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LHAASOWCDA中基于电流型TOT技术的前端读出ASIC设计.docx

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LHAASOWCDA中基于电流型TOT技术的前端读出ASIC设计 Introduction TheLargeHighAltitudeAirShowerObservatory(LHAASO)isaprojecttoobservecosmicrayswithunprecedentedenergyandspatialresolution.TheWaterCherenkovDetectorArray(WCDA),oneofthemaindetectorsofLHAASO,isresponsiblefordetectinghigh-energygammaraysfromcosmicsources.Inordertoachieveitsscientificobjectives,theWCDAneedsahighlysensitiveandpreciseReadoutASICtorecordthesignalsfromthedetector. OneofthemostimportantfeaturesoftheWCDAReadoutASICistheTimeOverThreshold(TOT)technique,whichusesthetimedifferencebetweentheinputsignalexceedingacertainthresholdandthesignal'samplitudefallingbelowthethresholdtoestimatetheamplitudeofthesignal.ThispaperaimstodiscussthedesignoftheWCDAfront-endReadoutASICbasedonthecurrent-modeTOTtechnique. WCDAReadoutASIC TheWCDAReadoutASICconsistsofafront-endASICandaback-endASIC.Thefront-endASICisresponsibleforamplifyingandshapingthesignalsfromthedetector,whiletheback-endASICprocessesanddigitizesthesignalsfromthefront-endASIC.Thefront-endASICisthefocusofthispaper. Current-modeTOTtechnique Thecurrent-modeTOTtechniqueisbasedontheprinciplethatacapacitorconnectedbetweentheinputsignalandtheinputstageoftheamplifierwillchargewhenevertheinputsignalexceedsthethresholdanddischargewhentheinputsignalfallsbelowthethreshold.Thetimedifferencebetweenthesignalexceedingthethresholdandthecapacitordischargingisproportionaltotheamplitudeoftheinputsignal. Thefront-endASICoftheWCDAReadoutASICusesacombinationofafastresponseamplifierandacurrent-modeTOTtechniquetocapturethesignalsfromthedetector.Theamplifierisdesignedwithalowinputimpedanceandagainof10,000tomaximizethesignal-to-noiseratio.TheTOTcircuitconsistsofacomparator,acurrentsource,andacapacitor.Whentheinputsignalexceedsthethreshold,thecomparatorgeneratesapulsethattriggersthecurrentsourcetochargethecapacitor.Whenthesignalfallsbelowthethreshold,thecapacitorbeginstodischarge,andthetimedifferencebetweentheseeventsisproportionaltotheinputsignalamplitude. ASICdesign Thefront-endASICdesignconsistsofth