector cross sectionBelle II experimentTOP counterFor barrel part(Time Of Propagation)TOF + ACC(ACC: Threshold type Aerogel Cherenkov Counter)

TOP CounterDec. 1, 20103Fast Timing WS, Cracow


Kt ~ O(100ps)K, with p = 4GeV/cTOP = 40ps (L ~ 1m, C = 6mrad)TOF = 30ps (L ~ 1m)Time Of Propagation counterRICH + TOF techniqueCherenkov radiator + time sensitive screenPosition (x, y) (RICH) Position + time (x, t)Very compact & simpleRadiation hardnessPerformance & Important DevicePerformance definition

photodetector : TTS of photodetector

Ndet: number of detected photonsDec. 1, 2010Fast Timing WS, Cracow4

Separation power :Photo-detector is very importantOur selection: MCP-PMTRequirementsTTS : 20%@=400nmAvailable in B -field

> ~ 50ps (Chromatic)Square-shaped MCP-PMT: SL10Dec. 1, 20105Fast Timing WS, Cracow

11mm27.5mm27.5mmOrdinary cylindrical MCP-PMTSquareMCP-PMTCo-development withHamamatsu Photonics K.K.

Typical signal shapeSingle photon irradiationCatalog specPhoto-cathodeMulti-alkali / Super bi-alkaliMCP Channel 10mMCP bias angle13MCP thickness400mMCP layers2Al protection layerOn 2nd MCPAnode channels14 / 44Sensitive region64%HV~ 3000 3500 V

~400mChannel ~ 10m

~4mmMCP(Micro channel plate)Performances of SL10Dec. 1, 20106Fast Timing WS, Cracow

Wavelength [nm]QE [%]Multi-alkali PC

TDC [25ps]Number of eventstts = 40 [ps]All requirements satisfiedRemaining factor: stability(Lifetime)in high photon rate~7x1012 photons/cm2/year~0.17 C/cm2/yearEstimated with TOF trigger hit rateCylindrical type: enough lifetime

ADC [0.25pC]Number of eventsPedestalG ~ 106Single photon irradiationDec. 1, 2010Fast Timing WS, Cracow7

For single photon test~40-photon/pulse1k 40kHzParametersTTSphotodetectorGainSingle photon detectionEnough statistics for TTSQENdetLifetime measurement for SL10Load of photons & single photon testdone in same setupMeasured PMTYJ0006YJ0011Anode channel4444Al protection layer1st MCP2nd MCPInitial gain (106)0.411.1calibration PMTResult: TTS, GainDec. 1, 2010Fast Timing WS, Cracow8Decrease

Good Stability

TTS is stableSingle photon detection is OK

00.4 Time in Belle II experiment [years]No problemQE differenceSL10

CylindricalDec. 1, 2010Fast Timing WS, Cracow9LifetimeQE degradation: predominant factorGain: linearly decrease; still OK for single photon detection & TTSTTS: Stability confirmedWhy?Result: QE

CylindricalPreviousSL10Lets see QE in detail

QE Variation: WavelengthIncrease of work function dominatesDec. 1, 2010Fast Timing WS, Cracow10

Wave length [nm]QE [%]Before agingAfter agingWork functionFitting: ratio of QE

Three step model:T : transmittanceA: mechanical factor (effective region): work function: variation of work function

A(t)/A(t=0) 0.980.04 0.270.07eV 1.560.13eVYJ0011QE Variation: PositionDec. 1, 201011Fast Timing WS, CracowQE before aging

x [mm]y [mm]QE after aging

y [mm]x [mm]Surrounding part: large QE dropIon feedback?Structure?

xy116Effect of Ion Feedback?Ion feedbackMask: no effect

Ion feedbackDec. 1, 2010Fast Timing WS, Cracow12

Lifetime test with mask

QE variation without maskQE variation with mask

Positive Iondamages same positionas signal photon irradiationLifetime test with maskMaskMCP-PMTWindow

Inner Structure & Possible CauseOnly NEUTRAL gas can pass through gap (electric field)

Dec. 1, 201013Fast Timing WS, CracowInner structure of Cylindrical type & square-shaped MCP-PMTsWindowPC1st MCP2nd MCPAnodeWindowPC1st MCP2nd MCPAnodeENeutral gasCylindrical: separatedSquare: connectedPoisoning of multi-alkali PC with different gasses(INFN Milano LASA, Via F.lli Cervi 201, 20090)We also found report saying CO2 and H2O affect QE:(Japanese Journal of Applied Physics 29, No. 10, p. 2087 (1990))Too much oxidation of Csvariation of band gapincrease of work functionAl-filmCeramic tubeStainless tubeAl-filmModification of Inner StructureSeparate space to PC-side & anode-sideIt is not high airtightMCPs are changed with that of low outgassing typeTo reduce amount of out gas

Dec. 1, 2010Fast Timing WS, Cracow14WindowPC1st MCP2nd MCPAnodeCeramicinsulatorCeramicinsulatorAl-filmLifetime for New SL102.5 [C/cm2] for relative QE 80%1.21014[photons/cm2]Dec. 1, 201015Fast Timing WS, Cracow

AftermodificationBefore modificationRelative QEOutput charge [C/cm2]0101 Time in Belle II experiment [year]DOI:10.1016/j.nima.2010.10.145

SL10 is availableSummaryWe are developing TOP counter for Belle-II experimentTOF + RICH technique TTS & Nphotons are importantSquare shape MCP-PMT (SL10) is developed for TOPSatisfies required performances (TTS, gain) for TOPLifetime of QE in high photon rateWe find possible cause of QE drop: Neutral gas (CO2 & H2O) Improvement of inner structure against gas damageSeparate space to PC-side & anode-side by ceramic insulatorLow outgassing MCP

2.5C/cm2 for relative QE 80% achieved> 10 years under ~71012 photons/year/cm2

Dec. 1, 201016Fast Timing WS, CracowBackupDec. 1, 2010Fast Timing WS, Cracow17Photon Hit Rate EstimationDec. 1, 2010Fast Timing WS, Cracow18Main source: spent electrons EM shower Cherenkov lightTOF hit rate in Belle experiment: 187kHz @ L=1034cm-2s-1Belle spent electron simulator: 400 500 kHz @ L=1034cm-2s-1Use 500 kHz electron Geant simulationTOP counter is implemented Quartz radiator: 265045420[mm3] Without expansion volume QE: 20% @ =400nm CE: 60% To be conservativePhoton hit rate of MCP-PMT: 300kHz/(TOP module)Factor 20 is expected for Belle-II experiment with L~1036cm-2s-1(20300 / (45.42))365/2246060 / (QECE)= 6.91012 [photons/cm2/year] effective factor(20300 / (45.42))365/2246060Ge = 167 [mC/cm2/year] Gain: 106 Photon hit rate Typical output chargePerformance of TOP CounterPerformance definition

top= (MCP-PMT2 + chromatic2 + others2)Ndet: number of detected photonsDec. 1, 201019Fast Timing WS, Cracow

Separation power :

Photo-detector is very important

zxyNdet 0.8Ndet S 0.9SSuppression of Chromatic DispersionWavelength cutDec. 1, 201020Fast Timing WS, Cracow

Group velocityof lightNumber ofCherenkov photonsTransmittance ofwavelength cut filter350nm

Suppression of chromatic dispersionwith 350nm wavelength cut filterwavelength cut TTS improveNdet decreasefine tunechromatic5025psPath length in quartz: 1mNumber of detected photonsDec. 1, 2010Fast Timing WS, Cracow21

Photo-detectorRequirementsGain : 1.0106TTS : 20%@=400nmAvailable in B -fieldDec. 1, 201022Fast Timing WS, Cracow

(Micro Channel Plate)Only photo-detectorsatisfies requirementsMCP-PMTSquare type MCP-PMTCo-developmentwith Hamamatsu Photonics


Channel ~10m, Bias angle of MCP : 13Available in B-fieldSL10Dec. 1, 2010Fast Timing WS, Cracow23

Cylindrical & SL10Dec. 1, 2010Fast Timing WS, Cracow24

Lifetime differenceCylindrical

SquareDec. 1, 2010Fast Timing WS, Cracow25

For single photon test~40-photon/pulse1k 40kHzCylindricalSquareLifetimeQE degradationpredominant factorGain & TTSstability confirmedWhy?Lifetime measurement for SL10Gain decreaseDec. 1, 2010Fast Timing WS, Cracow26

Before photon loadAfter photon loadOutput chargeADC plotsE - Dec. 1, 2010Fast Timing WS, Cracow27

How the QE Degradation Occur?QE fall is not uniformIon feedback is not reasonableDec. 1, 201028Fast Timing WS, Cracow

x [mm]QE [%] (y = 10[mm])QE fallBeforeAfter

Wave length [nm]QE [%]BeforeAfterIncrease of work functionBefore measurement

x [mm]y [mm]After measurement

y [mm]x [mm]How the QE Degradation Occur?QE fall is not uniformIt is not reasonable if it caused by Ion feedbackDec. 1, 201029Fast Timing WS, Cracow

x [mm]y [mm]Initial QE

x [mm]y [mm]Terminal QE

x [mm]QE [%] (y = 10[mm])QE fallInitialTerminalPossibility of neutral gas

Inner structure of CT0790 & square-shaped MCP-PMTsNeutral gas assumptionDec. 1, 2010Fast Timing WS, Cracow30


Lifetime of SBA-PCDec. 1, 2010Fast Timing WS, Cracow31

0101 Use in Belle II [years]SBA1SBA2MASet up for Beam TestDec. 1, 201032Fast Timing WS, Cracow

electron beam2GeV/cMCP-PMTTimingCounterMWPC2MWPC1Veto counterTriggerCounterTOPCounterxyxySubtract EM-shower eventsBeam trajectoryt0 determinationQuartz + MCP-PMT

Fuji test beam lineat KEKPrototype test for TOPConsistency confirmedDec. 1, 2010Fast Timing WS, Cracow33TTS1st peakData76.02.0 [ps]Simulation77.72.3 [ps]


1st 2nd3rd

1st 2nd3rd transit time[25ps]N [photons]transit time[25ps]datasimulationElectron beam irradiation875mm915mmquartz3rd 2nd1st