Author: Colocho, W.S.
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TUP070 Energy Jitter Minimization at LCLS 523
 
  • L. Wang, A.L. Benwell, A. Brachmann, W.S. Colocho, F.-J. Decker, Z. Huang, T.J. Maxwell, T. Tao, J.L. Turner
    SLAC, Menlo Park, California, USA
 
  The energy jitters of the electron beam can affects the FEL in self-seeded modes if the jitter is large compared to the FEL parameter. We work in multiple ways to reduce the jitters, including hardware improvement, optimization linac set-up. This paper discusses the optimization of linac set-up. The solutions always suggest that we can largely reduce the energy jitter from a weak compression at BC1 and a stronger compression at BC2. Meanwhile a low beam energy at BC2 also reduce the energy jitter, which is confirmed by the experiment. The results can be explained by a simple model. Experimental results are also presented, demonstrating better than 20% and 40% relative energy jitter reduction for 13.6 and 4 GeV linac operation, respectively.  
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WEP022 Photon Energies beyond the Selenium K-Edge at LCLS 630
 
  • F.-J. Decker, W.S. Colocho, Y. Ding, R.H. Iverson, H. Loos, J. Sheppard, H. Smith, J.L. Turner
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) was designed for a photon energies of 830 eV to 8.3 keV. This range was widened and up to 11.2 keV photons were already delivered for users. The Selenium K-edge at 12.6578 keV is very interesting since Selenium can replace Sulfur in biological structures and then that structure could be precisely measured. To reach this the electron energy would need to be raised by about 6% which initially didn't seem possible. The trick is to change the final compression scheme from a high correlated energy spread and moderate R56 in the compression chicane to moderate energy spread and high R56. The same bunch length can be achieved and RF energy is freed up, so the overall beam energy can be raised. Photons up to an energy of 12.82 keV (1.3% above the K-edge) with a pulse intensity of 0.93 mJ were achieved. The photon energy spread with this setup is wider at around 40-50 eV FWHM, since less correlated energy spread is left after the compression.
 
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