Two-color free-electron laser driven by a radio-frequency linear accelerator

The radio-frequency linear accelerator is an ideal driver for a two-color free-electron-laser (FEL) system. Such two-color FEL operation, in which two synchronous optical beams are produced at different frequencies and in which each frequency (or “color”) can be tuned independently over a broad range, would make an unprecedented variety of pump–probe experiments feasible. Modifications to the Superconducting Accelerator/Free Electron Laser at Stanford University that will be required for two-color FEL operation are described. Expected optical-beam parameters at wavelengths extending from 15 μm are given.