Progress with PWI activities Progress with PWI activities at UKAEA Fusion 2004-5at UKAEA Fusion 2004-5
GF Counsell, A Kirk, E Delchambre, S Lisgo, M Forrest, M Price, J Dowling, F Lott, B Dudson, A Foster, S Tallents, J Martin
Disruption studies - 1Disruption studies - 1
Target heat flux width broadens by factor ~8 during thermal quench
Significant poloidal and toroidal variability
Core losses prior to thermal quench average 50%
Pre thermal quench losses can increase target peak heat flux significantly
Could exceed values during quench
Disruption studies - 2Disruption studies - 2
At high (approaching DND), significant energy flows to upper divertor during thermal quench
Disruption studies - 3Disruption studies - 3
Wide angle IR reveals significant wall interactions during thermal quench in some types of disruption
Flash-lamp head
IR image of W-coated CFC tileIR image of W-coated CFC tile
NDT of JET tile coatingsNDT of JET tile coatings
Flash-lamp heating of coating coupled with fast IR imaging looks like promising technique
a b c
Plasma exposed tile
Non-exposed tile after air duster
Non-exposed tile after polishing
Modelised flash lamp heat flux
IR transient studies - 1IR transient studies - 1
ELM simulation (75-375MW/m2) on various surfaces
Plasma exposed tile (MAST)
Non-exposed tile
Non-exposed tile after air duster
Non-exposed tile after polishing
~89 MW/m2
~63MW/m2
~59MW/m2
~37MW/m2
IR transient studies - 2IR transient studies - 2
Derived power load vary widely due to surface effects and hot spots
IR transient studies - 3IR transient studies - 3
Initial temperature 303 K (MAST)
Initial temperature 523 K (JET )
• Longer wavelength IR significantly ameliorates problem
• Even 4.5-5 m filter can help
• Problem reduced at higher target base temperature
=140 kW/m²/K=30 kW/m²/K
unfiltered data
• Tokamak tile characteristics for IR change with time
• With care, reasonable error bars can be obtained but fudge factors required - unsatisfactory
IR transient studies - 4IR transient studies - 4
Dust modelling for ITERDust modelling for ITER
Deposition possible inside separatrix on MAST
Dust dynamics model in development, compatible with B2SOLPS5.0
ITER runs on-going
MAST DIII-D ASDEX Upgrade
Filamentary structure of ELMs beings investigated in similarity experiments and communal analysis on MAST and Asdex Upgrade
Relationship to Wall loads
ELM studies - 1ELM studies - 1
Observations on 2 machines highly complementary
Large field line angle on MAST allows for clearer interpretation of images
AUG allows field and wall proximity effects to be explored
ELM studies - 2ELM studies - 2
ELM studies - 3ELM studies - 3
Observations on AUG of target ‘stripes’ explained by modelling at UKAEA
Direct consequence of filaments expanding into SOL and change of L//
T Eich et al
Aat the start of the ELM localised wall deposition observed but < 1% of WELM
Later on – up to 25-40% of WELM observed on targets
ELM studies - 4ELM studies - 4
A H
errm
ann
et a
l
Many questions remain – UKAEA modelling shows individual filaments only contain 1% of ELM losses, consistent with AUG measurements
But wall losses can reach 40% in AUG – how? (no change in SOL h)
Flash-lamp trials in JET BeHF
• Flash-lamp footprint covers ‘large’ area ~30cm2
• Peak power density ~375MW/m2 at target for 500J flash
• Pulse half-width is short - less than 150 s is typical
Treated areas
Untreated areas
Heavily treated area with initially thick powdery deposit
• Clearly visible changes to co-deposit in treated areas
Flash-lamp trials in JET BeHF
Ongoing or planned activitiesOngoing or planned activities
Combined TAE/ELM ergodisation coils: 3 (n=3) to be installed in early 2006. Upgrade to 12 (or 24) coils in 2007SOL flows and SOL radial transport: several new diagnostics: reciprocating Gundestrup probe, multi-wavelength 2D divertor spectroscopy & toroidal gas puffing, ‘windowframe limiter’2nd LW IR camera: studies of target power transients at wider range of wavelengthsSpectroscopic erosion diagnostic: coded implanted layers exposed from reciprocating materials probe‘Gap deposition’ probe: ITPA D&S experimentReciprocating RFA probe: exploration of Ti in ELM filaments