Precision Phase Adjustment of a Linear Accelerator High Power Waveguide Feed Network

Each klystron of the SLAC accelerator feeds four consecutive 10-foot accelerator sections through approximately 25 feet of earth shielding. The high power waveguide network which divides and guides the power to the four sections is adjusted so that the rf waves traveling within the accelerator sections are, at the end of each section, phased within ± two degrees of an ideal wave traveling at the velocity of light. A modulated reflection technique is used to compare the electrical phase length from a single input port through the four arms of the network during adjustment. The inclusion of the previously tuned accelerator sections in the network allows the total phase error to be minimized if careful control is exercised over the section terperatures. The measuring system, the reflection modulators, and the possible errors involved are discussed.