The number of proposals for LCLS science has rapidly increased as all six LCLS x-ray instruments have come online. It
created rising demand on beam time. Statistics shows that only about 25 % of LCLS proposals can be allocated beam
time. One way to increase access is to share the x-ray beam between the different instruments. The purpose of this study
is to quickly switch the x-ray beam between the Matter in Extreme Conditions (MEC) Instrument and the Coherent X-ray
Imaging (CXI) or X-ray Correlation Spectroscopy (XCS) Instruments, in order that two of the instruments can
perform experiments simultaneously. In the most common operational mode, the MEC Instrument uses one x-ray pulse
every 10 minutes, limited by the repetition rate of the high power nanosecond laser system. The MEC M3H mirror steers
the x-ray beam to the MEC Instrument from the XCS or CXI Instruments. If the M3H mirror could switch the x-ray
beam to MEC within a fraction of the 10 minutes waiting time, multiplexing of the x-ray beam would be achieved. The
M3H mirror system has two motion stages for translation and rotation. The long path, 230 m, from the mirror to MEC
hutch makes the pointing resolution 0f 100 microns and stability requirements challenging. The present study
investigates such capabilities by measuring the correlation between the translation speed and the beam pointing
reproducibility. We show that mirror translation can multiplex the LCLS x-ray beam.
During the last years, scanning coherent x-ray microscopy, also called ptychography, has revolutionized nanobeamcharacterization at third generation x-ray sources. The method yields the complete information on the complex valued, nanofocused wave field with high spatial resolution. In an experiment carried out at the Matter in Extreme Conditions (MEC) instrument at the Linac Coherent Light Source (LCLS) we successfully applied the method to an attenuated nanofocused XFEL beam with a size of 180(h) × 150(v)nm<sup>2</sup> (FWHM) in horizontal (h) and vertical direction (v), respectively. It was created by a set of 20 beryllium compound refractive lenses (Be-CRLs). By using a fast detector (CSPAD) to record the diffraction patterns and a fast implementation of the phase retrieval code running on a graphics processing unit (GPU), the applicability of the method as a real-time XFEL nanobeam diagnostic is highlighted.
A hard x-ray free-electron laser (XFEL) provides an x-ray source with an extraordinary high peak-brilliance, a time structure with extremely short pulses and with a large degree of coherence, opening the door to new scientific fields. Many XFEL experiments require the x-ray beam to be focused to nanometer dimensions or, at least, benefit from such a focused beam. A detailed knowledge about the illuminating beam helps to interpret the measurements or is even inevitable to make full use of the focused beam. In this paper we report on focusing an XFEL beam to a transverse size of 125nm and how we applied ptychographic imaging to measure the complex wavefield in the focal plane in terms of phase and amplitude. Propagating the wavefield back and forth we are able to reconstruct the full caustic of the beam, revealing aberrations of the nano-focusing optic. By this method we not only obtain the averaged illumination but also the wavefield of individual XFEL pulses.
Current and upcoming X-ray sources, such as the Linac Coherent Light Source (LCLS) at the Stanford Linear Accelerator Center (SLAC, USA), the SPring-8 Angstrom Compact Free Electron Laser (SACLA, Japan), or the X-ray Free Electron Laser (XFEL, Germany) will provide X-ray beams with outstanding properties.<sup>1, 2</sup> Short and intense X-ray pulses of about 50 fs time duration and even shorter will push X-ray science to new frontiers such as, e. g., in high-resolution X-ray imaging, high-energy-density physics or in dynamical studies based on pump-probe techniques.<p> </p>Fast processes in matter often require high-resolution imaging capabilities either by magnified imaging in direct space or diffractive imaging in reciprocal space. In both cases highest resolutions require focusing the X-ray beam.<sup>3, 4</sup> In order to further develop high-resolution imaging at free-electron laser sources we are planning a platform to carry out high-resolution phase contrast imaging experiments based on Beryllium compound refractive X-ray lenses (Be-CRLs) at the Matter in Extreme Conditions (MEC) endstation of the LCLS. The instrument provides all necessary equipment to induce high pressure shock waves by optical lasers. The propagation of a shock wave is then monitored with an X-ray Free Electron Laser (FEL) pulse by magnified phase contrast imaging. With the CRL optics, X-ray beam sizes in the sub-100nm range are expected, leading to a similar spatial resolution in the direct coherent projection image. The experiment combines different state-of-the art scientific techniques that are currently available at the LCLS. In this proceedings paper we describe the technical developments carried out at the LCLS in order to implement magnified X-ray phase contrast imaging at the MEC endstation.