alberto loarte eu plasma-wall interaction task force meeting – jozef stefan institute 13-15 – 11...
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Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 1
Report onEU-PWI SEWG on Transient Loads
Alberto Loarte
European Fusion Development Agreement
Close Support Unit - GarchingContributors to SEWG :
CEA : F. Saint-LaurentCRPP : R. PittsENEA : G. MaddalunoIPP : G. Pautasso, A. Herrmann, T. EichITER : G. Federici, G. StrohmayerFZJ : K.H. Finken, M. Lehnen, J. Linke, T. HiraiFZK : I. Landman, S. Pestchanyi, B. BazylevUKAEA : V. Riccardo, P. Andrew, W. Fundamenski, G. Counsell, A. Kirk
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 2
Outline
1. Summary of work in 2006
Effects of transient loads on materials
Characterisation of ELM loads
Characterisation of Disruption loads
Disruption mitigation
2. Plans for 2007
3. Conclusions
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 3
Expected transient loads at ITER divertor/first wall are uncertain but have strong implications for PFC lifetime
Expected loads in ITER transients (I)
0.0 0.5 1.0 1.5 2.00
50
100
150
Mol
ten
laye
r th
ickn
ess
(m
)Energy density (MJ/m2)
t = 0.1 ms t = 0.3 ms t = 1.0 ms
Raclette - G. Federici & G. Strohmayer
0.0 0.5 1.0 1.5 2.00
10
20
30
Eva
pora
ted
thic
knes
s (
m)
Energy density (MJ/m2)
t = 0.1 ms t = 0.3 ms t = 1.0 ms
Be
Be
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 4
As guideline for experiments the following energy ranges and plasma impact energies have been defined
Divertor target (CFC and W without/with Be coatings) Type I ELM : 0.5 – 4 MJ/m2, t = 300-600 s, Ee ~ Ei ~ 3 – 5 keV
Thermal quench : 2.0 – 13 MJ/m2, t = 1-3 ms, Ee ~ Ei ~ 3 – 5 keV
Main wall (Be) Type I ELM : 0.5 – 2 MJ/m2, t = 300-600 s, Ee ~ 100 eV, Ei ~ 3 keV Thermal quench : 0.5 – 5 MJ/m2, t = 1-3 ms, Ee ~ Ei ~ 3 – 5 keV
Mitigated disruptions : 0.1 – 2.0 MJ/m2, t = 0.2-1 ms, radiation
Expected loads in ITER transients (II)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 5
FZJ e-beam Judith facilities
Forschungszentrum Jülichin der Helmholtz-Gemeinschaft
JUDITH II JUDITH I
electron beam power: 200 kW 60 kW
acceleration voltage: 30 - 60 kV 120 - 150 kV
electron beam diameter: ~ 5 mm ~1 mm
power density: < 10 GW/m² < 15 GW/m²
pulse duration: > 1 ms > 1 ms
scanning frequency: 10 kHz 100 kHz
max. scanning area: 500 x 500 mm² 100 x 100 mm²
combination of different loads: yes no
n-activated or toxic components: yes yes
installed components per test: 2 x 2 1
Status of JUDITH IIInstallation of:electron beam gun: Sep. 04vacuum chamber: Sep. 04heat exchanger: Aug. 04power supply: Dec. 04
start-up of JUDITH II: Feb. 05standard operation: Apr. 05
JUDITH II - October 2004
1. electron beam (EB) gun; 2. vacuum chamber; 3. cooling circuit; 4. test component; 5. diagnostics; 6. carrier system; 7. alternative flange for the EB-gun.
The new electron beamtest facility JUDITH II
J. Linke
T. Hirai
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 6
QSPA facility provides adequate pulse durations and energy densities. It is applied for erosion measurement in conditions relevant to ITER ELMs and disruptions
Plasma flow
Target
Diagnostic windows
Vacuumchamber
600
The diagram of QSPA
facility
View of QSPA facility
Plasma parameters (ELMs +Disruptions):
• Heat load 0.5 – 2 MJ/m2 / 8 – 10MJ/m2
• Pulse duration 0.1 – 0.6 ms• Plasma stream diameter 5 cm• Magnetic field 0 T• Ion impact energy ≤ 0.1 keV• Electron temperature < 10 eV• Plasma density ≤ 1022 m-3/≥ 1022
m-3
Conditions for ITER ELMs & disruptions not easily reproducible in tokamaks
QSPA reproduces :
Energy density & Timescale
with plasma pressure ~ 10 too highnT3/2|QSPA=nT3/2|ITER but T|ITER =10-100 x T|QSPA
TRINITI facilities QSPA (I)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 7
-6 -4 -2 0 2 4 6
-4
-3
-2
-1
0
1
2
3
4
X, cm
Y,
cm
10 20 30 40 50 60 70 80 90 100
-6 -4 -2 0 2 4 6
-4
-3
-2
-1
0
1
2
3
4
X, cm
Y,
cm
30 40 50 60 70 80 90 100
The energy density distribution on CFC surface,%
The energy density distribution on W surface,%
Typical energy density profile on CFC surface
X,Y, cm2
En
erg
y d
ensi
rt,
MJ/
m2
X,Y, cm2
En
erg
y d
ensi
rt, M
J/m
2
Typical energy density profile on W surface,%
TRINITI facilities QSPA (II)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 8
Typical micrographs of the tungsten droplets tracks
Surface of th
e
sample
Plasma stream direction
3 ms after first shotMass loss 67 mg/shot
Surface of th
e
sample
Plasma stream direction
3 ms after 60th shotMass loss 2 mg/shot
During the first shot droplets ejected mainly from the edges of the tiles.
As a result of edge smoothing and bridging of gaps the droplet ejection was reduced and mass losses were decreased.
TRINITI facilities QSPA (III)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 9
TRINITI facilities QSPA (IV)
W and CFC erosion at ~ 1.5 MJm-2
CFC4, L3, 0 exposures CFC4, L3, 100 exposures
1mm 1mm
CFC4, L3, 0 exposures CFC4, L3, 100 exposures
1mm 1mm
CFC4, L3, 0 exposuresCFC4, L3, 0 exposures CFC4, L3, 100 exposuresCFC4, L3, 100 exposures
1mm 1mm
QSPA can reproduce plasma-interaction
processes at ITER-like load levels :
Melt layer displacement under plasma pressure Vapour shielding formation and effects on damage developmentExtrapolation to ITER requires modelling (Pressure too high, no magnetic field, etc.)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 10
1. Under ITER-like heat loads erosion of CFC was determined mainly by the erosion of PAN-fibers:
2. Noticeable mass losses of a sample took place at an energy density of 1.4 MJ/m2
3. Severe crack formation was observed at energy densities ≥ 0.7 MJ/m2
(cracking of pitch fibre bundles)
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
CFC
CFC results
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 11
1. Under ITER-like heat loads erosion of tungsten macrobrush was determined mainly by melt layer movement and droplets ejection:
2. Noticeable W erosion mainly due to droplet formation took place at wmax = 1.6 MJ/m2. The average erosion was approx. 0.06 μm/shot (1 μm/shot during the first shot, and then decreased to 0.03 μm/shot after 40th pulse).
3. Cracks formation was observed at energy densities ≥ 0.7 MJ/m2.Metallographic sections show crack depths ranging from 50 to 500 µm.
energy density / MJm-2
0.5 1.0 1.5
neg
lig
ible
ero
sio
n
mel
tin
g o
f ti
le e
dg
es
mel
tin
g o
f t
he
fu
ll t
ile
surf
ace
(no
dro
ple
t e
ject
ion
)
dro
ple
t ej
ecti
on
and
bri
dg
ing
of
tile
s a
fter
50
sho
ts
W
W results
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 12
ELMs in JET cause significant impurity influx (& deposition) particularly when ~ 1MJ ELMs is reached
0.0 0.2 0.4 0.6 0.8 1.0 1.20.0
0.2
0.4
0.6
WELM
radiation ~ 0.25 WELM
WE
LM
rad
iatio
n (M
J)
WELM
(MJ)
Impurity generation and deposition by ELMs can dominate in ITER even if target lifetime is OK 0.15 g-C/ELM 150 g-C per shot
Determination of impurity influx and C-deposition during ELMs (W & C comparison)
ELMs erosion/deposition and impurity influxes
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 13
Main plasma ELM energy loss
ELMELMpedpedELMpedpedELM VnTTnW )33( ,, WELM correlated with nped, Tped ( <n>, <T>) & transport loss mechanism
Conduction Convection
Convective ELMs obtained so far in regimes not compatible with ITER QDT= 10 scenario
i) q95 ~ 3 (Ip ~ 15 MA) but too high * (~ n/T2) or ii) low * but q95 > 4 (Ip ~ 11 MA)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 14
During ELM event energy flows to divertor target and main chamber PFCs
e,i losses along B
to divertor
Inner divertor
Outer divertor
ASDEX Upgrade Herrmann
e,i losses along B
to divertor
i losses across B to main wall
vELM ~ km/s
ASDEX Upgrade Herrmann PPCF 2004
Kirk PPCF
ELM power fluxes to PFCs (I)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 15
222
exp1)(ttt
tqELM
Eich JNM 2005Loarte PoP 2004
qELM,div (t) more than 60% of WELM,div arrives after qELM,divmax
smaller TsurfELM
Fundamenski PPCF 2006
Energy balance of ELM divertor power pulse
in agreement with PIC simulations
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 16
Eich PSI 2006
ELM energy deposition at divertor in/out asymmetric
asymmetry depends on B direction but extrapolation of observations to next
step devices remains unclear
In/out asymmetries of ELM divertor power fluxes
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 17
Formation and dynamics of ELM filaments and energy deposition at main chamber starts to be well diagnosed
ELM energy fluxes to main chamber PFCs (I)
Vtor ~ 0 before filament leaves LCFS
vr goes from 0 at LCFS to 1–3 km
Filaments leave LCFS at
different times
MAST-Kirk
Energy flux to the wall by individual filaments
Herrmann-AUG
Energy per filament < 2.5 % WELM (MAST)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 18
JET-IR Eich
0.05 0.10 0.15 0.200.0
0.2
0.4
0.6
0.8
1.0
1.2DOC-L = 0.27 1.2MA q
95 = 3.1
2MA q95
= 3.7
2MA q95
= 4.6
3MA q95
= 3.1
WE
LM
IR/
WE
LM
WELM
/Wped
ELM energy deposition at main chamber given by competition of parallel and perpendicular transport (JET-Fundamenski + Pitts validated model)
larger VELM (MELM) larger WELMwall
ELM energy fluxes to main chamber PFCs (II)
AUG-Kirk
Correlation between vELM and WELM found experimentally :
vELM/cs ~ (WELM/Wped) with > 1 (deduced from DIII-D, Loarte IAEA 2006)
vELM/cs ~ (WELM/Wped) with = 1/2 (JET, Fundamenski PSI 2006)
vELM/cs ~ (WELM/Wped) with = 0 (Kirk, AUG)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 19
Riccardo NF 2005 Riccardo NF 2005, Pautasso EPS 2004H-L
transitionthermal quench
Pre-disruption energy confinement degradation (I)
Wplasma at thermal quench usually much smaller than Wplasmafull-performance (except
for VDEs and ideal- limits) caused by E deterioration
Size scaling and/or disruption amelioration actions ?
VDEs-limits (ITBs)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 20
Pre-disruption energy confinement degradation (II)
Does this hold across devices ?
Confinement deterioration takes place in timescales ~ E except for fast H-L transition
& growth/locking of modes but p does not change much
Most disruptions largest divertor surface temperature rise is caused by power fluxes
during thermal quench rather than pre-disruption events
T ~ qdiv 1/2
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 21
Timescale of thermal quench power fluxes
timescale of thermal quench fluxes increases with R but large disruption-to-disruption variability
222
.. exp1)(ttt
tq qt
qt.q,div (t) more than 75% of WELM,div arrives
after qt.q.,divmax
smaller Tsurft.q.
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 22
Footprint of thermal quench power fluxes
Power flux during thermal quench broadens significantly (even after radiation correction) & can develop toroidal asymmetries ( ~ 2-3)
A. Herrmann - ASDEX Upgrade
G. Counsell - MAST
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 23
Power fluxes on PFCs during ITER ELMs & disruptions
Extrapolation of power fluxes to PFCs based on experimental evidence & models
toroidal symmetry assumed
ITER PFCs’ lifetime can be evaluated from these loads tolerable WELM & Wt.q.
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 24
Material erosion by ELM/disruption transient loads - no vapour shielding & no redeposition (Raclette, Federici & Strohmayer)
CFC target lifetime requires qELMmax < 1.5-2.0 GWm-2
WELM/Wped < 0.05 (convective ELMs)
qUpper-BeELM < 50 MWm-2 No Be melting
Calculated ELM-driven/disruption erosion in ITER
0 2 4 6 8 10 121E-3
0.01
0.1
1
10
CFC Be W 250 s rectangular waveform 500 s rectangular waveform 250 s rise time experimental waveform 500 s rise time experimental waveform
Power Density (GWm -2)
Ero
ded
CF
C (m
)
106 ELMs CFC divertor lifetime
1
10
100
Depth of U
pper Be-m
odules and W divertor m
elt pool (m) 0 2 4 6 8 10 12
0
50
100
C Be W experimetal waveform t
t.q. = 1.0 ms
experimetal waveform tt.q.
= 3.0 ms
Ero
ded
CF
C (m
)
300 disruptions divertor lifetime
Power Density (GWm -2)
0
200
400
600
Depth of U
pper Be-m
odules and W divertor m
elt pool (m)
CFC target lifetime requires qdis,max < (2-4) GWm-2
Wped/Wplasmafull-performance < 0.4 (typical for JET ELMy H-modes)
qUpper-BeELM ~ 100-400 MWm-2 No Be melting for qexperimental(t)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 25
Massive gas injection systems available in ASDEX-Upgrade, JET, TEXTOR and TORE-Supra
Disruption mitigation (I)
G. Counsell - MAST
F. Saint-Laurent – Tore Supra
He injection in Tore-Supra very effective in suppressing e runaway generation in disruptionsTime to t.q. depends on pressure but He penetration does not depend on pressure He injection does not suppress e runaways already produced
M. Lehnen – TEXTOR
no neutral penetration in MGI shots dynamics of disruption correlated with impurity mass Ar + D produces fast termination reduction of thermal
loads and runaway suppression (pure Ar produces runaways)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 26
ECRH has been used to suppress disruption by affecting evolution of MHD
Disruption mitigation (II)
Density limitG. Maddaluno – FTU
Mo-injectionG. Maddaluno – FTU
ECRH power and localisation requires optimisation for different disruption type(central for DL and peripheral for Mo-injection)
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 27
Plans for 2007 (I)
Proposed joint activities
Comparison of models for material damage during ELMs and subsequent plasma
evolution with existing experimental data (mainly from JET) : FZK, FZJ, JET,
CSU Garching, IPP
Analysis of pre-disruptive thermal confinement deterioration and associated power
fluxes on PFCs for similar disruptive triggers (density limit, low q disruption,
ideal limits, etc.) and pre-disruptive regimes (L-mode, H-mode, ITBs, …) :
FZJ, CRPP, ENEA, UKAEA, CEA, IPP, JET, CRPP, CSU Garching
Determination of spatial and temporal characteristics of power fluxes during
disruption thermal quenches for comparable disruptions : FZJ, CRPP, ENEA,
UKAEA, CEA, IPP, JET, CSU Garching
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 28
Plans for 2007 (II)
Proposed joint activities
Comparative studies for the optimisation of disruption mitigation by massive gas
injection for runaway suppression and thermal load minimisation : FZJ, CEA,
IPP, JET, CRPP, HAS, CSU Garching
Determination of spatial and temporal characteristics of power/particle fluxes during
ELMs for comparable plasma conditions : CRPP, UKAEA, IPP, JET, CSU
Garching
Alberto Loarte EU Plasma-Wall Interaction Task Force Meeting – Jozef Stefan Institute 13-15 – 11 – 2006 29
Conclusions
Experiments and modelling of material damage under ITER-like transient loads are providing firm basis to determine maximum tolerable
ELM/disruption loads for acceptable lifetime
Coordinated experiments and data analysis on disruptions and ELMs are starting to provide a physics-based extrapolation of expected
transient loads in ITER Further progress in 2007 expected in by coordinated experiments and data analysis
Many EU devices are now equipped with systems for disruption mitigation by massive gas injection significant progress in 2007 expected in this area by inter-machine comparison