Search Results (6 total)

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.

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.

We report the first measurements of z-dependent coherent optical transition radiation (COTR) due to electron-beam microbunching at high gains ( >10⁴) including saturation of a self-amplified spontaneous emission free-electron laser (FEL). In these experiments the fundamental wavelength was near 530 nm, and the COTR spectra exhibit the transition from simple spectra to complex spectra ( 5% spectral width) after saturation. The COTR intensity growth and angular distribution data are reported as well as the evidence for transverse spectral dependencies and an “effective” core of the beam being involved in microbunching.

Nonlinear harmonic generation can be a very useful and important phenomenon for single-pass free-electron lasers (FELs) operating in the high-gain regime. Strong bunching at the fundamental wavelength and its associated higher harmonic content allow significant radiation at shorter wavelengths to be emitted without serious effects upon the output power at the fundamental. Here, we analyze the relative sensitivities to beam quality variations of the output fundamental and harmonic powers for a visible-wavelength FEL operating in the high-gain regime.

Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator.