Lithium Effects on Edge Neutral Density

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Lithium Effects on Edge Neutral Density

• Patrick Ross

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Edge Neutral Density Diagnostic (ENDD) measures
light emitted by the plasma edge
Inboard
Outboard
The ENDD uses a 2-D ccd camera to measure Dß
emissions. The emission profile is then
Abel-inverted to provide a radial profile.
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XP 719, Day 1 Edge Neutral Dß Emissions
Day 1, most of the shots had a fairly long
current flattop (250-750 ms).
Shot lithium total
123474 0 0
123479 40 270
123483 249 759
123489 260 1876
Arbitrary Units
Radius
Edge Neutral emissions by radius. Shot 12474 is
the reference shot, after which the lithium
deposition began. Lithium in excess of 200 mg
had a measurable effect on the plasma.
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XP 719, Day 1 Edge Neutral Dß Emissions
Day two deposited over 9 grams of lithium. Later
shots were not used because they did not run as
long.
Shot lithium total
123505 0 0
123508 239 676
123512 257 3699
123414 278 4237
Radius
Day 2 consisted of increased deposition between
shots. After depositions gt 300 mg, the shots
were short, with lt100ms flattop. The edge
neutral emissions decreased with increasing
lithium.
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Day 2- High Lithium Deposition shortened shots
Shot lithium total
123505 0 0
123511 2283 3442
123514 278 4327
123419 516 6473
Radius
During day 2 of XP 719, much more lithium was
deposited. After periods where gt300 mg of
lithium was deposited, the shots were either
fizzles or significantly shortened. In general,
they exhibited the same behavior as shots with
less lithium.
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Lithium Edge Neutral Effects only last for a few
shots
The reference shots from day 1 to day 2 are very
similar, even though more than 1.8 grams of
Lithium was deposited into NSTX during Day 1
operation. The lithium effects are seen in the
final shot of Day 1 (shot 123489), but have
completely disappeared by the reference shot of
Day 2 (123505).
Radius
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Edge Temperatures are not significantly different
with Lithium while densities vary somewhat
Although the central electron temperature is
significantly higher after lithium deposition
(1.5x), the edge electron temperature does not
appear to change significantly before and after
lithium deposition.
The edge electron density is slightly higher near
the seperatrix before lithium deposition. Beyond
150 cm, the electron densities are the same.
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Edge Neutral Density Affects Charge Exchange
Losses
TRANSP Calcluations of Beam Power Losses due to
Edge Neutral Density of shot 120442. Density is
cm-3 and lost power is in kW.
Run Density CXX CXI LIM Total Input Power
P04 1e10 41 44 300 385 9
P06 1e11 221 36 285 542 13
P08 1e12 627 20 247 894 21
BPCXX External Charge Exchange Loss (Beam
particles charge exchange outside Last Closed
Flux Surface) BPCXI Internal Charge Exchange
Loss (Beam particles C-X inside LCFS) BPLIM
Fast Ions born on bad orbits, lost immediately to
the wall
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Conclusions

• The lithium affects the edge neutral emissions,
  but the effects are short lived. Within a few
  shots after the lithium deposition, the effects
  are gone and the plasma returns to the previous
  state
• Edge electron temperatures are not sigificantly
  affected by lithium
• Edge electron densities are decreased due to
  lithium by nearly 50 inside the seperatrix, but
  outside, the electron density is unchanged.
• TRANPS calculations show that decreased edge
  density may increase beam power deposited into
  the plasma.