The free-electron laser

In a Free Electron Laser (FEL), radiation is initially produced by spontaneous synchrotron radiation. After this has been reflected by two mirrors located at the ends of an undulator, the radiation is amplified in the course of subsequent passes with an electron beam located within a superconducting magnet. In the case of an FEL storage ring configuration, the electrons are reaccelerated by the device's radio frequency system after they have given off energy to the laser beam, and are then reinjected into the undulator to further interact with the radiation beam. In Raman FELs, the electromagnetic radiation and the undulator field can excite collective oscillation modes in the electron beam, and the frequency of the radiation generated is shifted downwards. The tunability of the FEL renders it ideal for photochemical applications, especially isotopic separation.