ELMs / LLD

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The Two Types of Discharges in XP-913
ELMs / LLD
Standard Fiducial
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Six Interesting Features from XP-828

• The (apparent) extreme efficacy of Li aerosol at
  increasing confinement
• The extremely square Te and ne profiles seen
  during the NBI overdriven L-H transition
• The reduced OH consumption during aerosol
  injection
• The transient suppression of ELMs
• The concomitant reduction in radiated power /
  Zeff
• The lack of CS gas fuelling

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Standard Fiducial
Baseline XP-913
Baseline XP-913 No CS Gas
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Standard Fiducial
Baseline XP-913
129012
130388
LFS
CS
Li Flux
Baseline XP-913 (No CS Gas)
130389
Flux Profile A
Li Flux
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Flux Profile B
Flux Profile C
Li Flux
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Shot 121522 A Discharge Used to Deposit Li on
the CS for the Benefit of the
Following Discharge
30 ms
250 ms
500 ms
600 ms
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Another Tactic for Directing Li Ions - In This
Case to the Lower Divertor
Example Shot 128279
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Extra Slides
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Comparison Zeff(0) from Metals
No Li 700 mg LITER 7mg Early Li Aerosol
Estimated Contribution of Metals to Zeff
0.6
LITER
0.4
Dimensionless
Aerosol Injection
0.2
No Li
0
0
0.2
0.4
0.6
0.8
S. Paul
Time (sec)
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Goal(s) of the XP

• Establish whether or not the 1st aerosol
  experiment was a fluke.
• Fiducials H mode by early NBI overdrive - no
  CS gas
• Early aerosol injection before L-to-H
  transition
• 10 mg/s and higher probe the limit of
  Li aerosol mass flux
• Push plasma performance
• If problems try OH shot or two
• -------------------------- If time permits
  ------------------------------------
• 2. Investigate effects on ELMs.
• Can aerosol trigger small ELMs at higher flux
  rates (gt35mg/s)?
• 3. Investigate whether more Li atoms can be
  injected than D2 atoms.
• LLD loading - need relevant discharge
• 4. Investigate Li efficacy with double null
  discharges

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Shot 130388 Early Injection of Li Powder

• Nominal aerosol trajectories shown by red
  vertical lines

Plasma Encounters Aerosol Particles
X-Point Established (H-mode _at_ 180 ms)
Stored Energy Steady State
Li1 Rings Observed (Fig 12)
25 ms
509 ms
102 ms
80 ms
58 ms
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2005 First LSN NBI D Shot After 25 mg of Li
Pellet Injection Exhibited Factor 50 Decrease
in Density
Lower single-null divertor discharges, 0.45T, D2
gas fueling 3.5mg

• 25 mg of Li pumping of edge density saturated
  after the 3 similar D discharges and returned to
  pre-Li wall conditions, as expected if most
  injected gas reacts with the deposited Li.
• Rate of density rise is below NBI fueling rate.

H. Kugel M. Bell
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Camera View of Early Li Aerosol InjectionTaken
at t 60 ms
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The Subtle Difference Between 130386 and 130389
130386 _at_ 85 ms No Li
130389 _at_85 ms Early Powder
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Why a Double Null Discharge Would be Interesting
Powder Injector
Li Ions Head Preferentially for Upper Strike
Points
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Getting Toward the Center Stack ( or LLD) -
Early (Using a Splash Plate)
45 Deg Inverted Spoon
45 Deg Flat Plate
Present Design
Flat Plate LLD
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Aerosol Injection
10 mg/s
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Aerosol Injection
10 mg/s
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Early Powder Injection
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Early Li 2 sec shot
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Li Has Unique Energy Structure Easy to Create
Li1
Can We Exploit This to Save Early Volt Secs ?
H He Li Be B C N O
13.6 24.6 5.39 9.32 8.30 11.3 14.5 13.6
54.4 76.6 18.2 25.1 24.4 29.6 35.1
123 154 37.9 47.9 47.4 54.9
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Ionization Energy (eV)
2
3
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Shot 121522
30 ms
250 ms
500 ms
600 ms
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Shot 123862
30 ms
250 ms
500 ms
800 ms
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