One-channel, multi-mode active pulse compressor

Abstract

Basic studies of factors that limit RF fields in warm accelerator structures require experiments at RF powers that can be produced using pulse compression. This approach is being implemented to compress output pulses from the Yale/Omega-P 34-GHz magnicon to produce ~100-200 MW, 100 ns pulses. A new approach for passive pulse compression is a SLED-II type circuit operating with axisymmetrical modes of the TE0n type that requires only a single channel instead of the usual double channel scheme. This allows one to avoid a 3-dB coupler and need for simultaneous fine tuning of two channels. A 30 GHz passive prototype was tested at low power level in order to demonstrate key principles. The prototype showed a power gain 4.5 at a compression ratio 6:1 for an efficiency 63%. An active version of the onechannel pulse compressor is also suggested. It is attractive due to the possibility to achieve higher power gain. The active version naturally requires an electrically controlled coupler. In particular, as active elements of the coupler we suggest to use either gas filled discharge tubes or ferroelectrics.

Configurations for short period rf undulators

“…The first approach is to use a cavity where the copropagating and counterpropagating waves are modes with different transverse field structures, so that electrons interact only with the counterpropagating wave, provided the copropagating mode has zero fields along the beam trajectory [17,18].…”