Author: Berg, W.
Paper Title Page
Hard X-ray Self-seeding at the Linac Coherent Light Source  
  • P. Emma, J.W. Amann, F.-J. Decker, Y.T. Ding, Y. Feng, J.C. Frisch, D. Fritz, J.B. Hastings, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, S. Spampinati, D.R. Walz, J.J. Welch, J. Wu, D. Zhu
    SLAC, Menlo Park, California, USA
  • W. Berg, R.R. Lindberg, D. Shu, Yu. Shvyd'ko, S. Stoupin, E. Trakhtenberg, A. Zholents
    ANL, Argonne, USA
  • V.D. Blank, S. Terentiev
    TISNCM, Troitsk, Russia
  Funding: Work supported by US Department of Energy, contract number DE-AC02-76SF00515.
We report on experimental results of FEL self-seeding with Angstrom wavelengths at the Linac Coherent Light Source (LCLS) at SLAC. The scheme, suggested at DESY*, replaces the 16th 4-m long undulator segment (out of 33 total) with a weak magnetic chicane and a diamond-based monochromator in Bragg transmission geometry. The monochromatized SASE FEL pulse from the first half of the undulator line then seeds the second half. This demonstration of hard x-ray self-seeding is shown to narrow the FEL bandwidth by a factor 40-50, allows longitudinally coherent x-ray pulses near the Fourier-transform limit, and may eventually allow an increases in peak brightness by 1-2 orders of magnitude after applying an aggressive undulator field taper.
* G. Geloni, V. Kocharyan, E. Saldin, DESY 10-133, Aug. 2010.
slides icon Slides WEYB02 [5.946 MB]  
WEPPR083 New Sector 37 Chamber Design and Installation for High-Current Operation of the APS Storage Ring 3123
  • Y.-C. Chae, R. Bechtold, W. Berg, L. Erwin, M. Givens, J.E. Hoyt, L.H. Morrison, K.M. Schroeder, R. Soliday, J.B. Stevens, G.J. Waldschmidt
    ANL, Argonne, USA
  Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract No. DE-AC02-06CH11357.
The Advanced Photon Source is a 7-GeV hard x-ray synchrotron light source consisting of 40 sectors. Sector 37 accommodates four radio-frequency cavities followed by a short straight section, which is set aside for the future installation of a diagnostic device. The 60-cm-long section of spool pieces can be isolated by two gate valves and has an independent vacuum pump. The spool pieces are normally under high vacuum condition when the total current is below 100 mA. However, at the higher current required for the APS Upgrade, rf heating causes an unacceptable rise in temperature. We analyzed this situation by wakefield simulation, which led to a new chamber design. Proper fabrication and careful installation with twelve thermocouples ensured a temperature rise under 40-50 degrees Celsius at 100 mA. A brief thermal analysis shows that the present observed temperature rise in the new chamber is mainly due to the resistive wall.