Update on Self-Consistent Plasma Modeling of ARIES Baseline Design Points

1. Update on Self-Consistent Plasma Modeling of ARIES Baseline Design Points • A.D. Turnbull, • R. Buttery, M. Choi, L.L Lao, • S. Smith, H. St John • General Atomics ARIES Team Meeting Bethesda Md April 04 2011

2. Approach, Optimization, and Recent Progress • Proposed approach: • Outline • New features • Optimization procedure: • Physics optimization • Code linkages • Progress: • Reconstructed ARIES-AT Base configuration with added H-mode pedestal: • EFIT calculation reproduced 2000 equilibrium • Run ONETWO calculation to obtain profiles of ne, ni, Te, Ti, current density, and bootstrap current: • Using density and temperature profiles from Jardin and Kessel 2006 • Simulated LHCD and ICRF to make up the shortfall in current density • Main Results: • LHCD can provide up to 0.63 MA for ne(0) ~ 3 x 1020 m-3 • LHCD efficiency is poor at higher densities • Future plans

3. Proposal to Perform a Self-Consistent Analysis of ARIES Design Points • Similar analysis was done in the past for ARIES designs but: • Design points have been updated with improved Systems Code modeling • Understanding of physics issues has also evolved considerably: • Particularly pedestal modeling and interaction with the core • Analysis will involve: • Coupled equilibrium, transport, current drive, fuelling, and stability calculations to obtain a steady state solution • In a self consistent simulation using: • Latest core transport models • Coupled to edge pedestal models • The simulation would use the same tools as used to model DIII-D and FSNF, providing a consistent up-to-date set of models and tools across the spectrum of current and planned facilities

4. Proposal is Intended to Repeat Previous 2000 Effort For ARIES-AT With Improved Tools and Understanding • New optimized target configuration • Self consistent steady state solution • Transport model TGLF in place of GLF23: • Real shaped geometry instead of GLF23 shifted circle model • Self consistent H-mode pedestal: • Realistic pedestal height and width predictions with EPED1 • Full-wave Lower hybrid modeling • Improved resistive wall stability understanding: • Stabilization at low rotation • Role of error fields in braking at low rotation • New angular momentum transport models • Key technical issue is that core transport is stiff: • Largest leverage to improving confinement is from increasing pedestal height • Conversely, H-mode pedestal and ELM physics depends crucially on the heat and particle fluxes coming from the core

5. Optimization Procedure • Aim to use IMFIT to start with for the core loop of transport self consistently optimized with heating and current drive: • Re compute EFIT equilibria as needed • Incorporate a pedestal optimization: • EPED1 model to predict pedestal height and width given pedestal b • b optimization: • Initialize with bN = 5.7 • Check ideal stability with DCON or GATO? • Optimize to converge to maximum stable bN • q profile optimization: • Adjustment of q profile to improve stability and current drive potential • Step will need judgement rather than automation • Shape and size optimization: • Elongation, triangularity and aspect ratio • Size adjustments as needed

6. Physics Overview of Optimization Logic First guess: previous ARIES + pedestal, pass through H&CD & force balance Heat & current drive  Transport solutionONETWO & GENRAY to align profiles Re-EPED when b changes Re-EFIT at every stage b optimization: vary pressure to optimize stabilityDCON or GATO codes q profile optimization:to improve transport & stabilitychanges in H&CD deposition Shape optimization: vary elongation, triangularity & aspect ratio. Ultimately change size to ensure target performance is reached

7. Code Linkage Overview of Optimization Procedure • IMFIT code structure

8. Base Line ARIES H-mode Case From 2000 Study • ARIES H-mode cross section: • q profile:

9. Previously Optimized ARIES Lower Hybrid Heating and Current Drive Scenarios Using CURRAY • Aimed to drive non-inductive off-axis current in 0.8 <ρ< 1.0 • (S.C. Jardin, Fusion Engineering and design (2006)) • Two scenarios studied with different density: • 4 or 5 wave spectra of LH grills, each centered at a different N//, were determined to have relatively broad profile Scenario 1 Scenario 2 ne(0)=2.93×1020 m-3, Te(0)=26.3keV, Zeff=1.9 ne(0)=2.74×1020 m-3, Te(0)=28.2 keV, Zeff=2.0 133-09/MC/

10. Scenario 1 Studied Using Initial Density and Temperature Profiles From Jardin 2006 Fusion Engineering and Design • Modified to include H-mode edge density pedestal but Te set to be consistent with original pressure from 2006 published result ne(axis) = 5.0x 1020 m-3 T (keV) n (1013 cm-3) Te=TD=TT Electron Zeff=1.69 D and T Normalized toroidal flux Normalized toroidal flux

11. For Scenario 1 GENRAY Predicts 0.63 MA Total Driven Current From Lower Hybrid System Total grill1 grill2 grill3 grill4 grill5 LHCD driven current (A/cm2) GENRAY Driven current at higher density is much smaller Normalized toroidal flux

12. Additional Current Driven by ICCD System in Core • ICCD System: GENRAY • f = 96 MHz • N//=2.0 • P=4.7MW • θ = -15o LHCD ILHCD=0.63 MA Driven current (A/cm2) ICRF IICCD=0.11MA Normalized toroidal flux

13. Comparison of Driven Current Profiles from GENRAY with CURRAY Results Show Lower Current Driven • Lower current drive found than in 2006 paper probably due to additional density pedestal in new simulation GENRAY CURRAY Driven current (A/cm2) LHCD ILHCD=0.63 MA LHCD ILHCD=1.07 MA ICRF IICCD=0.11MA ICRF IICCD=0.15MA Normalized toroidal flux

14. Tools for Self Consistent Optimization of ARIES-AT Design Point Are in Place • Initial case set up: • Equilibrium with H-mode pedestal reproduced • Simulated electron and ion densities and temperatures (ONETWO): • Edge density pedestal produced consistent with equilibrium pressure pedestal • No temperature pedestal • Current drive from Lower Hybrid and ICCD systems reproduced using GENRAY: • Driven current shortfall compared with 2006 CURRAY results • Presumably due to H-mode pedestal

15. Future Steps Will Complete Self Consistent Optimization of ARIES-AT Design Point • Consistent pedestal included: • Both Temperature and density modified to reproduce H-mode pedestals • Consistent with equilibrium H-mode pressure pedestal • Equilibrium pedestal modified for consistency with peeling-ballooning (ELM) stability • EPED1 model to provide pedestal height and width for given pedestal bpol • Self consistent steady state scenario iteration: • Heating and current drive optimization using TGLF transport mode • Pedestal optimization for bpol consistent with transport simulation and EPED1 model • Iteration on b, q profile, and ultimately cross section: • Varied around design point as needed • Resistive wall mode stability considered

16. Backup slides

17. Case1 : Plasma Density and Temperature Profiles Based on C.E. Kessel’s Paper Ref) C.E. Kessel, Fusion Engineering and design (2006) Zeff=1.69 ne(axis) = 5.0x 1020 m-3 Electron Te=TD=TT Density (1013 cm-3) Temperature (keV) D and T Normalized toroidal flux Normalized toroidal flux

18. Case1 : High Density Profile with N//s and Powers of Scenario 1 Predicts Small CD Efficiency • Grill 5 with N//=5 seems to produce too much current near plasma edge GENRAY grill1 grill2 grill3 grill4 grill5 LHCD driven current (A/cm2) Total Total driven current by LH is 0.15 MA Normalized toroidal flux

19. LHCD Driven Current Profiles from GENRAY and CURRAY GENRAY CURRAY ILHCD=1.07 MA Case 2 ILHCD=0.63 MA LHCD driven current (A/cm2) Case 1 ILHCD=0.15 MA Normalized toroidal flux ne(0)=2.93×1020 m-3, Te(0)=26.3keV