Progress with PWI activities at UKAEA Fusion 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 - 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 - 2 At high (approaching DND), significant energy flows to upper divertor during thermal quench

Disruption 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 tile NDT of JET tile coatings Flash-lamp heating of coating coupled with fast IR imaging looks like promising technique

abc Plasma exposed tile Non-exposed tile after air duster Non-exposed tile after polishing Modelised flash lamp heat flux IR transient studies - 1 ELM simulation (75-375MW/m 2 ) 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 - 2 Derived power load vary widely due to surface effects and hot spots

IR transient studies - 3 Initial temperature 303 K (MAST) Initial temperature 523 K (JET ) Longer wavelength IR significantly ameliorates problem Even 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 - 4

Dust modelling for ITER Deposition possible inside separatrix on MAST Dust dynamics model in development, compatible with B2SOLPS5.0 ITER runs on-going

MASTDIII-DASDEX Upgrade Filamentary structure of ELMs beings investigated in similarity experiments and communal analysis on MAST and Asdex Upgrade Relationship to Wall loads ELM 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 - 2

ELM 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

A at the start of the ELM localised wall deposition observed but < 1% of W ELM Later on – up to 25-40% of W ELM observed on targets ELM studies - 4 A Herrmann et al 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 ~30cm 2 Peak power density ~375MW/m 2 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 activities Combined TAE/ELM ergodisation coils: 3 (n=3) to be installed in early Upgrade to 12 (or 24) coils in 2007 SOL flows and SOL radial transport: several new diagnostics: reciprocating Gundestrup probe, multi-wavelength 2D divertor spectroscopy & toroidal gas puffing, windowframe limiter 2 nd LW IR camera: studies of target power transients at wider range of wavelengths Spectroscopic erosion diagnostic: coded implanted layers exposed from reciprocating materials probe Gap deposition probe: ITPA D&S experiment Reciprocating RFA probe: exploration of T i in ELM filaments