Study of NSTX Electron Density and Magnetic Field Fluctuation using the FIReTIP System

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Study of NSTX Electron Density and Magnetic Field
Fluctuation using the FIReTIP System

• K.C. Lee, C.W. Domier, M. Johnson, N.C. Luhmann,
  Jr.
• University of California at Davis
• H. K. Park, E. D. Fredrickson, S. A. Sabbagh, S.
  Zweben
• PPPL, Princeton University
• NSTX Research team
• Princeton Plasma Physics Laboratory

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Abstract

• The Far Infra Red Tangential Interferometry and
  Polarimetry (FIReTIP) system on NSTX is capable
  of simultaneously measuring fluctuations of
  electron density and magnetic field. Magnetic
  fields fluctuations (?B) can be isolated during
  MHD activity such as internal kinks, since
  interferometry provides electron density
  information while polarimetry provides Faraday
  rotation data along the same beam path. In this
  paper, a comparison study of the electron density
  fluctuations with the fluctuations measured by
  the Gas Puffing Image (GPI) at the boundary
  plasmas will be discussed. A discussion of the
  measurements from 3 channels at different
  tangencies including comparisons with EFIT
  equilibrium parameters and the structure of MHD
  modes will be presented. L/H transition study by
  Gyro-Center Shift and ELMs propagation study are
  in progress.
• This work was supported by U.S. DoE Contracts
  DE-FG02-99ER54518 and DE-AC02-76CH03073

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Contents

• Overview of FIReTIP system
• Introduction
• Upgrades of 2005/2006
• TAE, EPM Measurement
• Localized Measurements by FIReTIP
• Magnetic Field Fluctuation
• Comparison with GPI data
• ELMs Study by FIReTIP
• H-mode transition Gyro-center shift
• Summary

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3-D CAD of Far Infra Red Tangential Interferomete
r Polarimeter
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Principle of FIReTIP system on NSTX
Rommers Howard 3-laser system
wLO w1 4.01.0 MHz wLO w2 6.01.0 MHz
Sampling rate 500kHz (2005)gt 1MHz (2006)
K.C. Lee et.al., IEEE Trans. on Plasma
32,1721(2004)
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FIReTIP channels (ch1, ch2, ch3, ch7 for 2005)
GPI

• New for 2005
• Optical components of Ch4 Ch5 are installed
• Test run of Ch5 heterodyne visible two color
  compensation for Ch7 are in progress

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TAE/f.b.s measurement by FIReTIP
Ch1
Ch2
Electron density fluctuation spectrum of 113655
?TAE 150200kHz compared with Magnetic coil
data showed similarity and difference in
different channels ?localized fishbones similarit
y in Ch1, Ch2 Ch3 due to entire coverage of
core plasma of measurement
Ch3
Ch7
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EPM measurement by FIReTIP
Electron density fluctuation spectrum of
113114 ?EPM (Energetic Particle Mode) at
0.370.4 sec showed higher harmonics up to 12th
order ?periodic fishbones (0.340.37 sec)
localized mainly on Ch3 with chirping frequency
around 20kHz
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Faraday rotation measurement by FIReTIP
? Faraday rotation and electron density data on
MHD oscillation showed phase difference ? Phase
difference gt information of magnetic field
oscillation ? Different channels showed
different pattern of oscillations lt mode
structure of MHD
time (sec)
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Magnetic fluctuation measurement by FIReTIP
In case of constant frequency (MHD) oscillations,
Faraday rotation
,
where
From measurements
(Polarimetry)
(Interferometry)
,
Polarimetry and interferometry data provide
magnetic field fluctuation
,
, where
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Magnetic fluctuation measurement by FIReTIP
Phase of magnetic field fluctuation have tendency
to increase with beta toroidal.
?
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Comparison FIReTIP and Gas Puffing Image (GPI)
?Periodic Oscillation for the known edge MHD
modes (n2, m2) ? Phase difference of GPI and
FIReTIP edge channel agreed to the mode numbers
and location differences of two measurements ?
outer channels measure only one poloidal mode
peak while the inner channels measure both peaks
simultaneously
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H-mode transition study by FIReTIP (2004)
Er and Vp begin to change 10 to 20 ms before L-H
transition (here at t 0.220 sec)
Shot 113350
Ip (MA)
H-mode
Er (kV/m)
Er (kV/m)
VT (km/s)
Vp (km/s)
Time (s)
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H-mode transition study by FIReTIP (2005)
FIReTIP Ch7(edge) Rt150cm
Da(lower)
Da(upper)
EFIT-Gap (bottom)
EFIT-r (mid-out)
EFIT-r (mid-in)
Te (max)
time (sec)
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H-mode transition study by FIReTIP (continue)

• no Er pre-cursor was showed on 2005 experiment.
• electron density of FIReTIP edge channel showed
  density perturbation (green circles) just before
  the L/H transition of ohmic plasmas (LSN).
• perturbations last msec.
• among EFIT plasma locations gap-bottom was
  coincident with transition time gt importance of
  neutral flow at diverter
• H-mode transitions occurred while plasma
  temperature was increasing.
• application of Gyro-Center Shift theory to NSTX
  is in progress.

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ELM propagation measurement by FIReTIP
ELMs propagate clockwise
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Gyro-Center Shift by Charge Exchange
hot ion
neutral
boundary
core
Submitted to Physics of Plasmas K.C. Lee
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Gyro-Center Shift Calculation
average gyro-center shift over (-rL r
rL) per reaction
reaction rate of an ion with rL and
gyro-center at a point
average gyro-center shift rate
x

svi ?rf(r)nn(r)dr svi ?f(r)nn(r)dr
(½)rL(n-n-)/(nn-)
(¼)svirL(n-n-)
(½)svi(nn-)
current density (charge separation)
different from frictionDlppolito02
by
and
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Gyro-Center Shift Calculation (continue)
Radial electric field calculation result for
DIII-D
Gyro-center shift by charge exchange reaction
gt major source of Er formation
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Summary and Future Plan

• 2005 measurement and analysis
• Localized TAE and f.b.s measurements
• Energetic Particle Mode (RPM) measurements with
  higher order harmonics
• Faraday rotation analysis with comparison of
  electron density fluctuation on MHD oscillations
• gt Study of magnetic field fluctuation
• Comparison with GPI data with mode structure of
  MHD
• FIReTIP edge channel density perturbation at the
  H-mode transition
• ELM propagation measurements by FIReTIP
• FIReTIP system upgrade and future works
• Channel 5 (Rt132 cm) will be tested for profile
  reconstruction of electron density
• Hetero-dyne visible two color vibration
  compensation for Ch7
• Application of Gyro-Center Shift theory to NSTX