PROTON EFFECTS AND TEST ISSUES FOR SATELLITE
VBANDDESIGNERS:TEST ISSUESDISPLACherylJ. lConsultantCenterFOREFFECTS
CherylNASA/GoddardElectricalDesignersEffectsJ. MarshallSpace FlightSystemsGreenbelt,SatelliteCenterCenter / Code 562Maryland20771Paul W. MarshallConsultant7655 Hat CreekBrookneal,1.0 gyand Defectin MaterialsLoss Rate (NIEL)52Formation53and DevicesConcept.2.3.3Calculationof esTest Issues otodetectors3.3.4Lasers3.3.5Optocouplers3.3.6Solar Cells .Devices.and LightEmittingDiodes.IV-5059.Studies56.in the Use of NIEL .Introductionto Device.Limitations3.1of NIELand Tools .2.3.2DisplacementReferencesMechanismsThe CorrelationOn-OrbitSummary512.3.15.0 99100100
1.0Microelectronicbombardedandby a varietyINTRODUCTIONphotonicof chargedsystemsparticlesin edprotons,arecosmicrays, and solar particles(protonsand other heavy ions).These incidentparticlescauseboth ionizing and non-ionizingeffects when traversinga device, and the effects can beeither transientor permanent.Theprotonis lost to ionization,creatingdose(TID)effectsin y"displacementin sectioncausesactivedamage,"of the displacementprotonssince theyvast majorityof the kineticenergyof an incidentthe single event effects (SEEs)and total ionizingIVA.atomsdefectsHowever,theto be removedcan significantlydegradeportionof energylosttheirlatticesites andformdefects,i.e.,fromin semiconductormaterials.devicedamage effects in the naturalare plentifuland extremelysmallTheseperformance.In general,mostspace environmentcan be attributedtoenergetic(and thereforenot readilyshielded against).For this reason, we consideronly proton induced displacementin this course.(Nevertheless,we identify solar cells as an importantexampledamageof a casewhere both electronand proton damage can be importantsince only very lightis feasible.)The interestedreader is encouragedto explore the three previousshieldingNSRECand ment,protonspecificationsfor proton-richenvironments.damage analysistools for on-orbitperformancemust providethe relevantprotonHopk97]A of thisspectrawhichalso treatsegmentshieldingdisplacementof theissues,shortandcourserequirementsIn order to exercisethe displacementpredictions,the requirementsdocumentin additionto the eninteractionsstudiedandextensivelythenaturefor overof thedisplacementhalf a century,yet theyinvestigation.In this section,a descriptionof the mechanismsdamage is producedwill be followed by a summaryof the majorperformancecharacterizedin a space environment.Often the degradationby a damage factor (measuredin a laboratorythat is simply the change in a particularfluence.In addition,we will describe(NIEL) whichdisplacements.quantifiesthat portionIt has been calculateddamagestill remaingeneratea subjectofby which displacementconsequencesfor deviceof a device parametercan beusing monoenergeticprotons)electricalor optical parameterthe conceptof a non-ionizingof the energyas a functiontheyper unit protonenergyloss ratelost by an incident ion that goes intoof proton energy, and is analogousto(and has the same units as) the linear energy transfer (LET) for ionizing energy.We willdiscoverthat, to first order, the calculatedNIEL describesthe energy dependenceof themeasuredprotondeviceinduceddamagedeviceNIEL and relativelydevice vationin a on both thecalculatedfew laboratorytest measurements.The methodologyof such on-orbitpredictionswill be described,as well as the limitations.classesmodefactors.of devicesof radiationfor whichinduceddisplacementdegradationIV-51damageis a significantwill be presented.The(if notexamples
willillustrateand over,variousaspectsthat the impactof displacementof a particulardamagelevelin moreof damagedetail.on deviceWe will see, overperformanceis veryapplication-dependent.It will also becomeclear that uncertaintiesin the on-orbitpredictionfor devicessensitiveto displacementdamagemay requiresignificantlyincreasedradiationdesign margins.All too often, the design engineeris more familiarwith basictotal ionizingdoseto thdemandto(TID)and traditionaltesting,anduncertaintiesemploySEE effects,especially,anyin displacementdisplacementdamageandmay find it edevicesdesignThere(e.g.,is anchargecoupleddevices(CCDs),photodetectors,light emittingdiodes(LEDs),optocouplers,solar cells, and high precisionlinear devices)in harsh proton environments(and/oronlonger missions).This has led to a renewedinterest in hardnessassurancetechniquesforsuch devices[LaBe98].It is hoped that this coursewill providethe understandingnecessaryfor a erto identifyuse the currenttechnologiesliteraturerequiringto makefirstdeviceperformance,and help ensure that appropriatelaboratoryanalyses are performed.For those readers interestedin tingandproton induceddeviceeffects(as opposedto performingdisplacementdamageanalyses),we recommendreadingsection2.2 on displacementeffectsin devices followedby section3.3 whichincludes case studies of those technologiesmost affectedby HANISMSIn this section,we describefor deviceperformanceanddescriptionof the orbitpredictionWe beginthat generatewithdisplacementtoolsa generaldamage.Theinitial productionof defects in the semiconductorby incident protons, and the subsequentevolutionof this damageto its final stable defect configurationis then describedinsection2.1.semiconductorWe discussthe processesby which these defectselectricallyalter thematerial,and thereby impact device performancein section 2.2.Section2.3 containsa eunderstandingthe limitationsconceptof differentbetweenfluenceof the correlationenablesenergiesdisplacementdamagedose" (section 2.3.4).the protonof the non-ionizingcorrelationenergyloss rateNIELandobserved.We identify the implicationsmechanismsdescribedin sectionThe NIELprotonsordercomparison(or a spectrumafterdegradationof this correlation2.1,and providein sectionwhichwethatisin terms of thethe basisfor2.3.2.of the displacementof proton(NIEL),deviceenergies)damagevia on2.3.3), or the "displacementdamageThis is analogousto the calculationof total ionizing dose based onand LET[see sectionIVA, equation1]. Usingthesetoolswe establisha methodologyfor on-orbitdeviceperformancepredictionsin section2.4.Figure1summarizesthe methodused to predictthe on-orbitdevice(or circuit)responsetoIV-52
displacementdamage.ionizingdose effectsNotethat somedevicesmayhavesignificantconcurrenttotalthat must also be considered.Irradiation of Devicewith MonoenergeticProtonsCalculation ofIncident ProtonSpectrum forGiven MissionMeasurement ofParametricDegradationCalculation ofSpectrum at DeviceLocation BehindShieldingCalculation ofDevice DegradationversusDD Dose*Calculation ofDD Dose* forGiven MissionNIELlPredictionof On-OrbitDevice PerformanceI ,I* DD Dose is displacement damage dose. Alternatively one may substitutethe displacement damage equivalent fluence for a selected proton energy.Figure 1 Block diagram of the generic methodologyfor performing a on-orbit predictionsdevice performancewhen device degradation is dominated by displacementdamage effects.2.1DisplacementDamageAs indicatedabove,Mechanismsandthe interactionDefectbetweenand a solid cause both ionizing and non-ionizingincident proton is lost in interactionswith atomsofFormationa chargedparticle(suchas a proton)effects.Most of the kinetic energy of anin the semiconductorthat transferenergyto the electronclouds causingexcitationor ionization.However,( 0.1%) of the energy loss causes the atoms to be displacedfroma very small fractiontheir equilibriumsites,and canleadto latticewithnucleusanddisplacedisorder.it fromAn incidentsufficientlyenergetic,the PKA displacesuntil the magnitudeof energy transferreddisplacements.energyfromAt a givenprotonits site producingincidentnear zero up to somemaycollidea primaryknock-ona semiconductoratom(PKA).Ifmore atoms, and the collisioncascade proceedsbecomesless than the thresholdrequiredforprotonmaximumenergy,the recoildeterminedIV-53atomsby collisioncan varymechanisms.in kineticBoth
the averagerecoil energymass, and chargeandthe shapeof the incidentparticleof therecoilspectrumenergy,STABLE IT0on theand the mass of the target.EXITINGPARTICLEOdependDEFECT.* ,\O .-o0o/e;!o o0oo'. /. / s0',' )VacancyDopant of Impurity AtomFigure 2a Cartoon showing the displacement of an atom from its lattice site by an incomingproton, thereby forming a vacancy-interstitial(Frenkel) pair.Surviving vacanciesmigratethrough the lattice and often form electricallyactive stable defects in conjunctionwith animpurity or dopant atom.Regardlessisolatedof whetherlower energypermanentdamagedefects.However,and ultimatelyan atomPKA,is displacedresults.The interstitialthe vacanciesthat escapeformas a part of a damagemost of the initial vacancy-interstitialrelativelylong-livedSi atoms dorecombinationand immobilecascadeor as anpairs recombineand nonot form electricallyactivemigrate through the latticedefects.Figure2a is a cartoonillustratinghow the initial formationof a Frenkel pair, which is unstable,results in the formation of a stable defect.These defects have energy levelsbandgapof the semiconductor.divacancyFor example,in Si, two vacanciesthat is stable up to about 300 C, or a vacancyatom may form an E center(or A center)respectivelyWalk73[e.g.,Watk64,whichis stableand Kime79].may combineand a phosphorousup to aboutThe vacancyultimatelywithin theto form a(or oxygen)150 C (or 350 C),itselfis mobileevenatliquid nitrogen temperatures,so it is not practical to attempt to prevent the formationofthese defects.The process during which the initial vacancy-interstitialpairs evolve intostableroomSi devices,Mess86].temperaturedefectsresultsand is usuallycompleteFigure 2b is a qualitativeof survivingdefects.very dilute.LongerNotetermthatroomthein the so-called"shortterm annealingeffects"inwithin about a second[Srou70,Hein83,Gove84,pictorialshowing the time evolutionof the dis oftenin a spaceobservedenvironmentovera periodisof
days or weeks,consideredbut it is generallyto be a "permanenta smallFor this seffect.Vacancy-I r erstitialRecombinationMStable DefectFormation1TimeFigure 2b Illustration the time evolution of the initial vacancy-interstitialpairs to the formationof stable defects. The annealing of Frenkei defects occurs in less than 1 millisecond and stabledefects are formed on the time scale of seconds.DisplacementDamageProcessesIIin SiPROTON ENERGY 20 MeVLog NFREEDEFECTS,CoulombMANY SUBICASCADE,SINGLENuclear ElasticCASCADES,NuclearReactionsIRECOIL1-2 keV12-20ENERGYkeVFigure 3 Pictorial relating the initial defect configuration to the primary knock-on atom (PKA)energy in Si material. Note from the plot of the number of interactions (N) versus incident protonenergy that most interactions are Coulomb events producing isolated defects. For recoil energiesIV-55
above a couple of keV, the overall damage structure is relativelyof cascades and subcascades.Atter [Wood811.The final configurationhas beenissuea topicof muchis at the heartenergyloss rateof a devicethe sthosewith branchesdefectsformedby particleandto predictbe seenthe displacementfromtheplotof theincidentprotonenergy,with E e old E -2fewertheseeventswithAs we will see thisof calculateddamageof thenuclearare far moreelasticlogthedamagedand has the undregionelasticof hisresult[Lars78, Nara81an averagesizemodelsderivedliterature2.2withthefor oesof 4 nm for aenergies.Asproducesingleformlasta tree-like5-10TheyinitialIt is clearmicroscopyetching techniquesdevices performedmodels.Peas87,Effectsactivity(4) the compensationtheregions extendingmore recent work.ThethebeenkeVfoundofthatadimensionofthat this size .Wein the last decadereaderthatandearlylaterwasalso note thator so are alsomayreferto theDale88].in Materialsof a givenof donorsthatfor 200 nm andgapis ultimatelyproducedby five basic processesgenerationof electron-holepairs, (2) the recombinationtrapping,reactionis consistentwith transmissionelectronmicroscopy] of 1 MeV, 14 MeV and fission neutron-irradiatedSi thatshownto be compromisedby faultyelectricalmeasurementson irradiatedinconsistentofcan contributeat higher protonabout 2-10 keVin excessnumbersubcascades.scatteringcluster models based on heavilydamagedreferencestherein]are not supportedbyclusterresponseeventsare Coulomband result in keV,single cascadeis likely to have 2-3 terminalclusterswith a characteristic5 nm, connectedto each other by a string of dilute displacements.(Noteannon-ionizingFigure 3 is a pictorialof the spatial distributionofin Si investigatedusing the results were obtainedfor Si by Muelleret al. who also investigatednear the end of the recoil track.The term "terminalcluster"hasto e usefractionof the total displacementin the figure, recoils with energiessubcascades,structuredamageactivedue to the formationbut is still not well understood.N) esearch,of understandingin a proton s.of electricallyunchangedor acceptors,IV-56and Deviceswithan energylevel(F a) in theas illustratedin figure 4: (1) theof electron-holepairs, (3) carrierand (5) the tunnelingof carriers.
IIH;iII H i i s.-v\Tunneling,--eGenFigure 4 Schematic of the electrical effects that may occur due to the presenceinduced defect levels in the band gap of a semiconductor.Atter [Gove84].Physically,electron-holepair generationoccursfrom the valance band to the defect level followedMidgapenergyin a deviceat a defect,energylevelsbe assedtrapsin theare mostform of lightvibrations)lifetime,by the recombinationa carrier is capturedFilledregionby the thermalexcitationof an electronby its emission to the conductionband.effectivewhichwhich(radiativeis termedis a key ptoror in the formrecombination.performance,ofTheis determinedrate [e.g., Schr82].Carrier trappingrefers to the process wherebyat a defect and then releasedto its originalband.In the case ofchargemay be trappedonly to be releasedaftercausing the charge transfer efficiencyof the devicewiththerecombination),in devicea movalresultswhenCompensationis also responsiblefor carrier removal.material),at generatingvia this process.Recombinationoccurs when a carrier of one sign is capturedand not re-emittedbefore a cartier of the oppositesign is also captured.ThemayCCDs,alreadyin a depletionof radiationelectronslevelsprovidedtherebythe resistancein a lightly dopedthis type of carrierremoval.by thereducingcollectorFinally,shallowscatteringthe signalto degradecenterstherebypackethas[Mohs74].reducinga majoritycarrieris trapped.As seen in the figure (for n-typedonorthe net carrierlevelsareconcentration.compensatedbyFor example,of a bipolar transistorcan increaseas a resultdefectlevelscan assisttunnelingthroughofapotentialbarrier in the bandgap.This effect can produceincreasedcurrent in a reversebiased junction,and is most significantin materials with small bandgapsand high electricfields.IV-57
re the mportantdevicesconcentrationmaterialqualityof fetime,majorityregionsnot generallya result,thethat can act to decreasean issueexceptat verywhose primarycharacteristicsmost sensitive to timemobility.most[Schr82],Typically,theis high so that there is at least an order of magnitudeand generationcentersas comparedto the ers)will impact the minoritycarriernoticeablereductionin carrier concentration.The samedepletionpracticalthe generationthe generationhighdegradationin time well before there is ais true for defects producedindisplacementdepend on minoritydamage.of defectslevels.Hence,or timeswillconcentrationbeandmobilityin turn impact device characteristicssuch as transistorgain, transconductanceand saturationvoltage,dark current,detectorresponsivity,etc.As just described,thereductionof the minoritycarrier lifetime is a principalcause of degradationin a numberof Rs),decreasedsolarincludereducedgain reductionin bipolarresponsivityin photodiodescell efficiency,etc. Deviceswith lightlytransistorsand siliconand Schottky-barrierdopedactiveregionsaremost susceptibleto degradationcaused by carrier removal.Semiconductorlight sourcessuch as lasers and LEDs are generallyrelativelyradiationhard since the carrier lifetimesin theactivedeviceregionsare din some optocouplers,are a notable exceptionand are quite sensitiveinduced displacementdamage for reasons that are not completelyunderstood.Displacementdamageeffectsdo not limit the performancewhich depend on majoritycarrier transport.Exceptionstypes such as the charge injection device (CID) and chargeareextremelyincreasessensitiveresultingto time,efficiency(CTE) degradationdue to carrier trapping.beingmajoritycarrierdevices,are generallyvery[e.g.,Hash94]high protonsecondary)althoughtheirexposurelevels.of displacementtransconductancemayTable 1 summarizesdamagein manyto protonof most MOSincludecoupledoptoelectronicdevice hichcurrenttransferJFET and MESFETtechnologies,robustto displacementdamagebe degradedby carrierremovalatthe of devicetype sensitivitiesdamage.Summariesof these[e.g., Mess86,Raym87].descriptionsTheHolm93]caseof displacementstudieslastyearshasledtoageneraland degradationmodesin responsetoefforts may be found in generalradiationand in a numberto be considereddamage20effectsIV-58of summarypapersin this coursein selecteddevicewilltypes.[e.g.,alsoGove84,provide
Table1.DisplacementDamageMechanismsfor VariousLifetimeDeg gIMobilityDegradationSi MOS Transistors & ICsSCharged Coupled DevicesPSi Bipolar Transistors & Linear ICsPPhotodetectorsPLEDs & Laser DiodesPpn JunctionsPPSPPJFETsPPGaAs Transistors & ICsPP Primary;Non-IonizingEnergyLossRateAs we will see in the next ialcan be predictedalso can be primary(NIEL)it has beenreasonablywellsectionsandvia both uclearradiationconcernsConceptthat the radiationon calculationsdamage energy imparted to the primaryknock-onrate (NIEL)can be calculatedanalyticallyfromcrossintroducedSS Secondary1After [Srou88a]. Note that TID and SEEsfor these technologies.2.3SNIELelastic,andof theresponseofamountofatoms.The non-ionizingfirst principlesbasedonis thatnuclearpartinelasticof theenergyinteractions,whichproducesthe initialvacancy-interstitialpairsand phonons(e.g.,vibrationalenergy).NIEL can be calculatedusing the followinganalyticexpressionthat sums theelastic and inelastic contributionsas:NIELThe o'sionizationgramderivedatomicare total cross sections,loss usingatomicweight (N/A)the T's are effectivethe Lindhardtheoryof the targetmaterial.as a superpositioncomponent[Zeig84].(1)[oeTe oiTi].[Lind63],averagerecoilenergiesN is Avogadro'sIn the case of compounds,number,correctedforand A is thethe total NIELis(weightedby mole fraction)of the contributionsfor eachNotice that the units of NIEL, (keVcm2/g),are the same asIV-59
those for stopping power (or LET) describingper unit length.Burke has correctionaverage[Burk86].in therecoilMoretreatmenthas beenenergyrecentof theappliedof the targetenergy transfer by ionization and excitationin silicon for protons and other ions over acalculationsnuclearbyelasticandto the differentialatoms.BurkehaveinelasticrecoilThe more nsteadis givenandof to theby(2)NIEL N/A S L[T(O)]T(o)[aa/an tnwhereda/dfenergy,and[Lind63].is the differentialL[T( )]In theabout 300 keV,energy increasesis thecasecrosssectionfor a recoilfractionof therecoilof Si, themaximumin directionenergyamountthethatgoesof displacementO, T( )intois the recoildisplacementsdamageregardlessof the energy of the recoilingatom.The maximumwith atomic number,and is about 2 MeV for GaAs.Figureenergyisdamage5 showsboth the LET and NIEL for Si as a functionof incidentprotonenergy.Burkehascalculatedthe proton NIEL for a variety of other materials.The most recent publishedNIEL calculationscan be found in the DecemberIEEE Transactionsof NuclearSciencecited as follows:InGaAs[Mars92],GaAs and InP [Summ93],and Si [Dale94].lOOO"lOO1o(nu")o.z ,.(.9u,Iz0.1Non-lonizingO.OluJl,----.l.l l.l ,l0.001I1I 10!i i100PROTONENERGY1000(MeV)Figure 5 Comparison of the energy loss rate through ionization and excitation of the Si lattice(LET), and through atomic displacements(NIEL) over a wide range of proton energies.The LETwas calculated as in [Zeig85], and NIEL as in [Dale94].IV-60
The natureof displacementdamageasa functionof proton energyis governedbythe interactioncross sections,andthe non-ionizing energyof the PKAs as governedbythe Lindhard function. For proton energiesbelow about 10 MeV, Coulomb elasticscatteringis by far dominant in Si, and producesatomic recoils with non-ionizingenergiesin the hundredsof eV. At higherenergies,the bendin the ore importantresultingin recoils with non-ionizingenergiesin the tenthsof MeV range. As the incident protonenergyincreasesthe elasticcrosssectiondecreasesathoughit is still largerthanthe inelasticcrosssection. By about100 MeV half of the non-ionizing energy imparted to the Si lattice is from nuclearinelasticreactionswith a meanPKA non-ionizingenergythat is still about0.1 MeV (dueto the Lindhard partition).NIEL hasalsobeencalculatedby other meansincludingMonteCarloprogramssuch as HETC [Alur91],CUPID [MeNu81,McNu94]and TRIM [Zeig84].A comparisonbetweenthe most recent Burke and CUPIDcalculationsof Si NIELis discussedin[Dale94].AlthoughHETC,a functionof incidentCUPIDprotonand Burke'senergyshowcalculationssimilartrends,of the recoiltheydifferdistributionsin detailsas[Dale94].The TRIM programonly includes the Coulombicinteractions,so it is not appropriatetouse it directlyfor damagecalculationsfor protonenergiesabove about 8 MeV or so,dependingthefacton the targetmaterial.Note that all of the above calculationsthe most of the initiallyproducedthereforedo not produceelectricallyassuminga displacementthe actualvalue.Thisrecombinationof theenergypracticeactiveinclude a "fudgevacancy-interstitialdefects.For examplemustvacancy-interstitialbe scaledpairs.In otherto fit the experimentalThe CorrelationDeviceof NIELdegradationdamageconstant,materialparametersin a radiationor a damagesuchto Devicefactor.as t maydetailed device modelexecutedcodessuchascollisionpoint forall currentNIELunlessof the tDamagecarrieris ot en characterizedconstantslifetimedescribeor diffusionthelengths,given fluenceof protonsof a specificenergy.(Fluenceis definedincidentparticlesper unit target area, and has units of cm'2.) Damageexceptis oftenCarloaround eachIn essence,damageratios are compared.As we shall see, it is the calculationis relevant,not the absolute values of NIEL.2.3.1TRIMforandthresholdof 25 eV, which is considerablyhigher thanhelps to accountfor the efficiencyof the initialMARLOWE,one also has the option to define a radiuswhichall the tor" that accountspairsrecombinethe observedradiationinducednot be readilyis not available.reducedto basicIV-61degradationmaterialby definingchangeproducedas thefactorsof deviceparametersain basicby anumberofare similaror systembecausea
The following well known equationdescribesthe degradationin minority carrierdevicesthat results from the reduction in the diffusion length that accompaniestheintroductionof radiationinduceddefectrecombinationcenters:1/I ,2 1/I- ,o 2 K .The initialdamagetermsand post-radiationconstant,andof the minoritydiffusiondiffusionlength is given by Lo and L, respectively,is the protoncarrier(3)fluence.lifetime,(Sometimesx, usingthe relation,this equationL (Dx) '5, whereparameter,the satelliteand definesdesignera relevantor test engineerdamagefactor.is interestedcase,thedevicein the linearparameterregion.detectorresponsivity,linear response,mayfluences.functionin questionIn the caseNote that parameters(We will also see examplesstudieswherecurrentcan be usedcorrelationmeasurementthe degradationratioto follow,due to differentemitter1/hFEois theinitialreciprocal dependenceparticles1 ]hFEo4"operatingconditions)Figureions normalizedenergyby performing6 showsto thefor a varietyof the device[Summ87].gain,with aprotonsuchas LEDin theprotondamageIn principle,predictionsLikewise,is(as aNIELfactorsuch abasedon theif neutrondataK(E)transistor:(4)is theparticleandenergydependentis the incidentparticle fluence.The transistorgainto base currents)decreaseswith increasingprotondeviceafter incrementalgaindamage1 MeV-equivalentcarrier lifetime in the base region.The damage factor is determinedmeasurementsexposuresthe measuredof Si bipolarlinearlyK(E)fluence primarilyas a result of the decreasedminorityA more detailed descriptionmay be found in [Mess86].experimentallytransistorof interestnot behavehFE, of a bipolargain,displacementdamagefactor, and (given by the ratio of the collectoror elseto predict the device responseto protons.Inequationis used to describethe radiationDC gain,1/hFEwhereparameterdoesalso providesthe basis for on-orbitperformanceof a damagefactor at a single proton energy.of the commonfluence,bipolarwe willdamage factor,and so on.Infor a varietyof incidentparticlesin order to determinewhetherthethe energyalready exists, the correlationcan be usedthis work, the well-knownMessenger-Sprattwithsuch as inversea devicetransferboth to predictlinearlydevicewhich have a well-definedregimeresponseat very low or very highBipolartransistorgain measurementsof energy)have been performedand to correlateresponsechangesand CCD dark current,also exhibit a nonlinearlight output or optocouplerfluence regime of interest.)functionD is thein a particularsee examplesof other useful device damage factors such as the CCD CTEthe dark currentdamage factor, the solar cell lyeachK is theappearsat a givenfactors(Si) neutrontransistors.(Weequivalencein a later section, and neutrondamageFor the present purposeswe note that by comparingIV-62(fora particularprotonfor
bombarded by a variety of charged particles including electrons, trapped protons, cosmic rays, and solar particles (protons and other heavy ions). These incident particles cause . The interstitial Si atoms do not form electrically active defects. However, the vacanc
Unit 10: Acids and Bases – The Voyage of the Proton 2 makes it an acid. It serves as a proton donor because in a reaction it will give up the extra proton. And conversely, the hydroxide ion OH-is missing a proton relative to water. In a reaction it is a proton acceptor, and therefore it is a base.
proton beam radiotherapy, due to an insufficient evidence base. However, individual patient cases should be discussed by the Proton Therapy Referral Rounds. 5. For all cases, the referral for proton beam radiotherapy must come from the consultant Radiation Oncologist who has seen and assessed the patient. The referral can only be made if the Proton
Possible applications of pe scattering (inverse kinematics): Proton charge radius measurement Polarized (anti)proton beams ( ) e Beam polarimeters for high energy polarized proton beams, Novisibirsk (1997). Elastic ep scattering is a privileged tool for learning on the internal structure of the proton.
(3) protons and electrons. (4) protons and neutrons. 4. An electron has a charge of (1) –1 and the same mass as a proton (2) –1 and a smaller mass than a proton (3) 1 and the same mass as a proton (4) 1 and a smaller mass than a proton 5. What is the total number of neutrons in an atom of an element that has a mass number of 19 and
Selected Proton Therapy Bibliography 03 September 2015 REFERENCE WORKS Charlie Ma C.M. and Lomax T., “Proton and Carbon Ion Therapy”, 2012, CRC Press. This user guide for proton and carbon ion therapy in modern cancer treatment covers the physics and radiobi
proton and its conjugate base. Alternately a base B can combine with a proton to yield the conjugate acid BH of the base. In general terms, this may be written as Acid1 Base2 "" Acid2 J:3ase1 in which the proton is pat titioned between two bases and the equilibrium constant is determined by the relative affinities for the proton.
Herein, we conceive a new "acid-in-clay electrolyte" (AiCE) approach to prepare a series of novel proton electrolytes. Owing to the advantages of superfast proton permeability, excellent selectivity, and enhanced stability, we demonstrate the superiority of the proton electrolytes in solving two main challenges in proton batteries :
The first of the current generation of proton therapy equipment was installed at the Francis H. Burr Proton Therapy Center in 1993. Massachusetts General Hospital Proton Therapy Facility . *Formerly Procure . This facility is capable of treating up to 1,200 patients per year with 1 gantry, 2 inclined beams and 1 fixed beam treatment rooms.
