Fourth generation light sources

Abstract

Concepts and designs are now being developed at laboratories around the world for light sources with performance levels that exceed present sources, including the very powerful and successful third generation synchrotron radiation sources that have come on line in the past few years. Workshops [1,2], have been held to review directions for future sources. A main thrust is to increase the brightness and coherence of the radiation using storage rings with lower electron-beam emittance or free-electron lasers (FELs). In the infra-red part of the spectrum very high brightness and coherence is already provided by FEL user facilities driven by linacs and storage rings. It now appears possible to extend FEL operation to the VUV, soft X-ray and even hard X-ray spectral range, to wavelengths down to the angstrom range, using high energy linacs equipped with high-brightness rf photoinjectors and bunch-length compressors. R&D to develop such sources is in progress at BNL, DESY, KEK, SLAC and other laboratories. In the absence of mirrors to form optical cavities, short wavelengths are reached in FEL systems in which a high peak current, low-emittance electron beam becomes bunch-density modulated at the optical wavelength in a single pass through a long undulator by self-amplified spontaneous emission (SASE); i.e.; startup from noise. A proposal to use the last kilometer of the 3 kilometer SLAC linac (the first 2 kilometers will be used for injection to the PEP II B-Factory) to provide 15 GeV electron beams to reach 1.5 Å by SASE in a 100 m long undulator is in preparation.[1] M. Cornacchia and H.

On Directional Dendritic Growth and Primary Spacing—A Review

“…They have provided quantitative data to test theory [217][218][219][220], however, the low penetration depth of X-rays within metals has limited synchrotron X-ray analysis to only a few hundred microns [221]; enough volume for investigation into the growth of a few metallic dendrites. It is hoped that the development of fourth-generation synchrotron light sources with multi-bend achromat synchrotron storage rings and free-electron lasers, will improve the brightness and coherent fraction of the x-ray light, whilst shortening the pulse duration [222]. However, to translate the progress in light source quality into improvements in wavelength resolution, spatio-temporal limits, and new science, requires similar progress in aspects such as X-ray optics, sample preparation, beamline technology, data analysis, and detectors [223].…”

Accurate experimental characterization of the labile N–Cl bond inN-chloro-N′-(p-fluorophenyl)-benzamidine crystal at 17.5 K

“…In the last two decades, extremely brilliant X-ray sources enabled a revolution in solid state chemistry by putting within the reach of diffraction-based techniques the understanding of complex structures and dynamic phenomena, down to the femtosecond timescale. 1 However, the high photon flux of modern high-brilliance facilities may degrade the sample within hours or even minutes, 2 for example when protein crystals 3 or reactive compounds 4 are studied. The lost information can be retrieved, at least to some extent, by scaling and merging data from different fresh crystals, assuming that several high-quality 5 samples are available.…”

Patterns in Directionally Solidified Alloys

“…They have provided quantitative data to test theory [230][231][232][233] , however, the low penetration depth of Xrays within metals has limited synchrotron X-ray analysis to only a few hundred microns 234 ; enough volume for investigation into the growth of a few metallic dendrites. It is hoped that the development of fourth-generation synchrotron light sources with multi-bend achromat synchrotron storage rings and freeelectron lasers, will improve the brightness and coherent fraction of the x-ray light, whilst shortening the pulse duration 235 . However, to translate the progress in light source quality into improvements in wavelength resolution, spatiotemporal limits, and new science, requires similar progress in aspects such as Xray optics, sample preparation, beamline technology, data analysis, and detectors 236 .…”