tfe th loarer – sewg – 12 september 2007 1 euratom th loarer v philipps 2, j bucalossi 1, d...
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TFE
Th Loarer – SEWG – 12 September 2007 1
Euratom
Th Loarer
V Philipps2, J Bucalossi1, D Brennan3, J Brzozowski4, N Balshaw3, R Clarke3, G Esser2, M Freisinger2, S Grünhagen5, J Hobirk6, S Knipe3, A Kreter2,
Ph Morgan3, R Stagg3, L Worth3 and JET EFDA contributors*
Fuel retention in L and H-mode experiments in JET
1 - Association EURATOM-CEA, DSM-DRFC, CEA Cadarache, 13108 St Paul lez Durance, France.2 - IPP, Forschungszentrum Juelich, D-52425 Juelich, Germany3 - Euratom-UKAEA Association, Fusion Culham Science Centre, Abingdon, OX14 3EA, UK.4 - EURATOM/VR Association - Fusion Plasma Physics, EES, KTH, Stockholm, Sweden5 - FZ Karlsruhe, Postfach 3640, D-76021 Karlsruhe, Germany6 - Max-Planck IPP-EURATOM Association, Garching, Germany*See Appendix of M.L.Watkins et al., Fusion Energy Conference 2006 (Proc. 21st Int. Conf.
Chengdu) IAEA, (2006)
Outline
Introduction
Evaluation of fuel retention at JET
Short and long term retention; associated particle fluxes
Recycling flux and ELMs
Recovery between discharges
Summary
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Euratom Introduction
- Evaluation of hydrogenic retention in present tokamaks is of high
priority to establish a database for ITER (400 sec ~ 7min…10-20 sec
today).
- A retention of 10% of the T injected would lead to the limit of 350g
(working guideline for initial operation) in “only” 35 pulses.
- Fuel retention experiments in JET studied in a series of repetitive and
identical discharges to minimise the contribution from previous
experiments (history), achieve a high accuracy (~1.2%)
- Reference database under C-wall conditions completed before Be/W
Evaluation of Long term fuel retention with different materials
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physics: material erosion, migration & fuel retention
• QMB measurements
• Spectroscopy
• Gas balance measurements
• Deposition probes
• 13C migration
• Post mortem tile analysis
D,T
Mechanisms for fuel retention
Two basic mechanisms for
Long term fuel retention
Deep Implantation, Diffusion/Migration,
Trapping
C, Be C, Be, D ,T
In JET (and other carbon wall devices ) Codeposition dominates retention (also expected for Be wall conditions, JET ILW, ITER)
Codeposition
Short term retention (Adsorption: dynamic retention)
Recovered by outgasing in between discharges
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Calibrated Particle Source
(Gas, NBI…)
Divertor cryo-pumps
Retention (wall)
Long & Short Term
Procedure on JETRegeneration of the cryopump before and after the session (1.2%) Repeat the same discharge (~10) w/o conditioning between pulses
Plasma
Injection = Pumped + Short Term Ret + Long Term Ret
Total Recovered from Cryo regeneration:Pumped + outgassing in between pulses ~800s (Short Term Ret)
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Euratom Gas Balance
From cryo-pump regeneration (~1%) and calibrated gas injection
Evaluation of the pumped flux
- During the plasma
- Between pulses
t (s)0 10 100 1000
Plasma
During plasmainj>pump
Retention>0
Short & Long term
Between pulsesinj=0
pump= OutgasingRetention<0
Short term retention only(dynamic retention)
Evaluation of Short and Long term retentionInjection = Long Term Ret + Short Term Ret + Pumped flux
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Euratom Type III ELMs
# 68619
Ip/BT=2.0MA/2.4T,
6.0MW ICRH “only”
13 repetitive pulses
Also in L mode and Type I ELMy H-mode
Reproducible plasma
conditions in all shots
Type III ELMs53-70 s
PTOT ~ 6.0MW
Density
Fueling 5.8 1021Ds-1
D (in & out)
Div Pressure
Vessel pressure
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L-mode
Total Injected: 1.349 1024 D (4.511g)
Total Recovered (Pumped flux and outgassing in between pulses): 1.208 1024 D (3.946g)
Long Term Retention: 0.141 1024 D (0.472g) Heating Phase (81 s) Injection Long Term Ret
~1.8x1022Ds-1 1.74x1021Ds-1 ~10%
L-mode, Type I & III ELMy H-mode
Evaluation of Short and Long term retention during the pulse
Heating Phase Injection Long Term RetType III 221s ~0.6x1022Ds-1 1.31x1021 Ds-1 ~20%
Type I 32 s ~1.7x1022Ds-1 2.83x1021Ds-1 ~17%
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Euratom Particle fluxes: L mode
Drop of retention not only due to decrease of inj
Ip=2.0MA, BT=2.4T1.2MW ICRH “only”
@15 sec,
Ret~6.5x1021Ds-1
LongRet=1.74x1021Ds-1 (25%)
ShortRet=4.8x1021Ds-1 (75%)
@25 sec,
Ret~4.65x1021Ds-1
LongRet=1.74x1021Ds-1 (35%)
ShortRet=2.91x1021Ds-1 (65%)
Injection
Pumped flux
Retention
Long term Ret
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Euratom During the pulse: H mode Type III
Ip=2.0MA, BT=2.4T
~5MW ICRH “only”ITER_like conf.
@16 sec, Ret=53%
Ret~6.3x1021Ds-1
LongRet=1.3x1021Ds-1 (33%)
ShortRet=2.0x1021Ds-1 (66%)
@28 sec, Ret=43%
Ret~2.35x1021Ds-1
LongRet=1.3x1021Ds-1 (55%)
ShortRet=1.05x1021Ds-1 (45%)
Injection
Pumped flux
Retention
Long term Ret
Lower gas rate (1/3) but codeposition becomes dominant
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Euratom Particle fluxes: H mode Type I
From L mode to Type I ELM H-mode Increase of long term retention- with the recycling flux- with ELMs Energy
Ip=2.0MA, BT=2.4T
13MW NBI+ICRH ELM Energy~150kJ
@16 sec,
Ret~5.2x1021Ds-1
LongRet=2.8x1021Ds-1 (54%)
ShortRet=2.4x1021Ds-1 (46%)
@20 sec,
Ret~2.9x1021Ds-1
LongRet=2.8x1021Ds-1 (97%)
ShortRet=0.1x1021Ds-1 (3%)
Injection
Pumped flux
Retention
Long Term Ret
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Strong increase of the recycling flux in Type I ELMy H-modeSame behavior observed with CIII
Recycling flux: D signals
D Inner leg
D Outer leg
D Horizontal viewType IType IIIL mode
- L mode and Type III Similar recycling (D ) In, Out and Horizontal.
- No significant variation on the Outer leg region (“small” ELMs~150kJ).
-Strong increase of recycling flux (D) when moving to Type I ELMy H-mode
- Same behavior on the Horizontal view as on the inner leg.
Type IType IIIL mode
CIII Horizontal view
CIII Inner leg
CIII Outer leg
Higher recycling and ELM Enhanced carbon erosion and transport leading to stronger carbon deposition and fuel codeposition
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Integrated Hα and CIII horizontal light (L-mode, Type III and Type I ELMs)
The slope for Type I ELMy H-mode show enhanced recycling and total carbon source.
Integrated particle fluxes
H α
CIII
Type I ELMs
Type III ELMs
L mode
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Recovery in between pulses
• Small fraction recovered > plasma content ~ 0.5x1022D (70m3, <ne>~5-6 1019m-3)
• Except for disruptions, this amount is ~constant and independent of Ip, BT, ne, Pin, inj, Wdia (plasma scenario)
• Independent of inventory accumulated during the pulse and previous pulses
Within a factor of ~2 the recovery is constant in the range 1-3x1022DNo major contribution on the overall retention
6
5
4
3
2
1
0
Rec
over
ed a
fter p
ulse
(x
1022
D)
6543210
Total injected (x 1023
D)
Type III Type I L mode
6
5
4
3
2
1
0
Rec
over
ed a
fter p
ulse
(x
1022
D)
6543210
Total Injected (x 1023
D)
Type III Type I L mode High Ip (Type I ELMs) Mixed L mode, Type I & Type III
Short term retention
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Euratom Summary
- Repetitive pulses on JET for fuel retention analysis (accuracy ~1.2%)Evaluation of both short and long term retention
Confirm the strong concerns about fuel retention in C tokamak ITER with mixed material (C, Be, W)Burning Phase Injection Long Term Ret 400s ~ 5x1022Ts-1 ?
- In all the cases, the recovery in between pulses corresponds to a weak contribution in the overall fuel retention (short term retention)
Heating Phase Injection Long Term RetL mode 81s ~1.8x1022Ds-1 1.74x1021 Ds-1 ~10%
Type III 221s ~0.6x1022Ds-1 1.31x1021 Ds-1 ~20%
Type I 32 s ~1.7x1022Ds-1 2.83x1021Ds-1 ~17%
- Increase of long term retention- with the recycling flux- with ELMs Energy
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Slides in reserve
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Euratom ELM induced C deposition
QMB1 (inner): Deposition per ELM vs. ELM energy
- Increased deposition due to thermal decomposition of co-deposited layers - Enhanced carbon erosion (Recycling and ELM energy) and transport
leading to stronger carbon deposition and fuel codeposition
Fit formula:y = 1012 * x * exp(x/165)
C d
epo
siti
on
per
EL
M [
ato
ms/
cm2 ]
WELM [kJ]0 100 200 300 400 500
1013
1014
1015
1016
"Area" term "Thermal" term
1
3
4 6
7
8
LBSRP
QM
B 1
QM
B 5
B field configuration
A.Kreter, H.G.Esser
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Injection
(integral:1.8 x 1023 D-atoms)
Divertor pumping
Wall pumping
Long term retention (codeposition)
2 x 1021 D/s
Dynamic wall retention (decrease in 10 sec by about 50%)
3.9 x 1021
2.2 x 1021
Integrated wall pumping 3 x 1022
Measured long term outgassing (800s)
2.85 x 1022
Example: particle balance in 70534 during steady state phase
Long and short term retention
V Philipps
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1. Campaign averaged retention about 5 times smaller due to effects of long term outgassing, thermal release from subsequent plasma
operation, GDC, disruptions (reasonable)
Codeposition
DC
C, D
Local C-erosion and redeposition does not contribute much to retention (similar D content of eroded and deposited layers)
Needed: long range transport from net erosion to deposition areas
main chamber to divertor
outer strike zone to PFR, inner divertor ,..
freshly deposited C-layers are D-rich (analysis after about 2h)
Further reduction by long term outgassing (reduction by about a factor of 2 between 2h and 24h ) and subsequent plasma operation
Discussion