Ferroelectric Switch for Active RF Pulse Compressor for NLC

70131 Radio frequency (rf) pulse compression will be needed to achieve the high pulsed rf power levels required for a future electron-positron collider such as the Next Linear Collider (NLC). In principle, active rf pulse compression can provide greater flexibility in compressor design than passive compression because higher compression ratios can be achieved at higher efficiency. This project will develop active rf switches for this application. The switches will employ ferroelectrics at X-band, based on the principal of using the fast variation of dielectric constant with applied voltage to vary the resonance frequency of a cavity containing ferroelectric elements. Cavity designs will be developed for which the rf field levels and rf losses in the ferroelectric elements are within acceptable levels, and for which the required switching voltages are reasonable, for 0.4 ¿sec compressed rf pulses up to 600 MW. Phase I will develop a design for a fast X-band rf switch employing available ferroelectric switching elements in a resonance cavity, and low-power cold tests of the switch will be carried out. A high-power X-band version of the switch also will be designed, in order to specify the required tunability and acceptable loss tangent for the new ferroelectric ceramics that will be needed to realize a switch suitable for high peak and average rf power levels. In order to maximize compressor efficiency and to provide flat pulses, the designs will allow variations in switch reflectivity during both the energy storage and energy discharge phases in rf pulse compression. Commercial Applications and Other Benefits as described by the awardee: Active rf switches, embodying resonance cavities whose reflectivity can be changed rapidly in an rf pulse compressor, could result in adoption of such switches for use in a future electron-positron collider. Thousands of these switches would be required, constituting a potential commercial market of several tens of millions of dollars.