Abstract: The present invention provides in a Free electron laser a means to increase the temporal resolution of the optical pulses while simultaneously increasing the spectral resolution of the pulse train. The increase in temporal resolution is achieved by introducing a quadratic temporal phase variation (i.e. linear frequency chirping) across the pulses, and then propagating the outcoupled pulses through a dispersive relay line to compress them to the transform limit of the broadened spectrum.

Abstract: An electron gun (10) that suppresses the non-linear space charge forces and phase-dependant focusing forces that are chiefly responsible for the high emittance of conventional electron guns. The gun comprises a resonant microwave cavity (15), a cathode (12) mounted in the cavity wall, and a momentum analyzer system (17). The resonant microwave cavity, when supplied with microwave power, supports an electromagnetic field having a high-gradient electric component directed along an acceleration axis. The cavity is formed with an exit aperture (32) at a location relative to the cathode such that emitted electrons are accelerated along the axis and pass through the exit aperture. The cavity length is chosen to allow the microwave field within the cavity volume to accelerate the electrons to an energy of about 0.5-1.0 MeV prior to the electrons' passing through the aperture. Bunching is provided by the momentum analyzer.