APS_2018_poster_KZ
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 Electron temperature and density profiles of C-2W FRC plasmas in different experimental configurations
K. Zhai, T. Schindler, A. Ottaviano, E. Parke, M. C. Thompson, and the TAE Team
TAE Technologies, Inc., 19631 Pauling, Foothill Ranch, CA 92610
       C-2W FRC experiment
Formation section (both sides)
Eight neutral beams, ~21 MW, ~30 ms
Inner divertor with biasing electrodes (both sides)
Outer divertor with plasma gun and biasing electrodes (both sides)
 Parameter
Value
Bext
~0.1–0.3 T
rs
~40 cm
Ls
~3 m
ne
~3–5􏰀1013 cm-3
Ti
~1–2 keV
Te
~0.2–1 keV
Plasma lifetime
up to 30 ms
   Central confinement vessel
  C-2W Thomson scattering system calibration
• Polychromator spectral calibration
 dσRay N
S =dσTS *ΔΩ*E*N *L*F S =dσRay *ΔΩ*E*N *L*F N e=STS * dΩ * gas
N SRay
• 5-channel bandpass filter polychromators (in collaboration with GA):
Four spectral channels are optimized for electron temperature measurement from 10eV to 2keV.
One channel is at laser wavelength for Rayleigh scattering calibration.
• Dedicated temperature controlled polychromator room in diagnostics Lab for 22 polychromators, control unit, chiller, and data acquisition.
• Absolute system calibration for Ne measurement using Rayleigh scattering and Raman calibration
    TS dΩ e Ray dΩ gas dσTS SRay dΩ
gas : :Rayleighcalibrationcoefficient
      Stray light in edge channels for argon gas Rayleigh calibration, Raman calibration using nitrogen gas avoid laser stray light.
  C-2W single side FRC
Timing the six laser bursts at 13kHz to catch the transported single side FRC plasma.
At ~26us, TS measures the peak of both the electron temperature and density of the transported FRC plasma.
At ~300us, density increase indicates the bounced back FRC plasma moving into the center region again. However, Te is lower with the bounced back plasma.
        C-2W plasma performance improvement
• C-2W initial stage. Reproduce C-2U like FRC plasma
• Edge control with flaring magnetic field in divertor
• Edge control with flaring magnetic field and biasing electrodes in divertor
           With plasma edge control, C-2W has a hotter electron core.
   C-2W Central plane Thomson scattering system
   • System is supported from concrete floor, isolated from vessel vibration.
• Automated alignment HeNe laser and cameras.
• View dump and baffles in entrance/exit tube to reduce stray light.
• Beam path length from laser head to scattering region: ~7m. Entire beam path is enclosed in
opaque solid material.
• A temperature controlled room for lasers and beam transportation components.
• A temperature controlled room for polychromators.
• Most components, e.g. lasers, collection optics, polychromators, have been bench tested and
calibrated in lab before final installation.
Plasma Profile at 16 locations:
r= [-8, -4, 0, 4, 8, 12, 16, 20, 24, 28, 32, 36,
41.25, 49.25, 57.25, 65.25] cm Collection length L:
2.5cm
Collected photon number:
Central laser system:
• Nd:YAG at 1064 nm
• 30/6/4 pulses at 1KHz/13kHz/20kHz • 2J per pulse
• Divergence <= 0.5mrad
• Pointing stability <= 100μrad
  ~1.6´105 at ne=1013/cm3 and 2J laser pulse
   C-2W FRC and mirror plasma
• Typical FRC plasma electron temperature and density evolution
• Typical mirror plasma electron temperature and density evolution
Hollowed density and temperature of FRC plasma VS Peaked density and temperature profile
Higher electron temperature and broader electron density profile for FRC plasma as comparted to mirror plasma
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