Whispering Gallery X-Band Power Multiplier

72923-Radio frequency (RF) pulse compression is required to achieve the high peak powers needed for testing accelerator structures and components, and ultimately for driving the accelerator structures. This project will develop a whispering gallery resonator, or coupled pair of resonators, as a passive pulse compressor that can provide efficient peak power multiplication (greater than 4 to 1) at 11.4 GHz. A single whispering gallery mode, such as the rotating TM20,1,1 mode of a cylindrical barrel resonator, can function as a passive rf pulse compressor in much the same manner as SLED (SLAC energy doubler), with the two orthogonal modes that comprise the rotating mode serving as the two modes of SLED. In Phase I, a single-resonator pulse X-band compressor was designed and cold tested at low RF power, showing peak power gain of up to 7.5:1 at an efficiency of about 80%. Designs of single- and double-resonator compressors were developed to operate with either sudden 180 degree phase shift during the input RF pulse, or with a narrow frequency-modulated input pulse. A preliminary design was developed for a high-vacuum, high-power version of this novel pulse compressor. In Phase II, a single-resonator TM20,1,1 mode whispering gallery X-band pulse compressor will be engineered, built, and tested at input powers up to 50 MW. A double-resonator version will be designed and engineered for frequency-modulated input pulses. An analysis of the energy distribution of electrons, which would be accelerated in structures driven with RF pulses compressed in this manner, will be carried out. Commercial Applications and Other Benefits as described by awardee: A compact, high-peak-power RF pulse compressor could find scientific application in a future high-energy electron-positron collider, or in advanced radar and communications applications.