Design and test of a 100 MW X-band TE01 window

Research at Stanford Linear Accelerator Center (SLAC) is in progress on a TeV-scale linear collider that will operate at 5-10 times the energy of present-generation accelerators. This will require development of high power X-band sources generating 50 - 100 MW per source. Conventional pillbox window designs are capable of transmitting peak rf powers up to about 30 MW, well below the desired level required for the use of a single window per tube. SLAC has developed a 75 MW TE₀₁ window that uses a ´traveling wave´ design to minimize fields at the window face. Irises match to the dielectric window impedance, resulting in a pure traveling wave in the ceramic and minimum fields on the window face. The use of the TE₀₁ mode also has zero electric field on the braze fillet. Unfortunately, in-band resonances prevented this window design from achieving the desired 75 MW power level. It was believed the resonances resulted from sudden steps in the circular guide to match the 38 mm input diameter to the overmoded (TE₀₁ and TE₀₂ mode propagating) 65 mm diameter of the window ceramic.