The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material...
Transcript of The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material...
![Page 1: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/1.jpg)
1 Sherwood Whyte April 2012
The Future of Boundary Plasma and Material Science
Dennis Whyte Plasma Science & Fusion Center, MIT, Cambridge USA
Director, Plasma Surface Interaction Science Center (psisc.org)
APS Sherwood Meeting of Fusion Theory Atlanta, April 2012
![Page 2: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/2.jpg)
2 Sherwood Whyte April 2012
Outline
• Defining the Challenge for Fusion Energy Boundaries
• The Multiscale Science of Plasma-Material Interactions Ø Processes, measurement and exposure
• Developing a dimensionless parameter “wind-tunnel” for fusion PMI
• Critical needs for boundary plasma understanding & prediction.
![Page 3: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/3.jpg)
3 Sherwood Whyte April 2012
Outline
• Defining the Challenge for Fusion Energy Boundaries
• The Multiscale Science of Plasma-Material Interactions Ø Processes, measurement and exposure
• Developing a dimensionless parameter “wind-tunnel” for fusion PMI
• Critical needs for boundary plasma understanding & prediction.
COMMENTS ���
- Boundary/PMI science is too broad to be inclusive of every topic of interest���
- The following comments reflect my personal views on critical paths forward in both experiment, theory and computation
![Page 4: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/4.jpg)
4 Sherwood Whyte April 2012
Outline
• Defining the Challenge for Fusion Energy Boundaries
• The Multiscale Science of Plasma-Material Interactions Ø Processes, measurement and exposure
• Developing a dimensionless parameter “wind-tunnel” for fusion PMI • Critical needs for boundary plasma understanding & prediction.
![Page 5: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/5.jpg)
5 Sherwood Whyte April 2012
Demo constants: T > 1000K, Pheat/S ~ 1 MW/m2 for 30,000,000 seconds.���
ITER falls far short ITER ARIES-AT ARIES-CS ARIES-ST
Duration (s) 400 3x107 3x107 3x107
Ambient T (K) 400 1300 1000 900 R (m) 6.2 5.2 7.8 3.2
R/a 3.1 4.0 4.6 1.6
Pfusion / S (MW/m2) ~1 4.3 2.6-5.4 4.9
P/S (MW/m2) 0.21 0.85 0.7-1.1 0.99 P/Adiv (MW/m2) 2.4 10 >20 20
Adivertor / S ~ 5-10%
![Page 6: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/6.jpg)
6 Sherwood Whyte April 2012
Boundary/PMI Science “Gap” to FNSF/Reactors is More like a 3-D Chasm
![Page 7: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/7.jpg)
7 Sherwood Whyte April 2012
Boundary/PMI Science “Gap” to FNSF/Reactors is More like a 3-D Chasm
Why these axes?
![Page 8: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/8.jpg)
8 Sherwood Whyte April 2012
The PMI Science Challenge & Fusion Viability are inextricably linked
Fusion Viability���
1. Average neutron���power loading ~ 4 MW/m2
PSI Challenge���
1. Global average exhaust power��� P/S ~ 1 MW/m2
![Page 9: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/9.jpg)
9 Sherwood Whyte April 2012
PFCs must be thin (~5 mm) to satisfy heat exhaust ���but thick to resist erosion & material removal & Continually maintain conformability to B field
Steady-state 10 MW/m2 heat exhaust pushes high-T He gas cooling to limits, no allowance for transients.
“Small” Transient heat loading limits lifetime of even best materials
While loss of conforming surface to B greatly accelerates loss of PFC viability & severe plasma effects.
![Page 10: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/10.jpg)
10 Sherwood Whyte April 2012
The PMI Science Challenge & Fusion Viability are inextricably linked
Fusion Viability���
1. Average neutron���power loading ~ 4 MW/m2
2. Continuous 24/7 power production.
PSI Challenge���
1. Global average exhaust power��� P/S ~ 1 MW/m2
2. Global energy
throughput ���> 30 TJ/m2 delivered by plasma
![Page 11: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/11.jpg)
11 Sherwood Whyte April 2012
Erosion limits are set by complex PMI interplay ���& total energy throughput:
Extrapolation from present devices to FNSF/reactors at least x10,000
300 s 4,300 s 9,000 s 2,000 s 22,000 s
The wall surface never truly equilibrates because erosion cannot be turned off at all surfaces.
Tungsten main-wall: ~1-10 tons of erosion from charge-exchange neutrals
![Page 12: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/12.jpg)
12 Sherwood Whyte April 2012
Material limits set by complex PMI & total energy throughput: Extrapolation from present devices to FSNF/reactors at least x10,000
300 s 4,300 s 9,000 s 2,000 s 22,000 s
Example of 10 micron W surface microstructure over ~1/4 day in PISCES lab plasma at 1100 K
Micron deep W fuzz grown in Alcator C-Mod divertor in ~10 seconds at 1500 K!
Baldwin et al PSI 2008 Wright et al NF 2012
![Page 13: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/13.jpg)
13 Sherwood Whyte April 2012
The PMI Science Challenge & Fusion Viability are inextricably linked
Fusion Viability���
1. Average neutron���power loading ~ 4 MW/m2
2. Continuous 24/7 power production.���
3. Thermo-dynamics demand high ambient temperature .
PSI Challenge���
1. Global average exhaust power��� P/S ~ 1 MW/m2
2. Global energy
throughput ���> 30 TJ/m2 delivered by plasma���
3. Fundamental new regime of physical chemistry for plasma-facing materials.
![Page 14: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/14.jpg)
14 Sherwood Whyte April 2012
Required High-T walls present a fundamentally new regime of physical chemistry for PMI science that has not even been
approached in an integrated manner
Rates ∝ exp − Eo
Tmaterial
⎛⎝⎜
⎞⎠⎟
≈ exp − 11,600K(500 −1000)K
⎛⎝⎜
⎞⎠⎟
Arrenhius equation
![Page 15: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/15.jpg)
15 Sherwood Whyte April 2012
Example from PISCES test-stand: Nano-”fuzz” highly T dependent
Tungsten surface after exposure to ~1 hour Helium plasma.
900 K
1120 K
1320 K Baldwin et al PSI 2008
![Page 16: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/16.jpg)
16 Sherwood Whyte April 2012
Outline
• Defining the Challenge for Fusion Energy Boundaries
• The Multiscale Science of Plasma-Material Interactions Ø Processes, measurement and exposure
• Developing a dimensionless parameter “wind-tunnel” for fusion PMI • Critical needs for boundary plasma understanding & prediction.
![Page 17: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/17.jpg)
17 Sherwood Whyte April 2012
The plasma-surface interface is perturbing & complex e.g. the divertor surface is reconstituted ~100 times per second
ordered crystal
Simplified Surface Picture
sputteredimurity atom
Realistic Surface Picture +
-
sheath potential
chemicalremoval
implantationreflection
secondaryelectronemission
sputteringte gnggngg
ionization
redeposition
charge-exchange
Fuel RecyclingMaterial RecyclingIon impactLong-rangematerial transport
ionization
dissociation
recombination
++
+ +
++
++
+ +
vacancy/void defectsfrom ion andneutron radiation
fuel diffusion &permeation
surface fuel saturationbubbles &blisters
amorphousfilm growth
H/D/T fuel ion PFC material atomH/D/T fuel neutral atomPFC material ionElectron Redeposited PFC material atom+ +
fuel trappingat defects
fuelcodeposition
nm
mm
surface
excitatio
n!
Wirth, Whyte, et al MRS 2011
![Page 18: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/18.jpg)
18 Sherwood Whyte April 2012
PMI/Boundary plasmas in a confinement device set by coupled, multi-scale processes
![Page 19: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/19.jpg)
19 Sherwood Whyte April 2012
The “Core” of Multi-scale PMI Science is ���Hyper-Sensitive to Material Temperature
Rates ∝ exp − Eo
Tmaterial
⎛⎝⎜
⎞⎠⎟
≈ exp − 11,600K(500 −1000)K
⎛⎝⎜
⎞⎠⎟
Arrenhius rates
![Page 20: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/20.jpg)
20 Sherwood Whyte April 2012
The Plasma-Surface Interaction Science Center:���addressing multiscale diagnosis
http://psisc.org
![Page 21: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/21.jpg)
21 Sherwood Whyte April 2012
The Plasma-Surface Interaction Science Center: addressing multiscale modeling & simulation
http://psisc.org
![Page 22: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/22.jpg)
22 Sherwood Whyte April 2012
We seriously think we can figure out this mess by measuring surfaces every year or so in tokamaks?*
* What we do now
http://psisc.org
![Page 23: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/23.jpg)
23 Sherwood Whyte April 2012
AGNOSTIC: Proof-of-principle diagnostic development on Alcator C-Mod to provide first shot-to-shot diagnosis
of plasma-facing surfaces
(4) Advanced in-vessel neutron and gamma spectroscopy, unoflred with GEANT4, maps all surface properties (depth resolved!)"
Hartwig, et al, Rev. Sci. Instrum 2010
![Page 24: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/24.jpg)
24 Sherwood Whyte April 2012
AGNOSTIC* requires leading edge nuclear transport modeling and simulations
Full 3-D model of tokamak GEANT4 simulation of Scintillation detection
*Accelerator-based Gamma and Neutron Observing Surface-diagnosing Tool for In-situ Components
![Page 25: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/25.jpg)
25 Sherwood Whyte April 2012
Example: Complete synthetic diagnostic of Boron film thickness in Alcator C-Mod
![Page 26: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/26.jpg)
26 Sherwood Whyte April 2012
Outline
• Defining the Challenge for Fusion Energy Boundaries
• The Multiscale Science of Plasma-Material Interactions Ø Processes, measurement and exposure
• Developing a dimensionless parameter “wind-tunnel” for fusion PMI • Critical needs for boundary plasma understanding & prediction.
![Page 27: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/27.jpg)
27 Sherwood Whyte April 2012
Proposal: Use dimensionless similarity to study coupled issues of edge plasma, PMI and
materials in a scaled-down device* • Dimensionless parameter scaling techniques are a powerful tool to study
complex physical systems (e.g. wind-tunnel for aeronautics) Ø Especially in tokamak fusion experiments where full-size cost is
prohibitive.
• Objective: provide similarity for critical parameters in reactor while avoiding technology limits in scaled-down device Ø Full similarity is not possible Ø The well-known “P/R” divertor scaling does not meet these objectives
• A new “P/S” scaling (actually a set of requirements) provides fidelity to reactor divertor conditions in a small device which is used as the physics basis for Vulcan.
* Special Issue on the Vulcan Conceptual Design, Fusion Engineering Design March 2012
![Page 28: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/28.jpg)
28 Sherwood Whyte April 2012
Lessons about using dimensionless similarity in core
• Critical dimensionless parameters are posited based on physical reasoning (without proof), for example Kadomtsev constants
Mi
M p
~ aR
q ~ BTBP β ~ nT
B2ν* ~ nR
T 2 ρ* ~ T1/2
BR
n ~ R−2 T ~ R−1/2 B ~ R−5 /4
Leads to size scaling of plasma parameters
![Page 29: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/29.jpg)
29 Sherwood Whyte April 2012
Lessons about using dimensionless similarity in core
• Critical dimensionless parameters are posited based on physical reasoning (without proof), for example Kadomtsev constants
Mi
M p
~ aR
q ~ BTBP β ~ nT
B2ν* ~ nR
T 2 ρ* ~ T1/2
BR
n ~ R−2 T ~ R−1/2 B ~ R−5 /4
Leads to size scaling of plasma parameters
• But now the “reality” of the scaling effort must be accounted ��� 1) Magnetic field B has a hard technology limit at fixed aspect ratio��� 2) Reactor must max. B since power density ~ B4
• Therefore “full” matching is not practically useful: what to “relax”? • One chooses rho* based on physical reasoning
• Far below unity and therefore avoids any “threshold” effect. • Is practically difficult to vary in one device. • N.B.: this “practical” strategy leads to experimental validation*
* Luce et al PPCF 50 (2008)
![Page 30: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/30.jpg)
30 Sherwood Whyte April 2012
The challenge is that many more parameters become important in boundary / PMI. “Cleverness in similarity is mandatory”
• Lackner and others (90’s) made reasonable argument that atomic physics important in SOL: posited T/Eatomic=cst. à T = cst.
Global power balance // Spitzer conduction // Pressure balance
“P/R” scaling
• Much is implicit in P/R scaling! • Radial power width λr ~ R, which requires q// ~ 1/R !!
• This guarantees cannot implement P/R scaling in a scaled-down device since power density must be near technology limit ~10 MW/m2
• Aspect ratio must be matched (ST does not simulate AT reactor) • Density must be much larger in smaller device (current drive)?
Lackner, Cont. Plasma Physics 15 (1994), Whyte, et al Fus. Eng. Des. (2012)
![Page 31: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/31.jpg)
31 Sherwood Whyte April 2012
The challenge is that many more parameters become important in boundary / PMI. ���“Cleverness in similarity is mandatory”
• Lackner and others (90’s) made reasonable argument that atomic physics important in SOL: posited T/Eatomic=cst. à T = cst.
Global power balance // Spitzer conduction // Pressure balance
“P/R” scaling
• N.B. much implicit in P/R scaling! • Radial power width λr ~ R, which requires q// ~ R-1 !!
• This guarantees cannot implement P/R scaling in a scaled-down device since power density must be near technology max. ~ GW/m2 in reactor
• Aspect ratio must be matched (ST does not simulate AT reactor) • Density must be much larger in smaller device (current drive)?
Not practical
![Page 32: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/32.jpg)
32 Sherwood Whyte April 2012
Basic argument: If atomic physics is important in boundary plasma then surely PMI is too!
Which dimensionless parameters?
![Page 33: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/33.jpg)
33 Sherwood Whyte April 2012
Basic argument: If atomic physics is important in boundary plasma then surely PMI is too!
Material removal through sputtering
ED+
EB
~ TeEB
Yphys ~ f (T e
EB
, MD
MW
)
Ychem ~ f (T e
EB
, MD
MW
,TWEB
)
![Page 34: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/34.jpg)
34 Sherwood Whyte April 2012
Basic argument: If atomic physics is important in boundary plasma then surely PMI is too! ���
Electrostatic redeposition
λMFP ~MWEW( )1/2ne SW
λMFP
LDebye~ EW
1/2 MW−1/2 ne
−1/2 Te−1/2SW
−1
λMFP
LPresheath~ λMFP
ρH+
~ B EW1/2 MW
−1/2 ne−1 Te
−1/2 SW−1
![Page 35: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/35.jpg)
35 Sherwood Whyte April 2012
Basic argument: If atomic physics is important in boundary plasma then surely PMI is too! ���
Gyro-orbit redeposition
λMFP
ρW +
~ B MW−1 ne
−1 SW−1
Reactor divertor n ~ 1021 m-3 T ~ 10 eV B ~ 6 T
One surface atom can theoretically undergo ~billion of these cycles in one year.
![Page 36: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/36.jpg)
36 Sherwood Whyte April 2012
PMI figures of merit in reactor à Must match divertor ���n, T, B in scaled down device to avoid thresholds in figures
of merit à But relaxed divertor collisionality OK
Vulcan Special Issue FED 2012
![Page 37: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/37.jpg)
37 Sherwood Whyte April 2012
Basic argument: If atomic physics is important in boundary plasma then surely PMI is too! ���
Plasma & ambient T à material physics TWEW
~ n T 3/2 B⊥
BδWκW
+Tambient
σ Thermal
σ Yield
~ n T 3/2 B⊥
BδWRW
DH inW ∝ exp −EW , HTW
⎛⎝⎜
⎞⎠⎟
![Page 38: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/38.jpg)
38 Sherwood Whyte April 2012
Basic argument: If atomic physics is important in boundary plasma then surely PMI is too! ���
Plasma & ambient T à material physics TWEW
~ n T 3/2 B⊥
BδWκW
+Tambient
σ Thermal
σ Yield
~ n T 3/2 B⊥
BδWRW
DH inW ∝ exp −EW , HTW
⎛⎝⎜
⎞⎠⎟
![Page 39: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/39.jpg)
39 Sherwood Whyte April 2012
Material physics figures of merit in reactor à Must match divertor n, T, B AND ���
ambient temperature in scaled down device
Vulcan Special Issue FED 2012
![Page 40: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/40.jpg)
40 Sherwood Whyte April 2012
Proposed “P/S scaling” rules provide matched divertor/SOL parameters in scaled-down device ���à reactor PMI “wind-tunnel” VULCAN
1. Non-inductive steady-state operation (arbitrary long pulses) 2. Areal heating power density P/S (~1 MW/m2) 3. Magnetic field B (~6-7 Tesla) of reactor { λp ~ R through ballooning limit} 4. Geometry matched: R/a, q, L///R, etc. 5. Core density: n ~ R-2/7 6. Ambient wall temperature matched (> 500 C)
With an implicit 7th requirement that embodies the philosophy of the scaling law: 7. The scaling laws must actually allow for the construction and operation of the scaled down device (duh!)
![Page 41: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/41.jpg)
41 Sherwood Whyte April 2012
“P/S scaling”:���A practical approach to
providing a high fidelity reactor PMI
wind-tunnel������
P/R inherently fails to match atomic
physics (n~R-1) & cannot be operated due to violation of
heat flux limits
![Page 42: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/42.jpg)
42 Sherwood Whyte April 2012
Vulcan design scope:���R=1.2 m, PLHCD~20 MW
Vulcan Special Issue FED 2012
![Page 43: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/43.jpg)
43 Sherwood Whyte April 2012
Double-can vacuum vessel:���High Temperature wall
• Points here
![Page 44: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/44.jpg)
44 Sherwood Whyte April 2012
And the MOST important material��� in magnetic fusion?
![Page 45: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/45.jpg)
45 Sherwood Whyte April 2012
And the MOST important material��� in magnetic fusion? The MAGNET!
• Points here
YBCO high-T superconductors coils could revolutionize magnetic fusion by up to x2 increase in B
![Page 46: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/46.jpg)
46 Sherwood Whyte April 2012
YBCO Superconductor tapes à Demountable SC coils à Vertical lift-off maintenance
• Points here
![Page 47: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/47.jpg)
47 Sherwood Whyte April 2012
YBCO Superconductor tapes à Demountable SC coils à Vertical lift-off maintenance
• Points here
![Page 48: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/48.jpg)
48 Sherwood Whyte April 2012
Double-can vacuum vessel:���High T-wall + eliminate sector maintenance
• Points here
![Page 49: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/49.jpg)
49 Sherwood Whyte April 2012
Double-can vacuum vessel:���High T-wall + eliminate sector maintenance
• Points here
![Page 50: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/50.jpg)
50 Sherwood Whyte April 2012
VULCAN ���The 24/7 PMI “wind-tunnel”���
p.s. we should design ST and stellarator versions too!
• Points here
Vulcan Special Issue FED 2012
![Page 51: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/51.jpg)
51 Sherwood Whyte April 2012
Vulcan addresses the PMI chasms ���to FNSF/reactors
![Page 52: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/52.jpg)
52 Sherwood Whyte April 2012
The US and world will lose its first glimpse of a reactor divertor environment with the ���
C-Mod termination on the eve of the hot W divertor
• Comments
Bulk tungsten outer divertor ���from room temperature à 600 C
/w reactor-like P/S, ne, Te, B
Innovative divertor design: toroidally continuous aligned W surfaces
à 0.5 degree grazing incidence ���à can actually exploit high flux
expansion vertical or snowflake topology
![Page 53: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/53.jpg)
53 Sherwood Whyte April 2012
Outline
• Defining the Challenge for Fusion Energy Boundaries
• The Multiscale Science of Plasma-Material Interactions Ø Processes, measurement and exposure
• Developing a dimensionless parameter “wind-tunnel” for fusion PMI • Critical needs for boundary plasma understanding & prediction.
![Page 54: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/54.jpg)
54 Sherwood Whyte April 2012
We desperately need coherent data and a validated model for the SOL width
• Recent experiments across US devices indicates width only depends on poloidal field à 1 mm widths in ITER (like C-Mod)���
λSOL ~aI p~ 1Bp
Makowski, et al APS 2011
![Page 55: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/55.jpg)
55 Sherwood Whyte April 2012
We desperately need coherent data and a validated model for the SOL width
• Recent experiments across US devices indicates width only depends on poloidal field à 1 mm widths in ITER (like C-Mod)���
• Yet the separatrix pressure is well constrained Ø Pedestal stability: psep ~ 5% pped Ø Power exhaust: P ~ λSOL psep T1/2
![Page 56: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/56.jpg)
56 Sherwood Whyte April 2012
We desperately need cohesive data and a validated model for the SOL width
• Recent experiments across US devices indicates width only depends on poloidal field à 1 mm widths in ITER (like C-Mod)���
• Yet the separatrix pressure is well constrained Ø Pedestal stability: psep ~ 5% pped Ø Power exhaust: P ~ λSOL psep T1/2���
• A 1 mm SOL width in ITER
would require a separatrix pressure equal to that at the top of the pedestal??
![Page 57: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/57.jpg)
57 Sherwood Whyte April 2012
The inevitable x2-3 increase in areal energy density from ITER à reactor will disallow ���
any significant instability
30 mm
�
Wth
Awall τ1/ 2 ~
pVA(R /cs)
1/ 2 ~ Pfusion1/ 2 εR1/ 2
Material Tmax (K)
Limit MJ m-2 s-1/2
Be 1550 8 C 4000 42 W 3680 45
ITER
ARIES-RS
ARIES-AT ARIES-ST
Limit
Material thermal limits
![Page 58: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/58.jpg)
58 Sherwood Whyte April 2012
ELMs will not be allowed à ELMy H-mode is not a reactor relevant confinement regime à extremely high priority to
develop intrinsically ELM-free pedestals (QH, I-mode)
30 mm
�
Wth
Awall τ1/ 2 ~
pVA(R /cs)
1/ 2 ~ Pfusion1/ 2 εR1/ 2
ITER
ARIES-RS
ARIES-AT ARIES-ST
Limit
Tungsten���Before���
exposure
After���5 “large”
ELMs ~30 ���
MJ/m2/s1/2
![Page 59: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/59.jpg)
59 Sherwood Whyte April 2012
ELMs will not be allowed à ELMy H-mode is not a reactor relevant confinement regime à Extremely high priority to
develop intrinsically ELM-free pedestals (QH, I-mode)
Tungsten���Before���
exposure
After���5 “large”
ELMs ~30 ���
MJ/m2/s1/2
![Page 60: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/60.jpg)
60 Sherwood Whyte April 2012
Magnetic Fusion Plasma Design ���Report Card
Design issues from ���core à edge
Experimental Demonstration
Validated Predictive Theory/Simulation
Core pressure/kink limits ✓ ✓
Current drive and bootstrap ✓ ✓
Pedestal stability boundary ✓ ✓
Self-regulated pedestal w/o ELMs ✓ X
SOL heat width ? X Divertor T and heat flux below limits ✓ X
PMI & PFC response @ T > 500 C X X
Erosion / redeposition control for 30,000,000 seconds + 20 dpa
X X
![Page 61: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/61.jpg)
61 Sherwood Whyte April 2012
Take away messages
• The boundary plasma and its material interface will continue to grow in importance and challenges for integrated ���fusion devices à reactor
• This is not simply a technology issue, there is no “unobtainium”, rather we must push ourselves to the knowledge frontiers of boundary plasma and material science.
• Fusion theory and computation must become more than plasma theory and will be critical in achieving success.
![Page 62: The Future of Boundary Plasma and Material Science · The Future of Boundary Plasma and Material Science! ... Example from PISCES test-stand:! ... unoflred with GEANT4, maps](https://reader031.fdocuments.us/reader031/viewer/2022022606/5b811e517f8b9ae97b8b9720/html5/thumbnails/62.jpg)
62 Sherwood Whyte April 2012
Extra
• Comments