Improved Performance Of The Boeing/LANL Fel Experiment

Abstract

We observed significant improvement in the performance of the Boeing/LANL free-electron laser (FEL) experiment in the last year. Some of the more graphic demonstrations of this improved performance are presented in the time-resolved optical spectral measurements (streak/spectrometer) and the electron-beam spectral measurements. We have observed an extraction efficiency of about : % for the uniform wiggler and nearly 1% for the tapered-wiggler experiment. We also present experimental evidence consistent with a sideband instability and its suppression by cavity-length detuning.

Upgrades of beam diagnostics with application to emittance-exchange experiments

“…The studies were also complicated by the roughly 100 times stronger signal of the scintillator compared to the OTR screen for a given charge, and the effects of the rf amplitude and phase flatness over a pulse train. Our initial comparison of the powder screen and OTR in the same geometry is shown in Table II These results are consistent with our previous hypothesis that the YAG:Ce powder screen has a limiting resolution term to be addressed [8].…”

“…The former YAG:Ce 50-m thick powder screens on an Al substrate oriented at 45 degrees to the beam direction [7,8] (with updated spatial resolution term in Sec. III) have been now replaced by 100-m thick YAG:Ce single crystals oriented normal to the beam direction followed by a 45 mirror to direct the radiation to the optical system.…”

Three-dimensional, time-dependent analysis of high- and low-Q free-electron laser oscillators

“…Furthermore, electrostatic accelerators are capable of long to continuous wave electron pulses, that can result in single longitudinal mode oscillation with a relative linewidth of about 10 −8 over a time of 5 𝜇s, which was set by the voltage droop present in the accelerator [5] at the time of measurement. On the other hand, the short duration of and spread in electron energy for the electron pulses produced by RF linacs typically leads to a relative linewidth of the order of 10 −4 to 10 −2 [12,28,[39][40][41][42][43][44][45][46][47][48][49][50][51][52], unless additional spectral filtering is used. For example, using the Vernier effect of a double cavity resonator to reduce the number of intra-cavity longitudinal modes and subsequent external filtering, an RF-linac-based FEL oscillator was able to provide a single longitudinal mode [53].…”