THE ADVANCED TOKAMAK DIVERTOR

Transcription

1 I Department of Engineering Physics THE ADVANCED TOKAMAK DIVERTOR S.L. Allen and the team 14th PSI QTYUIOP MA D S O N UCLAUCLA UCLA UNIVERSITY OF WISCONSIN

2 THE ADVANCED TOKAMAK DIVERTOR S.L. Allen and the team 14th PSI Outline of Presentation Detached divertor solution Extend to AT Regime Particle control Profile control QTYUIOP UNIVERSITY OF WISCONSIN MA D Department of Engineering Physics I S O N UCLAUCLA UCLA

3 Detached divertors for particle and power handling Data Shows Low Te R (m)

4 Detached divertors for particle and power handling Data Shows Low Te R (m) Model Shows Low Te R (m) Electron Temperature (ev)

5 Detached divertors for particle and power handling Data Shows Low Te Recombining Plasma Near Plate (Dγ/D α ) R (m) Model Shows Low Te R (m) Electron Temperature (ev)

6 Detached divertors for particle and power handling Data Shows Low Te Recombining Plasma Near Plate (Dγ/D α ) R (m) Model Shows Low Te Divertor Heat Flux is Reduced Erosion is Reduced R (m) Electron Temperature (ev) Heat Flux (W/cm 2 ) Major Radius (cm) Shot 79341@32ms 18 2 Ve (cm/exp-yr) 3 erosion deposition DR OSP (cm)

7 We have a high density divertor solution We have a reasonable scientific basis for a conventional long-pulse tokamak divertor solution at high density (collisional edge, detached) Low Te recombining plasma leads to low heat and particle fluxes at wall Adequate ash control, compatible with ELMing H mode confinement Appropriate for future tokamaks (e.g. to high density ITER-RC) Concerns about simultaneously handling disruptions/elms and tritium inventory which shorten divertor lifetime

8 We have a high density divertor solution We have a reasonable scientific basis for a conventional long-pulse tokamak divertor solution at high density (collisional edge, detached) Low Te recombining plasma leads to low heat and particle fluxes at wall Adequate ash control, compatible with ELMing H mode confinement Appropriate for future tokamaks (e.g. to high density ITER-RC) Concerns about simultaneously handling disruptions/elms and tritium inventory which shorten divertor lifetime The challenge is to find self consistent operating modes for other configurations... (U.S. Snowmass working group, July 2)

9 Improved confinement and stability can lead to more compact tokamak designs ITER final design report Reduced cost ITER LAM Reduced cost ITER IAM

10 Improved confinement and stability can lead to more compact tokamak designs Advanced Tokamak ITER final design report Reduced cost ITER LAM Reduced cost ITER IAM

11 An AT operates at higher H (~3) and β N (~5) Definition evolves as progress is made Plasma shapes beyond circular were once advanced, now standard H mode was advanced, now standard A standard tokamak Has a peaked current profile (q = 1, sawteeth present) characteristic of ohmic heating J(r) Therefore has a beta limit β N 3 Has standard confinement (L or H mode scaling) Low bootstrap fraction (J T 3/2 ) r

12 An AT operates at higher H (~3) and β N (~5) Definition evolves as progress is made Plasma shapes beyond circular were once advanced, now standard H mode was advanced, now standard A standard tokamak Has a peaked current profile (q = 1, sawteeth present) characteristic of ohmic heating J(r) Therefore has a beta limit β N 3 Has standard confinement (L or H mode scaling) Low bootstrap fraction An advanced tokamak Frees the current profile from the ohmic constraint With wall stabilization has potentially β N up to 6 Exploits transport barriers for improved confinement Has bootstrap fractions potentially 1% Potential for steady-state, reduced size fusion systems J(r) (J T 3/2 ) r r

13 Plasma shaping allows higher β N AT operation, requires new divertor β ~ 2.5%, ~ 5%, ~ 12.5%, ~ 35%, Plasma shaping (κ,δ,ε) increases the fraction of the total field line tragectory that is in the high magnetic field region resulting in improvement in the confinement concept Favorable for confinement High Magnetic Pressure B T Plasma Pressure Profile Unfavorable for confinement Low Magnetic Pressure R

14 Plasma shaping allows higher β N AT operation, requires new divertor β ~ 2.5%, ~ 5%, ~ 12.5%, ~ 35%, Plasma shaping (κ,δ,ε) increases the fraction of the total field line tragectory that is in the high magnetic field region resulting in improvement in the confinement concept High Magnetic Pressure B T Favorable for confinement Plasma Pressure Profile High - δ divertor Unfavorable for confinement Low Magnetic Pressure R

15 Shape is important for high pedestal pressure and good confinement 6. Pedestal Pressure Increases with δ 2 p e /I P (kpa/ma 2 ) Type I ELMs Averaged over ELMs.1δ UPPER.3.5

16 Shape is important for high pedestal pressure and good confinement 6. Pedestal Pressure Increases with δ 1.6 Confinement Increases with Pedestal Pressure ITER SHAPE, q 95 = 3.2, I p = 1.5MA 2 p e /I P (kpa/ma 2 ) H-ITER93H TYPE I ELMS TYPE III ELMS L MODE..1 Type I ELMs Averaged over ELMs.1δ UPPER ped p e (kpa, Averaged over ELMs)

17 Significant progress has been achieved in long pulse AT operation 2 ELM-free H-mode ELMy H-mode L-mode edge β N H89p DIII-D Advanced Tokamak Target ARIES-RS Conventional Tokamak τ duration /τ E

18 Significant progress has been achieved in long pulse AT operation β N H89p ELM-free H-mode ELMy H-mode L-mode edge DIII-D Advanced Tokamak Target ARIES-RS Conventional Tokamak τ duration /τ E 1999 Progress β N H = 9 for 16 τ E H89 β N 4 li β 2 sec N H Time (s) ARIES-RS ARIES-RS ARIES-RS

19 The AT scenario with off-axis ECCD P EC (MW) 2.3 P FW (MW) 3.5 P NBI (MW) 4.1 β N 4. H 89P 2.8 n/n G (MA/m 2 ) 1..5 J NB ρ

20 The AT scenario with off-axis ECCD P EC (MW) 2.3 P FW (MW) 3.5 P NBI (MW) 4.1 β N 4. H 89P 2.8 n/n G (MA/m 2 ) 1..5 J BS J NB ρ

21 The AT scenario with off-axis ECCD P EC (MW) 2.3 P FW (MW) 3.5 P NBI (MW) 4.1 β N 4. H 89P 2.8 n/n G (MA/m 2 ) 1..5 J BS J ECCD J NB ρ

22 The AT scenario with off-axis ECCD P EC (MW) 2.3 P FW (MW) 3.5 P NBI (MW) 4.1 β N 4. H 89P 2.8 n/n G (MA/m 2 ) 1..5 J tot J BS J ECCD J NB ρ

23 C Mod AT operation at β N ~3.5 (no wall stabilization necessary) 8 1 J(MA/m 2 ) Total =.8MA f BS =.75 P LH = 3MW q q = 4 q min = r/a r/a.8 1.

24 Density control and noninductive current sustainment are required for AT operation Current profile diffuses to unstable profile 12 L mode 1 Early H mode Late H mode J (A/cm 2 ) ρ

25 Density control and noninductive current sustainment are required for AT operation Current profile diffuses to unstable profile 12 L mode 1 Early H mode Late H mode J (A/cm 2 ) ρ

26 Density control and noninductive current sustainment are required for AT operation Current profile diffuses to unstable profile 12 L mode 1 Early H mode Late H mode J (A/cm 2 ) ρ

27 Density control and noninductive current sustainment are required for AT operation Current profile diffuses to unstable profile Density continuously grows at constant β J (A/cm 2 ) 12 L mode 1 Early H mode 1 Late H mode n e (1 19 m 3 ) 6 4 L mode Early H mode Late H mode ρ ρ

28 Density control and noninductive current sustainment are required for AT operation Current profile diffuses to unstable profile Density continuously grows at constant β J (A/cm 2 ) 12 L mode 1 Early H mode 1 Late H mode n e (1 19 m 3 ) 6 4 L mode Early H mode Late H mode ρ ρ

29 Density control and noninductive current sustainment are required for AT operation Current profile diffuses to unstable profile Density continuously grows at constant β J (A/cm 2 ) 12 L mode 1 Early H mode 1 Late H mode n e (1 19 m 3 ) 6 4 L mode Early H mode Late H mode ρ ρ

30 With available ECH power on, density and impurity control are critical - these are provided by the divertor 4 3 Simulation P EC =3 MW; ρ EC =.48 I p = 1.2 MA / I (ka) 2 I ECCD I OHMIC n e (1 19 m 3 ) #98549 unpump ICD Te 1 n e (Zeff + 5)

31 With available ECH power on, density and impurity control are critical - these are provided by the divertor 4 3 Simulation P EC =3 MW; ρ EC =.48 I p = 1.2 MA / I (ka) 2 1 I ECCD I OHMIC CY2 #99411 pump CY1999 #98549 unpump x Density H Factor H 93 ~1 n e /n egw n e (1 19 m 3 ). 2. D α ICD Te 1 n e (Zeff + 5) Time (ms)

32 With available ECH power on, density and impurity control are critical - these are provided by the divertor 4 3 Simulation P EC =3 MW; ρ EC =.48 I p = 1.2 MA / I (ka) 2 1 I ECCD I OHMIC CY2 #99411 pump CY1999 #98549 unpump x Density H Factor H 93 ~1 n e /n egw n e (1 19 m 3 ). 2. D α ICD Te 1 n e (Zeff + 5) Time (ms)

33 divertors can compare open (low-δ) and closed (high-δ) operation with flexible pumping Visible Spectroscopy (Several Views) Calibrated EUV SPRED (Carbon, Recombination) Bolometer Arrays IRTV s (Several Views) Divertor Thomson Scattering (ne, Te) X-Point Sweep Used to Obtain 2-D Profiles Pressure Gauges (Pump Exhaust, D 2 and Impurity) Langmuir Probes (Ion Flux, T e, T i ) Visible Tangential TV (Carbon & D α, β, γ ) EUV Tangential TV (CIV 155 ) Tangential Spectroscopy (Flows, T i, Recombination) Scanning Probe-- (MACH Tip) DIMEs Surface Probe (Erosion and Deposition)

34 divertors can compare open (low-δ) and closed (high-δ) operation with flexible pumping Visible Spectroscopy (Several Views) Bolometer Arrays IRTV s (Several Views) Divertor Thomson Scattering (ne, Te) Cryopumps ASDEX Gauges (ORNL) Langmuir Probes (SNL) Calibrated EUV SPRED (Carbon, Recombination) Magnetic Probes Penning Gauge (ORNL) X-Point Sweep Used to Obtain 2-D Profiles Pressure Gauges (Pump Exhaust, D 2 and Impurity) Bolometer Array(LLNL&GA) Langmuir Probes (Ion Flux, T e, T i ) Visible Tangential TV (Carbon & D α, β, γ ) EUV Tangential TV (CIV 155 ) Tangential Spectroscopy (Flows, T i, Recombination) Digital IRTV (LLNL&GA) Visible Spectrometer (GA & ORNL) Bolometer Array(LLNL&GA) Tangential Visible and XUV TVs (LLNL) Scanning Probe-- (MACH Tip) DIMEs Surface Probe (Erosion and Deposition)

35 RDP 2 is a closed divertor and reduces core ionization source (even without cryopumping) RDP-1999 Data F = 2.5 UEDGE F = Shots 93866, 93743, Times 24, 24 ms SOL Flux Surfaces: cm 1. Detailed ne profile used to calculate Core Ionization Relative to Open Divertor (Defined to be F) OPEN Electron density m -3 4 Divertor R (m) Open Lower Divertor Z-Z sep (m)

36 RDP 2 is a closed divertor and reduces core ionization source (even without cryopumping) RDP-1999 Data F = 2.5 UEDGE F = 3.5 RDP-2 Data (Prelim.) F ~ 5 UEDGE (Prelim.) ~ Shots 93866, 93743, Times 24, 24 ms SOL Flux Surfaces: cm 1. Detailed ne profile used to calculate Core Ionization Relative to Open Divertor (Defined to be F) OPEN Electron density R (m) Open Lower Divertor 1 19 m Divertor-2 Divertor Z-Z sep (m)

37 Experience gained in lower divertor (with DTS) is applied to upper divertor (with simplified diagnostics) OSP on Ceiling Tile Private Flux Baffle Central Column Attached Plasma at Low Density

38 Experience gained in lower divertor (with DTS) is applied to upper divertor (with simplified diagnostics) OSP on Ceiling Tile Private Flux Baffle Central Column Attached Plasma at Low Density OSP on Ceiling Tile Private Flux Baffle Central Column Detached Plasma at High Density

39 Magnetic balance can be used for power and particle control 1..5 Divertor Heat Flux Balance (Top - Bot)/Total. B Magnetic Balance

40 Magnetic balance can be used for power and particle control 1..5 Divertor Heat Flux Balance (Top - Bot)/Total. B Magnetic Balance

41 Magnetic balance can be used for power and particle control Divertor Heat Flux Balance (Top - Bot)/Total.5 Divertor Particle Flux Balance (Top - Bot)/Total Magnetic Balance Magnetic Balance

42 New physics in the x-point and private flux region Flow Reversal Reversal in Plasma Flow Mach number.5. Flow Reversal Height from Target Plate Z (cm)

43 New physics in the x-point and private flux region Flow Reversal E x B Drifts Reversal in Plasma Flow 25 Electric Field En Plasma Potential H Mode Mach number.5. V p (V) E n E B Away From Plate E n E B To Plate Flow Reversal Height from Target Plate Z (cm) Ψ n

44 New physics in the x-point and private flux region Flow Reversal E x B Drifts Recombination in Private Flux Reversal in Plasma Flow 25 Electric Field En Plasma Potential H Mode D α Mach number.5. V p (V) E n E B Away From Plate E n E B To Plate Flow Reversal Height from Target Plate Z (cm) Ψ n Appreciable T e, n e In this Region

45 Divertor Carbon Source Is Reduced, Core Content Is Similar!.1.1 Y chem 3 Boronizations have reduced the carbon sputtering yield Shot CII / D α CII / D γ The divertor carbon source is reduced by a factor of Shot D. Whyte 7/ jy

46 Divertor Carbon Source Is Reduced, Core Content Is Similar!.1.1 Y chem 3 Boronizations have reduced the carbon sputtering yield Shot CII / D α CII / D γ The divertor carbon source is reduced by a factor of Shot 1 OVI / D Lyβ CIII / D Lyβ 1 Core content is similar Shot D. Whyte 7/ jy

47 Divertor Carbon Source Is Reduced, Core Content Is Similar! Y chem Shot CII / D α CII / D γ Shot 1 OVI / D Lyβ CIII / D Lyβ 3 Boronizations have reduced the carbon sputtering yield The divertor carbon source is reduced by a factor of 4 z (m) White Arrows Illustrate Carbon Flow Radial Flow in Far SOL Shot Core content is similar Strike Plate Major R (m) Strike Plate D. Whyte 7/ jy

48 Puff And Pump In Both The Open And Closed Divertors D 2 Puff Open Divertor Argon Enrichment Divertor vs Core (D 2 puff) Carbor and Argon Radiation Increase Closed Divertor Also good enrichment Exhaust D 2 Puff Impurity 13- jy

49 Puff And Pump In Both The Open And Closed Divertors D 2 Puff Argon D 2 Puff Density X-point puff Upstream puff D 2 Puff Impurity Exhaust 2. Argon puff Argon density Time (ms) jy

50 Impurity Control In AT Plasmas With Careful Tile Shaping Up the Centerpost Wall Strike point moved UP wall from old tiles to new shaped tiles Heat Flux HIGH on Edges of Old Tiles Infrared Camera Signal 2 flat Toroidally Along the Centerpost Wall 8 3 Carbon Concentration (%) Edge RDP-1999 Core Time (ms) 13- jy

51 Impurity Control In AT Plasmas With Careful Tile Shaping Up the Centerpost Wall Strike point moved UP wall from old tiles to new shaped tiles Heat Flux LOW on shaped tiles Heat Flux HIGH on Edges of Old Tiles Infrared Camera Signal flat contoured Infrared TV Temperature Signal is NOT peaked on Shaped Tiles Toroidally Along the Centerpost Wall 8 3 Carbon Concentration (%) is Reduced Compared to Previous Operation Edge RDP-1999 RDP-2 Core Time (ms) 13- jy

52 AT Scenario Uses Divertor Shapes For Real-time Control UN Pumped L mode Maintain l i in L mode Density profile fw NBI absorption drsep +2 to raise H mode threshold B 13- jy

53 AT Scenario Uses Divertor Shapes For Real-time Control UN Pumped L mode L To H mode Transition drsep ~ B 13- jy

54 AT Scenario Uses Divertor Shapes For Real-time Control UN Pumped L mode L To H mode Transition drsep ~ Pumped H mode Maintain low n e drsep ~1 for pumping B 13- jy

55 AT Divertors are not just for heat flux reduction Advances in detached plasmas by this community have made possible a high density divertor solution (with some caveats, of course!)... Now divertor particle control is vital for AT modes Shaped plasmas are "standard", needed for high performance Real Time Shape control enables H-mode power threshold control, particle control Current profile control (ECCD) is at the heart of the AT, Impurities are important! Heat flux control in AT plasmas is expected to require impurity flow control "Puff and Pump" or active flow control, need progress in understanding flows Lots of new, exciting physics in the pedestal and x-point region 13- jy

56 Wall stabilization avoids the Resistive Wall Mode Discharge β N ~3.8 Sensor loops o C-coil (MW) (gauss) (mv-s) Diamagnetic Flux n=1 B r P NBI Ip=1.2 MA, Bt=1.6 T q min ~1.7, q 95 ~5.5 β N limited to about 4li (no wall limit) by bursty RWM Higher NBI power improves stability and duration x β N xh 89p Time (s) 75 % current non-inductive >5% bootstrap

57 Non-inductive current is needed at the half radius for steady state operation J (A/cm 2 ) J J BS J OH ρ

58 UEDGE shows core refueling fraction (I core /I div ) is lower in closed divertors I core = 4.1 % I div I core = 2.1 % I div I core =.7 % I div.6 gas density (Ipp47) 1.4 gas density (upp4).6 gas density (AT: 4MW, 7e19m 3 ) 1.2 Z (m) 1. Z (m) 1. Z (m) R (m) Open PUMP R (m) RDP R (m) AT log(n [m 3 ]) log(n [m 3 ]) log(n [m 3 ]) P c = 6 MW P c = 6 MW P c = 4 MW Neutrals are confined to divertor region by better baffling in RDP and AT divertors