We have evaluated the applicability of vertically-focusing kinoform lenses for tailoring the vertical coherence
length of storage-ring undulator x-ray beams so that the entirety of the coherent flux can be used for small
angle multi-speckle x-ray photon correlation spectroscopy (XPCS) experiments. We find that the focused beam
produced by a kinoform lens preserves the coherence of the incident unfocused beam and that at an appropriate
distance downstream of the focus, the diverging beam produces speckles nearly identical to those produced by
an equivalently-sized unfocused beam. We have also investigated the effect of imperfect beamline optics on the
observed coherence properties of the beam. Via phase contrast imaging and beam-divergence measurements,
we find that a horizontally-deflecting mirror in our beamline precludes us from seeing the true radiation source
point but instead acts as an apparent source of fixed size at the center of our insertion device straight section.
Finally, we discuss how expected near-future optimization of these optics will greatly benefit XPCS measurements
performed at beamline 8-ID-I at the Advanced Photon Source.
A novel ultra-high-vacuum (UHV)-compatible x-ray monochromator has been designed and commissioned at the
undulator beamline 8-ID-I at the Advanced Photon Source (APS) for x-ray photon correlation spectroscopy
applications. To meet the challenging stability and x-ray optical requirements, the monochromator integrates two new
precision angular positioning mechanisms into its crystal optics motion control system: An overconstrained weak-link mechanism that enables the positioning of an assembly of two crystals to achieve
the same performance as a single channel-cut crystal, the so called "artificial channel-cut crystal"; A ceramic motor driven in-vacuum sine-bar mechanism for the double crystal combined pitch motion.
The mechanical design of the monochromator, as well as the test results of its positioning performance are presented in
We present design and characterization results of a novel ultra-high-vacuum-compatible artificial channel-cut monochromator that has been installed at the undulator beamline 8-ID-I at the Advanced Photon Source. The monochromator has been designed to meet the challenging stability and optical requirements of the x-ray photon correlation spectroscopy program hosted at this beamline. In particular, the device incorporates a novel in-vacuum sine-bar drive mechanism for the combined pitch motion of the two crystals and a flexure-based high-stiffness weak-link mechanism for fine tuning the pitch and roll of the second crystal relative to the first crystal.
Building blocks with a nanoscale dimension (typically <100nm) have different properties compared with their bulk counterparts. For instance, the absorption and photoluminescence of semiconductor quantum dots show a strong size dependence [1, 2]. Charge injection onto a single quantum dot has to overcome a strong Coulomb charging energy. The magnetic moment of the surface atoms are strongly enhanced due to unquenched orbital moments in transition metal clusters . Fundamentally, all these new phenomena can be attributed to two major effects on the nanometer scale, namely the quantum confinement of charge and spin  and the low coordination of surface atoms . Development in colloidal chemistry during the past two decades has produced a variety of high quality nanoscale building blocks with many unique properties [6-10]. Although it is possible to study and utilize the physical properties of nanoparticles on a single particle level, it remains to be a technically challenging task. On the other hand, experiments on macroscopic 2D and 3D nanocrystal superlattices are more accessible. Self-assembly of nanocrystal building blocks not only provides a way to connect the nanoscale dimension to the macroscopic length scale, but it also creates a revolutionary new class of materials. New collective behavior is expected to emerge because of the strong coupling between building blocks [11, 12].
This paper describes the design and analysis of a contact-cooled channel-cut germanium monochromator for use on a high-heat-load x-ray beamline. This channel-cut monochromator is designed in the shape of a "Z" so that polishing the diffraction surfaces is easier. The incident x-ray beam, which is reflected from a mirror at a 0.15° angle, diffracts from one surface of the Z-monochromator, passes through an opening, and diffracts from the second surface. The monochromator is located 60 meters from the undulator x-ray source. The normal heat flux of the incident beam can be up to 7 W/mm<sup>2</sup>. Thermal and structural analyses are presented, and the deformation caused by gravity is considered.