NeutronDamageofCCDsinATLASEndcap

CamilaPazosBrandeisUniversityJ.Bensinger, K.Hashemi,L.Simpson, R.Studley

RadSimWGMeetingMay21,2019

CCDsintheATLASendcapalignmentsystemcanexperienceabuildupofchargeinpixelsfromthermallygeneratedelectrons,calleddarkcurrent,causedbyneutrondamage.

WemeasurethedarkcurrentintheATLASCCDsandmodeltherelationshipbetweendarkcurrentandneutrondosewiththeequation

I = α D e(T−20°C)/(12°C) counts/px/mswhere,I isdarkcurrentincountsperpixelpermillisecondD istheneutrondosein1012 1-MeVNEcm-2 (Tn)T istemperatureincentigradeα isarateconstantthatdescribesthedarkcurrentgeneratedperneutrondose incounts/px/ms/Tn

Measurementsoftheamountofdarkcurrentinoursystemcouldbeusedasmeasureofneutronflux.

AlignmentSystem&CCDs

BRANDEISUNIVERSITY- CamilaPazos 221-May-19

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Pre-ProductionExperiments

LowellExperiment:• In1998,fourTC255PCCDheadsweresubjectedtovaryingneutrondoses(between2.0Tnand8.0Tn)over9hourswithaneutronsourceatUniversityofMassachusettsatLowell.

PROSPEROExperiment:• Thefollowingyear,8TC255PCCDheadsweresenttothePROSPEROreactorinFrance.Theyreceivedneutrondosesbetween0.5Tnand10.0Tn.

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I = 0.28 D e(T−20°C)/(12°C) counts/px/ms

I = 0.26 D e(T−20°C)/(12°C) counts/px/ms

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NeutronDamageinATLAS

DataSetInformation• ImageswerecapturedwitheachCCDandanalyzedtofinddarkcurrentduetoneutrondamage.• Eachdatasetcontainsimagesfrom2670CCDs.• 30datasetscollectedbetween2016- 2018.• RecordtheaveragetemperatureintheATLAScavernforeachdataset.

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20- 15- 10- 5- 0 5 10 15 20Z (m)10-

5-0

510X (m)

10-

5-05

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Y (

m)

ATLAS Endcap CCD Map

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ATLAS Endcap CCD Map

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NeutronDamageinATLAS

• Wemeasuredalldarkcurrent(usingbrightpixels)presentinourCCDsinATLASonOctober16,2018.• ThedarkcurrentdecreaseswithdistancefromIPalongthebeamlineandradiusfromthebeamlineasexpected.

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0

0.002

0.004

0.006

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counts/px/msOct16: Dark current by distance from IP

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NeutronDamageinATLAS- FLUGG

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a(counts/px/ms/Tn) )-1 Dose (after 154 fb-2 1MeVNE cm12Oct16: Dark Current per 10

C°T = 24 = 14TeVsFLUGG,

= 0.104aavg = 0.247amax

= 0.037amin

http://young.web.cern.ch/young/RadiationMap/

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NeutronDamageinATLAS– GEANT4

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0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 |z| (cm)

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a(counts/px/ms/Tn) )-1 Dose (after 154 fb-2 1MeVNE cm12Oct16: Dark Current per 10

C°T = 24 = 13TeVsGEANT4,

= 0.172aavg = 0.672amax

= 0.049amin

http://radsim.cern.ch/RadiationSimulation/G4_Run2_NIEL_0_1200_0_2400_1_78.txt

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ber o

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value distribution by simluation useda

FLUGG = 0.104aavg

= 0.098amedian

GEANT4 = 0.171aavg

= 0.141amedian

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α Values- FLUGGvs.GEANT4

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NeutronSpectra

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.2] @

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/cm

kin

(E

10

/ d

log

Fd

kin Neutron Fluences vs. E = 13TeVsGEANT4,

= 0.672, |z| = 2160cm, r = 310cm a max = 0.049, |z| = 760cm, r = 460cm a min

= 0.141, |z| = 1120cm, r = 750cm a med

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/cm

kin

(E

10

/ d

log

Fd

kin Neutron Fluences vs. E = 13TeVsGEANT4,

closest to IP, |z| = 720cm, r = 200cm = 0.109a

farthest from IP, |z| = 2170cm, r = 1190cm = 0.214a

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Conclusion

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• Wemeasureddarkcurrentin2670ATLASendcapCCDs.Usingsimulatedneutronfluxdata,wecalculateddarkcurrentperneutrondosereceived.Wecomparedthesemeasurementstotheresultsobtainedinpast,controlledexperiments:

Experiment α (count/px/ms/dose)

1998Lowell 0.28

1999PROSPERO 0.26

2018 ATLAS- FLUGG 0.104

2018ATLAS– GEANT4 0.172

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Backup

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(counts/px/ms/Tn) )-1 Dose (after 154 fb-2 1MeVNE cm12Oct16: Dark Current per 10

C°T = 24

= 14TeVsFLUGG,

= 0.104aavg = 0.247amax

= 0.037amin

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NeutronDamageinATLAS- FLUGG

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0 2 4 6 8 10 12 14 16 18 20 22 24 |z| (m)

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(m)

a

(counts/px/ms/Tn) )-1 Dose (after 154 fb-2 1MeVNE cm12Oct16: Dark Current per 10

C°T = 24

= 13TeVsGEANT4,

= 0.172aavg = 0.672amax

= 0.049amin

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NeutronDamageinATLAS– GEANT4

BRANDEISUNIVERSITY- CamilaPazos21-May-19