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9th ITPA Meeting on Divertor and SOL Physics, 10/5/07 1
Max-Planck-Institutfür Plasmaphysik
Initial operation of ASDEX Upgrade with 100 % tungsten PFCs
Rudolf Neu
With contributions from: V. Bobkov, R. Dux, A. Kallenbach, T. Pütterich, H. Greuner, Ch. Hopf, C.F. Maggi, H. Maier, M. Mayer, V. Rohde, ASDEX Upgrade Team
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 2
Operation with 100 % W PFCs
• Transition to W PFCs in ASDEX Upgrade
• Boundary Conditions for Experimental Campaign
• Arguments on boronisation
• First Results of initial operation
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 3
Steps in ASDEX Upgrade towards a full W device
guard/ICRHlimiter
aux.limiter
hor.plate
lower PSL
roofbaffle
2007
W-coating startingwith campaign
2003/2004
2004/2005
2005/2006
guard/ICRHlimiter
aux.limiter
hor.plate
lower PSL
roofbaffle
2007
W-coating startingwith campaign
2003/2004
2004/2005
2005/2006
Steady increase of area of main chamber W PFCs since 1999
Rationales:- risk minimisation- physics investigations- partitioning of installation
time - production capacity
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 4
Optimisation of VPS coatings / HHF tests in GLADIS
200 µm W VPS (Plansee) on SGL R6710
Thermal Screening:• surface temperatures
> 2000°C no macroscopic defects
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 5
Optimisation of VPS coatings / HHF tests in GLADIS
Cyclic Loading:
200 pulses @ - 10.5 MW/m²- 3.5 s- Tsurf > 1600°C
coatings qualified for use in the lower divertor
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 6
Steps in ASDEX Upgrade towards a full W device
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 7
Steps in ASDEX Upgrade towards a full W device
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 8
Operation with 100 % W PFCs
• Transition to W PFCs in ASDEX Upgrade
• Boundary Conditions for Experimental Campaign
• Arguments on boronisation
• First Results of initial operation
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 9
• AUG is operated with the help of three flywheel generators:– EZ2 (1.45 GJ / 167 MVA): toroidal field– EZ3 (500 MJ /144 MVA) + EZ4 (650MJ/220MVA):
OH, pol.field, aux. heating
• Reconfiguration of power supplies necessary:
less power, less energy available
Ip 1.0 MA, pulse length 3-4 s, Paux 7.5 MW,
intermediate densities / triangularities (@ 1 MA)
Constraints imposed by damage of EZ4
0
5
10
15
20
New
-EZ3
(kA
)
0.4 0.6 0.8 1.0 1.2Ip(MA)
EZ3 > 11 kAEZ3 ≤ 11 kA
Limit: 11 kA
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 10
Setup of program for 2007 campaign
I. Exploration of W compatibility (discharges in agreement with general boundary conditions)
II. Extension of working space - rad. cooled plasmas - impr. H-Mode (high low density)
III. Other ITER related physics investi- gations, compatible with above results and requirements
envisaged rel. weight(whole campaign)
priority
30%
20%
50%
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 11
Guidelines during initial operation
Boundary conditions set by W-PFCs (during phase I., to be refined):• density: 7e19/m³ (gas puff rate > 6e21/s)• q-edge: > 3.2• f(ELM): > 60 Hz• dominant central heating (no pure off axis heating)• Pheat < H-mode threshold or Pheat > 2xH-Mode threshold• power/energy limits for upper divertor (5 MW 4s, 10MW 1s)• monitoring of limiter (and divertor) glow (restrictions on shape,
power, energy: to be adjusted)• power/energy limits for lower divertor from operation / results
of radiatively cooled plasmas
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 12
Research Topics of W-programme at AUG for the upcoming campaign(s)Investigation will concentrate on:
• transition to C-(low-Z) free machine:- radiatively cooled (integrated) scenarios by simultaneous use
of noble gas puff, central heating and ELM pacemaking - optimization of gas species/injection • evolution of hydrogen retention:
- influence on gas balance and D inventory in PFCs • disruption characteristics:
- differences in current decay / run-aways• optimization of ICRF: - is the simultaneous use of with high-Z PFCs possible
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 13
Operation with 100 % W PFCs
• Transition to W PFCs in ASDEX Upgrade
• Boundary Conditions for Experimental Campaign
• Arguments on boronisation
• First Results of initial operation
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 14
Reminder: Unboronized start-up with W HS successful
H ~ 1, Prad ~ 30 %main
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 15
Why Boronisation
• Conditioning- large O getter (even in non plasma exposed areas): easier break down higher density limit facilitates start up
- use of BD6 pre-loading of wall, strong pumping larger D puffing rates easier transition to D:
• Coating of surfaces- suppression of W influx- suppression of other intrinsic metallic impurities
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 16
Estimates for B Erosion
Thickness of boron layer Main chamber: 50 nm 3e21/m²Limiter: 50 nm 3e21/m²Divertor: 10 nm 5e20/m²
Particle fluxes / Particle temperatures (energies) /B YieldMain Chamber: 1e21 / (E 100 eV) / 1e-2Limiter: 1e22 / T= 20 eV / 1e-2Divertor: 1e23 / T=5 eV / 5e-4
Live-time of boron layerMain chamber: 300 s (100 disch)Limiter: 30 s (10 disch)Divertor: 10 s (3 disch)
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 17
Effect of boronisation
• strong reduction of W influx and concentrations
• for ICRH only, H-Mode threshold increases stronger than for NBI for aged boronisation
• time constants shorter than typical distance between boronisations
• recovery of W influx depends on particle and energy load
800 kA 1.8MW ICRH
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 18
Effect of boronisation
• strong reduction of W influx and concentrations
• for ICRH only, H-Mode threshold increases stronger than for NBI for aged boronisation
• time constants shorter than typical distance between boronisations
• recovery of W influx depends on particle and energy load
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 19
Benefits of start-up without boronization
• Operation/investigation of W machine without (any) intrinsic low-Z radiator
• Comparison of boronised / un-boronised machine: maybe able to proof of hypothesis on B influence
• D retention ‚without‘ low-Z (C,B) contamination• Comparison of D pumping W wall / boronised W wall
and H-D transition
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 20
Aims for the unboronized phase
Milestone: Steady state H-Mode at intermediate density and heating powerwith H~1
Specific Investigations: • Exposure of deposition probes to measure:
evolution B,C,W impurities, D retention• Particle Balance (in co-op. TS)• Influence of ICRH• Documentation of edge plasma parameters / radiative cooling
(if applicable/necessary)
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 21
Operation with 100 % W PFCs
• Transition to W PFCs in ASDEX Upgrade
• Boundary Conditions for Experimental Campaign
• Arguments on boronisation
• First Results of initial operation
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 22
Conditioning by baking - He / He-D glow
• 10 days baking @ 150°C• overnight glow in He
(He+10%D2, 500V, 4x1.8A)
Strong pumping of C and O (through CO and CO2)
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 23
First Results of initial operation
• Re-start since 24/4/07 (5 days of operation)
• Reconfiguration of power supplies for OH/V-coils main issue
• Reliability of break-down not yet satisfactory (low-Z impurities, gas release)
• Divertor configuration succes- fully acchieved
• W contamination not important
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 24
First Results of initial operation
• Re-start since 24/4/07 (5 days of operation)
• Reconfiguration of power supplies for OH/V-coils main issue
• Reliability of break-down not yet satisfactory (low-Z impurities, gas release)
• Divertor configuration succes- fully acchieved
• W contamination not important
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 25
Long term evolution of W concentrations
• reduced cW at relevant auxiliary heating power and densities
9th ITPA Meeting on Div/SOL Physics, 10/5/07 R.Neu 26
Classification of proposals
• P prerequiste first few weeks• R related first half of campaign• E extended end of first half of campaign• C compatible first few months (lower
priority)• O orthogonal second half of campaign
Priority within categories by TFs