Fundamentals Of Plasmas - Plasma-school

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Fundamentals of PlasmasAchim von KeudellResearch Department Plasmas with Complex InteractionsRuhr-Universität BochumSchool 2016 Fundamentals of Plasmas A. von Keudell1

Plasma as the fourth state of matterPlasma-Gasliquid- --Solid state- - School 2016 Fundamentals of Plasmas A. von Keudell-2

DefinitionPlasma is a (hot) ionized gas with reactive particleslike electrons, ions, and radicals.More than 99% of visible matter is plasma.School 2016 Fundamentals of Plasmas A. von Keudell3

Plasmas in the universeplanetary nebula NGC 6853young brown dwarfspiral-galaxy NGC 1232School 2016 Fundamentals of Plasmas A. von Keudell4

Natural plasmas on earthpolar lightlightningSchool 2016 Fundamentals of Plasmas A. von Keudell5

Low temperature plasmas for our daily lifeshttp://www.nap.edu/catalog/11960.htmlSchool 2016 Fundamentals of Plasmas A. von Keudell6

weldingseat coverssurface hardeningautomotivesoot removalcolored plastic partspastinglampsSchool 2016 Fundamentals of Plasmas A. von Keudellignition7

Plasma methods Light generation (Plasmalamps)Plasmaetching in Microelectronics (Computerchips)Plasma based deposition (PECVD)Plasma sprayingSurface modification (z.B. Hardening of metals, textiles andpolymers)Surface sterilisation (z.B. inactivation of germs)School 2016 Fundamentals of Plasmas A. von Keudell8

Plasma in the biomedical sector Artifical knee – plasma coatedCatheders – plasma coatedStents – plasma coatedArtifical hips –plasmasprayingSterilisation in HospitalsDrugs – plasma treatedSterilisation of vialsSchool 2016 Fundamentals of Plasmas A. von Keudell9

Plasma for energy research Energy Storage (photocatalytic processes)Plasma switches (power plants)Solar panelsNuclear fusion W 7-X, IPP Greifswald ITER, Cadarache (Frankreich)School 2016 Fundamentals of Plasmas A. von Keudell10

Envorinmental Waste treatmentWater and air cleaningPlasma medicineSchool 2016 Fundamentals of Plasmas A. von Keudell11

Plasma vs. ne and TeSchool 2016 Fundamentals of Plasmas A. von Keudell12

Plasma Fundamentals - Outline1. What is a plasma ? Temperature Debye shielding Plasma frequency2. The edge of a plasma Sheath physics3. How to ignite a plasma Ignition, Paschen curve Streamer RF-ignitionSchool 2016 Fundamentals of Plasmas A. von Keudell4. Transport in a plasma Particle motion Plasma as a fluid Drift and diffusion5. How to sustain a plasma DC plasma Rf-plasmas Plasma heating13

What is a plasma ? Concept 1 - temperaturefxln fvDvzzHeatingIonisation V School 2016 Fundamentals of Plasmas A. von KeudellMore details in the lectureon kinetics, see also master class14

What is a plasma ? Concept 1 - temperatureTTeTg1 atmpHowever, the concept of temperature is only an approximation.Most plasmas are dominated by non-equilibrium.Distribution function are needed rather than temperatures.See also lectures on kineticsSchool 2016 Fundamentals of Plasmas A. von Keudell15

What is a plasma ? - Concept 2 – Debye shielding, quasineutralityExample extra positive chargeΦ0--Diffusion of e- due to n --- 0neAttraction of ee-Φ (r )r--e- -- - - - - - -- - - - -x 0Example extra negative chargeDiffusion of e- due to n0Repelling of e--Φ0 - - - - - - - - - -x 0School 2016 Fundamentals of Plasmas A. von Keudell16

What is a plasma ? - Concept 2 – Debye shielding (in formulas)Example extra negative chargeDiffusion of e- due to n0Repelling of e--Φ0 - - - - - - - - - -x 0withSchool 2016 Fundamentals of Plasmas A. von Keudell17

What is a plasma ? - Concept 3 – Collective phenomena – the plasma parameter- - --Φ (r )r- -- --School 2016 Fundamentals of Plasmas A. von Keudell18

What is a plasma ? - Concept 4 – the plasma frequency- -- - - E-- ---- -- - --- δSchool 2016 Fundamentals of Plasmas A. von Keudell19

What is a plasma ? - Concept 4 –the plasma frequency (formulas)- E δSchool 2016 Fundamentals of Plasmas A. von Keudell20

What is a plasma ? - Concept 4 –the plasma frequency (numbers)ionselectronsAssume:100 MHz RF plasma in Arne 1016 m-3Electrons can easily follow the RF cycle,ions can NOT !!School 2016 Fundamentals of Plasmas A. von Keudell21

What is a plasma ? – Concept 5 – ideal and non-ideal plasmasrelativisticn2/3107Eth me c 2106n1/ 3105T (eV)104103relativistic, degenerateideal102nonideal101EF me c 2Non-ideal plasma:Plasma crystal10010-1EF Ethdegenerate10-21051010101510201025103010351040n (m-3)degenerate plasma:electrons in a metalSchool 2016 Fundamentals of Plasmas A. von Keudell22

What is a plasma ? – Concept 5 – ideal and non-ideal plasmasIdeal plasma – plasma larger than the Debye length:Ideal plasma - many electrons in Debye sphere: fluid approach possibleSchool 2016 Fundamentals of Plasmas A. von Keudell23

What is a plasma ? – Concept 5 – ideal and non-ideal plasmasIdeal plasma – thermal energy must be larger than the Coloumb energyb0Relation between collision parameter and Debye lengthSchool 2016 Fundamentals of Plasmas A. von Keudell24

Parameter of a plasma – Nick Braithwaites Plasma CalculatorPLASMA CALCULATOR(N St J Braithwaite, European Summer School)Physical Constantse/Ck/J K -11.60E-19me/kg1.38E-23Mp/kg9.00E-31epsi0/F m -11.67E-27mu0/H m -18.85E-12c0/m s -11.26E-063.00E 08Gas datap/PaTg/K6.00E 00Mg/amu3.00E 02X-Sectn/m 24.00E 011.00E-19Plasma dataInstructionskTe/eVAdjust gas,plasma andsystem datane/m -32.00E 00(data boxes in this band are notprotected)1.00E 16Plasma parameters are immediately updatedSystem dataL/mRF/MHz1.00E-01B/T1.36E 01muwave/MHz1.00E-01rho Cu/ohm m2.45E in Cu2.48E-01L1.93E-051.00E-01Frequencies/rad s -1wpiwpe5.67E 09wce2.08E 07wRF1.78E 10wm8.52E 071.54E 10Frequencies/MHzfpefpi9.03E 02fce3.31E 00nu2.83E 03RF8.64E 01muwave1.36E 012.45E 03Speeds/m s -1ceve9.52E 05cs5.96E 05cg2.19E 033.97E 02Fluxes/m -2 s -1GiGg2.19E 191.44E 23Conductivity/ohm -1 m -1sigDC3.29E 00Re[sigRF]1.67E 00Im[sigRF]-1.65E 00Densities/m -3ngne1.45E 21% ionisation1E 160.00069Comments to n.s.braithwaite@open.ac.ukSchool 2016 Fundamentals of Plasmas A. von Keudell25

The edge of a plasmaSchool 2016 Fundamentals of Plasmas A. von Keudell26

A plasma in front of a wall – sheath physicsn0EFeniF n0School 2016 Fundamentals of Plasmas A. von Keudellnex s27

A plasma in front of a wall – sheath physics (formula)n0EFeniF n0nex sSchool 2016 Fundamentals of Plasmas A. von Keudell28

A plasma in front of a wall – sheath physics – potential, ion velocityΦΦpv(s)vBvthx0 λIonenpre-sheath λDebyesheathsSchool 2016 Fundamentals of Plasmas A. von KeudellΦW29

A plasma in front of a wall – sheath physics - special casesn0Multiple ionsEFeniF nnex sn0Sheath edge, x 00Electronegative plasmasEn nneαbαsSchool 2016 Fundamentals of Plasmas A. von Keudellx swith30

A plasma in front of a wall – sheath physics – plasma potentialΦAa AcΦΦAa AcACFlux balance ions and electronsAAPlasma potentialPotential difference going from plasma to wallSchool 2016 Fundamentals of Plasmas A. von Keudell31

A plasma in front of a wall – sheath physics – applying a voltage to an electrodeMatrix sheathChild Langmuir sheathΦ, En0n0niE ni nenesx 0sxΦ- V0School 2016 Fundamentals of Plasmas A. von Keudell32

A plasma in front of a wall – sheath physics – ion energy distributions - collisionsmany collisions in the sheathSchool 2016 Fundamentals of Plasmas A. von KeudellFew collisions in the sheath33

A plasma in front of a wall – sheath physics – ion energy distributions – rf-sheathsVaVbIrf cos ωtIbIa rfEBAsassbs0tSchool 2016 Fundamentals of Plasmas A. von Keudell34

A plasma in front of a wall – sheath physics – ion energy distributions – rf-sheathsM N(E)M EtSchool 2016 Fundamentals of Plasmas A. von Keudell35

A plasma in front of a wall – sheath physics – ion energy distributions - collisionsSchool 2016 Fundamentals of Plasmas A. von Keudell36

A plasma in front of a wall – sheath physics – applications in microelectronicsIons (CFx )School 2016 Fundamentals of Plasmas A. von KeudellNeutrals (CFx, F)37

Working point of a Plasma – global modelreactor geometry,Discharge typeE-FieldAtomic- and molecular physicsne, Te, f(E)Heating mechanismsSchool 2016 Fundamentals of Plasmas A. von Keudelln ,n-, n*flux tosurfaceTransport, DiffusionSheath physics38

Working point of a Plasma – global 2TeParticle balance determinesElectron temperatureSchool 2016 Fundamentals of Plasmas A. von Keudell39

Working point of a Plasma – global modelAbsorbed power is acomplicated functionof electon densityionisationPower lossto surfaces excitation, electron loss to surfacesPower balance determinesElectron densitySchool 2016 Fundamentals of Plasmas A. von KeudellMore on this in the lecture byM. Turner and L. Alves40

Transport in a plasmaSchool 2016 Fundamentals of Plasmas A. von Keudell41

Transport in a plasma – single particle motiony- Bxz-y E BxzSchool 2016 Fundamentals of Plasmas A. von Keudell42

Transport in a plasma – single particle motionelectronsSchool 2016 Fundamentals of Plasmas A. von Keudellions43

Transport in a plasma – single particle motion – example hall thrustersS S S SIonsN N N NEplasmaS S S SElectronse--gunSchool 2016 Fundamentals of Plasmas A. von Keudell44

Transport in a plasma – single particle motion example magnetronEFExBxBSNNSBSSSSSNSSNSSNSSSMore on this in the lecture of A. HecimovicSchool 2016 Fundamentals of Plasmas A. von Keudell45

Transport in a plasma – motion as a fluidRHS: plus source terms dueto ionization or recombinationParticle conservationMomentum conservationcollisionsEnergy conservationconvektionSchool 2016 Fundamentals of Plasmas A. von KeudellCompression/expansionHeat conductionOhmic heating46

Transport in a plasma – motion as a fluid – the drift diffusion approximationa typical solutionmobilitySchool 2016 Fundamentals of Plasmas A. von Keudelldiffusion47

Transport in a plasma – motion as a fluid – ambipolar diffusionforEambipolarnnineforand Te Tinine nxSchool 2016 Fundamentals of Plasmas A. von Keudell48

Transport in a plasma – magnetic confinementxD xx BD zyywithout inertiadrift diffusionSchool 2016 Fundamentals of Plasmas A. von KeudellExB-driftdiamag. drift49

Transport in a plasma – classical vs. Bohm diffusionxD x Bzyxclassical diffusionforSchool 2016 Fundamentals of Plasmas A. von KeudellD yBohm diffusion (empirical)Idea: instabilities induce electric fields, which drive ExB drift50

Transport in a plasma – magnetic confinementSchool 2016 Fundamentals of Plasmas A. von KeudellMHz MHz51

Ignition of a plasmaSchool 2016 Fundamentals of Plasmas A. von Keudell52

Ignition of a plasma – Townsend regimeU1. Townsend coefficientgas amplificationI-e-Ia Ionennzne-n d0 zdSchool 2016 Fundamentals of Plasmas A. von Keudell053

Ignition of a plasma – Townsend regime – Secondary effectsIonbombardmentat the cathodeionsee-Secondary ionemissionat the anodephotoeffectfastneutralse-hν-e- eFast neutralsionsprimary amplificationsecondary amplificatione-metastablesemetastablesSchool 2016 Fundamentals of Plasmas A. von Keudell54

Ignition of a plasma – the Paschen curveV2Gas11-2 metastableslong pathbreakdownpdSchool 2016 Fundamentals of Plasmas A. von Keudell55

Ignition of a plasma – High presssure - streamerspositive streamernegative streamer -neg.streamerhead--- - - - - streamerchannel---elec.avalanche - -- -elec. drift - --hv photoionisation-- streamerchannelpos.streamerhead-Meek criterionSchool 2016 Fundamentals of Plasmas A. von Keudell56

Ignition of a plasma – High presssure - streamersSchool 2016 Fundamentals of Plasmas A. von Keudell57

Ignition of a plasma – rf-voltagesE E0 exp(iωt) E rfe-νm 0Emaxνm 0tSchool 2016 Fundamentals of Plasmas A. von Keudell58

Ignition of a plasma – Paschen curve for rf-voltageslog EDiffusionlossesCollisionRate too highlog pSchool 2016 Fundamentals of Plasmas A. von Keudell59

Sustaining a plasmaSchool 2016 Fundamentals of Plasmas A. von Keudell60

Sustaining a plasma – current voltage characteristics of a DC leglowdischarge74365I I 2ignitionarcI8V110-4 A10-1 Alog I6School 2016 Fundamentals of Plasmas A. von Keudell61

Sustaining a plasma – instabilities at breakdown4756- I. Stefanovic et al.School 2016 Fundamentals of Plasmas A. von Keudell62

Sustaining a plasma – striationsKaufmann, Handbuch der Experimentalphysik, 1929Meyer, Berlin 1858RUBSchool 2016 Fundamentals of Plasmas A. von Keudell63

Sustaining a plasma – magnetron dischargesRcNSSNΘNSsrLB0wSchool 2016 Fundamentals of Plasmas A. von Keudell64

Sustaining a plasma – balanced / unbalanced magnetronsNSSNNNSchool 2016 Fundamentals of Plasmas A. von KeudellNSSbalancedSNSunbalanced65

Sustaining a plasma – High Power Pulsed Magnetron Sputtering (HPPMS)DCNVSNCu , Cu2 IAr tselfsputteringSchool 2016 Fundamentals of Plasmas A. von Keudell66

Sustaining a plasma – High Power Pulses Magnetron Sputtering (HPPMS)J. Gudmundsson, N. Brenning,D. Lundin, U. Helmersson, JVSTA 30, 030801(2012)School 2016 Fundamentals of Plasmas A. von Keudell67

Sustaining a plasma – High Power Pulses Magnetron Sputtering (HPPMS)steady state1: ignition2: plasma build-up3: gas depletion4: steady state orrunaway self sputteringJ. Gudmundsson, N. Brenning, D. Lundin, U. Helmersson, JVSTA 30, 030801 (2012)School 2016 Fundamentals of Plasmas A. von Keudell68

Sustaining a plasma – rf discharges – capacitive couplingsA Bs0stVaVbIrf cos ωtIbIa rfBAsasbs0sSchool 2016 Fundamentals of Plasmas A. von Keudell69

Sustaining a plasma – rf discharges – capacitive coupling/self biasΦΦI dQ/dt0ABA-VbiasΦBΦπ/2ABA-VbiasBΦΦπABBA-Vbias A BSchool 2016 Fundamentals of Plasmas A. von Keudell A B70

Sustaining a plasma – rf dischargesVaIrf cos ωt rfVVbIbIaBAelectron currentsasbs0sIon currrentt2πVbiasVapSchool 2016 Fundamentals of Plasmas A. von Keudell71

Sustaining a plasma – rf discharges - inductive coupling ICPVrfjSpuleVrfSiO2EEindδdBzRCylindrical configurationSchool 2016 Fundamentals of Plasmas A. von KeudellPlanar configuration72

Sustaining a plasma – ICP discharges – non linear power couplingVrfjSpuleSiO2EEindδdBzRSchool 2016 Fundamentals of Plasmas A. von Keudell73

Sustaining a plasma – ICP discharges - hysteresisSchool 2016 Fundamentals of Plasmas A. von Keudell74

Sustaining a plasma – electron cyclotron dischargesB, ωcexvresωµwxΦsourceResonancezone zBzΦsubstrateSubstrateSchool 2016 Fundamentals of Plasmas A. von Keudell75

Sustaining a plasma – high pressure discharges - filamentationδneneTgngSchool 2016 Fundamentals of Plasmas A. von Keudell76

Sustaining a plasma – barrier discharges---- - -- - -Return stroke,ions move to cathode- 3. Charging up dielectricum1. Townsend-Phase,electron avalanche-- - 2. streamer- -- - -- 4. extinctionfrom L. Stollenwerk,New Journal of Physics 11,103034 (2009)School 2016 Fundamentals of Plasmas A. von Keudell77

Summary1. What is a plasma ? Temperature Debye shielding Plasma frequency2. The edge of a plasma Sheath physics3. Transport on a plasma Particle motion Plasma as a fluid Drift and diffusion4. How to ignite a plasma Ignition, Paschen curve Streamer RF-ignition5. How to sustain a plasma DC plasma Rf-plasmas Plasma heatingSchool 2016 Fundamentals of Plasmas A. von Keudell78

Further reading:Books: Lieberman Lichtenberg,Principles of Plasma Discharges and Materials Processing Alexander PielAn Introduction to Laboratory, Space, and Fusion Plasmas F. ChenPlasma Physics and Controlled Fusion Pascal Chabert und Nicholas BraithwaitePhysics of Radio-Frequency PlasmasScripts: (in ion com content&view category&layout blog&id 47&Itemid 112 Introduction to Plasmaphysics I: Fundamentals Introduction to Plasmaphysics II: Low temperature plasmas Plasma Surface InteractionsSchool 2016 Fundamentals of Plasmas A. von Keudell79

Plasma Fundamentals - Outline 1. What is a plasma ? Temperature Debye shielding Plasma frequency 2. The edge of a plasma Sheath physics 3. How to ignite a plasma Ignition, Paschen curve Streamer RF-ignition 4. Transport in a plasma Particle motion Plasma

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