PTRANSP

1. PTRANSP Predictive Upgrades for TRANSP

2. US Predictive Modeling Effort • R. Budny, S. Jardin, C. Kessel, L. P. Ku, D. McCune (PPPL). • H. St. John (GA). • D. P. Grote, L. Lodestro, L. D. Pearlstein, T. D. Rognlien (LLNL). • G. Bateman, F. Halpern, A. Kritz (Lehigh). • J. Carlsson (Tech-X).

3. PTRANSP Plan • Leverage TRANSP: • Well validated source models (NBI, alphas, ICRF, LH, ECH/ECCD). • Strong connection to experimental data. • Fusion Grid production facility. • Add predictive capabilities to TRANSP: • Robust transport equation solver. • Free boundary equilibrium. • Connection to edge model. • Reuse existing software to extent possible.

4. Design Principles - 1 • Reuse TRANSP and Fusion Simulation Project (FSP) software (to minimize costs). • Two driver configurations: • Free boundary: (TRANSP computes sources; analyzes free boundary code results). • Prescribed boundary: traditional TRANSP with: • New transport solvers (FSP Solver, GCNM-P). • New MHD equilibrium solvers (FSP, TEQ).

5. Design Principles - 2 • Modular design: interchangeability of critical parts (create/use NTCC modules): • Transport solvers. • MHD equilibrium solvers. • Sources. • Leverage TRANSP archives: • Access to experimental data for validation. • NTCC module provided for data access.

6. PTRANSP Schematic XPLASMA (FSP upgrade in progress) TRDATBUF (access to experimental data) Plasma State Solver Equilibrium Sources GCNMP TEQ TRANSP Sawtooth FSP-Sol FSP-Equ FSP-Src Porcelli-L Porcelli-P ESC Controller Edge Pedestal Lehigh TRANSP-based controller PPPL FSP-based controller Postprocessing (initially) Bootstrap Curr NCLASS Stability Analysis Edge Analysis Hirsh-Sig. DCON UEDGE PEST-2 DEGAS-2

7. Transport Solver Dilemma • Current predictive transport models (e.g. GLF-23) are very stiff. • Standard numerical integration methods suffer severe oscillations and instability. • Attempts to “smooth” GLF-23 directly significantly changes prediction results. • Therefore: serious solver upgrade effort. • GCNM-P (General Atomics) & FSP (PPPL).

8. Transport Solvers • GCNM – Globally Convergent Newton Method – ONETWO Solver (St. John, GA). • Very general stiff PDE integrator. • Use of Jacobian, O(n**2) execution cost. • FSP Solver (Jardin & Ku, PPPL). • “Local” Newton method– forward implicit use of dependence of transport on grad(Ti,Te,…). • O(n) but may not be as stable as GCNM.

9. The PTRANSP FSP Solver - 1This has been implemented in the full solver in the FSP: Without linearization With linearization • ITER simulation • Linearization of dependence of GLF-23 fluxes on temperature gradients. • Behavior reproducible in simplified single-T analytic transport model. • Caveat: DIII-D experimental data validation attempt– not yet fully stable. S. Jardin / L. P. Ku

10. The PTRANSP FSP Solver - 2Convergence Tests: 3 Newton iterations per timestep Base case: 1 Newton iteration per timestep Reduce timestep by 3 Double # of zones S. Jardin / L. P. Ku

11. Results for a 500s ITER run: ions electrons Chi Values for entire run Chi vs radius at 250s ions electrons Profiles at 250s Powers vs time S. Jardin / L. P. Ku

12. PTRANSP Progress - 1 • Predictive Solver Improvement (as shown). • Both FSP solver and GCNM at GA. • TRANSP Improvements: • Export of source calculation results. • Accommodation of free boundary equilibrium. • Modification of internal loop structure to allow import of stiff transport solver results. • Trdatbuf_lib NTCC module– access to TRANSP input data (experimental data).

13. PTRANSP Progress - 2 • LLNL’s TEQ free boundary solver module in TRANSP. • NTCC module standards with error handling enhancement. • Time dependent NSTX test results look good. • UEDGE/TRANSP coupling: • LLNL design and prototype in place. • Includes TRANSP/UEDGE data exchange schema.

14. PTRANSP Progress - 3 • NTCC PEDESTAL module– predictive boundary condition option. • Lehigh University team making direct modifications to TRANSP (in progress). • Prototype installation in BALDUR. • Experience with L to H transition dynamics.

15. PTRANSP’s Next Step – APS • Drive TRANSP with ITER free boundary simulation: • TRANSP provides heating and current drive. • TRANSP uses free boundary simulation predicted temperatures and equilibria. • Architecture compatible with density prediction but testing of this capability likely to be postponed. • TRANSP archive produced: • Available as input to UEDGE, linear stability solvers, etc.

16. Summary • The PTRANSP project will provide a community predictive transport code with state-of-the-art capabilities. • Like TRANSP itself, it will run as a Fusion Grid production service with world wide access. • Control options will be provided for prescribed boundary or free boundary operation. • Example of integrated ITER simulation with realistic sources by APS-2006.