Page 1 - An Interesting Poster to look at from the Tri Alpha Energy Team in California
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                                                                                                                      Jet Outflow and Open Field Line Measurements on the C-2W Advanced Beam-Driven Field-Reversed Configuration Plasma Experiment
         Inner divertor MW interferometer
 Monostatic, Homodyne with phase detection embedded inside the waveguide
(see example N. L. Aleksandrov, et. al. J. Phys. D: Appl. Phys. 40 (2007) 4493–4502)
 Used to measure electron density at the inner divertor. Capable of measurements in the range of 1010-1012 cm-3
 5-10 chords, double pass@ 76-77GHz. 12.5cm spacing between channels. 250MHz separation between channels. Channels are effectively isolated from each other
 Optics include HDPE lenses, cylindrically curved reflector at the bottom of the divertor vessel, and
large MW transmitting PEEK window at the top port. Returning MW beam is elliptical.
 Electron density obtained from Abel inversion of line integrated density
4c2m
e
D. Sheftman1, R. Smith1, L. Schmitz2, D. Gupta1, M. C. Thompson1, and the TAE team
TAE Technologies, Inc., 19631 Pauling, Foothill Ranch, CA 92610
2Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA
Overview - Jet outflow measurements on C-2W
Accurate operation and high performance of the open field line plasma surrounding the Field Reversed Configuration (FRC) is crucial to achieving the goals of successful temperature ramp up and confinement improvement on C-2W. Knowledge and control of the open field line plasma requires extensive diagnostic efforts. A suite of diagnostics, which consists of microwave interferometry, dispersive spectroscopy and spatial heterodyne spectroscopy, is being developed to measure electron density, ion temperature and particle outflow velocity at various locations along the open magnetic field lines. A detailed overview of these diagnostics is presented.
 Plasma diffuses from the FRC core in the confinement section and flows through the open magnetic field lines towards the divertor end plates
 Several diagnostics instruments are located at various positions along the jet outflow stream. Divertor
Jet spectrometer
      Doppler spectrometer, measures ion velocity and temperature at different axial locations along SOL, for impurity and/or charge exchanged neutrals.
 Collection optics, inserted into vacuum by use of linear actuator, enable up to 20° field of view.
 Spectrum magnified by 2 cylindrical lenses to fit PMT arrays and enable maximal light throughput.
 Signal digitized at spectrometer location, to minimize background noise
Cyl1 M=30
Cyl2 M=10
To digitizers
Optical assembly at vacuum interface
To confinement
                ISO 320 Spectrometer
PMT arrays
106 V/A Amplifiers
           ItC1ACos t 0
3 Fiber optic chords
To inner divertor
    nedl 
Offsets and coefficients of I-Q singal (A,B,C1,C2) are found by calibration, using frequency sweep
0

interferometer
breadboard Interferometer
enclosure boxes MW beams
Jet plasma
 2
QtC2BSin0 t Calibration
Multiple reflections cause “drift” of the fringe pattern during frequency sweep. Drift subtracted by blocking returning signal
 Divertor Front view
(See J. Harlander, R. J. Reynolds and F. L. Roesler, The Astrophysical Journal, 396: 730-740 (1992) )
Confinement and Divertor side view
Spatial Heterodyne Spectroscopy (SHS)
Simple, high throughput, Fourier Transform Spectrometer absent of moving parts
         Raw signal Drift
corrected signal (raw-drift)
 Measures ion velocity profile at inner divertor.
 Diffraction gratings are placed at an angle near Littrow
angle. Wavelengths around the Littrow wavelength produce fringe patterns on the detector
 Prisms increase the field angle and enable 10-100 times more light throughput compared to theoretical limit of conventional FT spectrometers
 System optimized for 278.1nm, Wavelength of O4+, most abundant impurity in SOL plasma.
Precursor experiment-CTI test bed
Inverse Fourier Transform of the spatial fringe pattern yields the spectrum I(s
0

I(x) B(s) 1cos 2(4(ss0)tanLx ds   
      Divertor interferometer reflector
SHS line of sight
        Jet MW interferometer
• •
Compact toroid injector (CTI) tested for particle refueling on C-2W.
A prototype SHS was used to characterize the spectrum by collecting time averaged plasma radiation. Low speed utility camera was used for detection.
C III
            2 chord 300 GHz system, measures line integrated electron density at mirror field location.
 Measures zero crossings of phase of IF signal (80 MHz) to obtain phase difference induced by plasma, with respect to reference signal.
 Supplemented by 3 chord, two color CO2 interferometer. CO2 laser@10.6mm, and measures line integrated electron density during dense plasma regime, or mechanical vibrations during dilute plasma regime.
 Capable of measurements in the range of 1012-1017 cm-2
 For more details, see poster 6.13
Db
        Simulated data
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