Microwave production by a free-electron laser bunched beam driving a resonant cavity at 35 GHz

In the two-beam accelerator scheme, a high-current electron beam, bunched at the resonant frequency, traverses extraction cavities, where it generates power intended to drive accelerating cavities on the main beam. Here, we report on work performed to test some aspects of this scheme. We used a free-electron-laser (FEL) amplifier at 35 GHz to bunch a beam of electrons, which is then transported and focused into a resonant cavity. The results of earlier bunching experiments had demonstrated the capacity of the FEL supplied by an induction linac to generate an appropriate drive beam. A summary of this earlier work is presented along with measurements of power from the cavity. This constitutes the first observation of high-frequency power extraction using a FEL in this scheme.