Simultaneous DC measurements of ion current density and electron temperature using a tunnel probe

摘要

ThetunnelprobeisaconcaveLangmuirprobedesignedtooperateinstronglymagnetizedplasma.Duetoitsshape,thetunnelprobeisimmunetosheathexpansioneffectsandthusprovidesabsolutelycalibratedmeasurementsoftheparallelioncurrentdensity.Atwo-dimensional,self-consistentkineticmodelisemployedtomodeltheflowofchargeswithinthecavityofthetunnelprobe.Thecalculationpredictsthatthedistributionoftheionfluxontotheinnerconductorsdependsontheelectricfieldinsidethetunnel,whichinturndependsontheelectrontemperature.Therefore,ifthetunnelisdividedintotwonegativelybiasedcollectors,itispossibletousethesimulationresultstodeterminetheelectrontemperaturefromthemeasuredioncurrentratio.ThismeansthataDC-biasedtunnelprobecanbeusedtoprovidefast,simultaneousmeasurementsoftheparallelioncurrentdensityandtheelectrontemperaturewithoutcollectingasingleelectron.MeasurementsintheCASTORandToreSupratokamaksagreewellwiththenumericalsimulations...