title: BioCARS: a synchrotron resource for time-resolved X-ray science.
abstract: BioCARS, a NIH-supported national user facility for macromolecular time-resolved X-ray crystallography at the Advanced Photon Source (APS), has recently completed commissioning of an upgraded undulator-based beamline optimized for single-shot laser-pump X-ray-probe measurements with time resolution as short as 100 ps. The source consists of two in-line undulators with periods of 23 and 27 mm that together provide high-flux pink-beam capability at 12 keV as well as first-harmonic coverage from 6.8 to 19 keV. A high-heat-load chopper reduces the average power load on downstream components, thereby preserving the surface figure of a Kirkpatrick-Baez mirror system capable of focusing the X-ray beam to a spot size of 90 µm horizontal by 20 µm vertical. A high-speed chopper isolates single X-ray pulses at 1 kHz in both hybrid and 24-bunch modes of the APS storage ring. In hybrid mode each isolated X-ray pulse delivers up to ~4 × 10(10) photons to the sample, thereby achieving a time-averaged flux approaching that of fourth-generation X-FEL sources. A new high-power picosecond laser system delivers pulses tunable over the wavelength range 450-2000 nm. These pulses are synchronized to the storage-ring RF clock with long-term stability better than 10 ps RMS. Monochromatic experimental capability with Biosafety Level 3 certification has been retained.
authors.affiliation: Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637, USA. graber@cars.uchicago.edu
authors.forename: T
authors.initials: T
authors.lastname: Graber
authors.forename: S
authors.initials: S
authors.lastname: Anderson
authors.forename: H
authors.initials: H
authors.lastname: Brewer
authors.forename: Y S
authors.initials: YS
authors.lastname: Chen
authors.forename: H S
authors.initials: HS
authors.lastname: Cho
authors.forename: N
authors.initials: N
authors.lastname: Dashdorj
authors.forename: R W
authors.initials: RW
authors.lastname: Henning
authors.forename: I
authors.initials: I
authors.lastname: Kosheleva
authors.forename: G
authors.initials: G
authors.lastname: Macha
authors.forename: M
authors.initials: M
authors.lastname: Meron
authors.forename: R
authors.initials: R
authors.lastname: Pahl
authors.forename: Z
authors.initials: Z
authors.lastname: Ren
authors.forename: S
authors.initials: S
authors.lastname: Ruan
authors.forename: F
authors.initials: F
authors.lastname: Schotte
authors.forename: V
authors.initials: V
authors.lastname: Srajer
authors.forename: P J
authors.initials: PJ
authors.lastname: Viccaro
authors.forename: F
authors.initials: F
authors.lastname: Westferro
authors.forename: P
authors.initials: P
authors.lastname: Anfinrud
authors.forename: K
authors.initials: K
authors.lastname: Moffat
mesh_terms: D018360:Crystallography, X-Ray; D017356:Synchrotrons