Progress with PWI activities at UKAEA Fusion 2004-5 GF Counsell, A Kirk, E Delchambre, S Lisgo, M Forrest, M Price, J Dowling, F Lott, B Dudson, A Foster,

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

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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