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1、IEEETRANSACTIONSONNUCLEARSCIENCE,VOL.52,NO.2,APRIL2005519AnomalousAnnealingofaHigh-ResistivityCCDIrradiatedatLowTemperatureMarshallBautz,GregoryPrigozhin,SteveKissel,BeverlyLaMarr,CatherineGrant,andSteveBrownAbstract—Thefront-illuminatedcharge-couple
2、ddevice(CCD)waswarmedupearlyinthemissionfollowingexposureofdetectorsintheChandraX-rayObservatory’sACISinstrumentthedetectorstolowenergyprotonsintheEarth’sradiationsufferedradiationdamagefromsoftprotonsfocusedbythebelts.Verysoonafterthedamageoccurred,
3、thefocalplanetelescopemirrorearlyinthemission.Inthecourseofassessingtemperaturewaselevatedto20–30for8hoursandthenthisdamage,thefocalplanewastemporarilywarmedfromitsnormaloperatingtemperature(then100C)to+30C.theCCDswerecooledbackdowntothenormaloperati
4、ngFollowingthisbakeout,theradiation-damagedCCDsexhib-temperature(atthatpointinthemission).Thisitedsignificantlygreaterchargetransferinefficiency(CTI).We“bakeout”causedthechargetransferinefficiency(CTI)oftheperformedalaboratoryexperimentwithasiblingofthe
5、flightfrontsideilluminatedCCDs,measuredusingtheon-boarddetectorsinanattempttoreproduceandbetterunderstandthiscalibrationsource,toincreasebyabout35%.phenomenon.ThetestCCDwascooledto100C,irradiatedby120keVprotonsandthenwarmedto+30Cfor8hours.AsTheliterat
6、ureonradiationdamageinCCDsisvast;acom-expected,aftertheinitialirradiation,butbeforedetectorwarmup,prehensiverecentreviewcanbefoundin[3].Mostofthisre-asubstantialCTIincreasewasobserved.Thesubsequentwarmupsearchisbasedondataacquiredontheground,andinalm
7、ostitselfthenproducedanadditionalfactor2.5increaseinCTI.allthecasesthedevicesunderinvestigationwereirradiatedatFollowingsmallersubsequentirradiationswiththedetectorcold,aroomtemperature.Itisrelativelydifficulttoperformexperi-bakeoutfor8hoursat60Cprodu
8、cednoobservableincreaseinCTI.However,asubsequentbakeoutto+30Cforanother8mentsinvolvingirradiationofdevicesincryogenicconditions,hoursresultedinanadditionalincreaseinCTIofroughly15%.especiallyiftheradiationinquestionisnotpenetrating,becauseTheCTIchang