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ID:34820384
大小:1.77 MB
页数:55页
时间:2019-03-11
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1、9TransportinToroidalPlasmasU.StrothInstitutf¨urExperimentelleundAngewandtePhysik,Christian-Albrechts-Univ.zuKiel,Olshausenstr.40,24098Kiel,Germanystroth@physik.uni-kiel.deAbstract.Tounderstandthemechanismsdeterminingconfinementofenergyandparticlesintoroidalplasmas,isoneofthemostpro
2、minentandambiguousobjec-tivesoffusionresearch.Thereisawidespectrumofdifferentphysicalprocessesinvolvedinplasmatransport,rangingfromthecomplexityofparticletrajectoriesinthree-dimensionalmagneticconfigurationsoverkineticeffectsrelatedtothepar-ticledistributionfunctionstothewidefieldofpl
3、asmaturbulence.Thischapteraimstogiveanoverviewandanintuitiveunderstandingofthevariousapproaches.Thestartingpointofthischapterisaplasmaconfinedinatoroidalmagneticfieldasproducedbytokamakorstellaratorexperiments(seealsoChap.7inPartII).Theplasmapressureisassumedtobelowenoughinordertogu
4、ar-anteeMHDstability(seeChap.4inPartI).Hencethezeroth-orderplasmaflowisdirectedtangentiallytothemagneticfluxsurfacesandtheradialcom-ponentofitvanishes.Suchaplasmaisneverthelessnotperfectlyconfined.Inordertomaintainconstantplasmaconditions,continuousheatingandpar-ticlerefuellingofthep
5、lasmaisrequired.Ifrefuellingandheatingcease,theplasmatemperatureanddensitydecayexponentially.Thecharacteristictimeconstantsofthedecayaretheparticleandenergyconfinementtimes.Particleandenergylossesarecausedbytransportduetotwodifferenttypesofprocesses,whichbothgobeyondthephysicsofline
6、aridealMHD.Resistivityorcollisionsbetweenparticlesinthepresenceofgradientsinthethermodynamicvariablesleadtodistortionsinthedistributionfunctions.Thiscausescollisionaltransportwhichisthebasicleveloftransportalwayspresentinaplasma.Inmanycases,collisionaltransportisonlyofminorimporta
7、nceforparticleandenergyconfinement.Sinceitneedsnottobeambipolar,however,itdeterminestheplasmapotentialandtheradialelectricfield.Thesecondandforconfinementtimesmoreimportantcomponentistheturbulentorsocalledanomaloustransport.AnintroductiontoturbulenceisgiveninChap.8inPartII.Itisdriven
8、byfluctuationsintheplasmaparameter
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