CHRISTOPHER D. NANTISTA, FUMIHIKO TAMURA** (SLAC)
In recent designs for multi-moded delay line distribution systems, the waveguide modes of choice have been TE01 and one or both polarizations of TE12 , . For the highly overmoded waveguide diameter of 4.75-in. (and out to ~7-in.) at X-band, these are the modes with lowest theoretical ohmic loss. Considerable experience with the use of TE01 has been gained in pulse compression development  over the past decade, and recent transmission experiments  have demonstrated the feasibility of using TE12. There may, however, be certain advantages to substituting TE02 for TE12. In the past, this mode has been passed over largely because ideas for selective launching and extracting depended on modes being distinguishable by the azimuthal variation of their fields. The new design approach, however, of manipulating modes in overmoded rectangular waveguide  and transitioning to circular waveguide via special tapers, suggests that we could work instead with the rectangular TE20 and TE40 modes. We present reasons to consider a TE01/TE02 system and describe waveguide circuits for launching and directing the above rectangular modes.
 S.G.Tantawi, et al., 'A Multi-Moded RF Delay Line Distribution System for the Next Linear Collider,' proc. of the Advanced Accelerator Concepts Workshop, Baltimore, MD, July 5-11, 1998, pp. 967-974.
 Christopher D. Nantista and Sami G. Tantawi, 'Multi-moded Passive RF Pulse Compression Development at SLAC,' proc. of the Advanced Accelerator Concepts Workshop, Santa Fe, NM, June 10-16, 2000.
 S.G. Tantawi, et al., 'The Generation of 400-MW RF Pulses at X Band Using Resonant Delay Lines,' IEEE Trans. MTT, vol. 47, no. 12, pp. 2539-2546, Dec. 1999.
 Sami G. Tantawi, et al., 'Evaluation of the TE12 Mode in Circular Waveguide for Low-Loss, High-Power RF Transmission,' to be published in Phys. Rev. ST Accel. Beams.
 Christopher D. Nantista and Sami G. Tantawi, 'A Planar, Rectangular Waveguide Launcher and Extractor for a Dual-Moded RF Power Distribution System,' these proceedings.
* Work supported by Department of Energy contract DE-AC03-76SF00515.
** Also with Tokyo University.
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