Antenna and transmission system for high power electron cyclotron heating in a compact helical system

A new electron cyclotron emission imaging antenna was designed and installed outside the torus on LHD. To improve the signal quality, we developed a local oscillator integrated antenna array (LIA), in which each channel has an internal local oscillation supply from a frequency-multiplier-integrated circuit. The labyrinth structure of the optical system comprises five mirrors to protect the LIA from plasma neutron emission. The initial results were obtained from the 2017 LHD experimental campaign. The MHD fluctuations and their fluctuation profiles were observed.

Section: Ecei Optics On Lhdmentioning

confidence: 99%

Installation of New Electron Cyclotron Emission Imaging in LHD

Takahashi

Kuwahara

Tokuzawa

et al. 2018

“…In other words, the mirror surface is defined as the constant surface of the difference between Φ in and Φ out . This is a phase matching condition or a constant phase distance condition of between input and output beam on the mirror, and can be interpreted as a generalization of the elliptical mirror that satisfies a constant distance between focal points for a geometrical optics [1]. It should be noted that the input beam and the output beam are Gaussian beams.…”

Section: Definition Of the Mirror Surfacementioning

confidence: 99%

“…In the geometrical optics limit, the mirror surface is expressed as part of the ellipsoid, which satisfies a constant distance from the focal points of the input beam and the output beam. In the case of Gaussian optics, the constant phase distance surface defines the quasi-optical mirror [1].…”

Section: Introductionmentioning

confidence: 99%

Development of the Grating Mirror for the High Power Transmission System and Its General Theory

Goto

Kubo

Tsujimura

2018

In the transmission system of the high power Electron Cyclotron Heating (ECH), many mirrors have been installed in the injection antenna section in particular. In some cases, it is difficult to design a normal mirror due to the restriction of the boundary condition. A grating mirror is one of the solutions in such cases. Moreover, controlled power splitting or combining at high power can be realized by a grating mirror. Diffraction angle, efficiency, and distortion/conversion of the polarization can be controlled by the grating shape design. In this study, we developed a grating mirror to efficiently separate the second harmonics component from the fundamental high power beam at 82.7 GHz and higher harmonics. The performance of this grating is confirmed experimentally for the use of vortex beam formation. During this development, the design procedure of a grating mirror is established and generalized to apply for various purposes.

“…The corrugated waveguide, with inside diameter of 63.5 mm, matches well with the Gaussian beam. To improve the coupling, the surface of the concave mirrors is designed using the constant phase concept [2]. We consider the Gaussian beams incident on and reflected from a mirror when the waist size w 0,in , w 0,out and waist position r w,in , r w,out are known.…”

Section: Constant Phase Mirrormentioning

confidence: 99%

“…Because the beam radius is a function of distance from the waist position, the values of w 0,in , w 0,out , r w,in , and r w,out are required to match the waist size at the mirror position. If the matching is satisfied, the mirror surface can be numerically designed using the concept of constant phase given by the following relation [2]:…”

Section: Constant Phase Mirrormentioning

confidence: 99%

Design and Installation of a New Electron Cyclotron Emission Diagnostic Antenna in LHD

Takahashi

Nagayama

Kawahata

et al. 2011

A new electron cyclotron emission (ECE) antenna was designed and installed outside of torus, when the heating and diagnostics systems were reconfigured in LHD. Its design is based on Gaussian beam optics and consists of two plane and two concave mirrors. The mirror surfaces are defined using the concept of constant phase to improve matching to the corrugated waveguide. The new ECE antenna was used in a 2010 experiment to measure the electron temperature profile and its fluctuations.