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Demonstration of High Harmonics from Echo-enabled Harmonic Generation with Small Energy Modulation |
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- D. Xiang
SLAC, Menlo Park, California, USA
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Funding: This work was supported by the US DOE under Contract No. DE-AC02-76SF00515.
5th harmonic from EEHG has been observed at SLAC's NLCTA [1], yet with energy modulation amplitudes about 80 times larger than beam slice energy spread. While the experiment demonstrated that long-term memory of phase space correlations could be preserved, it was incapable of providing insight into the underlying physics of EEHG that high harmonics can be generated with small energy modulation. Here we report generation of the 7th harmonic from EEHG technique in realistic scenarios where the laser energy modulation is comparable to the beam slice energy spread. The experiment demonstrates the supreme up-frequency conversion efficiency of EEHG technique and indicates that scaling to X-ray wavelength may be possible.
[1] D. Xiang et al., Phys. Rev. Lett, 105, 114801 (2010).
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Slides WEOB4 [0.981 MB]
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| WEPB15 |
Reversible Electron Beam Heater for Suppression of Microbunching Instabilities Based on Transverse Deflecting Cavities |
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- C. Behrens
DESY, Hamburg, Germany
- Z. Huang, D. Xiang
SLAC, Menlo Park, California, USA
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The presence of the microbunching instability due to the compression of high-brightness electron beams at existing and future X-ray free-electron lasers (FEL) results in restrictions on the attainable lasing performance and renders diagnostics like beam imaging with optical transition radiation impossible. The instability can be suppressed by introducing additional energy spread, i.e. heating the beam, as demonstrated by the successful operation of the laser heater system at the Linac Coherent Light Source. The increased energy spread is typically tolerable for self-amplified spontaneous emission FELs but limits the effectiveness of seeded FELs. In this paper, we present a reversible electron beam heating system based on two transverse deflecting cavities (TCAV) in front and behind a bunch compressor chicane. The additional energy spread will be introduced in the first TCAV, which suppresses the microbunching instability, and then will be eliminated in the second TCAV. We show the feasibility of the suppression of microbunching instabilities based on calculations and simulations, and set limits to the acceptable jitter tolerances.
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