Abstract
The optical design and performance of the recently opened 13A biological small-angle X-ray scattering (SAXS) beamline at the 3.0 GeV Taiwan Photon Source of the National Synchrotron Radiation Research Center are reported. The beamline is designed for studies of biological structures and kinetics in a wide range of length and time scales, from angstrom to micrometre and from microsecond to minutes. A 4 m IU24 undulator of the beamline provides high-flux X-rays in the energy range 4.0-23.0 keV. MoB4C double-multilayer and Si(111) double-crystal monochromators (DMM/DCM) are combined on the same rotating platform for a smooth rotation transition from a high-flux beam of ∼4 × 1014 photons s-1 to a high-energy-resolution beam of ΔE/E ≃ 1.5 × 10-4; both modes share a constant beam exit. With a set of Kirkpatrick-Baez (KB) mirrors, the X-ray beam is focused to the farthest SAXS detector position, 52 m from the source. A downstream four-bounce crystal collimator, comprising two sets of Si(311) double crystals arranged in a dispersive configuration, optionally collimate the DCM (vertically diffracted) beam in the horizontal direction for ultra-SAXS with a minimum scattering vector q down to 0.0004 Å-1, which allows resolving ordered d-spacing up to 1 µm. A microbeam, of 10-50 µm beam size, is tailored by a combined set of high-heat-load slits followed by micrometre-precision slits situated at the front-end 15.5 m position. The second set of KB mirrors then focus the beam to the 40 m sample position, with a demagnification ratio of ∼1.5. A detecting system comprising two in-vacuum X-ray pixel detectors is installed to perform synchronized small- and wide-angle X-ray scattering data collections. The observed beamline performance proves the feasibility of having compound features of high flux, microbeam and ultra-SAXS in one beamline.
Highlights
Synchrotron small-angle X-ray scattering (SAXS) beamlines often emphasize on, for instance, biological SAXS (BioSAXS), grazing-incidence SAXS or ultra-SAXS (USAXS), according to the needs of local user communities
Our result demonstrates that orientations and ordered sizes of hierarchically ordered structures could be correlated conveniently and faithfully in one single imaging
The high flux above 1014 photons sÀ1 for studies of structures and kinetics is enabled with the 4 m-long IU24 source and an efficient double-multilayer monochromator; the USAXS is enabled with a long camera length of 10 m and a low X-ray energy beam with small beam divergence and low scattering background, achieved with the combined vertically oriented DCM and horizontally oriented 4BCC; these together allow resolving hierarchically ordered structures up to 1 mm length scale
Summary
Synchrotron small-angle X-ray scattering (SAXS) beamlines often emphasize on, for instance, biological SAXS (BioSAXS), grazing-incidence SAXS or ultra-SAXS (USAXS), according to the needs of local user communities. At the National Synchrotron Radiation Research Center (NSRRC), SAXS activities were initiated in 2002 at the 17B1 wiggler beamline of the synchrotron Taiwan Light Source (TLS) 1.5 GeV storage ring (Hsu et al 2005). These activities were carried further to the 01B super-bending beamline with an expansion to simultaneous small- and wideangle X-ray scattering (SAXS-WAXS), using two Gabriel gastype linear detectors of length 200 mm (Lai et al, 2005). The TPS 13A BioSAXS beamline aims to provide high flux and synchronized, time-resolved SAXS-WAXS for studies of biomacromolecular solution structures over a wide range of length and time scales. The optical designs and performance of the new TPS 13A BioSAXS beamline are detailed below
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