halo current studies with self-consistent mhd simulations
TRANSCRIPT
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Disclaimer: The views and opinions expressed herein do not necessarily reflect those of the ITER Organization
Halo current studies with self-consistent
MHD simulations
for ITER 15 MA plasmas
F.J. Artola1, G.T.A. Huijsmans2, M. Lehnen1, I. Krebs3, A. Loarte1
1. ITER Organization, SCD, 13067 Saint Paul Lez Durance Cedex, France
2. CEA, IRFM, F-13108 Saint-Paul-Lez-Durance, France
3. Princeton Plasma Physics Laboratory, Princeton, New Jersey, USA
email: [email protected]
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Outline
โข The JOREK-STARWALL code for halo current modelling
โข 2D VDE benchmark with M3D-C1 and NIMROD
โข Understanding the 2D halo currents at ITER (15 MA/5.3T)
โข Prediction of the halo properties and B.C.s
โข Conclusions and future work
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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The JOREK-STARWALL code
for halo current modelling
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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The JOREK-STARWALL code for halo current modelling
JOREK
โข 3D non-linear MHD equationsโข Toroidal geometry
โข C1 Finite elements in poloidal plane
โข Fourier harmonics for ๐ directionโข Fully implicit time evolution
[Huysmans, NF2007]
STARWALL
โข Solves Maxwellโs equations and Ohmโs law
โข Greenโs function method
โข Thin wall approximation
[P. Merkel, 2015]
Implicit coupling through B.C.s for ๐ต
[Hoelzl, 2012]
๐ตtan = ิฆ๐ ๐ต๐, ๐
Tangential fieldNormal field Wall currents
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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The JOREK-STARWALL code for halo current modelling
EM boundary conditions
Reduced MHD, the E-field is
โซ has resistive wall free-boundary conditions
โซ Ideal wall BCs for poloidal E-field
โซ Poloidal currents calculated from
force balance
Strong assumption. Poloidal
currents do not decay in the
wall (infinite conductivity in
the poloidal direction)
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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2D VDE benchmark with
M3D-C1 and NIMROD
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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2D VDE benchmark with M3D-C1 and NIMROD
VDE based on the NSTX #139536 discharge
[I. Krebs, F.J. Art ola, C. Sovinec 2019]
Phase 1: Hot VDE until wall contact
Phase 2: Artificially triggered TQ
when the plasma becomes limited
(increasing ๐ โฅ )
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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2D VDE benchmark with M3D-C1 and NIMROD
VDE based on the NSTX #139536 discharge
[I. Krebs, F.J. Art ola, C. Sovinec 2019]
Phase 1: Hot VDE until wall contact
Phase 2: Artificially triggered TQ
when the plasma becomes limited
(increasing ๐ โฅ )
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents
at ITER (15 MA / 5.3T)
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Halo current different regimes
โซ Hot VDE regime
๐ผ๐ ~ cte during VDE
โซ Ideal wall regime
๐๐๐ฅ๐๐ = ๐(๐ผ๐) [D. Kiramov 2017 PoP]
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Parametric scan in CQ time
Plasma resistivity is prescribed as a flux function
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Scan in CQ time (scaling plasma resistivity profile)
๐ผ โ๐๐๐/๐ผ ๐0(%
)
๐๐ถ๐/๐๐ค (Log-scale)
โข Strong dependence on
CQ time to wall time ratio
(๐๐ช๐ธ/๐๐)
โข Maximum at ๐๐ถ๐/๐๐ค โ โ
Halo currents stabilize
VDE
โข Minimum at ๐๐ถ๐/๐๐ค โ 0
Eddy currents stabilize
VDE
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Scan in CQ time (scaling plasma resistivity profile)
๐ผ โ๐๐๐/๐ผ ๐0(%
)
๐๐ถ๐/๐๐ค (Log-scale)
โข Strong dependence on
CQ time to wall time ratio
(๐๐ช๐ธ/๐๐)
โข Maximum at ๐๐ถ๐/๐๐ค โ โ
Halo currents stabilize
VDE
โข Minimum at ๐๐ถ๐/๐๐ค โ 0
Eddy currents stabilize
VDE
CAT I I EM loads(up to 300 events
at 15 MA)
CAT I EM loads
(up to 3000 events
at 15 MA)
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Halo current different regimes
โซ Hot VDE regime
โข Cold halo
โข Hot halo
โซ Ideal wall regime
โข Cold halo
โข Hot halo
also discussed in [Boozer PoP 2013]
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Hot VDE + cold halo
โซ Currents are lost in wall and halo
faster than in plasma core
โซ Currents are re-induced in plasma
edge (large current densities)
โซ Big drop of edge safety factor
๐ผ๐ is largely conserved (๐๐ โ ๐2)
โซ Potential destabilization of
external kink modes
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Hot VDE + hot halo
โซ Toroidal current is transferred into
the halo region as the plasma
moves vertically
โซ Halo currents stabilize vertical
motion
โซ After stabilization, motion is given
by resistive decay of core + halos
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Hot VDE + hot halo
Halo resistivity scan
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Hot VDE + hot halo
Halo resistivity scanLarger ๐ผ๐(faster halo
decay)
Smaller halos
Less vertical stabilization
Faster VDE
Larger halo drive
Increase in halos
Regulating
mechanism for
๐ผโ๐๐๐,๐
๐ฐ๐๐๐๐,๐ depends weakly on ๐ผ๐
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Hot VDE + hot halo
Halo resistivity scan
But ๐ฐ๐๐๐๐,๐๐๐ depends strongly
on ๐ผ๐ through ๐๐
Finally increasing the halo
resistivity gives larger poloidal
halo currents
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Hot VDE + hot halo
Halo width scan
๐ฐ๐๐๐๐,๐ also has a weak
dependence on the halo width
Weak dependence through
๐๐ โ ๐๐/๐ผ๐
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Hot VDE + hot halo
Halo width scan
๐ฐ๐๐๐๐,๐ also has a weak
dependence on the halo width
Weak dependence through
๐๐ โ ๐๐/๐ผ๐
But ๐ผโ๐๐๐,๐๐๐ has a much
stronger dependence
through ๐๐. More effective
at narrow halos.
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Ideal wall regime
Halo resistivity scan
Halo currents also slow
down vertical motion
๐ฐ๐๐๐๐,๐ is also not
linear in ๐ผ๐(self-regulating
mechanism)
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Understanding 2D halo currents at ITER (15 MA / 5.3T)
Ideal wall regime
Halo resistivity scan
๐๐ and ๐ฐ๐๐๐๐,๐๐๐depend strongly on ๐ผ๐
The poloidal halo fraction (HF) is a factor 5-10 smaller than in the
hot VDE regime
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Prediction of the halo properties
and B.C.s
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Prediction of the halo properties and B.C.s
โซ Temperature dependence for resistivity and
parallel conductivity
โซ Ohmic heating term in energy equation
โซ Bohmโs boundary condition
โซ Sheath heat flux B.C.
Currently working VDE model
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Prediction of the halo properties and B.C.s
โซ Neutrals, recycling and atomic processes (key for
density evolution, now ๐๐(๐))
โซ Impurity evolution and radiation
โซ Limit on ion saturation current (๐ฝ โค ๐ฝ๐ ๐๐ก ), (in progress)
Missing ingredients of VDE model
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Prediction of the halo properties and B.C.s
โซ Upward ITER VDE, 15 MA / 5.3 T
โซ Post-disruption equilibrium (๐ฝ๐ = 0.05)
โซ Flat J-profile after helicity mixing (from DINA)
โซ No radiation (ohmic heating re-heats the plasma)
โซ Realistic Spitzer and Braginskii values for ๐0 and ๐ โฅ0
โซ ๐ โฅ = 4 m2/s, ๐พ๐ โ๐๐๐กโ = 8, ๐๐ = ๐๐, ๐๐ค = 0.5 s
Simulation setup
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Prediction of the halo width and B.C.s
ฮ๐กsim~0.48 s
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Prediction of the halo width and B.C.s
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Prediction of the halo width and B.C.s
Density scan (Zaxis=2.0 m)
Poloidal angle along the wall
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Conclusions and future work
JOREK / M3D-C1/ NIMROD benchmark: good agreement for 2D halo currents
2D VDEs ITER studies
โข Hot VDE limit (๐๐ค โช ๐๐) largest halo fractions (HFmax~50 %)
โข Ideal wall limit (๐๐ โช ๐๐ค) smallest halo fractions (HFmax < 10 %)
โข ITER mitigated disruptions (HFmax ~ 10 โ 25 %)
โข Self-regulating mechanism for ๐ผhalo,๐ , weak dependence on ๐โ โ ๐คโ/๐โ
โข Poloidal halo currents depend strongly on ๐๐ (๐ผhalo,pol = ๐ผhalo,๐ /๐๐), which
decreases at shorter ๐โ
โข Maximum HF at (๐๐ค โช ๐โ < ๐๐) with small halo widths
โข Influence of initial ๐๐ and core resistivity profile?
F.J. Artola, 7th annual Theory and Simulation of Disruptions Workshop
ยฉ 2019, ITER Organization
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Conclusions and future work
Prediction of halo width and temperature
โข Current VDE model including
โช Realistic resistivities and conductivitiesโช Energy balance in the halo: sheath losses and ohmic heating
โช Sheath B.C.s
โช Imposed density ๐ ๐
โข Still missing
โช Density evolution with neutrals and atomic physics
โช Impurity radiation
โช Limit on current density (ion saturation current)
โข Results for hot VDEs show
โช Large halo widths (for Jphi) at low temperature (on going density scans)