Advanced small- and wide-angle x-ray scattering beamline for frontier research in biological structures at the Taiwan photon source

The TPS 13A biological small-angle X-ray scattering (BioSAXS) beamline under construction is equipped with 4-m IU24 undulator for X-rays in the energy range of E = 4-23 keV (covering the K-edge absorptions from Ca to Ru). The beamline aims for cutting-edge researches in biomacromolecular structures and kinetics, in solid and solution, covering a wide length scale from atomic to micrometer scale and time resolution down to μs. To achieve the goals, the beamline integrates double-multilayer and double-crystal monochromators (DMM/DCM) to have an option of high flux of 4 × 10¹⁴ photons/s or a high energy resolution of ΔE/E = 1.5×10⁻⁴. The DCM together with a horizontal four-bounce crystal collimator (4BCC) will be implanted for low beam divergence to perform 2D ultra-SAXS (USAXS). To keep a common X-ray beam path of the operation modes, DMM and DCM are integrated into one rotating cradle in a same chamber for a common beam exit. Microbeam with reasonable beam divergence for SAXS/WAXS structural mapping will be realized with a virtual source defined by a set of high precision/stability slits and another set of K-B mirrors for a focus at the sample position with a demagnification close to 1.3:1. Two beam position monitors, with intensity and position feedbacks respectively to the virtual source slits and the 4BCC and a vertical deflection mirror, are used mainly to stabilize microbeam intensity and position within 1 μm in the vertical and horizontal directions. This TPS 13A BioSAXS beamline will be commissioning at the end of 2019.