Plasma Switch for 11.4 GHz Active Sled-II RF Pulse Compressor

70518S02-II High pulsed radio frequency (RF) power, needed for a future electron-positron collider such as NLC, will require RF pulse compression, for which a number of approaches are currently under study. Active RF pulse compression can, in principal, provide greater flexibility in compressor design than passive compression, because higher compression ratios at higher efficiency can be achieved. This project will develop a plasma switch for an active SLED-II RF pulse compressor with a compression ratio greater than 8:1 and efficiency greater than 75%. The plasma switches will be used with resonance structures having a reflection coefficient that can be rapidly shifted during the RF pulse from a klystron. Changing both the reflection coefficient of the switch and the phase of the klystron output will allow high compression ratios with high efficiency. In Phase I, three versions of an X-band resonance structure were designed to couple RF power from a klystron into a pair of delay lines and thence, upon switching, into an accelerator structure. Low-power cold tests were conducted, and, for one version, 70 ns RF pulses were produced with power gains up to 15:1. Improved plasma switch tube concepts were developed for implementation during Phase II, to allow operation at peak power levels exceeding 400 MW, with good pulse-to-pulse reproducibility. In Phase II, engineering designs for the RF structures and associated plasma switches will be completed, and plasma discharge tubes of both quartz and ceramic will be evaluated. Optimized plasma switches will be built and installed on the SLAC dual-mode X-band resonant delay lines for testing at high power, with the aim of producing 400 ns RF pulses with peak power >400 MW and efficiency >75%. Commercial Applications and Other Benefits as described by awardee: The RF plasma switches should be suitable for use in a future electron-positron collider such as the NLC. Thousands of these switches would be required, constituting a potential market of several tens of millions of dollars. Other markets for such switches could exist in advanced radar systems.