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The LCLS energy jitter: sensitivities and tolerance

Discusses sensitivities and tolerance for varying charge and compression at LCLS, focusing on operational shifts from 1nC to 150pC. Examines challenges and strategies for stable operation under hardware constraints.

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The LCLS energy jitter: sensitivities and tolerance

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  1. The LCLS energy jitter: sensitivities and tolerance J. Wu Meeting on “reduction of LCLS linac energy jitter”October 24, 2012 FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  2. Outline • Sensitivities are different for different charge, different compression • Original CDR was devoted to 1 nC • Operation is for 150 pC • Self-seeding is for 40 pC FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  3. LCLS CDR 1 nC FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  4. LCLS CDR 1 nC FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  5. LCLS CDR L1s -21.9o L1s -22o L1s -22.1o 150 pC: compressed to 3 kA DE/E ~ 2.1E-04 FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  6. LCLS CDR L1s -27.9o L1s -28o L1s -28.1o 40 pC: compressed to 2 kA DE/E ~ 2.8E-04 Ipk: 1-1.5 -2 kA FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  7. Electron bunch profile L1s -21.9o L1s -22o L1s -22.1o Elegant for LCLS (L1S RF phase jitter by ±0.1o) FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  8. Electron bunch profile Tail Head Elegant for LCLS (L1S RF phase jitter by ±0.1o) FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  9. Electron bunch profile Tail Head Elegant for LCLS (L1S RF phase jitter by ±0.1o) FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  10. 40 pC Electron profile @ FEL operation point: vary from shot-to-shot FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  11. RF phase fluctuation Taper starts @ 30 m with 0.4 %; Seed: 1 MW Different bunch compression, energy fixed FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  12. RF phase fluctuation Taper starts @ 30 m with 0.4 %; Seed: 1 MW Temporal profile FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  13. RF phase fluctuation Taper starts @ 30 m with 0.4 %; Seed: 1 MW spectrum FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

  14. Summary • In general, a seeded FEL tolerance on the seed properties, the RF jitter, the details of the current profile coupled to the collective effects, taper tolerance, etc. are much more demanding • Intrinsic fluctuation in power due to the SASE process in the seed generation • Other sources of seeded FEL jitter arise from energy, energy chirp, and beam distribution changes • Sensitivities can be measured, benchmark the existing measurement against simulation to validate the model • With this model, find a stable operation point given the hardware constraints. FEL and Beam Phys. Dept. (ARD/SLAC), J. Wu, jhwu@slac.stanford.edu

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