FieldEmissionMeasurementsFromCesiatedTitaniumand从cesiated钛场发射测量

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1、FieldEmissionMeasurementsFromCesiatedTitaniumandStainlessSteelElectrodesK.Surles-law,P.Adderley,J.Brittian,D.Charles,J.Clark,J.Grames,J.Hansknecht,M.Poelker,M.StutzmanFieldEmissionfrom25degElectrodesPOISSONmodelof25degelectrodeE-fieldsshownareforV=-100kVFieldEmissionElectronsareconfinedi

2、nametalbyapotentialwellEnergyofelectroninsufficienttoescapefrommetalElectronmustbegivenextraenergytoescape(thermal,photoemission)QMdemonstratestheelectronwavefunctionattenuatesrapidlyoutsidepotentialbarrierFieldEmissionApplicationofexternalfieldslowersandthinsthepotentialbarrierFowler-No

3、rdheimusedquantummechanicstodemonstratethatsomeelectronscantunnelthroughthepotentialbarrierandescapeintothevacuumFieldEmission:Fowler-NordheimEquationThisistheFowler-NordheimexpressionforfieldemissionEistheelectricfield(MV/m)Fistheworkfunctionofthematerial(eV)bisthefieldenhancementfactor

4、AistheeffectiveemittingareaFieldEmission:Fowler-NordheimEquationPlotofFowler-Nordheimequationwithb=200.TheelectricfieldgradientsweregeneratedfromPOISSONmodelofthe25degreeelectrode.Thepotentialvariedfrom10to125kVFieldEmission:Fowler-NordheimEquationOnecanuseexponentialformofFNtocomparefie

5、ldemissionfromTiandSSFieldEmission:Fowler-NordheimPlot210minofCsforTiandSSFieldEmission:Fowler-NordheimPlotMoreinterestingtoplotln(I/V^2)vs.1/VTheslopeofthefitteddataisproportionaltotheworkfunctiontothe3/2powerIfworkfunctionchanges,theslopeofFNplotchangesFieldEmission:Fowler-NordheimPlot

6、FieldEmission:Fowler-NordheimPlotNowlet’sobserveFNplotsforTiandSSwithnoCsand210minofCsFieldEmission:Fowler-NordheimPlotFieldEmission:Fowler-NordheimPlotFieldEmission:Fowler-NordheimPlotFieldEmission:Fowler-NordheimEquationNext,decreasecathode-anodespacingTakeFEdataforTiandSSwithnoCsCompa

7、reFEvs.spacing:IsTiorSSbetter,orsame?