Supported by:
16
Supported by: Office of Science . K. Mansfield a , H. W. Kugel a , R. Maingi b , M. G. Bell a , R. Bell a , E. Fredrickso . Kaita a , J. Kallman a , S. Kaye a , B. LeBlanc a , D. Mueller a , S. Paul a , R. Raman c , . Roquemore a , S. Sabbagh d , H. Schneider a , C. H. Skinner a , V. Soukhanovskii e , . Timberlake a , J. Wilgen b , L. Zakharov a and the NSTX Team ELM Suppression by Li Deposition on NSTX Graphite Divertor Surfaces a Princeton Plasma Physics Laboratory, Princeton, NJ 08543 b Oak Ridge National Laboratory, Oak Ridge, TN 37831 c University of Washington,, Seattle, WA 98195 d Columbia University, New York, NY 10027 e Lawrence Livermore National Laboratory, Livermore, CA 94551 DOE Contract DE-AC02-76CH03073 1
description
ELM Suppression by Li Deposition on NSTX Graphite Divertor Surfaces. Office of Science. D. K. Mansfield a , H. W. Kugel a , R. Maingi b , M. G. Bell a , R. Bell a , E. Fredrickson a , R. Kaita a , J. Kallman a , S. Kaye a , B. LeBlanc a , D. Mueller a , S. Paul a , R. Raman c , - PowerPoint PPT Presentation
Transcript of Supported by:
Supported by:
Office ofScience
D. K. Mansfielda, H. W. Kugela, R. Maingib, M. G. Bella, R. Bella, E. Fredricksona,R. Kaitaa, J. Kallmana, S. Kayea, B. LeBlanca, D. Muellera, S. Paula, R. Ramanc, L. Roquemorea, S. Sabbaghd, H. Schneidera, C. H. Skinnera, V. Soukhanovskiie, J. Timberlakea, J. Wilgenb, L. Zakharova and the NSTX Team
ELM Suppression by Li Deposition on NSTX Graphite Divertor Surfaces
a Princeton Plasma Physics Laboratory, Princeton, NJ 08543b Oak Ridge National Laboratory, Oak Ridge, TN 37831c University of Washington,, Seattle, WA 98195d Columbia University, New York, NY 10027e Lawrence Livermore National Laboratory, Livermore, CA 94551
DOE Contract DE-AC02-76CH03073 1
BT = 0.5 T
Ip = 800 kA
PRINCETON PLASMA PHYSICS LABORATORY
PPPL
Purpose : Study ELM Suppression by in situ Modification of NSTX Plasma Surface Interaction: Li on Graphite
R/a = 1.46
Lower Single Null
PNBI = 4 MW
Type 1 ELMS
Lithium Evaporators with Shutters
H. Kugel P2-58
B treated Graphite
2
Li10 min
Plasma 1 s
Li10 min
Plasma 1 s
He 6.5 min
Continuous Li Evaporation
Time
Newly-Installed Li Shutters Allow More Flexible Wall Conditioning and Improved Plasma Operations
H. Kugel P2-58C. Skinner P2-59
Previous Divertor PFC Conditioning Scenario
New Conditioning Scenario with Shutters
Shutters Closed
Shutters Closed
He 6.5 min
He 6.5 min
He 6.5 min
Advantages:• Windows clear• No He dilution• Shot cycle shortened
Disadvantages:• Window coatings• He co-deposition & dilution
3
O
H C
oil
Cur
rent
(kA
)
Pla
sma
Cur
rent
(M
A)
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.90
1
-20
0
20
Time (s)
NB
IP
ower (M
W)0
4
The Effects of Li Wall Conditioning on Inductive Flux Consumption Were Immediate and Pronounced
First Deposition 116 mg (~100 nm)
No Li
Fifth Deposition
No Li
4
No Li
No Li
ELM Suppression by 5th Discharge With LiNo ELMs Immediate Increase in Stored Energy
1st Li
5th Li
1st Li 5th Li
Sto
red
En
erg
y (1
02 kJ
)
0
2.5
D
(A
. U
.)
No Li
1st Li
5th Li
No Li 1st Li 5th Li
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9Time (s) 5
D
(A
.U.)
0.2 0.3 0.4Time (s)
*
*
* *
*
* **
Ratemg/min
Recent mg
Total mg
0 0 0
16 116 116
193 30916
16
16
16
161 471
168 638
171 809
How Does Wall Conditioning Suppress ELMs? - By a Series of Omissions …
129019No Li
129021
129022
129023
129024
129025
6
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
1
2
3
4
55
0
Da19n 3
Da38n 1.5
Da41n
0.90 Time n
Da
(A.U
.)n
eL (
1016
cm
-2 )
Sto
red
E
ner
gy
(102
kJ)
0
2.50
8
PN
BI (M
W)
0
46
2
Time (s)0 0.90.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
129019
129038
129041
No Li
No ELMS
No ELMS
129019No Li
129041129038
No Li129019 129038129041
Ratemg/min
Recent mg
Total mg
70 767 5734
70 970 8348
Complete ELM Suppression at Higher Li Evaporation Rates and Higher PFC Accumulations Higher Confinement
Beta Limit
7
Te
(keV
)
Ti
(keV
)
ne
(1019
m-3)
Vto
r (k
m/s
)
0
0.5
1.0
1.5
0
0.5
1.0
1.5
0
5
10
0
150
250
1.1 1.2 1.3 1.4 1.5R (m)R (m)
t = 515 ms
t = 515 ms
t = 485 ms
t = 485 ms
129041129019
1.1 1.2 1.3 1.4 1.5
• Pronounced Improvements in Discharge Parameters • Large Changes at Plasma Edge Due to Li
PronouncedPedestalFeatures
Li
8
129024 ELMs
Total Lithium: 638 mg
0
5
1
2
3
4
ne (
101
2 c
m-3)
Reflectometry Shows Clear Modification of SOL Density by Lithium / ELMS
1.46 1.48 1.50 1.52 1.54 1.56 1.58 1.60
Major Radius (m)
129041No ELMs
TotalLithium :8348 mg
LCFS
9
The Same Intermittent ELM Behavior was Observed After Evaporation Ended as Li Lost Effectiveness
129019 No Li
129057 Taken Next Day NoEvaporation
8348 mgResidual
10
Summary and Conclusions
• Actively modifying the plasma surface interaction in situ has completely eliminated ELMs.
• ELMs disappeared in a series of omissions with no apparent change in either amplitude or frequency.
• Thin films of Li (100 nm /discharge) can have pronounced effects on NSTX performance.
• The evidence supports the view that wall conditioning by Li modifies both the SOL and pedestal properties.
• Initial TRANSP run indicates increased current in outer region.Stability analysis underway (S. Kaye)
11
Extra Slides
Time (s)
Ze
ff(0
) F
rom
Met
als
No Li with ELMs
With Li, No ELMs Beta Limit
No ELMs Metals Accumulate in Core
Velocity at SOL = 4.5 m/sec
Powder InjectorLi
Possible ELMs Pacing with 40 m Li Powder Injected into Plasma SOL/ Pedestal
• Lithium Edge Conditions Yield ELM Suppression• TRANSP Analysis Finds Increase in Edge Current
No Li
S. Kaye
No Li
Stability Analysis in Progress
S. Kaye10
