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The Center for Multiscale Plasma Dynamics

The Center for Multiscale Plasma Dynamics. Maryland UCLA Princeton MIT Texas Dartmouth Berkeley Michigan General Atomics. The Broad Context. DOE announced a national competition for two Fusion Science Centers in 2004. There were a dozen or so serious contenders.

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The Center for Multiscale Plasma Dynamics

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  1. The Center for Multiscale Plasma Dynamics Maryland UCLA Princeton MIT Texas Dartmouth Berkeley Michigan General Atomics CMPD

  2. The Broad Context • DOE announced a national competition for two Fusion Science Centers in 2004. There were a dozen or so serious contenders. • We proposed to work on plasma physics problems for which the evolution of dynamics on disparate spatio-temporal scales is tightly coupled • We know how to derive first-principles models for some critical aspects (turbulence, reconnection) of various problems -- but how can we get at the big picture (transport, system evolution)? • What do experiments tell us we need to know? And how do we come to understand experimental data? • Maryland and UCLA won this compeition, with funding from 2004-2009 and the possibility of a five-year extension. Total 5-year funding is approximately $7.5 million. CMPD March 2005

  3. Why a Center for Multiscale Plasma Dynamics? • The development of multiscale techniques in plasma physics has been inhibited by the traditional programmatic boundaries between macro- and micro-scale physics • The Center brings together three key elements: • Applied mathematics • Powerful new techniques are revolutionizing the approach to multiscale problems • Traditional adaptive mesh refinement techniques cannot address the huge separation in time scales and the range of physics phenomena • Need new ideas, like equation-free projective integration and patch dynamics • Computation/theory • Members of Center played a central role in developing the current physics understanding of microturbulence and reconnection • Tactical advantage: we can build on these tools and theoretical insights • Experiment • Experimental observations motivate and guide development of physics models • Benchmarking is crucial to ensure that dominant physical processes are included • Basic experiments in simple geometries - LAPD, VTF, LDX • Complex experiments in the most advanced fusion facilities - DIII-D, NSTX, JET, C-Mod CMPD March 2005

  4. Annulus, Islands and TurbulenceMultiscale for NTMs and Sawteeth Space Scales. Island size > 1cm Turbulent Eddy size ~ 1cm Electron Layer ~ 0.025cm Banana width ~ 1cm Eigenfunction width ~ 1m Timescales - NTM Turbulent correlation time ~ 10s Transport relaxation time across island region ~ 1ms Island rotation times ~1ms Island growth time >1s Critical Kinetic Physics Bootstrap current Turbulent vsparallel transport CMPD March 2005

  5. The Transport Problem • Self-consistent modeling of fusion plasma evolution • Small scale turbulence (structures << device size) • Stiff, offset-nonlinear transport fluxes well-established • Self-consistent heating in next-generation machines leads to strongly coupled system; small scale dynamics determines system evolution • Brute force calculations require > 10,000 petaflops (SCALES report) These structures are ~ 1 ion gyroradius across, compared to a machine size of more than 1000 ion gyroradii CMPD March 2005

  6. Transport: A multiscale challenge • Use patch dynamics scheme of Kevrekidis and Gear • Use a few thin annular domains (flux tubes) • Compute fully nonlinear microscale dynamics in this region • Evolve coupled flux tubes on transport time scale • Requires finding gradient as a function of flux (done) CMPD March 2005

  7. The Sawtooth Crash Problem • Periodic instability of the core of tokamak plasmas • Loss of central plasma confinement • Times scales of 50-100 sec are much shorter than the resistive MHD theory • Central value of q remains below unity implying incomplete reconnection of the core magnetic field • But core energy is expelled without reconnection. Why? • Not seen in MHD model Yamada, et al., 1992 CMPD March 2005

  8. Sawtooth: A multiscale challenge • Critical non-MHD physics • Fast crash • Coupling to dispersive kinetic Alfven waves • Anomalous resistivity • Partial reconnection • Development of kinetic turbulence in steep gradients around x-line • Propagation of turbulent front into core • Production of energetic particles CMPD March 2005

  9. Education Aim: To attract and train a new cadre of plasma physicists • > 70% of center money is to be spent on new talent • Gap in training at the advanced student/post-doc level • Winter school on advanced plasma theory every year (2005 in conjunction with the IPAM workshop) • Include the worldwide community • Gyrokinetics, turbulence, HED plasma theory, etc. • An event where the next generation of plasma and fusion scientists meet and interact • Develop an advanced curriculum • video conference lectures and seminars • review articles and books CMPD March 2005

  10. Effort Summary(budget includes 15% matching) Ambitious center scientific program leverages existing efforts CMPD March 2005

  11. Budget overview(includes 15% matching) CMPD March 2005

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