H.E.A.T.�UPDATE
T. Looby, M. Reinke, A. Wingen
08/31/2020
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Demonstration
NSTX-U PFC Analysis
HEAT Overview
HEAT Roadmap
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Introduction to HEAT capabilities
Determination of NSTX-U operational space w/ respect to PFCs
HEAT architecture and module descriptions
Upcoming modules
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Demonstration
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NSTX-U graphite Plasma Facing Components (PFCs) are thermally limited at 1600°C
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Graphite has a sublimation limit of ~ 1600°C
NSTX-U Recovery PFC working group understood this limit, but lacked the tools to check physics scenarios against PFC sublimation
PFC temperature can constrain physics scenarios
8 MW/m2 heat flux applied to SGLR6510 surface for 5s pushes material past sublimation limit
Result above from PFC WG Memo 016 pg. 4: https://nstx.pppl.gov/DragNDrop/Working_Groups/PFCR/memos/PFCR-MEMO-016-00.pdf
First, an example from recent events at NSTX-U...
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OutBoard Divertor (OBD) tile has complicated 3D geometry and is aligned to conical surface
Note step between castellations (fish-scale)
conical surface
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OBD Tile
OBD
IBDV
CSAS
IBDH
NSTX-U Lower Divertor
Note: prototype
Stark contrasts in heat footprint can arise from discharges with identical plasmas
What is the source of the difference in heat loads between these two cases?
Identical:
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Case 1
Case 2
Note the shadows
Note the shadows
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Change of perspective to find the difference...
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View from center stack
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View
Small changes to PFC geometry can have a significant impact on heat flux footprint
‘Fish-scale’ step size: �0.0762 mm
‘Fish-scale’ step size:� 0.508 mm
Change of 0.4318 mm in step size drastically alters HF footprint!
This corresponds to a mass Δ of ~5g carbon per tile!
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View from center stack
View from center stack
Case 1
Case 2
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View
View
Fish-scales create magnetic shadows and ‘reassign’ power to new locations
Case 1 uses fish scale to redeposit power more uniformly
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Case 2
Case 1
B
Changing heat flux footprints on PFCs has thermal consequences...
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Case 1
Case 2
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Fish-scale size:
0.508 mm
Peak Heat Flux:
15.6 MW/m2
Sublimation T reached @ ~1.25s
Fish-scale size:
0.0762 mm
Peak Heat Flux:
17.5 MW/m2
Sublimation T reached @ ~1s
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Results shown for PSOL, LowerOuter = 4 MW using PFC WG Memo 010 Case 1.1 (g116313.00850.NfHz0+_0)
Time varying output simulated with HEAT�Diverted Example: 204118@300-1000ms
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30° Section of Lower Divertor
HEAT Overview
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HEAT couples disparate computational modules into a single integrated (open source) python suite
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CAD
HTML GUI
MHD
HEAT FLUX SIMULATOR
FVM
STP / CAD
(from Engineer)
EFIT (MDS+),
GEQDSK,
M3DC1*,
SIESTA*
grid
EQ
q(x,y,z,t)
PHYSICS
T(x,y,z,t)
Scalings, Models, �etc.
* = partially implemented
Material Properties
HEAT has a full-blown parametric CAD program built into the CAD python module
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FreeCAD is an open source parametric CAD modeler. https://www.freecadweb.org/
HEAT’s python wrapper uses FreeCAD for:
HEAT converts parametric surfaces into STL meshes in the CAD module
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Here, maximum mesh edge length of 3mm
A point cloud of points is generated using each mesh center for calculations
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Heat flux is calculated at divertor surface points incorporating flux expansion and incident angle
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Field line incident angle effect
Flux expansion effect
User defined heat flux profile �(here as function of poloidal flux)
Scaling coefficient
Divertor heat flux
Magnetic field is calculated at each point
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Subset of B field vectors
Incident angle effect is calculated at each point
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B
Poloidal flux (𝜓) is calculated at each point, then q|| calculated from user defined profile
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OBD
Heat flux is calculated across divertor surface by combining all terms
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Easy to identify shadowed points are determined using backface culling
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Backface culling (BC) is a technique from computer graphics and rendering
BC used in HEAT to identify potential loaded faces for further checking
Face is culled when:
User defined +/- 1.0
for each PFC
A. Wingen’s MAFOT code traces field lines from mesh points to identify shadowed faces
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Intersection face
Field line trace
Shadowed point
upstream tile
downstream tile
gap
Shadowed point
Shadowed points identified by checking for intersections with other mesh elements
upstream tile
downstream tile
A. Wingen’s (ORNL) MAFOT code can also be used to illustrate heat loading in toroidal gaps
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Note the heat in the gap between tiles
qGAP ~ 2.8 MW/m2 (...!)
HF Resolution = 3 mm, Wall Clock Time = 483 s
Pin = 2.8 MW, Pout = 2.903 MW
Memo 010 Case 1.21 (g116313.00851.NfHz0+_k)
OBD
IBDH
OBD
IBDH
A. Wingen’s (ORNL) MAFOT code can also be used to illustrate heat loading in toroidal gaps
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HEAT uses openFOAM for Finite Volume Methods (FVM) and Computational Fluid Dynamics (CFD)
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openFOAM is an open source package for:
https://www.openfoam.com/releases/openfoam-v1712/
HEAT uses openFOAM to:
ParaVIEW is under the hood of HEAT’s powerful visualization algorithms
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ParaVIEW is an open source package (originally from LANL) for:
HEAT uses ParaView to:
Global water surface temp by LANL
openFOAM “motorbike” tutorial by NVIDIA
Images from ParaVIEW website gallery
HEAT is accessible to anyone on the LAN via it’s HTML5 GUI built with DASH / plotly
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HEAT has a wide domain of tokamak physics modules in the requirements
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Completed:
Not Yet Completed:
* = outside PhD scope
In Progress:
NSTX-U PFC Analysis
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Memo 010 Case 1.1 is a static discharge with desired pulse length of 5s
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2.8MW
2.8MW
0.7MW
0.7MW
Power Sharing
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Pinj = 10.0 MW
frad = 0.3
BT = 1T
Ip = 2MA
∠ @ peak = 0.86°
Profile:
Gaussian Spreading
λq = 1.903mm (Eich)
S = 0.914 mm (Makowski)
Max Mesh Edge Length: �3 mm
OBD
IBDV
CSAS
IBDH
Psum,inner = 0.701 MW
Psum,outer = 2.881 MW
Memo 010 Case 1.1 can NOT be run for the 5s desired steady state duration!
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Tpeak = 2533 K
~2.41s
Probe locations
OBD
IBDH
Strike point sweep frequency (fsweep) can be used to reduce Tpeak on outer divertor tiles
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Memo 010 Case 2 Scan 4 (g135111.00500_k2.<#>), Pinj = 10MW, frad = 0.3, BT = 1T, Ip=2MA, DN, ResHF = 2.5mm
Strike point sweep frequency (fsweep) can be used to reduce Tpeak on Outboard Divertor (OBD)
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Memo 010 Case 2 Scan 4 (g135111.00500_k2.<#>), Pinj = 10MW, frad = 0.3, BT = 1T, Ip=2MA, DN, ResHF = 2.5mm
Δt until limit:
0.1Hz@1.55s
1.0Hz@4.95s
5.0Hz@>5s
3-5 Hz keeps tile within limits
Strike point sweep frequency (fsweep) can be used to reduce Tpeak on Inboard Divertor Horizontal (IBDH)
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Memo 010 Case 2 Scan 4 (g135111.00500_k2.<#>), Pinj = 10MW, frad = 0.3, BT = 1T, Ip=2MA, DN, ResHF = 2.5mm
Peak T:
4064K @ 0.1Hz
3449K @ 1.0Hz
2796K @ 5.0Hz
Even at 5Hz sublimation occurs!
~0.92s
HEAT has a built in gFile interpolator / stitcher that can be used to generate strike point sweeps
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fsweep = 0.1 Hz
Originally only 5 geqdsk steps
HEAT tool interpolates geqdsk to 50 steps
Strike point sweep frequency (fsweep) can be used to reduce Tpeak on Center Stack Angled Surface (CSAS)
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Memo 008 TSGTT 204a (g204062.01250_TT_2-04_<#>), Pinj = 2MW, frad = 0.3, BT= 0.75 T, Ip = 800kA, LSN, ResHF = 2.5mm
Strike point sweep frequency (fsweep) can be used to reduce Tpeak on Center Stack Angled Surface (CSAS)
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Memo 008 TSGTT 204a (g204062.01250_TT_2-04_<#>), Pinj = 2MW, frad = 0.3, BT= 0.75 T, Ip = 800kA, LSN, ResHF = 2.5mm
Lower CSAS Tile
Note: Tlimit not violated for this case
Time varying output simulated with HEAT�Limited Example: 204118@50-250ms
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PSOL = 3.0 MW
Profile Type: Limiter
λqN=3mm
λqF=5mm
Max Mesh Edge Length: 5 mm
Looking for more cases or discharges to run through HEAT
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Cases that demonstrate:
Was the 'intent' of the PFC requirements captured by the tiles?
HEAT Roadmap
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ROAD MAP
(NEAR TERM)
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Version 1.0 pushed to github
Aug 2020
Ion orbits physics module complete
Detachment physics module complete
3D Plasmas, M3DC1, ELMs, module complete
Nov 2020
Jan 2021
May 2021
Next module under development is ion gyro orbits
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Edge Loading
Heat in gap
J. P. Gunn et al., “Surface heat loads on the ITER divertor vertical targets,” Nucl. Fusion, vol. 57, no. 4, p. 046025, Apr. 2017.
Questions?
If you think HEAT could benefit your research, reach out! �We are seeking collaborators and contributors.
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