Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 1 ITER Design Review Activities on Steady State and Transient Power.

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 1

ITER Design Review Activities on Steady State and Transient

Power Loads in ITER

Alberto LoarteEuropean Fusion Development Agreement

Close Support Unit – Garching

Acknowledgements : EU-PWI TF, ITPA Divertor & SOL

Group, ITER and many others


Requirement to maintain li < during ramp-up/down Padd > 10 MW

Analysis of port limiter for ITER (Kobayashi NF 2007) shows :

for Ip < 6.5 MA qlimmax (MWm-2) ~ PSOL(MW)

Stable ramp-up Ptot/Prad ~ 0.3 + Ptot > 11-14 MW PSOL > 8-10 MW

qlimmax > 8-10 (MWm-2)

-2 0 2 4 6 8 10 12 14 16-8

-6

-4

-2

0

2

4

6

8

2.5MA4.5MA

6.5MA

7.5MA

Ramp-up/down Phase


New proposed scenario to full bore ramp-up with short ohmic phase (PSOL < 3 MW) , early X-point formation & heating

Ramp-down in X-point configuration

Full bore plasma : large plasma near first wall but low PSOL

New Proposed Ramp-up/down Phase

-2 0 2 4 6 8 10 12 14 16-8

-6

-4

-2

0

2

4

6

8

2.5MA

3MA


All divertor tomakaks measure plasma particle fluxes (II B) to

the main wall

Extrapolated plasma flux to the main wall in ITER 1.0 - 5 .0

1023 s-1 (1-5 % of div)

QDT = 10 steady plasma loads (I)

Lipschultz IAEA 2000

Lipschultz


Plasma fluxes predominantly on outer side of first wall Corresponding maximum IIB power densities up to : 5 MWm-2 (Upper X-

point) to 1 MWm-2 near outer midplane and 0.4 MWm-2 near inner midplane

QDT = 10 steady plasma loads (II)

LaBombard NF 2004

Conditions qx

(MWm-2)

far-SOLout

(m)

(mapped to outer

mid-plane)

Total plasma

power to outer

wall

(MW)

far-SOLin (m)

(mapped to outer

mid-plane)

Total plasma power

to inner wall

(MW)

Low edge

ne

5.3 0.03 3.0 0.006-0.01 0.6-1.0

High edge

ne

2.9 0.17 9.2 0.03-0.06 2.0-3.0


C-X particle fluxes vary along wall but C-X power fluxes change only by ~2

C-X particle flux ~ 2 Ion flux 0.2-1.0 1024 s-1 <qC-X> = 0.02-0.1 MWm-2

QDT = 10 steady C-X and radiation loads

Pedge > 1.3 PL-H Prad < 85 MW <qrad> < 0.12 MW m-2


Time scale of divertor ELM energy flux rise correlated with ion transport time

Eich JNM 2005PIPB 2007

Divertor ELM power fluxes : timescales

Plasma conditions affect ELMIR ~ II relation (pre-ELM divertor plasma, WELM, etc.)

JET-Eich-JNM 2003

rise,ELM = 200-500 s


qELM(t)

Large proportion of WELM arrives after IR smaller Tsurf for given WELM

222

exp1)(ttt

tqELM

down,ELM = 1-2 rise,ELM


Divertor Area for ELM power Fluxes (I)

Adiv,ELM ~ 3.5 m-2

Broadening ~ 1

Eich, PIPB’07

Ein,ELM/Eout,ELM = 1-2


Divertor Area for ELM power Fluxes (II)

TPFdiv,ELM ~ 1.0

Divertor ELM load near separatrix ~ toroidally symmetric but strong in/out asymmetries

Eich, PRL’4

Loarte, PPCF’03 from Leonard JNM’97

DIII-D


Tolerable ELM size

QSPA experiments on NB31 targets show

energy density / MJm-2

0.5 1.0 1.5

neg

lig

ible

ero

sio

n

ero

sio

n s

tart

sat

PF

C c

orn

ers

PA

N f

ibre

ero

sio

n o

ffl

at s

urf

aces

afte

r 10

0 sh

ot

sig

nif

ican

tP

AN

fib

reer

osi

on

afte

r 50

sh

ots

PA

N f

ibre

ero

sio

naf

ter

10 s

ho

ts

Tolerable ELM energy density 0.5 MJm-2 + no broadening + 2:1 in/out asymmetry WELM ~ 1MJ


Part of WELM is reaches the main wall PFCs energy flow along filaments

Fluxes to main wall during ELMs

AUG- Herrmann –PPCF’06

highest qwallELM by filament impact (A. Herrmann, AUG)

Example (JET-P. Andrew EPS)


Model of II vs. I B transport during ELMs in agreement with experimental findings:

ELM Ti > Te far from separatrix (Langmuir Probes + Retarding Field Analyser)

Deficit of divertor ELM energy for large ELMs (vr/cs ~(WELM/Wped)0.5 + Radiation)

ELM fluxes to Main wall fluxes

R

Fundamenski - PPCF 2006R JET- Pitts IAEA 2006 & Fundamenski JNM 2007


ELM fluxes to Main wall in ITER (I)

ELM power fluxes to PFCs in ITER evaluated by models/empirical extrapolation (input) : WELM

filaments/WELM , RELM, VrELM vs. WELM

(nped, Tped), IR (II)

qELM (r) = q1 exp-[(r-rw)/ELM-1] + q2 exp-[(r-rw)/ELM-2]

Conditions E1 (MJm-2) E2 (MJm-2) 1 (m) 2 (m)

Controlled

ELM

0.13-0.26 0.11-0.23 0.015 0.06

Uncontrolled

ELM

3.1-6.3 2.0-3.9 0.025 0.08

NSOLN

p

limlim

||

lim

||

noN

qq

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.350

5

10

15

20

ELM

IR = 250 s. Model by W. Fundamenski. n

ped = 7.5 1019 m-3, T

ped = 5 keV

Wfilaments

ELM= WPlasma

ELM & R

detachment = R

separatrix

qdiv

qBe-wall

Rsep

= 5 cm 10 cm 15 cm

WELM

/Wped

qdi

v,E

LM

perp

(GW

m-2)

0

5

10

15

20

25

30

35

40

qw

all,ELM

II(G

Wm

-2)

Conditions q1 (GWm-2) q2 (GWm-2) 1 (m) 2 (m)

Controlled

ELM

0.7 0.6 0.015 0.06

Uncontrolled

ELM

16.7 10.4 0.025 0.08

Controlled ELM WELM=1MJ fELM=20-40 Hz

Uncontrolled ELM WELM=20MJ fELM=1-2 Hz


ELM fluxes to Main wall in ITER (II)

<qELM>(r) = <q1> exp-[(r-rw)/ELM-1] + <q2> exp-[(r-rx)/ELM-2]

Conditions <q1> (MWm-2) <q2> (MWm-2) 1 (m) 2 (m)

Controlled

ELM

2.6-10.5 2.3-9.0 0.015 0.06

Uncontrolled

ELM

3.1-12.6 2.0-7.8 0.025 0.08

Average ELM power fluxes to PFCs require knowledge of filament dynamics


Energy Fluxes to main wall and divertor PFCs during Marfes

Plasma energy <Ewall> (MJm-2) Ewallpeak (MJm-2) . (s)

WMarfe-onset = 175 MJ

0.25 0.75 0.01-0.1

Pre-disruptive Marfes occur when plasma is already in L-mode In steady state Prad = Pinp = 70 -150 MW <qrad> = 0.1-0.2 MWm-2

Timescale for transient Marfes ~ 0.01-0.1 s (no clear size dependence) Poloidal peaking < 3


Energy Fluxes during disruptions (I)

Energy degradation before thermal quench for resistive MHD disruptions

Large broadening of footprint for diverted discharges but small for limiter discharges


Energy Fluxes during disruptions (II)

Timescale (~ R) but large variability (1.0-3.0 ms for ITER) Longer timescales in decay phase (> 2 rise phase)

Toroidal asymmetries (~2) seen in some cases but poor documentation/statistics

Systematic study of in/out asymmetries required


Proposed ITER specifications (M. Sugihara/M. Shimada)Scenario 2 : unit (MJ/m2)

Energy release at TQ (1/2-1/3)Wpeak Wpeak

E// near separatrix at outer midplane

200 - 70 400 - 200

E// near upper ceiling region(6 cm from 1st separatrix)

20 - 50 60 - 100

E// near lower baffle region(6 cm from 1st separatrix)

16 - 40 48 - 80

E// to divertor plate near 1st separatrix

280 – 90 (out)375 – 120 (in)

560 – 280 (out)750 – 380 (in)

=2.5 cm (left), 5 cm (right) Energy deposition time duration = 3-9 ms

Energy Fluxes during disruptions (III)


Energy release at TQ Wpeak (325 MJ)

E// near separatrix at outer midplane 510 - 255

E// near upper ceiling region(5 cm from 1st separatrix)

120 - 160

E// near lower baffle region(5 cm from 1st separatrix)

95 - 130

E// to divertor plate near 1st separatrix 730 – 365 (out)375 – 120 (in)

=2.5 cm (left), 5 cm (right) Energy deposition time duration = 3-9 ms

Proposed ITER specifications (M. Sugihara/M. Shimada)Scenario 4 : unit (MJ/m2)

Energy Fluxes during disruptions (IV)


Major disruptions during limiter phase :(M. Sugihara/M. Shimada)

Ip (MA) 4.5 6.5

Wpeak (MJ) 10 20

P ; peak energy density (MJ/m2)

7.7 15

Most severe assumption :No broadening of deposition width

(Kobayashi NF 07)2 limiter case

Energy Fluxes during disruptions (V)

If there is no broadening energy fluxes on limiter for disruptions can be similar or larger than for the divertor disruptions in scenario 2


Wpeak

Start of limiter config.

H-L transition

Fast energy loss phaseafter transition

TQ at q= 1.5

Energy loss phaseduring q decrease

1

2

3

W2

W3

WTQ

Energy Fluxes during disruptions (VI)

JET

ITER

Presently proposed ITER specifications based on JET based extrapolations input from other tokamaks is required

W2 = 20-55 MJ

2 = JET/L-modeJET (0.03-0.09)*L-mode

ITER

W3 = W(2)-dW/dt|L-mode*3


Downward VDE with fast CQ - EM load on BM / DIV by eddy (+halo) current

- Heat load on lower Be wall & W baffle

Upward VDE with fast CQ - EM load on BM by eddy (+halo)

- Heat load on upper Be wall during VDE and TQ

0

5

10

15

20

-6

-4

-2

0

2

640 650 660 670 680 690C

urr

ent

(MA

)Z

(m)

Time (ms)

Z

Ip

Ihalopol

(a)

(b)

(c)

(d)

VDE_downward

-500

-400

-300

-200

-100

0

100

300 400 500 600 700 800 900

Z (

cm)

R (cm)

(d)

(c)

(b)

(a)

1

2

3

4

18

17

16

15

14

0

100

200

300

400

500

300 400 500 600 700 800Z

(cm

)R (cm)

(d)

(c)

(b)

(a)

5

6

3

4

7

8 9

11

10

12

0

5

10

15

20

0

2

4

6

8

860 880 900 920 940

Cu

rren

t (M

A)

Z (m

)

Time (ms)

ZIp

Ihalo

pol

(a)

(b)

(c)

(d)

VDE_upward

Energy Fluxes during disruptions (VII)


Fast H-L transition ( loss in 1-2 s IW contact for up to ~ 5s) can lead to

large loads on the inner wall

0 5 10 15-0.10

-0.05

0.00

0.05

0.10

0.15

0.20 distance P

SOL

qII,wall

X Axis Title

Inn

er

Wa

ll/S

ep

ara

trix

Dis

tan

ce (

m)

0

50

100

150

200

250

300 PS

OL (M

W) q

II,wall (M

Wm

-2)

Confinement transients


Predicted runaway current 10 (MA)Energy spectrum of electrons (E0 for exp(-E/E0)) 12.5 MeVInclined angle 1 - 1.5Total energy deposition due to runaway current 20 MJAverage energy density deposition 1.5 MJ/m2

Duration of the average energy density deposition 100 msMaximum energy density deposition (end of the plasma termination) 25 MJ/m2

Duration of the maximum energy deposition 10 msNumber of event Every major

disruption

These specifications are generally reasonable but physics basis is weak (very poor experimental input)

Largest concern energy load by drifted electrons due to formation of X-point

Runaway electron fluxes on PFCs (I)


Runaway generation mechanisms for ITER like disruptions conditions studied in detail but runaway losses and dynamics

are worse known

Runaway electron fluxes on PFCs (I)


Current profile during runaway discharge peaks (seen at JET) X-point formation in Scenario 2

Runaway electron fluxes on PFCs (II)

Smith PoP 2006

EFIT reconstruction by S. Gerasimov


Runaway electron fluxes on PFCs (III)

Significant drift of runaways near upper X-point due to poloidal field null [f(E) = 1/E0exp(-E/E0) with E0 = 12.5 MeV]

Angle of impact of runaways on drift orbits at upper X-point < 1.5o but impact direction mainly toroidal


Conclusions

PID specifications for PFC loads in ITER considered for revision

following ITER Design Review Process New specifications will be used for modification to existing

design reasonable range and upper boundaries for loads

have to be provided Input and constructive criticisms from EU-PWI TF and ITPA are

gratefully acknowledged

Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 1 ITER Design Review Activities on Steady State and Transient Power.

Documents

elm slide

elm ir

w elm w

w elm filaments w elm

plasma fluxes

hz uncontrolled elm

radiation elm fluxes

divertor elm power fluxes