Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 1 Th Loarer with special thanks to S...
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Transcript of Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 1 Th Loarer with special thanks to S...
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 1
Th Loarerwith special thanks to
S Brezinsek, J Bucalossi, I Coffey, G Esser, S GruenhagenPh Morgan, V Philipps, R Stagg, J Strachan.
And alsoEU TF on PWI and JET EFDA contributors
Fuel retention in JETRecent results in L and H-mode
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 2
OUTLINE
Recent results in- L mode- Type I ELMy H-mode
Retention- Implantation- Co-deposition: correlation carbon source- EDGE2D
Further plan
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 3
Introduction
- Reference in carbon before moving to a full metallic wall: Quantify the benefit (?)
- Validation of the method
- Can we avoid the regeneration?
- Gas balance “on line” for each discharge?
- DT experiments (JET and TFTR) remain very good references for
- Gas balance
- Post mortem
- Fuel removal
- Comparison with other devices: AUG, JT-60U, but also limiter devices
- Extrapolation to ITER
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 4
Calibrated Particle Source
(Gas, NBI…)
Divertor cryo-pumps
Wall Retention
Long & Short Term
Gas balance procedure on JETRepeat sets of identical discharges (no intershot conditioning) to avoid history effects Plasma
Injection = Pumped + Short Term Ret + Long Term Ret
Total recovered from cryo-regeneration: Pumped + intershot outgassing over ~800s (assumed equal to Short Term Ret )
Regenerate cryopumps before and after expt. collect total pumped gas (accuracy~1.2%)
Dedicated series of experiments: L and H mode in 2007-2008 as ref for ILW
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 5
• 8 repetitive pulses
• Ip/BT=2.0MA/2.4T, 1.8MW ICRH “only”
(42MHz)
• All auxiliary pumps (NBI, LH, main Turbo pumps) off
• Regeneration of divertor cryopump before and after session
“Long Term” retention
Injected – Regenerated
(regeneration about 60 min after last shot)
L mode: short limiter phase
L-mode, HT3 with ~1.7x1022Ds-1 and Early X-point formation
Recent session Evaluate the contribution of the limiter phase
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 6
HT3 – Mode B (early X-point) and D
-Mode D “standard X-point” (~9s of limiter start-up phase) # 70534
- Mode B: Early X-point” (~1.3s of limiter start-up phase) # 73654
“Except” the limiter phase Comparable plasma parametersIp, BT, ne, ICRH, Gas rate, recycling…
Ip
ne
ICRH
Gas rate
Total injected
H
Limiter phase
Limiter phase
Ip/BT=2.0MA/2.4T,
1.8MW ICRH “only”
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 7
Heating and gas injection ~ 75 s (8 pulses) – Mode B (8th July 2008)
Total divertor time: ~ 170 s, Total limiter time: ~10s
Injection: 24.761 Barl 1.22 1024 D-atoms
Total recovered 21.02 Barl 1.03 1024 D-atoms
Retention 3.741 Barl 1.84 1023 D-atoms (~15%)
Comparison of L-mode experiments
Heating and gas injection ~ 81 s (6 pulses) – Mode D (March 2007)
Total divertor time: ~ 126 s, Total limiter time: ~60 s
Injection: 27.882 Barl 1.377 1024 D-atoms
Total recovered 24.454 Barl 1.208 1024 D-atoms
Retention 3.428 Barl 1.693 1023 D-atoms (~12%)
Detailed analysis of ramp-up and ramp-down phase in progress
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 8
Retention in L and H-mode
Pulse type
Injection(Ds-1)
Heating phase (s)
Long term retention (Ds-1)
Divertor phase (s)
Long term retention (Ds-1)
L-modeMode D
~1.8102
2
81 2.041021 126 1.271021
L-modeMode B
~1.7102
2
75 2.401021 170 1.051021
Type III ~1.7102
2
72 2.401021 126 1.371021
Type I ~1.7102
2
32 2.831021 50 1.71021Impact of the limiter phase in the fuel retention experiments with an early X-point (~1.2s of limiter phase) and late X-point formation (~8-10 s of limiter phase) is moderate. Normalisation “Divertor” vs. “Heating time” !
Consistent with the previous results, but “divertor time” and “limiter time” difficult to evaluate with accuracy.
Retention closely linked to the carbon source
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 9
Type I ELMy H-mode
ne~0.7nGW
PTOT (MW)NBI+ICRH~13MW
D(in) D (out)
Time (s)
#69260
Ip = 2.0 MA, B = 2.4 T
- Short term retention: “limited” to “fast” reservoir and recovered in between pulses (outgasing)- Long term retention: Co-deposition and implantation : Slow process compared to short term over 5-10 sec
WELM ~100 kJ ~ 60 Hz
Heating phase
Injection
Exhausted
Retention
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 10
High power discharge in JET
Ip=3.5MA, BT=3.2T
ne
Ptot (NBI + ICRH) ~ 23-24MW
Wdia~9.5MJ
Gas: 5.0x1022Ds-1
ELMs600-700kJ per ELM
Gas balance “on line”, w/o regeneration
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 11
Gas balance High power discharge
Using the same pumping speed Retention as high as ~3.3x1022Ds-1
Consistent with strong carbon erosion from recycling and ELMs Increase by ~10 of the retention To be confirmed by dedicated exp
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 12
C source for High power discharge
Type I ELMs (600-700kJ)
L mode
Type I ELMs (100kJ)
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 13
Carbon production and scenario
J Strachan et al. Nuc. Fus. 2003
L mode(3-4MW)
Type IH mode
10-15MW
- Increase of carbon source depends on scenario (ELMs, recycling flux…) enhanced retention by co-deposition
- Increase by a factor of ~2 of carbon source from L to type I ELMy H-Mode
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 14
Carbon production and scenario
J Strachan et al. PSI 2008
Carbon ionisation rate in the SOL as a function of D ionisation rate
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 15
D,T
Wall
Mechanisms for fuel retention
Two basic mechanisms for
Long term fuel retention
Deep Implantation, Diffusion/Migration, Trapping
C, Be C, Be, D ,T
Codeposition
Short term retention (Adsorption: dynamic retention)
~ Recovered by outgassing
Separate the contribution of implantation and co-deposition?
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 16
DT experiments in JET
Retention by implantation and co-deposition
“Same” retention although different scenario
TFTR
Phase 1 (June 1997)
Gas injection only 11.4g 2.34x1024T
injected
1.0x1024T retained (~40%)
80 pulses in L modePhase 1
Phase 2 (End 1997-Early 1998)
Both NBI and Gas injection
23g
~40% retained
High power discharges in H mode
Phase 2
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 17
Implantation and co-deposition
2.5x1024
2.0
1.5
1.0
0.5
0.0
Par
ticl
es
4176041740417204170041680Pulse Number
T Injected Cryopump regeneration
50-50% D/T 100% T
Early phase of DT experimentsRetention~100% for the 10 first discharges (~4x1023T)
Retention deduced fromCryo regeneration
Injection
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 18
Implantation
JET DT experiments- Implantation dominates in phase 1- Co-deposition main process in phase 2
- JET ~ 200 m2 : maximum retained fluence ~1021m-2 reservoir of ~ 2 1023 T consistent with implantation of particles with incident energy of ~ 200eV.
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 19
Summary…and further plans!
- No impact of the limiter phase in the gas balance analysis
- Retention linked to carbon production
- Implantation
Dominant process in early phases
Later co-deposition
- Further plans
Dedicated session with high power (ELMs) /injection
- Modelling correlate the retention with carbon
source (EDGE2D)
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 20
Retention: Short and long term
Short term retention- Depends on plasma scenario, wall conditioning and Material (Be, C)…-“Limited” to “fast” reservoir and recovered in between pulses (outgassing)
Actively cooled device Steady state operation-->Long term retention
Long term retention
- Co-deposition Correlated to C production
- Implantation Edge plasma, material structure…
Long term retention
Short term retention
5
4
3
2
1
0
1020
Ds-1
4003002001000
Time (s)
# 32299 # 32300
TS
Dynamic retention: ≈ 5 x1021D JET ≈ 2.5 1022 D ~ wall area ratio
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 21
Gas Balance (1/2)From cryo-pump regeneration (~1%) and calibrated gas injection
Evaluation of the pumped flux
- During the plasma
- Between pulses
0 10 100 1000 100001min 1hour 1day 1week
Plasma
During plasmainj>pump
Retention>0Short & Long term
Between pulses, session, days…inj=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
Th Loarer - SEWG on Fuel retention – JET, 22-23 July 2008 22
Gas balance (2/2)
Two complementary methods to measure the pumped flux
2 – Collection of all the total particles pumped (Tbo, Cryo…) into a separate calibrated volume (equivalent to the AGHS used at JET)
- Accurate neutral pressure measurement in volume (Temperature)- Analysis of the gas composition collected (H, D, T and Impurities)
1 – Neutral pressure and Pumping speed
Pumped flux = PDiv*SDiv + PNBI* SNBI + PDiag*SDiag
- Require enough pressure gauges located in the “pumping pipes”, regular calibration of both pressure gauges and pumping speeds.
- These 2 methods are complementary; the second method gives the equivalent of the integral of the first one.- Allow to check/limit/evaluate the possible drift of the neutral pressure measurements over long periods (days, weeks…).- These two methods are “technically easy” to be implemented.