Compact Probe for Power Detection from the Narrow Side of the Waveguide
Authors: C.C. Kung, S. Bernabei, J. Gumbas, N. Greenough, E. Fredd, J.R. Wilson, and J. Hosea
Date of PPPL Report: May 2004
Published in: IEEE Transactions on Plasma Science 33:2 (April 2005) 969-975
Phased array antennas with high directivity have a variety of applications. One of their applications is in radio-frequency (rf) heating for magnetically confined plasma fusion research. Among these rf heating schemes, waveguide arrays with careful phase control on each waveguide can act as a phased array antenna to deliver megawatts of power for heating fusion plasmas in the lower-hybrid range of frequencies (1 GHz-10 GHz). In order to achieve compactness, it is common to stack reduced height waveguide together to form the waveguide array. As long as the delivered power does not cause arcing in the waveguide, the waveguide height can be quite small. Due to this confined space in a stack of reduced height waveguides, power detection of the incident and reflected wave in the reduced height waveguide is extremely difficult. A new compact probe, which employs current loops, to monitor the incident and reflected wave from the narrow side of the reduced height waveguide has been developed. Its theory and performance will be reported in this paper.