C-2U Physics Overview

C-2U & C-2W
neutral-beam injectors
mirror plug
plasma FRC (core) gun
GTC Code Description
The Gyrokinetic Toroidal Code (GTC) is a first-principles, integrated PIC simulation code, that has been established and well-verified in tokamak simulations.
See http://phoenix.ps.uci.edu/gtc for full feature list See poster P3.034, J. Bao, Tu 10am-12pm
Early flux-surface simulations of FRC
n Simulation model used: Gyrokinetic ions and drift-kinetic electrons, electrostatic, perturbative (delta-f), single flux surface i.e. separate core and scrape-off layer (SOL).
n Conclusions: FRC core strongly stable! Finite SOL turbulence. Both FLR and gradient-B effects stabilizing. Qualitative agreement with measured doppler backscattering.
D. P. Fulton et al, Phys. Plasmas 23, 012509 (2016). D. P. Fulton et al, Phys. Plasmas 23, 056111 (2016).
Field-aligned mesh + cylindrical coord
Recently implemented to allow cross-separatrix simulation.
Verification case: SOL simulation
Verification against flux-surface simulations of SOL, using new field-mesh implementation.
Artificially high instability drive: κ =κ =1 L = 10.0 R
ANC Code Description
A New Code (ANC) is a first-principles, integrated PIC code, based on GTC, but designed specifically for FRC magnetic geometry, to capture large-orbit ion dynamics, and cross- separatrix transport.
n Code physics features:
- Fully-kinetic or gyro-kinetic ions (Vlasov equation). - Gyro-kinetic or Boltzmann electrons.
- Electrostatic field solver (Poisson equation).
- Perturbative (delta-f) model.
- Cylindrical coordinates (spanning separatrix).
n Parallelization and Programming Model: - Hybrid message passing/threading scheme.
- Group decomposition of particles by MPI task, OpenMP parallelization of particle loops.
- Spectral decomposition of electrostatic Poisson solver into toroidal modes, by MPI task. Laplace matrix inversion by PETSc. Loop level OpenMP parallelization.
- Demonstrated scaling beyond 10,000 cores.
Analytic Verifications
n Using gyro-kinetic ions and Boltzmann electrons.
FRC full-geometry: linear
n Localized gradient drive case:
κn =0.5κTi ;Te=80eV
Peaked response at location of drive, with frequency near ion transit frequency.
Introduction
A New Code (ANC)
DC magnets
confinement vessel
scrape-off layer (SOL)
C-2U is an Advanced Beam-Driven Field-Reversed Configuration (FRC) at Tri Alpha Energy
n Campaign timeline: March 2015- March 2016
n Achieved5mssustainmentinJune2015,andshotsexceeding10ms,
limited by beam pulse duration.
n Significantly exceeds classical FRC confinement time scaling.
n Successor C-2W aims to explore confinement scaling in extended parameter regime. First plasma: mid-2017.
n For more details:
See adjacent poster by A. Necas
See http://www.trialphaenergy.com/research-library/
Motivation for a Turbulent Transport
Model of Compact Tori
n Advanced beam driven FRCs at TAE are macroscopically stable, and transport limited. A great success!
But we want to understand why.
n Similar favorable scaling seen in spherical tokamaks motivates collaboration with broader compact tori community.
n Must capture several physics features not resolved by existing models: high-beta, large ion Larmour radius compared to plasma size, cross-separatrix coupling, kinetic electron effects.
Strategy and Vision
n Develop high-fidelity turbulent transport model, using two codes: established high-performance kinetic suite GTC, and FRC specific, light weight ANC.
n Verify the model implementation against both analytic cases and with cross-code comparison.
n Validate the model against C-2W, NSTX. Is the formulation faithful to real experiments?
n Calibrate a faster ad-hoc tool that may be used in real time.
n Predictively compute particle and energy fluxes, that may be used as input for macroscopic transport codes.
n Broad gradient drive case:
κn = 0.5 κTi ; Te = 80 eV (Artificially strong drive.)
SOL generated turbulence extends to FRC core.
Development of a First-Principles Simulation Model of Turbulent Transport in Compact Tori
D. P. Fulton1, C. K. Lau2, J. Bao2, A. Kuley2, Z. Lin2, T. Tajima1, and the GTC2 and TAE1 Teams 1TRI ALPHA ENERGY, INC., P.O. Box 7010, Rancho Santa Margarita, CA 92688-7010
2University of California, Irvine, CA 92697 Gyrokinetic Toroidal Code
Simulations were performed using resources at the Oak Ridge Leadership Computing Facility, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE- AC05-00OR22725, and the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
S. Divertor S.Formation N.Formation N. Divertor
electrostatic potential vs. time
electrostatic potential
Z (R0)
n T P
0
driftwave dispersion
ion acoustic wave dispersion
n Single azimuthal mode: n=30 with ion temperature gradient drive.GK ions and Boltzmann electrons.
Saturates, similar to slab-like ITG, mechanism unexplored so far
FRC full-geometry: nonlinear
+1 (A.U.)
-1
R (R0)