The Coherent X-ray Imaging instrument at the Linac Coherent Light Source

Abstract

The Coherent X-ray Imaging (CXI) instrument specializes in hard X-ray, in-vacuum, high power density experiments in all areas of science. Two main sample chambers, one containing a 100 nm focus and one a 1 µm focus, are available, each with multiple diagnostics, sample injection, pump-probe and detector capabilities. The flexibility of CXI has enabled it to host a diverse range of experiments, from biological to extreme matter.

Keywords: FEL; coherent diffracted imaging; protein crystallography; serial femtosecond crystallography; single molecule imaging.

Figure 1

Overview of the CXI instrument layout. Distances are indicated in meters from the 1 µm sample chamber (SC) and in parentheses for the 100 nm sample chamber. Each chamber is colored to match its corresponding KB pair. One set of Be lenses can be used to further control the focus in the 1 µm sample chamber and another set to refocus the unscattered beam to the serial sample chamber at 3.59. There are slits and diagnostic (S&D) along the beamline and a timing tool (TT) for fine timing between optical laser and X-ray beams for pump–probe experiments. The sample is located approximately 440 m downstream of the undulators.

Figure 2

In vivo grown crystals and three-dimensional structure of the T. brucei cathepsin B–propeptide complex. (a) Scanning electron micrograph of a group of Sf9 insect cells infected with TbCatB virus 80 h after infection showing crystals of overexpressed TbCatB. (b) Scanning electron micrograph of a single TbCatB crystal after isolation. (c) Cartoon plot of the TbCatB–propeptide complex exhibiting the typical papain-like fold of cathepsin B-like proteases. Gray, R domain; blue, L domain; beige, occluding loop. The native propeptide (green) blocks the active site. Two N-linked carbohydrate structures (yellow) consist of N-acetylglucos­amine (NAG) and mannose (MAN) residues (yellow, carbon atoms; blue, nitrogen atoms; red, oxygen atoms). [From Redecke et al. (2013 ▶), Science, 339, 227–230. Reprinted with permission from AAAS.]

Figure 3

Electron density maps are shown. (a) Single-wavelength anomalous dispersion (SAD) phasing using the PHASER software (McCoy et al., 2007 ▶). (b) Solvent flattening with the DM software package (Cowtan, 1994 ▶). (c) Automatic building using wARP (Langer et al., 2008 ▶). (d) Final map after refinement. The correlation between the respective maps and the final, refined electron density d is indicated. All maps are contoured at 1.0σ. [Reprinted by permission from Macmillan Publishers Ltd: Barends et al. (2014 ▶), Nature (London), 505, 244–247, copyright (2014).]

Figure 4

A section of the Cu () diffraction ring is magnified and its evolution is shown at 20 ps intervals. [From Milathianaki et al. (2013 ▶). Science, 342, 220–223. Reprinted with permission from AAAS.]