Compact S-Band Pulse Compressor

High-power RF sources are one of the main sources of accelerator inefficiency. To increase efficiency, we propose to design in Phase I, then fabricate and test during Phase II, a multi-beam klystron with a new type of depressed collector. This collector allows recovery of a larger portion of energy in the spent electron beams than could a conventional depressed collector, and will significantly increase the tube’s efficiency (say from 65% towards 80% in a single stage) and cut waste heat nearly in half. General statement of how this problem is being addressed: Externally-applied magnetic and electric fields, together with beam space charge forces, can allow a large increase in the depressed potential of the beam collector in a linear beam tube such as a multi-beam klystron, without causing reflected electrons from returning to the RF circuit or cathode. In this way, the portion of the spent beam that is collected at the depressed potential can be significantly increased, resulting in an increase in the tube’s efficiency with a corresponding decrease in waste heat. What is to be done in Phase I: Preliminary designs will be refined for a depressed collector with a grounded portion for use with our proven 2.8 MW 6-beam 1300 MHz multi-beam klystron, so as to maximize the improvement in overall tube efficiency, as compared to operation without a depressed collector. Plans will be made for fabrication during Phase II for a prototype of this collector on an improved version of this multi-beam klystron. Commercial Applications and Other Benefits: Energy savings and reductions in cooling demands for waste heat that would result from the projected increase in efficiency can be estimated for the 560 multi-beam klystron required for the two main ILC linacs: wall plug power would be lower by 13-19% and waste heat by 32-45%. Electricity cost savings, based on industrial rates in Japan, would exceed $10 million/year. These potential savings translate into a large commercial opportunity for licensing the collector design to industrial microwave tube manufacturers. Similar beam collectors for other high-power tubes for other accelerators also represent a significant commercial opportunity. Key words: efficiency enhancement; high-power microwave sources; international linear collider.