Controllable X-Ray Pulse Trains from Enhanced Self-Amplified Spontaneous Emission.

We report the demonstration of optical compression of an electron beam and the production of controllable trains of femtosecond, soft x-ray pulses with the Linac Coherent Light Source (LCLS) free-electron laser (FEL). This is achieved by enhanced self-amplified spontaneous emission with a 2  μm laser and a dechirper device. Optical compression was achieved by modulating the energy of an electron beam with the laser and then compressing with a chicane, resulting in high current spikes on the beam which we observe to lase.

Thermionic microwave gun for terahertz and synchrotron light sources.

Conventional thermionic microwave and radio frequency (RF) guns can offer high average beam current, which is important for synchrotron light and terahertz (THz) radiation source facilities, as well as for industrial applications. For example, the Advanced Photon Source at Argonne National Laboratory is a national synchrotron-radiation light source research facility that utilizes thermionic RF guns. However, these existing thermionic guns are bulky, difficult to handle and install, easily detuned, very sensitive to thermal expansion, and due for a major upgrade and replacement.

Phase-Stable Self-Modulation of an Electron Beam in a Magnetic Wiggler.

Electron beams with a sinusoidal energy modulation have the potential to emit subfemtosecond x-ray pulses in a free-electron laser. An energy modulation can be generated by overlapping a powerful infrared laser with an electron beam in a magnetic wiggler. We report on a new infrared source for this modulation, coherent radiation from the electron beam itself.

Precision Control of the Electron Longitudinal Bunch Shape Using an Emittance-Exchange Beam Line.

We report on the experimental generation of relativistic electron bunches with a tunable longitudinal bunch shape. A longitudinal bunch-shaping (LBS) beam line, consisting of a transverse mask followed by a transverse-to-longitudinal emittance exchange (EEX) beam line, is used to tailor the longitudinal bunch shape (or current profile) of the electron bunch. The mask shapes the bunch's horizontal profile, and the EEX beam line converts it to a corresponding longitudinal profile.