Optics System Design of Microwave Imaging Reflectometry for the EAST Tokamak

Abstract

A front-end optics system has been developed for the EAST microwave imaging reflectometry for 2D density fluctuation measurement. Via the transmitter optics system, a combination of eight transmitter beams with independent frequencies is employed to illuminate wide poloidal regions on eight distinct cutoff layers. The receiver optics collect the reflected wavefront and project them onto the vertical detector array with 12 antennas. Utilizing optimized Field Curvature Adjustment lenses in the receiver optics, the front-end optics system provides a flexible and perfect matching between the image plane and a specified cutoff layer in the plasma, which ensures the correct data interpretation of density fluctuation measurement.

Optimization of the optical system for electron cyclotron emission imaging diagnostics on the HL-2A tokamak

“…Also, the distance between the focal optics and the zoom optics increased by 150 mm in the new design to ensure that the image plane can reach the high-field side of the plasma. The change of the radius of curvature from −1100 mm to −1000 mm and of the surface type from cylinder to Y toroid (conic constant −2.5) of the zoom 2 lens make the main contribution to improvement of the image surface shape compared with that of the present optics [15][16][17][18]. Finally, the radius of curvature of lens H1/H1′ was adjusted to ±800 mm from ±720 mm in order to make sure that the Xdirection beam radius on the image plane is less than 30 mm.…”

The co-located arrangement of ECEI and MIR microwave imaging diagnostics on EAST tokamak

“…The transmitter mini-section was charged to extend the transmitter signal from the source and to illuminate widely the cutoff layer deep in the plasma, through the path marked with red arrows. Matching the illumination wave-front shape to the cutoff layer for normal incidence is necessary to minimize Doppler shift during plasma rotation [11,12]. The MIR is situated on the lower level within the complete optics housing, as depicted in figure 2b.…”

An intelligent remote control system for ECEI on EAST

“…The positions of the lenses driven by these step-motors vary in the range of 30 cm. Therefore, the imaging optics focusing position is changed while keeping the same spatial resolution of about 1 cm [10][11][12][13][14]. The time cost in changing the focus position from the edge to the core of EAST is about 15 s.…”