Author: Lutman, A.A.
Paper Title Page
MOOCNO01 Emittance Control in the Presence of Collective Effects in the FERMI@Elettra Free Electron Laser Linac Driver 6
 
  • S. Di Mitri, E. Allaria, D. Castronovo, M. Cornacchia, P. Craievich, M. Dal Forno, G. De Ninno, W.M. Fawley, E. Ferrari, L. Fröhlich, L. Giannessi, E. Karantzoulis, A.A. Lutman, G. Penco, C. Serpico, S. Spampinati, C. Spezzani, M. Trovò, M. Veronese
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  • P. Craievich
    PSI, Villigen PSI, Switzerland
  • M. Dal Forno
    University of Trieste, Trieste, Italy
  • G. De Ninno, S. Spampinati
    University of Nova Gorica, Nova Gorica, Slovenia
  • E. Ferrari
    Università degli Studi di Trieste, Trieste, Italy
  • L. Giannessi
    ENEA C.R. Frascati, Frascati (Roma), Italy
  • A.A. Lutman
    SLAC, Menlo Park, California, USA
 
  Recent beam transport experiments conducted on the the linac driving the FERMI@Elettra free electron laser have provided new insights concerning the transverse emittance degradation due to both coherent synchrotron radiation (CSR) and geometric transverse wakefield (GTW), together with methods to counteract such degradation. For beam charges of several 100's of pC, optics control in a magnetic compressor results to minimize the CSR once the H-function is considered*. We successfully extended this approach to the case of a modified double bend achromat system, opening the door to relatively large bending angles and compact transfer lines**. At the same time, the GTWs excited in few mm diameter iris collimators*** and accelerating structures have been characterized in terms of the induced emittance growth. A model integrating both CSR and GTW effects suggests that there is a limit on the maximum obtainable electron beam brightness in the presence of such collective effects.
* S. Di Mitri et al., PRST-AB 15, 020701 (2012)
** S. Di Mitri et al., PRL 110, 014801 (2013)
*** S. Di Mitri et al., PRST-AB 15, 061001 (2012)
 
slides icon Slides MOOCNO01 [6.919 MB]  
 
WEPSO09 Two-Color Self-seeding and Scanning the Energy of Seeded Beams at LCLS 514
 
  • F.-J. Decker, Y. Ding, Y. Feng, M. Gibbs, J.B. Hastings, Z. Huang, H. Lemke, A.A. Lutman, A. Marinelli, A. Robert, J.L. Turner, J.J. Welch, D.H. Zhang, D. Zhu
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
The Linac Coherent Light Source (LCLS) produces typically SASE FEL pulses with an intensity of up to 5 mJ and at high photon energy a spread of 0.2% (FWHM). Self seeding with a diamond crystal reduces the energy spread by a factor of 10 to 40. The range depends on which Bragg reflection is used, or the special setup of the electron beam like over-compression. The peak intensity level is lower by a factor of about five, giving the seeded beam an advantage of about 2.5 in average intensity over the use of a monochromator with SASE. Some experiments want to scan the photon energy, which requires that the crystal angle be carefully tracked. At certain energies and crystal angles different lines are crossing which allows seeding at two or even three different colors inside the bandwidth of the SASE pulse. Out-off plane lines come in pairs, like [1 -1 1] and [-1 1 1], which can be split by using the yaw angle adjustments of the crystal, allowing a two-color seeding for all energies above 4.83 keV.
 
 
WEPSO10 Increased Stability Requirements for Seeded Beams at LCLS 518
 
  • F.-J. Decker, W.S. Colocho, Z. Huang, R.H. Iverson, A. Krasnykh, A.A. Lutman, M.N. Nguyen, T.O. Raubenheimer, M.C. Ross, J.L. Turner, L. Wang
    SLAC, Menlo Park, California, USA
 
  Funding: Work supported by U.S. Department of Energy, Contract DE-AC02-76SF00515.
Running the Linac Coherent Light Source (LCLS) with self-seeded photon beams requires better electron beam stability, especially in energy, to reduce the otherwise huge intensity variations of more than 100%. Code was written to identify and quantify the different jitter sources. Some improvements are being addressed, especially the stability of the modulator high voltage of some critical RF stations. Special setups like running the beam off crest in the last part of the linac can also be used to reduce the energy jitter. Even a slight dependence on the transverse position was observed. The intensity jitter distribution of a seeded beam is still more contained with peaks up too twice the average intensity, compared to the jitter distribution of a SASE beam going through a monochromator, which can have damaging spikes up to 5 times the average intensity.