ITER mirrors and boronisation

→ Europe/Berlin
Participants
  • David Douai
  • Emmanuelle Tsitrone
  • Joao Figueiredo
  • Marot Laurent
  • Moser Lucas
  • Rohde Volker
  • Sebastijan Brezinsek
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  • LMo: ITER priorities
    • LMo: there are about 14 diagnostics needing Mirror Cleaning Systems. 
    • need samples exposed to eroded B for mirror cleaning recipes trial
    • Some (interferometer/polarimeter, DIP/TIP) not seen as critical with Be -- > Regular boronisation now becomes challenging over lifetime
    • For new diagnostic systems without shutter -- > need samples exposed to deposited B during boronisation (Mirror station without shutter) 
       
    • SB: pb is the B deposits before a shutter, which may migrate to the mirror
    • VR: no B observed in AUG divertor slits/tubes (width <5mm) after campaigns
       
  • AL: Review of sample exposure/mirror stations
    • focus on B related topics only
    • exposure of Mirror stations in AUG, DIII-D and TEXTOR
    • shutter on mirror stations did not work 100% reliably --> evaluation challenging, but reflectivity drop observed
    • wall conditioning dominates mirror contamination (TEXTOR, KSTAR) 
      • ratio boronisation/plasma time may be different in ITER long pulses ! --> need assessment
    • Mirror campaign in AUG: 
      • B/W/C mixed layers measured in divertor, highest below OSP
      • Reflectivity of all mirrors degraded, none of mirrors would survive in ITER without cleaning
      • not shown: mirror exposed in the mid-plane
         
  • LMa: Mirror Cleaning Systems:
    • All 14 systems needing Mirror Cleaning will use either Pulsed-DC or RF cleaning 
       
  • Discussion:
    • Mirror Cleaning  techniques to be qualified to remove B and mixed layers,
      • what is the effect of cleaning by sputtering 
    • shutters have to work reliably
    • LMo: need schedule of AUG/WEST campaigns to assess possibilities for exposure of mirrors
      • VR: parts from IO needed in May, closure of VV in Sept! next opening end 2025.
      • ET: VV closed in Sept, opportunity to install samples during summer
    • ITER DIP/TIP
      • VR/ET: Si wafers could be used in AUG/WEST to get information at the location (but no info on loss of optical properties)
      • LM: need drawings from AUG/WEST --> VR/ET to provide drawings
      • meeting then needed for a more detailed planning
    • ET to contact WEST DIAG team to get feedback 
      • on impact of B on diags (eg interfero-polarimeter)
      • on shutters
      • on ex-situ cleaning procedures
    • VR: analysis of B deposits on Si wafers exposed in AUG will be published next PSI Conference
       
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