ITPA, DivSOL, May 2007: Coster et al Coster, Bonnin, Corrigan, Wiesen, Chankin, Zagorski, Owen, Rognlien, Kukushkin, Fundamenski, … With contributions from Horton, Isler, Krstic, Reiter, Stotler Present status Lessons learned Plans Edge Code-code benchmarking

ITPA, DivSOL, May 2007: Coster et al Present status Phases –I: D, no drifts –II: D, drifts –III: D+C, no drifts –IV: D+C, drifts Code pairs –A: (i) SOLPS (B2-EIRENE) | (ii) EDGE2D-NIMBUS | (iii) EDGE2D-EIRENE –B: SOLPS (B2) | UEDGE –C: SOLPS (i) SOLPS4 | SOLPS5 (ii) SOLPS5.0 | SOLPS 5.1 (iii) SOLPS5.0 | SOLPS 6.0 Comparison technique –A: eproc routines based on “tran files” –B: UEDGE ability to read SOLPS b2fstate file; moving to MDSplus –C: comparison of MDSplus results Status –I A i/ii: done iii: in progress –III A: in progress –I B: in progress –III C i: hot topic (Bonnin/Kukushkin) –I C ii: re-done recently –I C iii: needs to be re-done –III C ii: need to be done –III C iii: need to be re-done

ITPA, DivSOL, May 2007: Coster et al SOLPS (B2-EIRENE) | EDGE2D-NIMBUS Same plasma grid Generated by GRID- 2D (A, B) Different surfaces seen by SOLPS-EIRENE EDGE2D-NIMBUS (EDGE2D-EIRENE matched to EDGE2D-NIMBUS) Orthogonal grid from UEDGE (C) A B C

ITPA, DivSOL, May 2007: Coster et al Some observations 1.The importance of flux limiters: SOLPS 0.5e19 Fl=0.15, 0.2, Unimportance of 5/9 pt stencil EDGE2D-NIMBUS 5pt stencil 9pt stencil SOLPS (5pt stencil) 0.5e19 Fl=10 Also: good agreement between SOLPS & EDGE2D-NIMBUS 1 2 SOLPS | EDGE2D-NIMBUS

ITPA, DivSOL, May 2007: Coster et al Some observations, II 3.Now started to include EDGE2D-EIRENE Cases EDG2D-NIMBUS (XB) SOLPS EDGE2D-NIMBUS (SW) EDGE2D-EIRENE (SW) 0.5e19 Fl= D+C, no drifts Cases EDGE2D-NIMBUS EDGE2D-NIMBUS (better BC) SOLPS Fl= SOLPS | EDGE2D-{NIMBUS,EIRENE}

ITPA, DivSOL, May 2007: Coster et al SOLPS(B2) | UEDGE Fluid neutral –More “difficult” than with kinetic neutrals Neutral flux limiters Atomic physics More ad hoc parameters Expect geometry closer to the target to play a greater role (5pt vs 9pt) Using an orthogonal mesh generated by UEDGE at the moment

ITPA, DivSOL, May 2007: Coster et al Boundary conditions (D only) Core –Neutrals leakage, recycled into ions –2.5 MW energy equally divided between electrons and ions Outer SOL surface –T e : 5 cm decay length –T i : 50 cm decay length –n D+ : 5 cm decay length –Gas puff of D 0 to control separatrix electron density Private flux surface –T e : 1 cm decay length –T i : 10 cm decay length –n D+ : 5 cm decay length –Leakage for D 0 Targets –Standard sheath boundary conditions Transport coefficients –D: 0.5 m 2 s -1 –  e,  i : 0.7 m 2 s -1 Flux limiters –Electron, Ion thermal: 10 –Viscosity: 0.5 –Neutrals:

ITPA, DivSOL, May 2007: Coster et al Progress … Started with fairly large disagreements Eliminated some possible causes –Moved to orthogonal mesh Reduced disagreements by –Introducing the factor in the neutral flux limits –Changing to pressure driven transport for the neutrals in UEDGE –Implementing the same method for calculating the neutral D’s,  ’s –Using the same atomic physics –Switching off a term in UEDGE which gives a contribution from molecular break-up –Using the same ion energy recycling coefficient –Braginskii/Balescu –…

ITPA, DivSOL, May 2007: Coster et al Status as of Nov 2006 Midplane profiles as of Nov. ‘06 are reasonably close Taken from a presentation by Tom Rognlien at ECC, April 2007 SOLPS | UEDGE

ITPA, DivSOL, May 2007: Coster et al Divertor profiles as of Nov. ‘06 differ substantially Taken from a presentation by Tom Rognlien at ECC, April 2007 SOLPS | UEDGE Status as of Nov 2006, II

ITPA, DivSOL, May 2007: Coster et al Present status SOLPS | UEDGE Midplane profiles still fit well Taken from a presentation by Tom Rognlien at ECC, April 2007

ITPA, DivSOL, May 2007: Coster et al Present status, II SOLPS | UEDGE Divertor profiles are now much closer with the various corrections noted Taken from a presentation by Tom Rognlien at ECC, April 2007

ITPA, DivSOL, May 2007: Coster et al Status SOLPS EDGE2D- EIRENE comparisons progressing SOLPS-UEDGE comparisons progressing –Challenging some of the implicitly made assumptions Status and Plans Plans SOLPS-EDGE2D- EIRENE –D+C –D, drifts SOLPS-UEDGE –“complete” D –D+C –D, drifts A large effort is going into these benchmarks

ITPA, DivSOL, May 2007: Coster et al Standard SOLPS simulations Minor variations in when the atomic physics files were created How may points were used in the interpolation table Barely detectable difference Changing the physics assumptions had a relatively small effect! Different atomic physics assumptions have a large effect! Atomic physics

ITPA, DivSOL, May 2007: Coster et al Atomic physics, in more detail TeTe nene TeTe nene TeTe nene TeTe nene Ionization rateRecombination rate Electron cooling rate Charge exchange rate

ITPA, DivSOL, May 2007: Coster et al Atomic physics, in more detail Ionization rate Agreement between the data sets – except for the standard rates used for the fluid model by SOLPS

ITPA, DivSOL, May 2007: Coster et al Atomic physics, in more detail Agreement between the data sets – except for the standard rates used for the fluid model by SOLPS Recombination rate

ITPA, DivSOL, May 2007: Coster et al Atomic physics, in more detail More complicated situation Ionization driven piece Recombination driven piece (plus Bremsstrahlung) Electron cooling rate

ITPA, DivSOL, May 2007: Coster et al Atomic physics, in more detail B2 used simple formula Not too bad! ADAS: 89: wrong 93: no file 96: file with 0 rates Now have “ADAS” format data from Horton Charge exchange rate

ITPA, DivSOL, May 2007: Coster et al Conclusion: Atomic physics Came as a surprise to me that the atomic physics made such a difference –Since this is all D –And I thought that the hydrogen atom was relatively well understood!

ITPA, DivSOL, May 2007: Coster et al Backup slides

Update on the UEDGE/SOLPS benchmark activity for edge fluid transport* Presented at the ECC Workshop April 20, 2007 San Diego, CA * Work performed under the auspices of U.S. DOE by ORNL and the Univ. of Calif. LLNL under contract Nos. DE-AC05-00OR22725 and W-7405-Eng-48. L.W. Owen, ORNL and T.D. Rognlien, LLNL X. Bonnin, Univ. Paris, and D.P. Coster, IPP Garching

Owen, Rognlien ECC April ‘07 Motivation US and EU 2D edge-plasma transport codes –mature, used widely to understand/ interpret tokamak edge –predict ITER divertor characteristics –benchmark is official ITPA Activity Integration of many plasma, neutral, and atomic physics processes included; nonlinear interactions abound Models are effectively the same and use exactly the same mesh

Owen, Rognlien ECC April ‘07 Strategy: a multi-stage “primacy hierarchy” to more efficiently uncover differences Carefully verify equations and coefficients UEDGE imports SOLPS solutions and fluxes (reverse process is also straightforward) Using SOLPS solution, UEDGE evaluates fluxes and sources; compare to SOLPS fluxes & sources After corrections, compare n i,g, T e,i, and u || (n g, n e,T e ) Simple primacy hierarchy Level 1 Level 2 Level 3 Eqns. Flux  n e (r) Source s p

Owen, Rognlien ECC April ‘07 Since the APS Nov. ‘06, a number of model differences have been identified and resolved 1.Convective energy transport coefficients differ: SOLPS typically uses (5/2)nTv  and (3/2)nTv || UEDGE typically uses 5/2 both places, or (3/2)  and (5/2) || 2.Hydrogen atomic physics rates are similar, but diff. matters: UEDGE uses data from Stotler, ‘96 SOLPS uses 3.Electron parallel thermal conductivity differs: UEDGE uses Spitzer/Braginskii SOLPS uses higher-moment Balescu coeff. - 35% larger(!) 4.Nonorthogonal mesh differences motivate first obtaining agreement on an orthogonal mesh

Owen, Rognlien ECC April ‘07 Similar, but different atomic physics rates can give significant variations in plate parameters Ionization and radiation loss rates depend nonlinearly on T e Variation in SOLPS results for different rate tables

Owen, Rognlien ECC April ‘07 Midplane profiles as of Nov. ‘06 are reasonably close

Owen, Rognlien ECC April ‘07 Divertor profiles as of Nov. ‘06 differ substantially

Owen, Rognlien ECC April ‘07 Present status: midplane profiles still fit well

Owen, Rognlien ECC April ‘07 Present status: divertor profiles are now much closer with the various corrections noted

Owen, Rognlien ECC April ‘07 Summary Verifying multi-component (integrated) models is a complex and time- consuming process Resolving discrepancies at a lower primacy level (i.e., fluxes, sources) is very useful Benchmarking process is a powerful way to uncover –more subtle programing errors –unrecognized, underappreciated model differences –sensitivity of solutions to model parameters EVEN “straightforward” (nonlinear) edge transport codes have many complexities that verification exercises help identify - very important