The swim slow mhd campaign overview mhd plans and accomplishments
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The SWIM “Slow” MHD Campaign: Overview, MHD Plans and Accomplishments. D. D. Schnack, T. Jenkins, J. Callen. C. Hegna. C. Sovinec, F. Ebrahimi University of Wisconsin, Madison, WI, E. Held, J.-Y. Ji, Utah State University, Logan, UT, S. Kruger, J. Carlson, Tech-X Corp., Boulder, CO.

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The SWIM “Slow” MHD Campaign: Overview, MHD Plans and Accomplishments

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The swim slow mhd campaign overview mhd plans and accomplishments

The SWIM “Slow” MHD Campaign: Overview, MHD Plans and Accomplishments

D. D. Schnack, T. Jenkins, J. Callen. C. Hegna. C. Sovinec, F. Ebrahimi University of Wisconsin,

Madison, WI, E. Held, J.-Y. Ji, Utah State University, Logan, UT, S. Kruger,J. Carlson, Tech-X Corp., Boulder, CO


What to get done this week

What to Get Done this Week

  • Begin dialog between MHD, RF, and CS researchers on “Slow MHD” problem

  • Provide update on MHD plans and progress

  • Get feedback from RF/ CS folks

  • Agree on technical plan and timeline

  • Produce report for PM addressing the following issues:


0 what problem are we trying to solve o 1

0. What Problem are We Trying to Solve? O(1/)

  • Demonstrate proof of principle of stabilization of resistive islands with some RF model?

  • Demonstrate coupling between RF and MHD physics codes?

  • Demonstrate proof of principle of stabilization of resistive islands with coupled RF/MHD models?


The swim slow mhd campaign overview mhd plans and accomplishments

  • Demonstrate stabilization of pre-existing (finite amplitude) NTM island with RF?

  • Demonstrate seeding, growth, and eventual RF stabilization of NTM island?

  • Understand physics of island stabilization (inner or outer regions)?

  • Evaluate efficacy of various experimental RF deposition scenarios?


The swim slow mhd campaign overview mhd plans and accomplishments

  • Determine how much RF power is required for ITER?

  • All of the above? (Do we have the resources?)

  • Some of the above? (Must match to resources)

  • None of the above? (Then, what?)


What are minimum requirements to satisfy sow o 1

What are MINIMUM Requirements to Satisfy SOW? O(1)

  • What is the technical plan for meeting this goal? Is it reasonable?

  • What resources are required, and are they available?

  • What is the timeline for meeting this goal? Is it reasonable?


What is required to do the problem better o

What is Required to do the Problem “Better” O()

  • Reasonable technical plan?

  • Resources?

  • Reasonable timeline?


What is required to do the problem right o 2

What is Required to do the Problem “Right” O(2)

  • Reasonable technical plan?

  • Resources?

  • Reasonable timeline?


Rf mhd dialog issues 1

RF/MHD Dialog Issues - 1

  • Is the MHD plan reasonable?

    • What information does MHD want from RF?

    • What information can MHD give to RF?

  • What is the RF physics plan?

    • What information does RF want from MHD?

    • What information can RF give to MHD?

  • What RF codes are involved?

  • Are substantial modifications to RF codes required?

    • Island geometry?


Rf mhd dialog issues 2

RF/MHD Dialog Issues - 2

  • Are there algorithmic issues that might affect numerical stability?

    • Can they be mitigated?

  • How do we envision the RF/MHD code coupling?

    • Strong coupling? (RF called from MHD)

    • Weak coupling? (Separate code execution)

  • What is the most efficient means of passing data?

  • Are there any CS obstacles?

    • Can they be mitigated?


Technical approach

Technical Approach

  • Recognize that problem is additive

    • Modified Rutherford equation:

  • Can approach problems in parallel

  • Don’t need to get NTM “right” before attacking RF

    • Can start with RF/tearing coupling


Implementation plan mhd

Implementation Plan (MHD)

  • I: Add RF source module and interface to NIMROD

  • II: Define “simple” RF closure (force on electrons)

  • III: ad hoc analytic source term (force on electrons) in Ohm’s law

    • Tearing mode stabilization => proof of principle

  • IV:Evolutionary equation for RF source

  • V:Revisit NTM calculations

    • Kruger/Hegna heuristic closure?

    • Collisional Braginskii nonlinear electron viscous stress tensor?

  • V: Couple to RF codes

  • VI: Throughout, refine theoretical closure models and implementations


Physics issues kinetic equation

Physics Issues (Kinetic Equation)

  • How to incorporate RF effects into fluid models?

  • Start with kinetic equation

Quasi-linear diffusion tensor

Output of RF codes


Physics issues closures

Force on electrons

Heating

Physics Issues (Closures)

  • Take moments

  • RF sources modify fluid equations

RF produces no particles

Existing closures are also modified!

RF closures


Information rf mhd

Information (RF <==> MHD)

  • Chapman-Enskog-Like theory can produce closures, i.e.,

Maxwellian

  • Moments can be computed by numerical integration in velocity space once DQL is specified

  • DQL(v) produced at each mesh point by RF codes


Rf mhd coupling

RF/MHD Coupling

  • NIMROD produces n(r,t), T(r,t), B(r,t) => RF codes

  • RF codes produce DQL(r,v) on rays => interpolated to NIMROD grid

  • NIMROD integrates in v => moments of Q => force on electrons and modified moments

  • NIMROD produces n(r,t+t), T(r,t+t), B(r,t+t)

  • t +t => t

  • Go to 1

RF module. Presently has model Jrf(r,t).


Issues

Issues

  • What are the most appropriate fluid moments?

  • What is the most efficient way to compute them?

  • Are there any new numerical stability issues?

  • Can NTM growth and saturation be demonstrated?

  • How often does RF need to be updated?

  • How should data be passed between MHD and RF codes?

  • Do RF codes need to be modified (islands, etc)?

  • Do we need to go beyond ECCD?

  • ???


Mhd results

MHD Results

  • Electron force localized in poloidal plane, toroidally symmetric

  • Current spreads over flux surfaces

  • Demonstrated in cylinder and DIII-D geometry


Tearing mode stabilization by rf in diii d geometry tom jenkins

Rutherford

Linear

Tearing Mode Stabilization by RF in DIII-D geometry(Tom Jenkins)


Mhd status

MHD Status

  • Closure procedure defined

  • Spitzer-like problem formulated

  • Data required from RF modules defined

  • General source modules and interfaces added to NIMROD

  • Simple axi-symmetric source implemented

  • Stabilization of 2/1 resistive tearing mode demonstrated in DIII-D geometry

  • Conversations with RF physicists beginning


More about the workshop

More About the Workshop

  • Informal!

  • Purpose is to have a dialog, not to impress with latest results!

    • 2-way communication

  • Allow plenty of time for discussion

  • Discussion leaders: Take notes!

  • Thursday morning: Produce coordinated technical plan and timeline

  • Will all be input for report to PM


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