• J.N. Corlett, K.M. Baptiste, J.M. Byrd, A.E. Charman, P. Denes, R.W. Falcone, J. Feng, D. Filippetto, C.M.R. Greaves, J. Kirz, D. Li, H.A. Padmore, C. F. Papadopoulos, G.C. Pappas, G. Penn, J. Qiang, M.W. Reinsch, R.D. Ryne, F. Sannibale, R.W. Schoenlein, J.W. Staples, C. Steier, T. Vecchione, M. Venturini, W. Wan, R.P. Wells, R.B. Wilcox, J.S. Wurtele
  LBNL, Berkeley, California
• E. Kur
  UCB, Berkeley, California
• A. Zholents
  ANL, Argonne

The Next Generation Light Source (NGLS) is a design concept, under development at LBNL, for a 10‐beamline soft x‐ray FEL array powered by a 2.4 GeV superconducting linear accelerator, operating with a 1 MHz bunch repetition rate. The CW superconducting linear accelerator is supplied by a high-brightness, high-repetition-rate photocathode electron gun. Beam is distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz, with even pulse spacing. Individual FELs may be configured for EEHG, HGHG, SASE, or oscillator mode of operation, and will produce high peak and average brightness x-rays with a flexible pulse format ranging from sub-femtoseconds to hundreds of femtoseconds.

• C. F. Papadopoulos, J.N. Corlett, D. Filippetto, J. Qiang, F. Sannibale, J.W. Staples, M. Venturini, M.S. Zolotorev
  LBNL, Berkeley, California

The Advanced Photoinjector Experiment (APEX) is a part of the Next Generation Light Source (NGLS), a proposed soft x-ray FEL concept being studied at LBNL. The requirements for the beam delivered to the FELs pose restrictions on the beam parameters at the injector. In addition, different modes of operation of the machine may pose different requirements on the beam. In order to optimize the performance of the injector, a genetic multiobjective algorithm has been used. A genetic algorithm is used because of the inherent complexity of the beam dynamics at the energy range in question (0-30 MeV) and the large number of parameters available for optimization. On the other hand, the multiplicity of requirements on the beam, which include beam emittance, beam pulse length, energy chirp, as well as pulse shape and peak current, leads to a mutliobjective approach for the optimization technique. In this paper, we present the status of the optimization simulations, using the ASTRA particle-in-cell code. Different injector setups are presented and the resulting transport solutions are compared to each other and the requirements of the downstream sections of the accelerator.

• S. Di Mitri, M. Cornacchia, P. Craievich, G. Penco
  ELETTRA, Basovizza
• S. Spampinati
  University of Nova Gorica, Nova Gorica
• M. Venturini, A. Zholents
  LBNL, Berkeley, California

Two machine configurations of the electron beam dynamics in the FERMI@elettra linac have been investigated, namely the one-stage and the two-stage electron bunch compression. One of the merits of the one-stage compression is that of minimizing the impact of the microbunching instability on the slice energy spread and peak current fluctuations at the end of the linac. Special attention is given to the manipulation of the longitudinal phase space, which is strongly influenced by the linac structural wake fields. The electron bunch with a ramping peak current is used in order to obtain, at the end of the linac, an electron bunch characterized by a flat peak current profile and a flat energy distribution. Effects of various jitters on electron bunch energy, arrival time and peak current are compared and relevant tolerances are obtained.