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ITER mirrors and boronisation
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Europe/Berlin
- 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
- 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
- Mirror Cleaning techniques to be qualified to remove B and mixed layers,
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