经典外文翻译底土的土壤结构和饱和导水率毕业论文设计.docx

经典外文翻译底土的土壤结构和饱和导水率毕业论文设计.docx

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经典外文翻译底土的土壤结构和饱和导水率毕业论文设计

英文原文：

Low-costprogrammablepulsegeneratorforparticletelescopecalibration

Abstract

Inthispaperwepresentanewcalibrationsystemforparticletelescopesincludingmultipulsegeneratoranddigitalcontroller.Thecalibrationsystemgeneratessynchronizedpulsesofvariableheightforeverydetectorchannelonthetelescope.ThecontrolsystemisbasedonacommercialmicrocontrollerlinkedtoapersonalcomputerthroughanRS-232bidirectionalline.Theaimofthedeviceistoperformlaboratorycalibrationofmulti-detectortelescopespriortocalibrationataccelerator.Thistaskincludesevaluationoflinearityandresolutionofeachdetectorchannel,aswellascoincidencelogic.TheheightsofthepulsessenttothedetectorsareobtainedbyMonteCarlosimulationoftelescoperesponsetoaparticlefluxofanydesiredgeometryandcomposition.ElsevierScienceB.V.Allrightsreserved.

Toassureacorrectinterpretationofdataobtainedwithscientificinstrumentsonboardsatellites,aswellastocomparethesedatawiththoseofsimilarinstruments,athoroughpre-flightcalibrationisrequired.Forsolarandcosmicrayparticletelescopes,thiscalibrationisusuallycarriedoutintwosteps:

first,acalibrationofeachindividualdetectorusingradioactivesourcesandstandardnuclearinstrumentation（NIMorCAMACmodules）,followingbyafinaltestofthewholetelescopeperformedinaparticleacceleratorsite.Thesuccessofcalibrationonacceleratorrequiresthat,priortotheexperiences,alldetectorsandelectronicsparameter（polarizationvoltages,amplifiergainsandshapingtimes,thresholds,etc.）havenearlydefinitivevalues.Hereweproposeacheapandsimplepre-calibrationprocedurebasedonanewsystemthatwehavecalledProgrammablePulseGenerator（PPG）.ThePPGdevelopedinourlaboratoryhasbeendesignedforaspecificinstrument,afour-detectorcosmicraytelescope,butitcaneasilybemodifiedforsimilarexperiments.

Thestandardcalibrationprocedureforindividualdetectorsandtheirelectronicchainsconsistsofintroducingpulsesofknownamplitudescomingfromapulsegenerator,togetherwiththepulsesreleasedinthedetectorbyparticlescomingfromaradioactivesource.However,thesestandardpulsegeneratorsdopresentseverallimitations:

Thepulseamplitudemustbesetmanually.Thus,togeneratethepulsesthatdifferentparticleswithdifferentenergieswouldreleaseonthedetectors,itisnecessarytochangethepulseheightseverytime.

Standardpulsegeneratorsonlyprovideoneoutputsignal,soeitherseveralmodulesareneededtocalibrateacompletetelescope,oritisnecessarytosplitthesingleoutputinordertogetseveralsignals.Itisdifficulttocheckthecoincidencelogicbecausethefoursignalsarenotindependent.

Toovercomethesedifficulties,pulsegeneratorsofprogrammableamplitudeandratehavebeenproposed.Abdel-Aal[1]presentedaprogrammablerandompulsegeneratorwheretheheightandseparationofindividualpulsesarecontrolledbysoftware.Butinhisschemethepulsesarereleaseddirectlyfromadigital-to-analogconverter（DAC）,thushavingthetemporalcharacteristicsoftheDACoutput.Ourpurposeistogeneratevariableheightanalogpulseswithsimilarshapetothatreleasedbynucleardetectors.

Thelow-costPPGpresentedhereisintendedtointroduceeverydetectorchannel，thepulsesreleasedbyanyparticlefluxsupposedtobeencounteredbytheinstrumentonrealexperiments（inourcase,onouterspaceenvironment）.Theproposedpre-calibrationschemeissketchedinthediagramofFig1.Forabignumberofsimulatedevents,theenergysignalsreleasedatthedifferentdetectorsofthetelescopearestoredonapersonalcomputer（PC）.Foreachindividualevent,theenergysignaldataaresentthroughabidirectionalRS-232-ClinetothePPG,whichtransformstheresultsofthesimulationintorealpulsesandsendsthemtotherealinstrument.

Fig1

2PPGdescription

ThedesignofthePPGisdividedintotwofunctionalmodules:

digitalelectronicsandanalogelectronics,whoseblockdiagramsareenclosedindashedboxesshowninFig2.ThedataarrivingatthedigitalmodulefromthePCaresentto12bitDAC.TheDACoutputvoltagesaretransformedintheanalogmoduleintosuitablepulses,readytobeintroducedintothetestinputoftherelateddetectorchannelofthetelescope.

AnaloganddigitalmodulesaredescribedwithsomedetailinSections2.1and2.2.InSection2.3wedescribesomenoiseproblemsrelatedwiththemicrocontroller,andthewaywefoundtosolvethem.

2.1Analogmodule

Thismodulemustbecapableofproducingsignalpulsessimilartothosegeneratedinthedetectorsbythepassageofenergeticchargedparticles,whoseshapecanbedescribedbythefollowingfunction:

（1）

Therelevantsignalparametersarethepulseheighto