P. Coad, J. Likonen, H. Bergsåker, M. Rubel, I. Uytdenhouwen, A. Widdowson JET mixed Be/C/O layers SEWG meeting on mixed materials, , JET
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 2 Dump plate, saddle coil protection tiles: Main erosion source? OPL: erosion divertor: deposition (inboard) erosion (outboard) IWGL: erosion deposition Erosion/deposition at JET
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 3 Inner divertor: heavy deposition Outer divertor: erosion SIMS depth profiles from centre of lower inner divertor wall tile: High vessel temperature Be/C > 1 Deposit: thickness ~8 m 3/3 Erosion/deposition at JET (MkIIA)
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 4 Micrometer and SIMS results Inner wall: thickness increase towards the bottom at inner divertor wall (points 1-8), reaching a maximum of about 90 m SIMS gives somewhat smaller values Floor: thick powdery deposits at points 10 and 16 Outer wall: small amounts of erosion/deposition Erosion/deposition at divertor (MkIIGB) 1 6/16/
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 5 Inner divertor: heavy deposition SIMS depth profiles from bottom of upper inner divertor wall tile: Deposit: 2 layers (thickness ~11 m). Surface layer: mostly D, C and Be Film underneath the surface layer: rich in Be Vessel temperature decreased in Dec Deposition at inner divertor (MkIIGB) bulk CFCBe-richC- 1/1 Re
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 6 layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) Composition of deposits (MkIIGB) RBS spectrum and SIMNRA simulation from the bottom of tile 1
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 7 t Surface analysis (SIMS, RBS, TOF- ERDA), inner divertor: Be 22 g t Assume that Be/C ratio (7%) arriving in the divertor is the same as the Be/C ratio in the main chamber (Be/C ratio on IWGL tiles is ~8%). C: 420 g Amount of deposited C: t Tiles 1, 3 and 4: 310 g (SIMS, RBS) t Louvres: g (QMB and deposition monitor sample) t Septum: 10 g (RBS) t Total: g t Good agreement between surface analyses and optical spectroscopy Be accumulation and C deposition (MkIIGB)
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 8 Inner divertor: heavy deposition SIMS depth profiles from bottom of upper inner divertor wall tile: Low vessel temperature Deposit: Be/C high Duplex structure of deposits on MkIIGB tiles due to He-phase at the end of C4 campaign 1/2 Deposition at inner divertor (MkIISRP) bulk CFC depositW marker
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 9 layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) Composition of deposits, RBS (MkIISRP) RBS spectrum and SIMNRA simulation from the bottom of tile 1 Cr O 13 C 12 C Be D
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 10 layerD (at%) Be (at%) 12 C (at%) 13 C (at%) O (at%) Composition of deposits, floor (MkIISRP) 12 C 13 C O Be D RBS SIMS
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 11 Erosion/deposition at JET Inner divertorOuter divertor MkIIAHeavy deposition, Be/C ratio highErosion (no markers) MkIIGBHeavy deposition, films have duplex structure (C- and Be-rich layers), no Be on floor tile, deposited C quantified Erosion (markers eroded completely) MkIISRPHeavy deposition, Be/C ratio high, some Be on floor tile Erosion/deposition (due to rev B campaign?) see our review paper Coad et al.: Overview of material re-deposition and fuel retention studies at JET with the gas box divertor, Nucl. Fus. 46 (2006) 350.
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 12 Nature of the films t All analysis is done ex-situ and this may introduce much of the observed oxygen and affects H/D/T levels t We have a good idea of the atomic Be/C composition, but no idea of the chemical composition. For example it is sometimes assumed that the Be/C is beryllium carbide – is this really true? t XPS/AES can demonstrate the chemical state, but only analyses a few monolayers at the surface, so needs to be combined with profiking in some way t Carbides may be detected by XRD, if present t There are many other film properties that would be of interest, such as density, electrical and thermal coefficients, thermal desorption etc
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 13 Erosion/deposition at JET divertor deposit 3µm W CFC W W
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 14 Micro beam analysis (MkIIGB) 2D image for D and Be on sample 3/1 Concentration profiles of Be and D on sample 3/1, taken from tile 3, exposed in JET
VTT TECHNICAL RESEARCH CENTRE OF FINLAND VTT 15 XPS analysis of tile sample 1-5 before and after sputter cleaning Before After
Sample 1-5, rough quantification Ni3s or Carbide ?
Conclusions Most important deposition in JET occurs at the inner divertor The deposits left on tiles 1 and 3 are mixtures of C & Be (+ other metals), most C migrates to inner divertor corner Almost nothing is known about the chemical state or physical properties of the films