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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 2
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 3
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 4
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 5
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 6
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 7
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 8
qELM(t)
Large proportion of WELM arrives after IR smaller Tsurf for given WELM
222
exp1)(ttt
tqELM
down,ELM = 1-2 rise,ELM
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 9
Divertor Area for ELM power Fluxes (I)
Adiv,ELM ~ 3.5 m-2
Broadening ~ 1
Eich, PIPB’07
Ein,ELM/Eout,ELM = 1-2
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 10
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 11
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 12
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)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 13
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 14
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
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 15
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 16
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 17
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 18
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 19
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)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 20
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)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 21
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 22
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 23
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)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 24
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 25
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)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 26
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)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 27
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 28
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
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – CIEMAT 29-31 – 10 – 2007 29
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