[IEEE 2003 IEEE International Symposium on Antennas and Propagation: URSI North American Radio Science Meeting - Columbus, OH, USA (22-27 June 2003)] IEEE Antennas and Propagation Society International Symposium. Digest. Held in conjunction with: USNC/CNC/URSI North American Radio Sci. Meeting (Cat. No.03CH37450) - The method of singular integral equations in the eigenvalue analysis of a coaxial gyrotron with a corrugated insert