[PPT] - Large Tokamaks Large Tokamaks Thomas J. Dolan ASIPP Hefei 2011 PowerPoint Presentation

SLIDE 1

Large Tokamaks Large Tokamaks

Thomas J. Dolan ASIPP Hefei 2011 2011

Ref. J. Wesson, Tokamaks, 3rd Edition, Ch.12 & 13

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 1

SLIDE 2

Large Tokamaks

Heating powers up to 50 MW, LHCD up to 3 MA Intense wall conditioning Quantitative theory - experiment Q y p H-mode “Advanced Tokamak” control J(r)  increase ℓi Low I  stability, high E and Ibs

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 2

SLIDE 3

Tokamak Fusion Test Reactor (TFTR)

dolan asipp 2011 3 Figures are from J. Wesson, Tokamaks, 2004

SLIDE 4

Tokamak Fusion Test Reactor (TFTR)

R/a = 2.4/0.8, 6 T, 3 MA, NBI = 40, ICRF = 16 Boronization and Li pellet injection (4x1020 atoms) Boronization and Li pellet injection (4x1020 atoms) "Supershot" Balanced NBI minimizes rotation peaked no/<n> ~ 2-3 Timax ~ 35 keV T

e ~ 12 keV imax e

nioTioE ~ 3x1020 m-3keV-s → QDT ~ 0.3 lasts only 1-2 s I > 50% IBS > 50%

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 4

SLIDE 5

TFTR Supershot d L M d and L Mode

1.4 MA, 22 MW NBI, 4.8 T

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 5

SLIDE 6

TFTR Supershot E Enhancement

Relative to L-mode scaling 4.8-5.1 T 0.8-1.8 MA

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 6

SLIDE 7

TFTR Ion Thermal Diffusivity

r/a = 0.3

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 7

SLIDE 8

TFTR Problems

carbon blooms carbon fibre composite tiles → better thermal conductivity p y ∇p driven tearing modes m/n = 3/2 "Reverse shear" qo=3 qmin=2 qa=6 Er po/<p>~8 ld l b bbl d d di ti cold plasma bubble preceded some disruptions rapid triton losses

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 8

SLIDE 9

m=1 Deformation  “C ld B bbl ”  “Cold Bubble”

50 s intervals 50 s intervals Followed by thermal quench

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 9

SLIDE 10

Triton Loss and MHD Activity

m=2

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 10

SLIDE 11

Toroidal Alfven eigenmodes (TAE) Toroidal Alfven eigenmodes (TAE)

 ~ vA/2qRo causes causes alpha particles NBI beams ICRF t d h t i ICRF trapped hot ions

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 11

SLIDE 12

TFTR Transport

current ramp → stored energy change i ti diff i ti l ~ resistive diffusion timescale Bohm transport scaling r/a = 0.3 to 0.8 g electrostatic drift-wave microinstability

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 12

SLIDE 13

TFTR Confinement Enhancement vs. ℓi ℓi = <B

2>/Ba 2

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 13

SLIDE 14

DT Fusion Experiments

5.5 T 2.7 MA 39.5 MW NBI 2.8 MW/m3 10.7 MW T 44 k V Tio = 44 keV, neo = 8.7x1019 m-3 tE

* = 0.33 s E

MHD instability H recycling  improvement with mass A0.9 E improvement with mass A

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 14

SLIDE 15

DT Fusion Power in TFTR

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 15

SLIDE 16

DT Fusion Experiments

tritium gas puff at t = 3.5 s N t d t  ( ) Neutron data nT(r) Alpha first orbit losses 3% at 2 MA High q doubles alpha loss High qo doubles alpha loss

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 16

SLIDE 17

Fraction of Alphas Lost

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 17

SLIDE 18

Joint European Torus (JET)

R/a=2.96/1.0, 3.8 T, 7 MA iron core pumped divertor , swept strike point 32 MW ICRF 20 s 32 MW ICRF 20 s 20 MW NBI 10 s 140 keV 12 MW LHCD 20 s

Figs. 12.3.1,

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 18

SLIDE 19

Jet Divertor

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 19

SLIDE 20

JET Limiter Operations JET Limiter Operations

Be gettering Be gettering Ohmic heating E ~ 1 s Vertical instability at b/a=1.7 Lifted 100 ton 1 cm At 7 MA  ~ 0 4 s At 7 MA E 0.4 s

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 20

SLIDE 21

JET Alternating Current Operation

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 21

SLIDE 22

JET Disruptions ℓi = <B

2>/Ba 2

current rise qa near 2 density limits ideal kink vertical instability n  P0.5

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 22

nedge  P0 5

SLIDE 23

Sawtooth Collapse

Sensors detect 2/1 mode onset Control system reduces elongation b/a Prevents or reduces vertical instability Fig.12.3.6 sawteeth m=1 instability in core Pm = Maximum g y x-ray power density ( kW/m3 )

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 23

SLIDE 24

X-ray emission during pellet injection

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 24

SLIDE 25

Central RF Stabilizes Sawteeth

Fast ions can stabilize Fast ions can stabilize sawteeth Fast alphas may Fast alphas may stabilize sawteeth in reactor.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 25

SLIDE 26

Toroidal Alfven Eigenmodes Observed

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 26

SLIDE 27

H-Mode and Transport H Mode and Transport

H mode transition: H-mode transition: Sudden change at edge, then at smaller r Reduction of turbulence ICRF L-mode  Bohm NBI H-mode  Gyrobohm NBI H-mode  Gyrobohm

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 27

SLIDE 28

H-Mode Power Threshold

Psep = power crossing t i separatrix Elongation and triangularity increase E

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 28

SLIDE 29

TF Ripple in JET

32 TF coils edge 1%, central 10-6 16 TF coils edge 10%, central 10-3 More ripple  30% energy reduction toroidal rotation suppressed H-mode required P 3 MW  12 MW H mode required P 3 MW  12 MW

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 29

SLIDE 30

Effect of TF Ripple

Smooth curve = 16 coils Dashed = 32 coils

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 30

SLIDE 31

Recycling in JET

Effective p* = p/(1-R) R = recycling coefficient y g High R  density buildup

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 31

SLIDE 32

Zeff vs. average density in JET

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 32

SLIDE 33

Single and Double Null Divertors

single null double null SOL target plates flow g p Inner outer

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 33

SLIDE 34

Power to Divertor Plates

Ion B drift: vd = 0.5i(BxB)v

2/B2

is vertical Drift towards target  q(outer) ~ 2q(inner) Drift towards target  q(outer) ~ 2q(inner) Drift away from target  nearly equal q B BxB x B B B(R) 

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 34

R 

SLIDE 35

Codeposition traps tritium in JET

40% f t iti t d i d it d l d ll 40% of tritium trapped in codeposited layers and walls After intensive cleaning 4 g still remained (of 35 g). Problem for future experiments like ITER.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 35

SLIDE 36

Electron pressure in JET SOL

Fi 12 3 14 Fig.12.3.14 N2 gas  Prad increased

2 rad

Prad cools plasma, facilitates recombination Divertor detachment Divertor detachment Low T

e and high neutral density near target

But N2  high Zeff ~ 3. “Argon frosting” cryopump  He*/ ~ 8.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 36

SLIDE 37

Current Drive in JET

LHCD (3 7 GHz) plus ICRF  I = 3 MA LHCD (3.7 GHz) plus ICRF  I = 3 MA CD = RnICD/Ptot = 0.22x1020 A/m2W CD

CD tot

IBS ~ 0.6 MA

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 37

SLIDE 38

Profile Control

C t l Central i ~ 3x(neoclassical i ) J(r) peaked off axis Steep pressure gradient Steep pressure gradient at r/a ~ 0.4 “ di l E fi ld h ” “radial E-field shear” dEr/dr important Shaded area uncertainties in Jbs

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 38

SLIDE 39

Internal Transport Barrier

LHCD  strong off-axis current  current “hole” Te* = (Ion Larmor radius)/(temperature gradient scale length) = (cs/ci ) / [ T

e / (dT e/dr) ]

= dimensionless measure of the steepness of T

e(r)

T * > 0 014 indicates transport barrier Te* 0.014 indicates transport barrier. Maintained for > 10 s.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 39

SLIDE 40

“Current Hole” in JET

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 40

SLIDE 41

Hot Ion Mode in JET

n < 2x1019 m-3 , T ~ 20 keV Ti ~ 20 keV, T

e ~ 10 keV

Lasts 1-2 s Termination by ELM

r n=1 external kink

“Triple product” noT

E ~ 9x1020 keV/m3s

 Q 1

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 41

 QDT ~ 1

SLIDE 42

Optimized Shear Mode

n ~ 2x1019 m-3, high power NBI Strong ITB Ti > T

e

Triple product ~ 11x1020 m-3keV-s Triple product ~ 11x10 m keV-s 1-2 s n=1 pressure driven kink  disruption

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 42

SLIDE 43

High Power D-T Operations in JET

3.6 T, 3.6 MA NBI = 22.3 ICRF = 3.1  16.1 MW fusion 60% thermonuclear 40% beam-plasma QDT ~ 0.62 Allowed < 2.5x1020 neutrons

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 43

SLIDE 44

Central Temperature vs. Alpha Power

Heating of T

e by P

good alpha confinement P = 1.3 MW  T

e(0) ~ 1.3 keV

(% tritium) Open diamonds: ICRF heating in pure deutrium pure deutrium.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 44

SLIDE 45

JT-60U Tokamak, Naka, Japan

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 45

SLIDE 46

JT-60U Tokamak, Naka, Japan

Single null R/a = 3.4/1.1 4.2 T 4.2 T 5 MA NBI = 40 (120 keV) (120 keV) ICRH = 7 LH = 8 ECH = 3 Negative ion NBI Negative ion NBI under development

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 46

SLIDE 47

JT-60U Operation

Usually L-mode H-mode at low n, high Pin H mode at low n, high Pin Pellet injection, peaked profiles  better  better E Graphite targets Radiative cooling in divertor He ash removal effective Boronization  f < 1%

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 47

Boronization  fox < 1%

SLIDE 48

Limiter H-Mode in JT-60U

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 48

SLIDE 49

Recycling Flux Decreases E

Recycling increase  Prad increase  Prad increase  E decrease Open circles have Open circles have no gas puffing.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 49

SLIDE 50

W-shaped divertor W shaped divertor

Better pumping  P(H-mode) reduced 30%

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 50

SLIDE 51

Helium residence time

Achieved He/E ~ 3-4, with f ~ 4% with fHeplasma ~ 4%. But with ITB He/E ~ 15.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 51

SLIDE 52

Current Drive

LHCD ~ 10 MW LHCD 10 MW 3.6 MA CD = RnICD/Pin LHCD LHCD = 0.34x1020 A/m2W NNBI = 0.16x1020 A/m2W ECCD = 0.05x1020 A/m2W

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 52

SLIDE 53

Bootstrap Current

fb  p Neoclassical  Neoclassical  ITB core and H mode edge H-mode edge High p case:

p

1.8 MA for 2 s (half NBI, half bootstrap) half bootstrap)

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 53

SLIDE 54

Current Hole

Reversed shear  current hole  current hole At r/a < 0.4 L t 5 Lasts 5 s

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 54

SLIDE 55

MHD Stability Diagram for JT-60U

Disruptions: density limits current rise current rise error field high-ℓi during current rampdown current rampdown kink-ballooning tearing modes If J(r) = Jo(1-r2/a2) then ℓi = ln(1.65+0.89) then ℓi ln(1.65 0.89)

ℓi = <B

2>/Ba 2

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 55

SLIDE 56

Internal Inductance vs. J(r)

ℓi = <B

2>/Ba 2

If J( ) J (1

2/ 2)

If J(r) = Jo(1-r2/a2) then ℓi = ln(1.65+0.89)

i

Large  narrow J(r)  large ℓi  disruption  large ℓi  disruption. Note: J(r) may have other shapes shapes.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 56

SLIDE 57

Mitigation of Disruptions

Neon pellets  0.2(divertor heat flux) Saddle coils  3/2 perturbations  suppress Saddle coils  3/2 perturbations  suppress runaway electrons O i l i l i i  ( i l i bili )  Optimal vertical position  (vertical instability)  Low po/<p>  ELMS limit edge pressure po p g p Ligh po/<p>  internal p collapses High triangularity  and ECCD  higher stable  High triangularity  and ECCD  higher stable .

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 57

SLIDE 58

Confinement

Boronization  4.5 MA H-modes H-mode threshhold Pth  B 5 10  t I ELM b d n = 5-10  type I ELMs, bad n > 10  type II “grassy” ELMs, yp g y , lower heat flux to divertor

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 58

SLIDE 59

Ripple Loss Fraction of PNBI

P /P Pripple loss/PNBI at midplane

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 59

SLIDE 60

High-p H-mode

2 4 MA 4 3 T 2.4 MA 4.3 T reversed shear Triple product = 15x1020 m-3keV-s QDT ≈ 0.4

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 60

SLIDE 61

High-p H-mode

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 61

SLIDE 62

NBI  ITB at r/a ~ 0.53

Steep gradients of p g Ti and toroidal rotation speed

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 62

SLIDE 63

NBI  Reversed Shear

2 6 MA 4 4 T 2.6 MA, 4.4 T 15 MW NBI  ITB at r/a ~ 0.6 <n> = 1019  no = 8x1019 m-3 Tio  20 keV n T  = 8 6x1020 m-3keV-s noTioE = 8.6x10 m keV-s QDT = 1.25 Surpasses “breakeven” conditions B t di t i kl But disrupts quickly. Low-n ideal kink ballooning modes.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 63

SLIDE 64

DIII-D, General Atomics Company

1.67/0.67 m 2 2 T 5 MA 2.2 T 5 MA NBI/ICRF/ECRH = 20/4.4/3 graphite+boroniz. pellet injection pellet injection helps H-mode

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 64

SLIDE 65

DIII-D Divertors

single null P (H mode)  B Pth(H-mode)  B double null Pth independent of B

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 65

SLIDE 66

ELMs in DIII-D ELMs in DIII D

Type I "giant" ELMs --> losses > 10% of plasma ions n=5-10 ballooning modes Type II "grassy" ELMs higher frequency, lower amplitude

ccur when s/q95

2 < 0.15

s = shear = d(ln q)/d(ln ) ~ dq/dr MHD activity n = 1 to 13. MHD activity n 1 to 13.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 66

SLIDE 67

H-Mode Transition

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 67

SLIDE 68

Effect of Er on H-Mode

H-mode is associated with a change of Er at plasma edge. Er = (Zenz)-1dpz/dr –vB + vB S i f d /d ld Steepening of dpz/dr could change sign of Er and trigger H-mode. gg Er change precedes other signals during H-mode transition signals during H-mode transition.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 68

SLIDE 69

Thermal Diffusivity Scalings

dimensionless parameters: * / * / *  * = i/a * = ii/e*  L-mode scalings: H-mode scalings e  * (Gyrobohm) e  * (Gyrobohm) i  -1/2 i   (Gyrobohm) i   i   (Gyrobohm) eff  *0.49

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 69

SLIDE 70

Energy Confinement Scaling

Ratio of H-mode to L-mode confinement time : H89 = (

H/ ITER89-P)

where 

ITER89-P

is L-mode H89 ( / ) where  is L mode Usually H89 ~ 2 (n/ngr )↑ → H89 ↓ Neon injection → H89 ↑ Impurities stabilize drift wave turbulence "Normalized beta" N =  / (IMA/aB) EAST:  =0.01, IMA =0.5, a = 0.48, B = 2.4 → N = 2.3

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 70

SLIDE 71

Figures of Merit

Fusion reactor needs high pressure , long confinement E "Figure of Merit" = N H89 "Triple Product" = n Ti E Triple Product = noTioE

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 71

SLIDE 72

VH-Mode

low impurities, recycling strong plasma shaping toroidal rotation “second stability regime” terminated after ~ 1 s Triple product ~ 5x1020 m-3keV-s  ~ 12.5%  5% N =  / (IMA/aB) N > 2.5

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 72

SLIDE 73

Magnetic Braking Hurts VH Mode

ExB rotation shear ExB rotation shear → stabilization E fi ld Error field → braking of rotation → E↓

E

High po/<p> → ℓi↑ → E↑ → ℓi↑ → E↑ H89 ~ 4.5 triple prod ct triple product ~ 6.2x1020 m-3keV-s

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 73

IBS broadens J(r) → ℓi ↓

SLIDE 74

Figure of Merit NH89

Best plasmas initially Best plasmas initially formed with negative central shear. N =  / (IMA/aB) H89 = E/L-mode

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 74

SLIDE 75

Maximum Stable Elongation

vertical displacement instability b/a injection of neon or argon stops vertical instability, b/a reduces damage.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 75

SLIDE 76

Correction Coil Stabilizes n=1 Modes

stable unstable

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 76

SLIDE 77

Beta Values in DIII-D

“Normalized beta” N = /(I/aB) Rotation helped suppress resistive wall modes (RWM) wall modes (RWM)

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 77

SLIDE 78

Feedback Stabilization of RWM

feedback to saddle coils

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 78

SLIDE 79

TAE Modes  Fast Ion Losses  Neutron Emission Decrease Neutron Emission Decrease

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 79

SLIDE 80

ICRF Fast Wave Current Drive

L Mode L Mode

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 80

SLIDE 81

Single and Double Null Divertors

single null double null SOL target plates flow g p Inner outer

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 81

SLIDE 82

Power Asymmetry to Divertor Targets

More Prad on inner leg  lower heat flux to inner target. Separatrix position controls power deposition between upper and lower targets. Higher gas injection plus cryopump  lower target heat flux T ~ 2 eV recombination significant T

e ~ 2 eV, recombination significant

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 82

SLIDE 83

ELMy H-Mode with Gas Injection

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 83

SLIDE 84

Helium Pumping

Argon frosting on cryopump He*/E ~ 8-13

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 84

SLIDE 85

ASDEX Upgrade

R/b/a = 1 65/0 85/0 5 R/b/a = 1.65/0.85/0.5 3.9 T, 1.4 MA 10 s flattop NBI 20 NBI = 20 ICRF = 6 ECH = 2

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 85

SLIDE 86

Divertor Design

Goals reduce target heat flux reduce He accumulation in core plasma Methods ionize hydrogen neutrals in SOL increase Prad in SOL  T

e < 5 eV

increase neutral pressure near target increase neutral pressure near target “compression” nm(pump duct)/ni(midplane) He*/E ~ 4-6

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 86

SLIDE 87

Radiation in ASDEX Divertor

Data unavailable

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 87

SLIDE 88

ASDEX Tungsten Tiles

Gradually C tiles  W tiles. Keep fw << 10-4 in core Usually fw ~ 2x10-5 Sputtered W redeposits nearby.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 88

SLIDE 89

Operating Regimes

1 MA, 2.5 T Avoid Type I ELMs. Type III are OK. Type III are OK. Neon puff detaches divertor lowers heat flux divertor, lowers heat flux. triangularity  ballooning stable at higher p 2 cm inside separatrix

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 89

SLIDE 90

Neon reduces divertor heat flux

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 90

SLIDE 91

H-Mode Ti(r) Profile Stifness

Ion Temperatue Gradient (ITG) mode --> turbulence i keeps same shape r/a = 0.3 to 0.8 Ti/∇Ti ~ constant limited by ITG mode limited by ITG mode T

e/T e ~ constant

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 91

SLIDE 92

Fueling and Density Profile

gas puffing  cooler edge  lower core parameters (density stiffness) (density stiffness) central fueling better Pellet injection from low-field side  gas cloud. time g diamagnetic plasmoid drifts back to low field side. Injection from high-field side is good.

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 92

SLIDE 93

Avoidance of NTM

Nearly double null Triangularity  = 0 42 Triangularity  = 0.42 Type II ELMs  l 0 5%

nly 0.5% energy

loss. N =  / (IMA/aB)

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 93

SLIDE 94

Bootstrap Current

Maximize p fbs + fNBI ~ 100% NBI during ramp-up  ITB ECCD counter to plasma current can sustain ITB p

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 94

SLIDE 95

NTMs cause energy losses

Tearing mode energy loss 4/3 <10% 3/2 10-30% 2/1 50% and disruption (qa < 3) p (qa ) N for onset  i/a ECCD can generate helical current within islands and stabilize tearing modes

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 95

SLIDE 96

Reactor Issues

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 96

SLIDE 97

Q vs. Triple Product

Q = (fusion power) / (input power) i t 3 TV/ (1/4)

2<

>V( /5) V l input power = 3nTV/E – (1/4)n2<v>V(/5) V=volume

Underlines denote radial averages

fusion power = (1/4)n2<v>V  = 2.82x10-12 J <v> ≈1 1x10-24 T2 m3/s T in keV <v> 1.1x10 T m /s T in keV

Assuming parabolic profiles:

Q= 5 / [ 60nT/(n2<v>E) – 1] ≈ 5 / [ 5x1021/(noT

E) – 1]

noT

E = 5x1021  Ignition Attained 1.5x1021

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 97

SLIDE 98

Reactor Requirements

Confinement:  and E (or NH89 ) To confine alphas plasma current I = 30 MA / H To confine alphas plasma current I 30 MA / H Fuel dilution NHe/N = 0.012/E < 0.1  E < 8 Disruption prevention and mitigation Disruption prevention and mitigation Heat removal : Heat flux at target < 10 MW/m2 Technology: magnets, structure, heating, current drive, tritium, vacuum, cryogenics, fuelling, diagnostics, tritium, vacuum, cryogenics, fuelling, diagnostics, feedback control, …

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 98

SLIDE 99

International Thermonuclear E i l R (ITER) Experimental Reactor (ITER)

Ignition 1988 High-Q 2005 g g Pf, MW 1500 500 Burn, s 1000 400 R/a m 8 1/2 8 6 2/2 0 R/a, m 8.1/2.8 6.2/2.0 I, MA 21 15 B, T 5.7 5.3 # TF il 20 # TF coils 20 1989 G$ 5.9 2.8 (~ 6 G$ 2008)

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 99

SLIDE 100

ITER ITER

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 100

SLIDE 101

ITER Wall & Shield ITER Wall & Shield

Be = 1 cm Cu = 1 cm Steel = 5 cm Steel & water = 35 cm Be Cu Steel Steel & Water

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 101

SLIDE 102

Summary – Large Tokamaks

TFTR a=0.8m NBI<40, ICRF<16 Pf ~ 10 JET a=1.25m 32 TF coils, LHCD  3 MA, ITB, hot ion mode noT

E ~ 9x1020

QDT ~ 1, Pf ~ 15 JT-60U a=1.1m noT

E ~ 15x1020

QDT ~ 0.4 DIII D a=0 67m E affect on H Mode  H ~ 10 DIII-D a=0.67m Er affect on H-Mode, NH89 ~ 10 feedback stabilization ASDEX-U a=0.5m neon in divertor, profile stiffness, pellets

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 102

SLIDE 103

Extra Slides Extra Slides

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 103

SLIDE 104

Edge magnetic shear delays ballooning

ELMs reduced

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 104

SLIDE 105

“Killer” Pellet Affects Disruption

dolan asipp 2011 Figures are from J. Wesson, Tokamaks, 2004 105