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| TUAAU01 | High Power FEL Developments – A Review | |
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| High power FELs have continued to make significant progress in the last few years. Power advances are taking advantage of the energy recovering linac technology on both superconducting and room temperature machines. In general, the limiting technology has been the injector current capability but there are a number of other technical factors which must be considered to successfully develop a high average power Free Electron Laser. With a number of groups poised to develop 100 mA ERLs, many with FELs, the importance of resolving limiting issues is becoming more critical. The Recuperator at Novosibirsk has the record current of 22 mA and has produced over 400 W of FEL power. Work is underway to extend the power and performance of this pioneering machine. Meanwhile, at Jefferson Lab, the Upgrade FEL achieved 14.3 kW of output while recirculating 8 mA. Numerous efforts are underway to increase the average brightness capabilities injectors: Brookhaven, Los Alamos, and Berkeley National Labs, Cornell University, Advanced Energy Systems, Daresbury Lab, KEK, and FZ Dresden among others have significant injector development programs underway. This talk will review the status of high average power FELs around the world and discuss the technical developments underway in injectors, optics, and other areas to achieve yet higher performance. | ||
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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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