Princeton Plasma Physics Laboratory Highlights of Theory Accomplishments and Plans

1. Princeton Plasma Physics Laboratory Highlights of Theory Accomplishments and Plans Department of Energy Budget Planning Meeting March 13-15, 2001

2. Selected Theory Research Highlights • MHD and Particle Codes Made Major Contributions to Stellarator Design: Optimization of Stability, Transport and Constructability. • Other Innovative Concepts also studied: Spherical Tori, Advanced Tokamaks, FRC. • Main Theory Groups: MHD (Jardin); Turbulence and Transport (Hahm); Waves/Energetic Particles (Cheng); Non-Axisym. Systems (Reiman); IFE & Non-MFE Plasma Science (Davidson); Laser-Plasma Interactions (Valeo) • Lead role in successfully establishing Plasma Science Advanced Computing Institute (PSACI). PPPL has helped establish stature/visibility of Plasma Science in Advanced Scientific Computing community. • Energetic particles: theory of RF-driven rotation.

3. Examples of “Experiment/Theory” Collaborations • Experiment/Theory investigations of shear-flow suppression of turbulent transport [K. Burrell (DIII-D) with T. S. Hahm] • ICRF-induced rotation and ripple loss in Tore Supra [X. Garbet, et al. (Cadarache) with R. White] • Collaborative development of RWM analysis capability for DIII-D with GA & Columbia U. [M. Chance -- @ GA for one year] • Highly productive collaborations on international facilities (JET, JT60U, LHD, ASDEX, ..) addressing Turbulent Transport (Rewoldt, Hammett); MHD (Manickam, Monticello); Energetic Particles (Cheng, Gorelenkov, White); Boundary Physics (Stotler).

4. Selected Technical Milestones for FY 2002 • Obtain technical results from nonlinear gyrokinetic full torus code (GTC) including electron dynamics (September, 02). • Compare DEGAS2 modeling results with analysis of experiments with lithium surfaces (September, 02). • Compare measured parametric dependencies of fluxes in NSTX with gyrokinetic-continuum and/or gyrofluid codes (September, 02). • Complete implementation of “virtual fluctuation” diagnostics in gyrokinetic, gyrofluid/GK-continuum nonlinear turbulence simulations (September, 02).

5. Selected Technical Milestones for FY 2003 • Obtain GTC simulation results for the generation and damping of zonal flows in stellarators to elucidate the effects due to the lack of a symmetry direction (September, 03). • Improve the NOVA-K code to include the effects of plasma flow and pressure anisotropy for tokamaks (September, 03). • Compare measured fluctuation spectra in NSTX core with predictions from nonlinear gyrokinetic and/or gyrofluid/GK-continuum codes using “virtual diagnostics” developed in FY02 (September, 03). • Provide capability for realistic simulation of a nonlinear resistive MHD disruptions for NSTX (September, 03).

6. Microturbulence & Transport Highlights • 3D Global Gyrokinetic Particle Simulation of Collisional Damping of Zonal Flow and Size Scaling (Lin et.al.) • bursting behavior seen in experiments • interplay between turbulence, flow damping and collisions • Simulation of Shear Alfven Waves in Gyrokinetic Plasmas • Split-Weight df Scheme (Lee et al.) • Hybrid Scheme w/ kinetic closure (Lin and Chen) • Other algorithmic improvements • Enhanced GTC: Self-consistent Radial Electric Field for neoclassical transport in 3-D Stellarators (Lewandowski et al.)

7. Progress in Stellarator Theory • New optimizer uses PIES code to heal magnetic islands in 3D configurations. New numerical diagnostic for accurate measurement of small changes in island widths. • Optimized physics design identified for NCSX, considering wide range of physical effects.New design has 50% better neoclassical confinement, simpler coils with lower current density, improved flux surface quality. • Code for designing stellarator coils that preserve finite-b equilibrium flux surfaces developed & applied to NCSX design • Flexibility and robustness studies have explored ability of proposed NCSX coils to produce stable plasma configurations with good quasi-axisymmetry for variety of current and pressure profiles.

8. Stellarator Theory Plans • Documentation for NCSX Physics Validation Review (end of March) • Incremental improvements in physics properties and flexibility of NCSX configuration thereafter. • GTC code modifications to allow drift wave simulations in stellarator geometry. • PIES calculations of neoclassical effects on stellarator island formation to be initiated. • Global optimization scheme being developed circumvents problem of trapping in local maxima of target function. • Improved optimizer will enhance capability for making configuration improvements. • Will also be applied in free-boundary optimizer to design experiments for addressing key physics issues.

9. Energetic Particle Physics Highlights • TAEs can be highly unstable in NSTX and fast ion loss due to TAEs can be large and comparable to prompt losses. • Two new types of TAE modes were observed with frequency chirping and are identified as Resonant TAE modes (R-TAE). • Ballooning modes can be stabilized by kinetic effects of trapped electrons finite ion Larmor radii in NSTX with the critical beta enhanced by at least a factor of 5 over MHD values. • Energetic circulating ions are found to have a stabilizing effects on fishbone modes at high beta in spherical tori. • Transport of energetic ions during relaxation oscillations in spherical tokamaks depends on beta. • Nonlinear simulations of fishbone using the MH3D-K code showed MHD nonlinearity to be as important as particle nonlinearity. • Theory to explain observed plasma rotation during ion cyclotron heating even though this heating process introduces negligible angular momentum.

10. OTHER PPPL THEORY RESEARCH AREAS • Wave-Particle Interactions (Energetic Particles) -- e.g, seminal contributions such as TAE with strong theory/exp. Impact • Boundary Physics (Neutrals Modeling) -- e.g., DEGAS-2 as powerful new tool for divertor/edge analysis with excellent MPP compatibility • PPPL Theory plays key role in Heavy Ion Fusion Virtual National Laboratory (HIF-VNL) with LBNL and LLNL. • lead positions in HIF-VNL: Deputy Director (R. Davidson) & Deputy Head of Theory & Modeling (W. Lee) • Advanced analytical and numerical modeling of intense beam propagation and beam-plasma interaction • Laser-Plasma Interactions -- for ICF & Plasma-based Accelerators {Presidential Early Career Award for Scientists & Engineers to G. Shvets, April 11, 2000}