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A Prototype Experiment on Remote Steering Antenna for ECRH System

B. K. Shukla, K. Sathyanarayana, P. Chattopadhyay, Pragnesh Dhorajia, D. Bora

Fusion Science and Technology / Volume 52 / Number 1 / July 2007 / Pages 68-74

Technical Paper

In conventional electron cyclotron resonance heating systems, beam steering for current drive is achieved by rotating the mirrors of the launcher. Alternatively, it could be achieved remotely using a rectangular/square-corrugated waveguide (SCW). Symmetric beam steering is achieved at a length L (8a2/), where "a" is the width of the waveguide and "" is the wavelength of the microwave while at L/2 (4a2/) antisymmetric steering is seen. At a length of 2a2/, beam splitting into two equal lobes is observed.

A low-power experiment on a remote steering antenna is carried out with an SCW at 2a2/ and a plane fixed mirror at the exit of the SCW, which diverts the microwave beam in one direction. The microwave instrumentation consists of a Gunn oscillator (82.6 GHz/~40 mW/TE10), an isolator, an attenuator, waveguides, and a mode converter (TE10 to HE11). The output of the mode converter is a 63.5-mm-diam corrugated waveguide, which couples the microwave beam to the SCW. The microwave power emerging from the waveguide is scanned in the far-field region using calibrated detectors. The power spectrum at the output of the SCW shows that the peak appears at the same angle input to the SCW. Effective steering is achieved for a smaller length of the waveguide at various input angles from 6 deg to 18 deg.

 
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