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Conceptual design of the tangentially viewing combined interferometer-polarimeter for ITER density measurements
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View: Figures


Image of FIG. 1.
FIG. 1.

Optical table layout of individual TIP chord. Red/blue labels show CO2/CO laser radiation frequencies and polarization. HeNe lasers are for alignment purposes only. Component description: 2.5 × = 2.5 × beam expander (1 CO2 and 1 CO), Atten = 50 W capable attenuator, BS1, BS3, BS6, BS7 = ZnSe beamsplitter (45° AOI, R ≈ 5%/T ≈ 95%, at 5.42 and 10.59 μm), AO1, AO2, AO3 = Germanium Acousto-Optic Modulator 38-42 MHz capable, λ/2 = CdS half-wave plate, DBS1, DBS2 = ZnSe beam combiner (45° AOI, R ≈ 99% at 632 nm/T ≈ 99% at 10.59 μm), TFP = ZnSe thin film polarizer, λ/4 = 10.59 μm CdS quarter-wave plate, DBS3, DBS4, DBS5, DBS6 = beam combiner (45° AOI, R ≈ 99% at 5.42 μm and T ≈ 99% at 10.59 μm and 632 nm), BS2, BS4 = ZnSe beamsplitter (45° AOI, R ≈ 10%/T ≈ 90% at 5.42, 10.59 μm and 632 nm), BS5, BS8 = ZnSe beamsplitter (45° AOI, R ≈ 50%/T ≈ 50% at 5.42, 10.59 μm and 632 nm), DET1, DET2, DET3, DET4 = HgCdTe PV detectors, Pol1, Pol2 = 10.59 μm ZnSe Brewster Angle Based Polarizer, AM1, AM2 = active piezo electric mirror mount, 4 × = 4× broadband reflective optic beam expander, QD1, QD2 = HgCdTe quadrant detectors, FSM = front surface mirrors.

Image of FIG. 2.
FIG. 2.

CATIA model of TIP layout on ITER. The five TIP chords enter ITER through equatorial port 9.

Image of FIG. 3.
FIG. 3.

Zemax calculated Gaussian beam radii from the laser to corner-cube retroreflector (CCR) for the (a) outermost and (b) innermost chords. Beam sizes are the same for the return path.

Image of FIG. 4.
FIG. 4.

(a) Shape of LCFS during current rampup. Tangency radii of the five TIP chords overlayed as colored diamonds (red = 4.191 m, green = 5.021 m, blue = 6.145 m, orange = 7.090 m, purple = 8.050 m). (b) Plasma current and electron density vs time. (c) Measured interferometer phase shift for the five tangency radii vs time. (d) Measured phase shift due to Faraday rotation vs time for the five tangency radii.

Image of FIG. 5.
FIG. 5.

Relative error for (a) interferometer and (b) polarimeter measurements during the current rampup time window shown in Fig. 4 . Each tangency radius is represented by a color corresponding to that in Fig. 4 .

Image of FIG. 6.
FIG. 6.

Refraction calculations for baseline (dashed line) and very high density cases (solid line). (a) Input density profiles. (b) Radial excursion of 10.59 μm beam at retroreflector due to refraction.

Image of FIG. 7.
FIG. 7.

Effect of finite temperature on the measured interferometer phase shift (ϕ) and Faraday rotation angle (α)—plotted as ratio of finite temperature shift or rotation over that for a cold plasma of the same density and field.

Image of FIG. 8.
FIG. 8.

Crosspower spectrogram of two DIII-D CO2 interferometer chords showing a variety of Alfvén eigenmodes, ELMs, and broadband fluctuations in discharge 129313.

Image of FIG. 9.
FIG. 9.

NOVA calculated density perturbation (δn e ) due to f = 58.7 kHz n = 10 TAE. (a) RZ cross-section of density perturbation. (b) Top view of cross-section through midplane of TAE density perturbation. Blue/yellow = positive/negative density perturbation. Solid lines are approximate locations of ITER TIP chords.

Image of FIG. 10.
FIG. 10.

(a) Fluctuating (δϕ) and equilibrium (ϕ) interferometric phase shift as a function of tangency radius for the n = 10 of Fig. 9 .

Image of FIG. 11.
FIG. 11.

Noise spectrum for (a) CO2 interferometer (not including vibration compensation) and (b) CO2 polarimeter on DIII-D.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Conceptual design of the tangentially viewing combined interferometer-polarimeter for ITER density measurements