CHRISTOPHER D. NANTISTA, SAMI G. TANTAWI** (SLAC)
The desire to reduce the amount of low-loss, circular-waveguide delay line required in a pulse-compressing power distribution system for the Next Linear Collider has led to the pursuit of multi-moded schemes . In such a system, power is delivered to different destinations through the same waveguide via different propagating modes. Current plans  utilize two modes, with manipulations done primarily in overmoded rectangular guide. We describe two key components of the system, a four-input/four-output, dual-mode launcher and an extractor for diverting one mode from the delay line to an accelerator feed while allowing the other to pass on to an upstream feed. These novel passive waveguide devices utilize the rectangular TE10 and TE20 modes. Because they must carry up to 600 MW pulsed rf power, h-planar symmetry is maintained in their designs to allow the use of overheight waveguide, and features that invite breakdown, such as coupling slots, irises, and septa, are avoided. Special rectangular-to-circular tapers  will be used to convert between the above modes and the circular TE11(12) and TE01 delay line modes, respectively.
 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.
 S.G.Tantawi, et al., 'New Developments in RF Pulse Compression,' invited talk, these proceedings.
 S.G. Tantawi, et al., 'RF Components Using Over-Moded Rectangular Waveguides for the Next Linear Collider Multi-Moded Delay Line RF Distribution System,' presented at the 18th Particle Accelerator Conference, New York City, NY, March 29-April 2,1999.
* Work supported by Department of Energy contract DE-AC03-76SF00515.
** Also with the Communications and Electronics Department, Cairo University, Giza, Egypt.
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