2007_Evidence of nonclassical plasma transport in hollow cathodes for electric propulsion

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1、JOURNALOFAPPLIEDPHYSICS101,063301
2007Evidenceofnonclassicalplasmatransportinhollowcathodesforelectricpropulsiona
IoannisG.Mikellides,IraKatz,DanM.Goebel,andKristinaK.JamesonJetPropulsionLaboratory,CaliforniaInstituteofTechnology,Pasadena,California,91109
R

2、eceived24September2006;accepted14January2007;publishedonline16March2007Measurements,simpliÞedanalyses,andtwo-dimensionalnumericalsimulationswithaßuidplasmamodelshowthatclassicalresistivitycannotaccountfortheelevatedelectrontemperaturesandsteepplasmapotentia

3、lgradientsmeasuredina25Ð27.5Aelectricpropulsionhollowcathode.Thecathodeconsistedofa1.5cmhollowtubewithan0.28cmdiameteroriÞceandwasoperatedwith5.5SCCM
SCCMdenotescubiccentimeterperminuteatSTPofxenonßowusingtwodifferentanodegeometries:asegmentedconeandacircu

4、larßatplate.ThenumericalsimulationsshowthatclassicalresistivityyieldsasmuchasfourtimescolderelectrontemperaturescomparedtothemeasuredvaluesintheoriÞceandnear-plumeregionsofthecathode.ClassicaltransportandOhmÕslawalsopredictexceedinglyhighelectron-ionrelative

5、driftspeedscomparedtotheelectronthermalspeed

4.Itisfoundthattheadditionofanomalousresistivitybasedonexistinggrowthrateformulasforelectron-ionstreaminginstabilitiesimprovesqualitativelythecomparisonbetweenthenumericalresultsandthetime-averagedmeasurements.S

6、impliÞedanalysesthathavebeenbasedlargelyontheaxialmeasurementssupporttheconclusionthatadditionalresistivityisrequiredinOhmÕslawtoexplainthemeasurements.Thecombinedresultsfromthetwo-dimensionalsimulationsandtheanalysesboundtherangeofenhancedresistivitytobe3Ð1

7、00timestheclassicalvalue.©2007AmericanInstituteofPhysics.DOI:10.1063/1.2710763I.INTRODUCTIONregiontheÒnearplume.ÓThetwo-dimensionalstructureoftheplasmapotentialisofparticularinterestbecauseitmayHollowcathodesemployedinelectricpropulsion
EPbedirectlyassoci

8、atedwithattainableionenergies.InthesystemsuseporoustungsteninsertssimilartothedispenserstudiescitedaboveithasbeensufÞcienttoregardtheexist-cathodetechnologiesthathavebeenusedfordecadesiningspati