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| TUAAU03 | A Comparison of Short Rayleigh Range FEL Performance with Simulations | |
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Previous three-dimensiontal simulations of Free-electron laser (FEL) oscillators showed that FEL gain doesn't fall off with Rayleigh range as predicted by one-dimensional simulations*. They also predict that the angular tolerance for the mirrors is much large than simplistic theory predicts. Using the IR Upgrade laser at Jefferson Lab lasing at 935 nm we have studied the performance of an FEL with very short Rayleigh range. We also looked at the angular sensitivity for several different Rayleigh ranges. We find that, even for large Rayleigh ranges, the angular sensitivity is much less than one might expect. The relative angle of the electron beam and optical mode can change by more than the 1/·102 divergence without reducing the laser gain. This is the first demonstration that 3-dimensional effects qualitatively change the performance of an FEL oscillator. We find very good agreement between simulations and measured gain. Surprisingly the gain continues to rise as the Rayleigh range is shortened and continues to grow even when the resonator becomes geometrically unstable. The same behavior is seen in both the experiment and simulations.
* W. B. Colson et al., "Short Rayleigh length free electron lasers",Physical Review Special Topics: Accelerators and Beams 9, 030703, 2006 |
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| THAAU01 | Experience and Plans of the JLAB FEL Facility as a User Facility | 491 |
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| Jefferson Lab’s IR Upgrade FEL building was planned from the beginning to be a user facility, and includes an associated 600 sq. m area containing seven laboratories. The high average power capability (multikilowatt-level) in the near-infrared (1-3 microns), and many hundreds of watts at longer wavelengths, along with an ultrafast (~ 1 ps) high PRF (10’s MHz) temporal structure makes this laser a unique source for both applied and basic research. In addition to the FEL, we have a dedicated laboratory capable of delivering high power (many tens of watts) of broadband THz light. After commissioning the IR Upgrade, we once again began delivering beam to users in 2005. In this presentation, I will give an overview of the FEL facility and its current performance, lessons learned over the last two years, and a synopsis of current and future experiments. | ||
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