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In this work, we demonstrate simultaneous phase-contrast imaging (PCI) and X-ray diffractionfrom shock compressed matter at the Matter in Extreme Conditions endstation, at the LinacCoherent Light Source (LCLS). We utilize the chromaticity from compound refractive X-ray lensesto focus the 24.6 keV 3rd order undulator harmonic of the LCLS to a spot size of 5lm on target toperform X-ray diffraction. Simultaneous PCI from the 8.2 keV fundamental X-ray beam is used tovisualize and measure the transient properties of the shock wave over a 500lm field of view.Furthermore, we demonstrate the ability to extend the reciprocal space measurements by 5 Angstroem, rel-ative to the fundamental X-ray energy, by utilizing X-ray diffraction from the 3rd harmonic of theLCLS.

Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murnaghan equation of state with a Berman-type thermal expansion model.

The magnetic and structural properties of cobalt were investigated under high pressure (160 GPa) and low temperature (50 K), by synchrotron K-edge x-ray magnetic circular dichroism and x-ray diffraction. A quasihydrostatic equation of state was measured up to 160 GPa. We found that uniaxial stress plays a role in the hexagonal close packed-face centered cubic (hcp-fcc) structural transition pressure. Also, our data provide the first experimental evidence that changes of the c/a ratio pressure derivative are related to the magnetic behavior. The complete extinction of ferromagnetism is observed above 130 GPa in a mixed hcp-fcc phase with no recovery upon cooling to 50 K, indicating that cobalt at 150 GPa is very likely nonmagnetic, i.e., characterized by zero local spin polarization. Density functional theory calculations point out that the K-edge x-ray magnetic circular dichroism (XMCD) signal is related to the 4p orbital moment rather than to the total spin moment and allow us to get a deeper insight into the K-edge XMCD measurements interpretation. The combination of novel theoretical results and experimental outputs provides a detailed scenario of the structural and magnetic properties of cobalt at these extreme conditions answering some previously unsolved issues.