Transcript Edge Plasma Energy and Particle Fluxes in Divertor Tokamaks

Introduction
Prediction of ITER loads and T retention
A. Loarte
Alberto Loarte
10th ITPA Divertor and SOL Physics Group
Avila – Spain
7/10 – 1 – 2007
1
Specification of ITER Loads
 Specification of ITER loads has been reviewed during ITER
Design Review  update to take into account present
physics understanding
 Particle/Power Fluxes to wall during diverted operation
 Redefinition of divertor controlled ELM loads
 Update of ELM divertor and wall power fluxes
 Update of disruption and VDE thermal loads
 Update of disruption and VDE EM loads
 etc.
Revised load specifications will be used to redesign details of
ITER PFCs (main wall)  Advice from ITPA required
Uncertainties in load specifications is considerable 
judgment to specify reasonable and non-fluctuating values
Alberto Loarte
10th ITPA Divertor and SOL Physics Group
Avila – Spain
7/10 – 1 – 2007
2
Evaluation of T retention in ITER
 T retention is one of the key drivers for plasma facing
materials choice in ITER  PFM foreseen strategy
based on present understanding of PWI in ITER
Change of CFC to W divertor to minimise T retention
 Prediction of T retention in ITER is a complex and uncertain
 Uncertain plasma fluxes and conditions
 ITER-specific issues (high Tsurf/Gplasma, n-irradiation, etc.)
 Formation of mixed-materials
 etc.
Determination of fuel retention for ITER on present
understanding, on-going R&D and Hydrogen phase results
crucial to decide on best timing for change of divertor plasma
materials in ITER programme
Alberto Loarte
10th ITPA Divertor and SOL Physics Group
Avila – Spain
7/10 – 1 – 2007
3
QDT = 10 steady plasma loads (I)
 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 Gdiv)
Lipschultz IAEA 2000
Lipschultz
Alberto Loarte
10th ITPA Divertor and SOL Physics Group
Avila – Spain
7/10 – 1 – 2007
4
QDT = 10 steady plasma loads (II)
 Plasma fluxes predominantly on outer side of first wall
 Corresponding maximum IIB power densities up to : 5 MWm-2 (Upper Xpoint) to 1 MWm-2 near outer midplane and 0.4 MWm-2 near inner
midplane
LaBombard NF 2004
Conditions
qx
-2
(MWm )
far-SOLout
Total plasma
far-SOLin (m)
Total plasma power
(m)
power to outer
(mapped to outer
to inner wall
(mapped to outer
mid-plane)
Low edge
wall
mid-plane)
(MW)
(MW)
5.3
0.03
3.0
0.006-0.01
0.6-1.0
2.9
0.17
9.2
0.03-0.06
2.0-3.0
ne
High edge
ne
Alberto Loarte
10th ITPA Divertor and SOL Physics Group
Avila – Spain
7/10 – 1 – 2007
5
Tolerable ELM size
QSPA experiments on NB31 targets show
0.5
1.0
1.5
PAN fibre
erosion
after 10 shots
significant
PAN fibre
erosion
after 50 shots
PAN fibre
erosion of
flat surfaces
after 100 shot
erosion starts
at PFC corners
negligible
erosion
energy density / MJm-2
CFC divertor target lifetime  20000 ELMs
Tolerable ELM energy density 0.5 MJm-2 + no broadening + 2:1
in/out asymmetry  DWELM ~ 1MJ
fELM ~ 20-40 Hz  8000-16000 ELMs/QDT=10 shot
Alberto Loarte
10th ITPA Divertor and SOL Physics Group
Avila – Spain
7/10 – 1 – 2007
6
Wall ELM loads
Wall ELM power/particle deposition starting to be
characterised/understood  extrapolation to ITER uncertain
-2
Uncontrolled ELMs
Model by W. Fundamenski and R. Pitts
0.25
10
0.20
0.15
1
0.10
0.05
0.1
0.00
0.0
0.2
0.4
0.6
0.8
1.0
VELM (km/s)
 AIIELM < Afil ~ Nfil dpol dr ~ 10 * 0.25 * 0.1 = 0.25 m-2 (A. Kirk)
 Uncontrolled ELMs  EIIELM > 8-16 MJm-2 (<qII,ELM> ~ 8-32 MWm-2 ) &
Ewall,ELM (4o) ~ 0.6- 1.1 MJm-2
 Controlled ELMs  EIIELM > 0.2-0.4 MJm-2 (<qII,ELM> ~ 4-16 MWm-2 ) &
Ewall,ELM (4o) ~ 0.01-0.03 MJm-2
Alberto Loarte
10th ITPA Divertor and SOL Physics Group
Avila – Spain
7/10 – 1 – 2007
7
DWELM,wall/DWELM
Uncontrolled ELMs  DWELM,wall = 2-4 MJ
Controlled ELMs  DWELM,wall = 0.05-0.1 MJ
tELM,wall ~ ½ tELM,divertor
Controlled ELMs
qIIELM (DRm.p. = 5 cm) (GWm )
Uncontrolled ELMs in ITER DWELM = 20 MJ
Controlled ELMs in ITER  DWELM = 1.0 MJ