X-ray transmission properties of a thin HPHT IIa diamond crystal were characterized around Bragg diffraction, using a
pseudo plane-wave setup at the 1-km beamline of SPring-8. Monochromatic x-rays of 19.75 keV were used for diamond
400 reflection from 120-μm-thick (001) diamond crystals, and 9.44-keV x-rays were used for diamond 111 reflection
from 180-μm-thick (111) crystals. These thin crystals were mounted on the aluminum plate using an ultraviolet-cured
resin. Several thin crystals showed rocking curve broadening due to bend. However, by limiting a small area of the
crystal, transmittance curves agreed well with those of calculation. We can select a practically usable region for various
applications: phase retarder, beam splitter, and also self-seeding of x-ray free electron laser.
Beam quality of diamond double-crystal monochromator was characterized at undulator beamlines of SPring-8. The <001<-growth (111) IIa diamond crystals were used for high-heat-load double-crystal monochromator. Main issue of IIa diamond monochromator was intensity non-uniformity of reflected beam that was enhanced at the experimental station more than 10 m apart from monochromator. The simple Fresnel diffraction models from segments of the crystal are introduced to explain the origin of non-uniformity. Lattice inclination across growth sector boundary with 0.5 μrad or more, or lattice step due to stacking faults may cause phase shift between segments. The non-uniformity increases up to ~50% using the simple models. We also characterized recently-available <111<-growth crystals at 1-km beamline of SPring-8. The quality is similar to that of previous <001<-growth crystals, regarding rocking curve width for whole region irradiation.
BL37XU (trace element analysis beamline) and BL39XU (magnetic materials beamline) at SPring-8 have been upgraded
to provide nano-probe analysis. We designed and installed Kirkpatrick-Baez (KB) mirrors and corresponding
manipulators, which have an X-ray focusing beam as small as 100 nm. To realize a high-flux 100-nm focusing beam, a
high-demagnification optical design was used, and new experimental hutches were constructed that are located about 80
m from the light source. By taking advantage of extended beamline, focusing photon flux density of over 1 x 10<sup>9</sup>(photons/sec/100x100nm<sup>2</sup>) is possible with a working distance of 100 mm at X-ray energy of around 10 keV. The
current status of these beamlines is reported.
A method is proposed to analyze the mutual coherence function of a general x-ray beam. The mutual coherence
function is shown to be the Fourier pair of the wavevector distribution of the beam inside a finite volume.
A rocking-curve profile to be measured with a perfect-crystal plate is calculated as a kind of one-dimensional
projection of the wavevector distribution of the incident beam. Collecting rocking-curve profiles measured with
several reciprocal lattice vectors, we can construct the wavevector distribution with a computed-tomography
technique, and then calculate the mutual coherence function. The mutual coherence function of a synchrotron
x-ray beam was analyzed with a high spatial resolution and a wide dynamic range.
For the stabilization of the SPring-8 double-crystal monochromator with water-cooled inclined-cut silicon crystals, we have changed the water path of the first crystal, remodeled the crystal holders and attached x-ray and electron shield parts. The improvements are effective to supply constant-intensity microbeam, to extend the life time of the elastomer O-rings for water seal, and to decrease the radiation damages of the electric cables of the motors.
The 1 Å microbeam with the size of 50 μm × 50 μm at an experimental station keeps constant intensity, though the intensity decreased by 26 % per hour before the improvements. The vibration of the mechanical stages is discussed as the remaining problem.
X-ray diffraction by perfect crystal is discussed from the viewpoint of mutual coherence of an x-ray beam. From
the time-dependent Takagi-Taupin equations that x-ray wavefields obey in crystal, the reflected wavefield is
formulated as an integral transform of a general incident wavefield with temporal and spatial inhomogeneity.
A reformulation of rocking-curve profile from the field solution of the time-dependent Takagi-Taupin equations
allows experimental evaluation of the mutual coherence function of an x-ray beam. The rigorous relationship of
the coherence functions before and after reflection clarifies how the coherence is transferred by a crystal.
As unique beamlines in the third-generation synchrotron facilities, a 25-m undulator beamline and a one-kilometer beamline were constructed and started in operation at SPring-8. The design and performance of the 25-m undulator beamline are presented. To diagnose the coherence properties of x-rays, an x-ray intensity interferometer was developed at the beamline. The correlation technique was applied to determining the interference condition with a bicrystal interferometer. High-quality synthetic diamond crystals are being developed for XFEL monochromator crystal.
A one-kilometer long synchrotron radiation beamline with an x- ray undulator source was completed at SPring-8. The beamline was planned to facilitate various applications of a wide-area coherent x-ray beam, development of bi-crystal x-ray interferometers for gravitational red-shift measurement and development of highly sensitive diagnostic methods of accelerator dynamics. This paper reports the structure of the long beamline as well as some selected first results including phase contrast imaging and diffraction imaging applications.
Most SPring-8 x-ray beamlines are installed double-crystal monochromators that are standardized. For x-ray undulator beamlines where power density of the beam are quite high, rotated-inclined double-crystal geometry is usually adopted, which enlarges the footprint of the incident beam on the crystal surface to reduce the power density. On the other hand, adjustable-inclined double-crystal geometry is adopted for bending-magnet beamlines to extend the available energy range with a limited Bragg angle range. The standardized monochromator mechanism is compatible to both of the geometries, only by changing crystal mounts. Detailed description of the monochromator mechanism is presented.
In SPring-8, the first crystals with pin-post water path have widely used at x-ray undulator beamlines. The crystals have been fabricated by using metal diffusive bonding technique. Although the initial crystals had sufficient endurance for high heat load, deterioration of the performance due to the strain induced by the water pressure was observed. Newly designed crystal showed better diffraction properties. Some problems to be improved are also discussed.
In SPring-8, water-cooled silicon crystals are widely used for the first optical element in the x-ray undulator beamlines. This was made possible by the development of pin-post cooling combined with rotated-inclined diffraction geometry. Fabrication of the crystal uses diffusive bonding technique. Characterization at a SPring-8 undulator beamline showed high cooling efficiency enough to handle the maximum power from the undulator, although some problems still remain in fabrication process and geometrical design of water distributors.
A Laue-Laue-Laue x-ray interferometer with the inclined third crystal plate was fabricated to demonstrate wavefront- dividing interferometry in x-ray region. Observed interference patterns showed the effects of spatial coherence of the incident wave, in addition to the incident angle dependent spatial fringes expected from the dynamical theory of diffraction. From the visibility of the interference pattern, the source size used was estimated using Van Cittert-Zernike theorem.
SPring-8 is a 3rd generation synchrotron radiation source that is characterized by high brilliance in the hard X-rays. Here we report our present status on the development of the focusing devices for hard X-rays. Supermirrors on silicon wafers were bent for 1D focusing to realize an energy- tunable hard X-ray focusing element with fixed focal length. A smooth high-reflectivity profile as a function of energy was realized with a wide energy band up to 40 keV. For imaging experiments such as for beam monitoring, linear and circular Bragg Fresnel zone plates were developed. An experiment to image the bending magnet source at the Photon Factory is described.