Harmonic Lasing in a Free-Electron-Laser Amplifier

A method is demonstrated that allows a planar wiggler high-gain Free-Electron-Laser (FEL) amplifier to lase so that the interaction with an odd harmonic of the radiation field dominates that of the fundamental. This harmonic lasing of the FEL is achieved by disrupting the electron interaction with the usually dominant fundamental while allowing that of a harmonic interaction to evolve unhindered. The disruption is achieved by a series of relative phase changes between the electrons and the ponderomotive potentials of both the fundamental and harmonic fields. Such phase changes are relatively easy to implement and some current FEL designs would require little or no structural modification to test the scheme

2D Bragg high power microwave source driven by an annular electron beam

The first successful cold microwave measurements of a 2D Bragg coaxial mirror were discussed. An important difference between 1D and 2D Bragg structures was demonstrated concerning the dependence of their reflection coefficient on the parameter αlz, where α denotes wave coupling coefficient and lz represents length. The minimum of the transmission was found to be the same for the 2D structures. The possibility of achieving single mode operation was also demonstrated for the Free Electron Masers (FEM) when driven by an oversized electron beam with D/λ∼25, where D denotes diameter of the microwave system used and λ stands for wavelength of radiation

X-ray free-electron lasers

With intensities 10(8)-10(10) times greater than other laboratory sources, X-ray free-electron lasers are currently opening up new frontiers across many areas of science. In this Review we describe how these unconventional lasers work, discuss the range of new sources being developed worldwide, and consider how such X-ray sources may develop over the coming years