WEOAA1
LBNL, Berkeley, California, USA
SLAC, Menlo Park, California, USA
JLAB, Newport News, Virginia, USA
Fermilab, Batavia, USA
We present an overview of design studies and R&D toward NGLS a Next Generation Light Source initiative at LBNL. The design concept is based on a multi-beamline soft x-ray FEL array powered by a CW superconducting linear accelerator, and operating with a high bunch repetition rate of approximately 1 MHz. The linac design uses TESLA and ILC technology, supplied by an injector based on a CW normal-conducting VHF photocathode electron gun. Electron bunches from the linac are distributed by RF deflecting cavities to the array of independently configurable FEL beamlines with nominal bunch rates of ~100 kHz in each FEL, with uniform pulse spacing, and some FELs capable of operating at the full linac bunch rate. Individual FELs may be configured for different modes of operation, including self-seeded and external-laser-seeded, and each may produce high peak and average brightness x-rays with a flexible pulse format.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
IBM T. J. Watson Center, Yorktown Heights, New York, USA
LBNL, Berkeley, California, USA
Multialikali antimonide cathodes provide high visible light quantum efficiency, with low thermal emittance and are excellent candidate materials for high average current next generation ERLs or high repetition rate FELs. Although these materials have some excellent characteristics, control of the growth mode of the thin film and ultimately the surface roughness is difficult and will effect the emittance that can be obtained in high gradient fields. To complement our growth studies of crystalline phases using x-ray diffraction studies, here we use the technique of grazing incidence small angle x-ray scattering (GI-SAXS) and atomic force microscopy (AFM) to measure the roughness as a function of film thickness. In this study, we demonstrate these techniques as applied to the growth of Sb, for a range of thicknesses, temperatures and growth rates, and show the wide range of moprphologies that can be formed with relatively minor changes in deposition conditions.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
PHOTONIS USA PENNSYLVANIA, INC., Lancaster, USA
LBNL, Berkeley, California, USA
ANL, Argonne, USA
Alkali Antimonide photocathodes have yielded the highest current on record for any photoinjector source (75 mA), with QE of ~10% for green light. However, traditional growth methods for these cathodes yield material that is inherently rough, leading to rise of the intrinsic emittance for high gradient injectors such as those for next-generation light sources. It this presentation we will explore the origin of roughness in these materials, as well as the growth dynamics, using in situ and in operando techniques, including Grazing Incidence X-ray Diffraction, Grazing Incidence Small Angle X-ray Scattering, X-ray reflectivity and in vacuum Atomic Force Microscopy.