Transcript Edge Plasma Energy and Particle Fluxes in Divertor Tokamaks

Report on ITER Design Review Sub-group on : Heat and Particle Loads to
in-vessel components associated with limiter and X-point operation, TF
ripple, H&CD systems, ELMs, disruptions, VDEs, Marfes and runaway
electrons in ITER
Alberto Loarte
European Fusion Development Agreement
Close Support Unit – Garching
Acknowledgements: A. Grosman, P. Stangeby, G. Saibene, R. Sartori, M. Sugihara, W.
Fundamenski, T. Eich, P. Snyder, V. Riccardo, G. Counsell, R. Pitts, B. Lipschultz, P.
Andrew, G. Pautasso, A. Leonard, G. Strohmayer, G. Federici, A. Kirk, J. Paley,
M.
Lehnen, B. Alper, C. Ingesson, etc.
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
1
Fluxes to limiter during Ramp-up/down (I)
ITER PID only specifies Pmaxlimiters = 15 MW (max 9 MW on one limiter)
 Reference ITER ramp-up(/down) has long
limiter phases up to Ip = 7 MA (10 MA) in which
plasma is limited by two limiters 180o apart
(power loads & erosion)
 2 limiter configuration and qlim = 5 lead to long
connection lengths in SOL (>> 200 m)
Magnetic shear + perpendicular transport  simple “single
exponential” power decay length (Kobayashi, NF 2007)
Main Uncertainties
 PSOL for all ITER reference scenarios (ramp up/down with heating)
 Scaling of SOL transport with Ip and R (JET extrapolation for Kobayashi NF 2007)
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
2
Fluxes to main wall and divertor during
diverted operation (I)
ITER power and power fluxes estimated with B2-Eirene for a range of burn
conditions (mainly QDT = 10) to maintain detachment but weak physics basis
for SOL transport and main chamber fluxes
 near SOL transport  lp = 5 mm (close to most pessimistic scalings 4 mm) for Ip = 15
MA (6 mm for scenario 3 (hybrid) and 8 mm for scenario 4 (ITB) if lp ~ Ip-1)
 qII = 570 – 760 MWm-2 for PSOL = 100 MW (typical for scenarios 1 & 2)
H-mode scenarios 1 & 2 Dwall = 5–20 cm  qIIwall < 0.04 MWm-2 lIB
L-mode scenarios 1& 2 (PSOL=35 MW, lL=2 lH) & Dwall=5–20 cm qIIwall < 1.0 MWm-2 IIB
0.5o < a < 15o  FW load < 0.5 MWm-2 fulfilled but loads on edges ? (2mm steps) and
edges of ports ?
Main uncertainties :
 In/out divertor power asymmetry (ballooning transport)
 Far SOL transport (wall fluxes)
 Scaling of lp
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
3
Fluxes to main wall and divertor during
diverted operation (II)
Particle flux to ITER main wall expected to be > 1023 s-1 (> 1% of Gdiv)
Lipschultz
o
Angle of incidence ()
2
6
10
17.5
15.0
Alberto Loarte
10
10.0
 qII < few MW II B on (outer) first wall  local
particle & power fluxes on edges and 5
10
edges of ports ?
0.00
 qperp < 0.3 MW m-2 < OK for FW panels
9th
5
12.5
ITPA Divertor and SOL Physics Meeting
7.5
5.0
up
2.5
0.0
0.00
low
qII
0.02
0.04
up
q0.06
perp
2
qII (W/m )
20.0
qII
0.08
low
0.12
perp
0.10
q
qperp (W/m )
“Scarce” data & ITER B2-Eirene modelling :
 n (Dsep ~ 5 cm) = 0.4 - 1.0 1019 m-3
 vSOL = 30 – 100 ms-1
 TSOL = 10 – 20 eV
 lSOL = 4.5 – 21 cm
L = 60 m, TSOL = 10-20 eV, VSOL = 30 - 100 m
0.14
4
Distance to active separatrix at midplane10
(m)
0.05
0.10
0.15
Distance to Separatrix (m)
IPP-Garching
7-10/5/2007
4
Fluxes associated with heating systems
and steady-state non-toroidal asymmetries
w/o convection
 NBI shine-through
limit ne > 3.7 1019 m-3 (30% nGW) for 0.5 MWm-2 (edges ?) but no
local ionisation or first orbit losses included
 Ripple losses expected to to lead to less than 0.3 MWm-2 (3-D effects ?)
 Effect of ELM RMP coils on power deposition assymetries ?
 ICRH (and LH) can lead to large power fluxes on PFCs near and far field (not included
in PID)
EFDA Task TW6-TPHI-ICFS2 (L. Colas, CEA)
P//=94kW (/20MW)
Q//=0.4|VRF|necs
with convection
Alberto Loarte
P//=88kW
•Integrated losses : typically 100kW for 20MW
injected (low density case)
•Localised peak at 10MW/m2 ; average
~2.5MW/m2
•These results depend crucially on the density
value in the first cm in front of the wall (farSOL transport ?)
• Sheath rectification may reach 2-3 kV 
Sputtering of surfaces!
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
5
Plasma Position and Shape Control
In transient events 1 cm SOL field line touches first wall for 1 s
If plasma in H-mode then depending on location of contact
 plasma stays in H-mode or H  L transition
H-mode
sin a = 1-8 10-2
sin a = 1.5-2.5 10-1
qIIcontact-wall
77 – 102 MWm-2
lpcontact-wall
0.5 cm
Dtcontact-wall
1s
HL
350 MJ  175 MJ
qIIL-H contact-
> 105 - 140 MWm-2
lpL-H
1.0 cm
tpL-H
< 1.7 s
wall
in “minor disruptions” separatrix can touch dome for ~ 1 s
qII in,dome ~ 380 - 570 MWm-2
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
6
Fluxes to main wall and divertor during
ELMs (I)
PID estimates of ELM loads for ITER carried out on simplified
experimental basis
Sugihara, ITER_D_22JYYU, 2005
700-950 MWm-2
3.5-4.7 GWm-2
Specified loads are of the right magnitude but can be improved to include ELM physics
understanding (time dependence, in/out asymmetries, relation “l” vs DWELM/Wped
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
7
Fluxes to divertor during ELMs (II)
2

 t 2
  t 2 
t


qELM (t )  1      exp    

 t 
 t   t 



Loarte, PPCF’03
DWELM < 30 MJ
tdown,ELM = 1-2 trise,ELM
Eich, PIPB’07
Eich
application of
Fundamenski PPCF’06
trise,ELM = 200-500 ms
Adiv,ELM = 4 m-2
Broadening < 1.5
Eich, PIPB’07
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
8
Fluxes to divertor during ELMs (III)
Divertor ELM load near separatrix ~ toroidally symmetric but strong in/out
asymmetries
Ein,ELM/Eout,ELM = 1-2
Eich, JNM’07
TPFdiv,ELM < 1.5
Loarte, PPCF’03 from Leonard JNM’97
Eich, PRL’4
DIII-D
Eich, JNM’07
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
9
Fluxes to divertor during ELMs (III)
DWdiv,ELM
Einmax (MJ)
Eoutmax (MJ)
5 MJ
< 3.3
< 2.5
30 MJ
< 20
< 15
Einmin (MJ)
Eoutmin (MJ)
qinmax (GWm-2)
qinmin (GWm-2)
< 2.5
< 1.7
< 6.2
< 1.9
< 15
< 10
< 37.5
< 11.3
qoutmax (GWm-2)
qoutmin (GWm-2)
trisemax (ms)
< 4.7
< 1.3
500
< 28.1
< 7.6
500
trisemin (ms)
200
200
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
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Fluxes to main wall during ELMs (I)
Part of DWELM is reaches the main wall PFCs  formation and ejection of
MAST- Kirk, EPS’06
filaments
DOC-L  = 0.27
1.2MA q95 = 3.1
2MA q95 = 3.7
2MA q95 = 4.6
3MA q95 = 3.1
IR
DWELM /DWELM
1.2
1.0
0.8
0.6
0.4
0.2
0.0
0.05
JET-Eich, PIPB’07
0.10
0.15
0.20
DWELM/Wped
?
AUG- Herrmann –PPCF’06
Alberto Loarte
Model of qII(t) for detached filaments developed
by Fundamenski (PPCF’06) and validated with
JET data (Pitts NF’06)  Application to ITER
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
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Fluxes to main wall during ELMs (II)
 ELM fluxes to main wall (beyond second sep) only on outer wall
 Power reaches the wall in filamentary structures (for ITER Snyder results in NF’04) :
 distance between filaments (m) = 15/n (if no break-up and all become unstable)
Herrmann-AUG
 filament poloidal width (m) = 3/n (rough estimate)
 Decay length of filaments in “limiter” shadow ~ Llim/LSOL ?
qII in filament estimated with model by Fundamenski  required input to model :
 nfil, Tfil, <vELM/cs,ped> & distance from sep @ filament detachment
From modelling by W. Fundamenski
5 cm from sep
10 cm from sep
15 cm from sep
10
5 cm from sep
10 cm from sep
15 cm from sep
1000
800
-2
qII (GWm )
-2
-3
Closed symbols detachment from DRsep = 0 cm
Open symbols detachment from DRped = - 5cm
400
200
0.1
Alberto Loarte
V
/C
5 cm from sep
9th ITPA Divertor ELM
andS SOL Physics Meeting
10 cm from sep
15 cm from sep
IPP-Garching
7-10/5/2007
0
-2
0.0000 0.0005 0.0010 0.0015 0.0020
0.0000 0.0005 0.0010 0.0015 0.0020
VELM/CS
Outstanding issues :
V /C
 Relation VELM & DWELM  vELM/cs,ped = 10-2 DWELM/Wped or 1.5 10-3 (DWELM/Wped)0.5ELM S
 nfil, Tfil Rfil at instant of detachment & tELMWall (~ tELMdiv ?)
 GwallELM  sputtering
(MWm )
0.1
1
lower-Be-wall
1
600
upper-Be-wall
10
19
nfil = 7.5 10 m , Tfil = 5 keV, detachment from DRped = - 5cm
qII
qII (GWm )
19
-3
From modelling by W. Fundamenski nfil = 7.5 10 m , Tfil = 5 keV
12
Fluxes to main wall and divertor during
Disruption thermal quench (I)
PID specifications generally in line with current evidence from disruption
loads but need to be refined to incorporate latest findings on divertor/wall
loads
 Classification of loads per disruption type (ideal MHD limits, etc.) and scenario
 Disruptions in limiter phase are absent in specifications
 Toroidal and in/out asymmetries ?
 Radiation during thermal quench ?
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
13
Fluxes to main wall and divertor during
Disruption thermal quench (II)
 Plasma energy at t.q. typically less than 40% expected from H98 = 1 (Size scaling ?)
 Dedicated experiments at JET in 2006/2007 show that Wt.q. < 0.4 W (Type I H-mode) for density
limits, radiative limits and NTM driven disruption
JET-Riccardo NF’05
t.q. timescale has large scatter associated with MHD
activity but similar to ELMs large amount of energy
reaches PFCs after qmax
MAST-Counsell
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
14
Fluxes to main wall and divertor during
Disruption thermal quench (IV)
Broadening of power width causes energy deposition IIB everywhere on PFCs
(TPF < 2)  significant amount of energy deposited outside divertor
JET-Paley-PhD Thesis ‘07
Disruptions in divertor conditions triggered by ideal MHD limits and in limiter seem
completely different many aspects
(P. Andrew, PSI’06, Riccardo NF’05, Finken NF’92, Janos JNM’92, TFR JNM’82)
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
15
Fluxes to main wall and divertor during
Disruption thermal quench (V)
Ideal MHD limit disruptions can lead to large interactions with inner-wall or outer
wall not seen in other disruption types  Not included in PID for scenario 4
(ITB)  implications for ITER ?
JET Pulse No. 69816 ITB grad-P disruption
PNBI (X 10 MW)
PICRH (X 10 MW)
Prad (X 100 MW)
Wdia (MJ)
Ip (MA)
n = 1 (a.u.)
n = 2 (a.u.)
Mode-lock (a.u.)
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
16
Disruptions in limiter phase
Not considered in PID but potentially serious because of lack of broadening of
power footprint for limiter disruptions (lt.q. < 1.5 ls.s.)
TEXTOR-Finken NF 1992
Janos-TFTR-JNM 1992
Disruptive-normal
discharge
Normal
discharge
For lp > 2 cm  Aeff,limiters = 2.5 m2 (H. Pacher)
 EOL-ramp-up : Ip = 7 MA, if Pinp = 5 MW  Wplasma (ITER-89) = 15 MJ
 BOL-ramp-down : Ip = 10 MA, if Pinp = 7 MW  Wplasma (ITER-89) = 24 MJ
Disruptions during limiter phases may cause loads > 6 – 10 MJm-2 with tt.q. ~ 1 ms
Major issue for power fluxes during VDEs  needs to be confirmed
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
17
Energy Fluxes to main wall and divertor
PFCs during VDEs (I)
Large discrepancy between PID specifications and new proposed
specifications in Sugihara NF ‘07
e ~ 134 MJm-2s-1/2
Possible Realistic scenario
 Plasma drifts towards wall in H-mode
 At some point L-mode transition (H-modes
with X-point behind target at JET)
 DWplasma (30-50 % of Wplasma) deposited on wall in
Dt < tL-mode with lp ~ 1 cm
 Plasma is in contact with wall in limiter L-mode
PSOL = 100 MW + dW/dt
 Plasma disrupts in limiters configuration when
q ~ 1.5-2 with Wplasma > 100 MJ
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
18
Energy Fluxes to main wall and divertor
PFCs during Marfes (I)
PID specifications for Marfe loads in ITER (physics model ?)
Three types of “Marfes” expected in ITER (L-mode Plasma) :
 Inner-wall Marfe  Potentially steady-state Prad < PSOL (100 MW) (<0.15MWm-2>)
 X-point Marfe  Potentially steady-state Prad < PSOL (100 MW) (<0.15MWm-2>)
 Pre-thermal quench divertor Marfe  short-lived (< 0.1 s in JET and AUG) period in
which ~ 0.25 of Wplasma (H98 = 1) can be radiated  Prad ~ 900 MW (<1.3 MWm-2>)
 Pre-thermal quench limiter Marfe  short-lived (< 0.1 s in JET) period in which a
fraction (?) of Wplasma (H89 =1) can be radiated  Prad < 240 MW (<0.35 MWm-2>)
 For all cases radiation peaks near X-point region or inner-wall
Main issue is to determine realistic timescales and peaking factors of radiation on wall
due to Marfe for ITER
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
19
Energy Fluxes to main wall and divertor
PFCs during Marfes (II)
Examples of Marfes at JET
Steady-state limiter Marfe
A. Loarte Memo to RI-mode working group’99
Transient limiter Marfe
J. Wesson-Science of JET’99
~ Steady-state X-point Marfe
A. Huber-PSI’06
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
20
Conclusions
 Many of the PID specifications for PFC loads in ITER are not far
from expectations from latest experimental/model results
 Other are in disagreement with present evidence and/or absent
 A detailed review and update of PID specifications is needed &
will be carried out as part of the design review
 Contributions from ITPA groups and collaboration with ITER-IT
will be essential to do this review
Expected loads in ITER will determine fine details of PFC
construction (edge shadowing, etc. ), overall PFC configuration &
will have implications for the use of diiferent PFM in various areas
of the device
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
21
Plasma Position and Shape Control (II)
Other transients following plasma disturbances and noise in
feedback/measurement system
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
22
Plasma Position and Shape Control (I)
Even if position control is recovered in 10s there are ~ 1s phases in which
separatrix gets dangerously close to areas designed for low power loads
SOB Minor disruption
Appendix E
qII in,dome ~ 380 - 570 MWm-2 for ~ 1 s
Control of plasma in ITER can lead to fluxes IIB on PFCs > 100 MWm-2 for timescales ~ 1s and
possibly fast H-L transitions
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
23
Energy Fluxes to main wall and divertor
PFCs during current quench
Most tokamaks find that close to 100 % of magnetic energy at
Wexp
t.q. is300
radiated with the exception of Alcator
C-mod (< 25%)
Wlin
80
200
40
Wmag = ½ Lp Ip2
a
max
60
qrad (MWm-2)
Wmag (MJ)
PradexpMW
PradlinMW
100
After t.q. 
bp= 0 (0.2-pre), li~ 0.5 (0.85-pre), Ip <18 MA (15 MA-pre) Wmag < 1.85 GJ
Most of Wmag  V.V. and in-vessel conducting structures  Wc.q.
20
PFCs
< 315 MJ
For fastest timescale of c.q. in ITER ~ 16 ms (exponential) 36 ms (linear)
0
0
10
max < 80 MWm
30 -2
qrad20
40
0
50
critical assumptions : Wc.q.PFCs < 315
MJ, 100% radiation & peaking factor < 1.4
t (ms)
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
24
Energy Fluxes to main wall and divertor
PFCs during mitigated disruptions
Mitigation of disruptions by massive gas injection is a promising
scheme but may lead to large fluxes on PFCs  specification of
wall loads for ITER not yet in PID
 Sugihara NF’07 assumes qrad = 0.5 – 1.0 GWm-2 in 1 ms
 Estimates from Whyte for ITER predict <qrad> ~ 4 GW/m2 for Dtrad < 200 ms
Whyte PRL’02
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
25
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  specification of local loads for ITER ?
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
26
Runaway electron fluxes on PFCs (II)
 Runaway electrons are not generated if q95 < 2-2.5 before current
quench (no r.e. in full VDEs but likely in disruptions)
 Runaway electrons are lost to PFCs by MHD turbulence when qedge =
3, 2 touches the wall
 Runaway beam has a peaked current profile ar.e. ~ 0.25 aplasma and is
vertically unstable
 Runaway impact point determined by vertical instability of column and
narrow e-folding length (~ few mm)  Aeff ~ 0.5 m2 (if toroidally
symmetric)
 Runaways are lost in bursts of ~ 100 ms over ~ 5-10 ms timescales
(JET and JT-60U)
Unclear whether all these facts are taken into account in present PID
specifications or not
Alberto Loarte
9th ITPA Divertor and SOL Physics Meeting
IPP-Garching
7-10/5/2007
27