• R.O. Hettel, K.L.F. Bane, K.J. Bertsche, Y. Cai, A. Chao, V.A. Dolgashev, J.D. Fox, X. Huang, Z. Huang, T. Mastorides, C.-K. Ng, Y. Nosochkov, A. Novokhatski, T. Rabedeau, C.H. Rivetta, J.A. Safranek, J. Seeman, J. Stohr, G.V. Stupakov, S.G. Tantawi, L. Wang, M.-H. Wang, U. Wienands, L. Xiao
  SLAC, Menlo Park, California
• I. Lindau
  Stanford University, Stanford, California
• C. Pellegrini
  UCLA, Los Angeles, California

Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515.

SSRL and SLAC groups are developing a long-range plan to transfer its evolving scientific programs from the SPEAR3 light source to a much higher performing photon source that would be housed in the 2.2-km PEP-II tunnel. While various concepts for the PEP-X light source are under consideration, including ultimate storage ring and ERL configurations, the present baseline design is a very low-emittance storage ring. A hybrid lattice has DBA or QBA cells in two of the six arcs that provide a total ~30 straight sections for ID beam lines extending into two new experimental halls. The remaining arcs contain TME cells. Using ~100 m of damping wigglers the horizontal emittance at 4.5 GeV would be ~0.1 nm-rad with >1 A stored beam. PEP-X will produce photon beams having brightnesses near 1022 at 10 keV. Studies indicate that a ~100-m undulator could have FEL gain and brightness enhancement at soft x-ray wavelengths with the stored beam. Crab cavities or other beam manipulation systems could be used to reduce bunch length or otherwise enhance photon emission properties. The present status of the PEP-X lattice and beam line designs are presented and other implementation options are discussed.

• K.L.F. Bane, C. Adolphsen, A. Jensen, Z. Li, G.V. Stupakov
  SLAC, Menlo Park, California

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.

An L-band (1.3 GHz) sheet beam klystron that will nominally produce 10 MW, 1.6 ms pulses is being developed at SLAC for the ILC program. In recent particle-in-cell transport simulations of the 115 kV DC beam through the klystron buncher section without rf drive, a hose-type instability has been observed that is the result of beam noise excitation of transverse modes trapped between the rf cells. In this paper we describe analytical calculations and numerical simulations that were done to study the nature of this instability and explore the required mode damping and changes in the beam focusing to suppress it.