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Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak
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Image of FIG. 1.
FIG. 1.

The layout of KSTAR reflectometer. The inside view of the installed antenna array is shown in the left side.

Image of FIG. 2.
FIG. 2.

The directivity of a long horn antenna (a) in E-plane and (b) in H-plane.

Image of FIG. 3.
FIG. 3.

The poloidal layout of antennas. The lower orange horn is a transmitting antenna and the upper one is a receiving antenna. The angle between two antennas is 2.8°; a is the minor radius, R (= 0.824 m) is the position of the antenna entrance. R (= 1.161 m) is the antenna phase center.

Image of FIG. 4.
FIG. 4.

The circuit diagram of Q band reflectometer.

Image of FIG. 5.
FIG. 5.

The circuit diagram of VCO driver. The single supply op-amp circuit converts the output voltage of AWG to the input voltage range of VCO.

Image of FIG. 6.
FIG. 6.

(a) The circuit diagram of 3 MHz high pass filter. (b) The designed characteristics of filter.

Image of FIG. 7.
FIG. 7.

Mica vacuum window. (a) Vacuum seal with gold gasket. 1 – antenna, 2 – wedge shaped waveguide, 3 – 10 CF flange, 4 – vacuum window, and 5 – waveguide. (b) The measurement of helium leak rate. The vacuum window is wrapped in a plastic bag for vacuum test in hood method. Helium gas is sprayed at time zero. (c) The microwave transmittance.

Image of FIG. 8.
FIG. 8.

The microwave transmittance of the filter bank of (a) W band, (b) V band, and (c) Q band. (d) The transmittance of Q band low pass filter.

Image of FIG. 9.
FIG. 9.

(a) Electric insulator made with Mylar sheet. (b) The microwave transmittance of the 0.3 mm and 0.9 mm thick Mylar electric insulators.

Image of FIG. 10.
FIG. 10.

The group delay of the microwave launched into vacuum. The microwave frequency is linearly swept.

Image of FIG. 11.
FIG. 11.

Phase measurement by wavelet transform.

Image of FIG. 12.
FIG. 12.

(a) The mixer output simulated for the plasma density profile and = 2 T. is the peak density, a is the plasma radius. (b) Experimental measurement of mixer output.

Image of FIG. 13.
FIG. 13.

Plasma density profile (shot No. 8137).

Image of FIG. 14.
FIG. 14.

Comparison of D emission and the plasma density contour measured by reflectometer (shot No. 7283).


Generic image for table
Table I.

Characteristics of the antenna.


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Scitation: Development of frequency modulation reflectometer for Korea Superconducting Tokamak Advanced Research tokamak