Deposition in the MKII - Gas Box Divertor Deposition in Septum M. Rubel, P. Coad, J. Likonen OUTLINE General deposition pattern on MKII-GB tiles Septum Summary

JET Divertors Results for MK-IIA presented on PSI GB innerouter MKII - GB Operation time ~ 18 months in both cases Mark II-A divertor

Beryllium and Deuterium: Comparison MKII-A and GB (shadowed areas on tiles 3 and 4 are not included) MKII-GB MKII-A D Be D Be Major differences: D/Be ratio < 1 on MKII-A D/Be ratio > 1 on MKII-GB Possible reason: Cleaning after DTE-1 to reduce T level. Significant co-deposition (and fuel inventory) in the shadowed corner of the outer divertor (tile 6). Possible reason: Shadowing due to geometrical factor (as in MKI divertor)

SEPTUM a b a: three support plates b: septum (divider) plate

Deposition on the GB tiles C-end D-end Central plate Thick deposit Shadow after the IPP deposition monitor

Deposition on the divider plates INNER OUTER

Deposition on the septum tiles: Central support plate A D

B C

Deposition on the divider plates: Inner divertor “Base” Top Base Central plate End rib Dusty

“Base” Base Top Central plate End rib Deposition on the divider plates: Outer divertor

Deposition on the septum tiles Summary Deposition on the plates is mainly seen in the near-plasma region from the inner divertor side (up to 25 mm from the edge). Thick deposits (> 50  m ?) only on a side of one plate (C-end). Little deposition deep inside the Gas Box (thin deposit, d < 10  m). Little deposition on the divider plate (thin deposit, d < 10  m). Small content of beryllium in the Gas Box. No C-13 (above the background level) found on the plates. Gas Box plates can not be considered as the major trap for transported and re-deposited material. The results also indicate that the direct across-divertor transport is negligible (if any).