Lattice design challenges for fourth-generation storage-ring light sources.

Third-generation low-emittance storage-ring light sources based on double- and triple-bend cells and undulator magnets have been in operation around the world for more than two decades. On the horizon is a new generation based on the multi-bend achromat (MBA) lattice concept promising two to three orders of magnitude higher brightness than is available in today's sources. In this paper, the challenges inherent in designing MBA lattices, as well as potential solutions, are described. Topics covered include lattice concepts, scaling of storage-ring performance, brightness optimization, nonlinear dynamics, beam lifetime and injection schemes.

Time-resolved phase measurement of a self-amplified free-electron laser.

We report on the first time-resolved phase measurement on self-amplified spontaneous emission (SASE) free-electron laser (FEL) pulses. We observed that the spikes in the output of such free-electron laser pulses have an intrinsic positive chirp. We also observed that the energy chirp in the electron bunch mapped directly into the FEL output. Under certain conditions, the two chirps cancel each other. The experimental result was compared with simulations and interpreted with SASE theory.

Characterization of a chaotic optical field using a high-gain, self-amplified free-electron laser.

We report on a characterization of the chaotic optical field from a high-gain, self-amplified spontaneous-emission (SASE) free-electron laser. The temporal structure of the amplitude and phase are measured in a single-shot mode, with a resolution well below the coherence length, and the statistics over multiple pulses is determined. The measurement is in excellent quantitative agreement with the prediction based on analysis of random noise, and further verifies the chaotic nature of the SASE optical field.