Novel scheme of the long wavelength FEL amplifier with a transverse electron current

A novel scheme of the long wavelength FEL amplifier with a transverse electron current has been discussed. In this scheme an amplified signal propagates across the electron beam and the operating wavelength is equal to the undulator period. A specific feature of the transverse current amplifier is the absence of saturation, i.e. under special optimization of the undulator field, the output power grows proportionally to interaction distance, which is defined by the beam transverse size. The X-band amplifier should be based on the U-2 accelerator at the Budker Institute of Nuclear Physics and produce 500 kV, 1 kA/cm sheet electron beam with transverse size amounts 140 cm (J. Appl. Phys. 72 (1992) 1657). It has been observed that a gain of ∼38 dB corresponding to a 6.5 GW output power and 10% efficiency could be achieved for a 2 kOe undulator field and a 1 MW seed signal. Additional optimization of guiding and undulator fields provides the possibility of increasing the output power up to 18 GW with an efficiency of 27%.