1. 9 th ITPA Meeting on Divertor/SOL physics, May 7-10, 2007, Garching Improvements to the B2 wall model: coatings and layers X. Bonnin, M. Warrier, D. Coster In the last few years, there has been an effort to include more explicit dependencies of PWI processes in SOL codes, as well as capabilities for mixed materials and hydrogen inventories PWI include: Physical sputtering (TRIM) Chemical sputtering (García-Rosales + Roth) RES, backscattering, thermal evaporation last 2 bullets functions of surface temperature T P The wall model has three options: –‘b2stbr_plate_model’ = ‘0’: steady-state 1-D heat transfer –‘b2stbr_plate_model’ = ‘1’: time-dependent 1-D heat transfer –‘b2stbr_plate_model’ = ‘2’: time_dependent 2-D heat transfer

2. 9 th ITPA Meeting on Divertor/SOL physics, May 7-10, 2007, Garching The B2 wall model Wall is located directly at edge of mesh Each boundary cell is a separate wall element Each boundary is a separate wall segment Each wall element can have its own: Material properties (C p, , , Z, …) Thickness ( L ) Coolant temperature or inertial vessel temperature ( T L ) Coating with separate properties A surface layer containing mixed materials inventory This new model is being applied to: - AUG C/CFC with W coating - JET CFC with Be coating (eventually ILW mix) - ITER (currently Be walls with C divertor)

3. 9 th ITPA Meeting on Divertor/SOL physics, May 7-10, 2007, Garching Mixed materials modelling: scenarios Considering three cases: –First multi-materials results (no follow-up of re-deposited species) but with temperature evolution of wall elements were obtained –We used C targets and Be walls AUG: P SOL = 520 kW, n e,core = 2.65  10 19 m -3, T coolant = R.T. JET: P SOL = 10 MW, n e,sep = 2.0  10 19 m -3, T vessel = 90 ºC ITER: P SOL = 100 MW,  D +,core = 9.1  10 21 s -1, T coolant = 100 ºC –Establish a baseline for mixed materials comparisons For PSI-17, runs were performed assuming constant wall temperatures and constant chemical sputtering yield Here, chemical sputtering yield is temperature and flux-dependent (Roth formula) Target thickness is adjusted to obtain “realistic” temperatures

4. 9 th ITPA Meeting on Divertor/SOL physics, May 7-10, 2007, Garching Mixed materials modelling: JET multi species Sample output: –Y chem along targets –T w increase on C targets –T w increase on Be walls –Net C erosion rate on targets Inner target Outer target Inner target

5. 9 th ITPA Meeting on Divertor/SOL physics, May 7-10, 2007, Garching Mixed Materials modelling: ITER mixed materials Layer content BulkBeC Layer temperatureLayer thickness 2.5 nm -1.5 nm

6. 9 th ITPA Meeting on Divertor/SOL physics, May 7-10, 2007, Garching Bundled charge states model Aim: –Be able to handle high-Z species, in particular W Means: –Bundle many charge states together into super-stages –Replace Z a, Z a 2, and E i with super-stage averages Requirements: –Full backward compatibility and user transparency Old species data format: Z a, Z n, A m, Z a 2 New data format: Z a,min, Z a,max, Z n, A m –Recovery of old results Current status: –Changed code for use of Z a and Z a 2 averages: version 01.001.024 –Tests with a D+Ar case with and without bundling are under way –Then series of sensitivity tests with different bundles of W ions

7. 9 th ITPA Meeting on Divertor/SOL physics, May 7-10, 2007, Garching Bundled charge states results Te Ti Ne “Natural” bundling: Ar +2 to Ar +6 and Ar +9 to Ar +14 Plotting fractional differences between usual case and bundled run -5% 25% -15% 15% -10%