Reciprocating Probe Edge/SOL Profiles in NSTX

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Reciprocating Probe Edge/SOL Profiles in NSTX
J. Boedo H. Kugel, D. Rudakov, H. Ji, T. Carter,
N. Crocker, D. Rudakov, M. Umansky, D. Gray, A.
Pigarov, D. DIppolitto, J. Myra, R. Maingi, V.
Soukhanovskii, Ricardo Maqueda (Nova Photonics),
S. Zweben and the NSTX Team CO3 ORAL session,
Monday afternoon, November 15
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L-mode, 0.8 MW, LSN plasmas with density scan
Plunges
0
0.1
0.2
0.3
0.4
Discharge fueling rate and probe insertion time
varied to sample various densities
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L-mode Te, ne, Profiles Obtained with high
spatial resolution
Profiles with high (2 mm) spatial resolution 3
ms time resolution Data inside the LCFS Plasma
exists far into the SOL Te is quite flat!! An
offset is needed for proper fits gtgt fast radial
transport
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Fixed Power, Density Scan.Scaling in lTe, lne,
can be obtained
lTe usually smaller than lne Trends of lTe, lne
with ne_av are opposite lTe, lne converge at
high both high and low ne_av (physics behind
this?)
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Fixed Power, Density Scan.
Amplitude, Te1, shows a marked dependence on
average density Ne1 does not! Te Profile shifts
out with density
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Fixed Power, Density Scan.
Offset Te0, Ne0, fairly constant (except at low
Ne?) SOL ballistic transport not too sensitive
to ne_av? Need to examine low Ne behavior with
more statistics
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L-mode vs H-mode SOL, LSN, 2 MW
Ne SOL decay length 3-4 cm in H-mode Ne SOL
decay length 10-30 cm in L-mode Te SOL decay
length gt50 cm in BOTH L and H mode. SOL radial
particle transport larger in L-mode SOL heat
transport ALWAYS large
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SOL Transport Probably Dominated by Intermittency
in NSTX
Conditional averaging results reveals that
Intermittency strong in NSTX in BOTH L and
H-mode Amplitude of Intermittent Plasma Objects
decreases with radius in L and H mode Future
fast Te measurement will resolve Te in the IPOs
to separate particle and heat flux
R-Rsep 1.6 cm
R-Rsep 10 cm
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L-H Mode Profile Difference Lies on the Number
of IPOs
R-Rsep 1.6 cm
R-Rsep 10 cm
Although IPO amplitude somewhat higher in L mode,
in NSTX the EVENT FREQUENCY is the chief
difference between L and H mode
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Conclusions

• Te profile 1) Narrower than Ne profile, 2) rises
  faster except at extreme ne, 3) most sensitive to
  ltnegt, 4) quite flat at 10-15 eV in the SOL gtgt
  SOL heat transport is fast!
• Ne profile 1) Also flattish in the SOL, 2)
  sensitive to ltnegt mostly via lne
• L-H comparison SOL lne length is much larger in
  L-mode, SOL lTe, ALWAYS large gtgt SOL particle
  transport faster in L mode, SOL heat transport
  ALWAYS fast!
• Intermittency is strong in NSTX. IPOs decay
  quickly with radius, drained by parallel
  transport
• Main difference on the intermittency between L
  and H mode NSTX is the frequency of the IPOs and
  not their amplitude

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Density Fluctuation Levels Decrease at LCFS
The shear layer/LCFS (marked by double lines)
and seen in the floating (not plasma) potential,
shifts out at high density Normalized density
fluctuation levels (Nrms/N) shift
accordingly Normalized fluctuation levels vary
from 0.2 in the shear layer to 0.7-0.8 at the
LCFS dropping to 0.5-0.6 in the SOL
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L-mode Vf, Er Profiles Obtained
Radial field increases quickly to 5.5
kV/m Poloidal tips well aligned No dedicated
H-mode data, mining database
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Electric field moves outward at high density
Clear transition at 3.0E13 cm-3 So far
(nominal 5 cm inside), no well. Need to make
further experiments and go further in.
?