• 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.

• F. Sannibale, B.J. Bailey, K.M. Baptiste, A.L. Catalano, D. Colomb, J.N. Corlett, S. De Santis, L.R. Doolittle, J. Feng, D. Filippetto, G. Huang, R. Kraft, D. Li, H.A. Padmore, C. F. Papadopoulos, G.J. Portmann, S. Prestemon, J. Qiang, J.W. Staples, M.E. Stuart, T. Vecchione, R.P. Wells, M.S. Zolotorev
  LBNL, Berkeley, California
• M. J. Messerly, M.A. Prantil
  LLNL, Livermore, California
• M. Yoon
  POSTECH, Pohang, Kyungbuk

The fabrication and installation at the Lawrence Berkeley National Laboratory of a high-brightness high-repetition rate photo-gun, based on a normal conducting 187 MHz (VHF) RF cavity operating in CW mode, is in its final phase. The cavity will generate an electric field at the cathode plane of ~20 MV/m to accelerate the electron bunches up to ~750 keV, with peak current, energy spread and transverse emittance suitable for FEL and ERL applications. The gun vacuum system has been designed for pressures compatible with high quantum efficiency but "delicate" semiconductor cathodes to generate up to a nC bunches at MHz repetition rate with present laser technology. Several photo-cathode/laser systems are under consideration, and in particular photo-cathodes based on K2CsSb are being developed and have already achieved a QE of 8% at 532 nm wavelength, or close to 20% including the Schottky barrier lowering. The cathode will be operated by a microjoule fiber laser in conjunction with refractive optics to create a flat top transverse profile, as well as a birefringent pulse stacker to create a flat top temporal profile. The present status and the plan for future activities are presented.