Masato Okui

Abstract A new electronic cam control system has been developed for a symmetrical layout double crystal monochromator, incorporating PID control with encoder feedback. The system improves the stability of the exit beam height over a wide Bragg angle range (7.3°–70.0°), achieving an accuracy of ±1.0 μm, as validated at BL10U, NanoTerasu. It also supports high-speed scanning at 1.0°/sec. Compared to the previous model, the updated system reduces relative height variation by half, while enabling faster scanning speeds and greater angular ranges. Future developments will focus on beam offset adjustability and automatic parallelism correction.

A symmetrical layout type monochromator controlled by electronic cam was developed and its demonstration test was performed on BL06 in NewSUBARU. As the result of the demonstration test, the monochromator shows enough performance to new generation synchrotron facilities. In this report, when the height of incident beam is shifted from ideal height, suitable alignment method of this type of double crystal monochromator was examined by ray tracing and control algorithm. As the result, It is thought better by beam offset value of symmetrical layout type double crystal monochromator shall be changed is better than solution by the single axis alignment when the height of incident beam is changed.

A demonstration test of a newly developed double crystal monochromator was performed on beamline BL06 in the NewSUBARU synchrotron radiation facility of Hyogo University. Due to the symmetrical layout of the 1st crystal and 2nd crystal units of the monochromator, a maximum rotation speed of the main axis of up to 5.0 degrees/sec could be achieved. The monochromator is controlled by a newly developed control board programmed with an electronic cam algorithm. The control system allows the speed of both Z₁ and Z₂ axes to be successively synchronized as the Bragg angle changes. The Z ₁ and Z₂ axes are moved apart by equal amounts from the center of gravity of the monochromator as the Bragg angle is increased. Also, the speed at which the Z₁ and Z₂ axes are moved apart increases with larger Bragg angle. This newly developed monochromator can maintain a stable exit beam height just as well as previous mechanical cam type monochromators proved on the height of the exit beam measured by an encoder system and observed by fluorescent screen. Due to the symmetrical layout and newly developed control system, the monochromator is suitable for industrial use because it can handle a wide energy range and allows high-throughput experiments to be carried out.

The BL07A beamline in New SUBARU, University of Hyogo, has been used for many studies of new materials. A new double crystal monochromator controlled by integrated computing was designed and installed in the beamline in 2014. In this report we will discuss the unique features of this new monochromator, MKZ-7NS. This monochromator was not designed exclusively for use in BL07A; on the contrary, it was designed to be installed at low cost in various beamlines to facilitate the industrial applications of medium-scale synchrotron radiation facilities. Thus, the design of the monochromator utilized common packages that can satisfy the wide variety of specifications required at different synchrotron radiation facilities. This monochromator can be easily optimized for any beamline due to the fact that a few control parameters can be suitably customized. The beam offset can be fixed precisely even if one of the two slave axes is omitted. This design reduces the convolution of mechanical errors. Moreover, the monochromator’s control mechanism is very compact, making it possible to reduce the size of the vacuum chamber can be made smaller.

A new ultra-high-resolution powder diffractometer for synchrotron radiation has been constructed at beamline BL15XU, SPring-8. The two-axis diffractometer is optimized for high-flux and high-coherent X-ray beams, which are provided by combining a planar undulator and a large offset rotated-inclined Si(111) double-crystal monochromator. The optics design of the diffractometer is based on transmission geometry, which employs a capillary specimen and reflection geometries using a flat-plate specimen. The intensity data are collected using a 2theta step-scan technique in both geometries. The diffractometer can be arranged in a variety of optical configurations, e.g. simple receiving slits, flat crystal analyzer of Ge(111) or Si(111), and in-vacuum-type long horizontal parallel slits. A minimum full width at half-maximum against 2theta was 0.00572 degrees at lambda = 0.63582 A for the (200) reflections from Si powder in the transmission geometry employing the Ge(111) crystal analyzer. A wide temperature range (32-900 K), which is controlled by a He/N(2) gas stream system, is available. 288 structure parameters of a zeolite ZSM-5 sample have been demonstrated to successfully refine with a R(wp) value of 6.96% by a Rietveld analysis of the high-resolution powder diffraction data from a 1 mm-diameter capillary specimen.

A 100mm offset rotated-inclined double crystal monochromator has been installed at BL15XU in SPring-8. The spatial profiles of the exit X-ray beam by using Si(1 1 1) in inclined geometry was measured from 5 to 20keV. The vertical deviation, due to refraction, between the first and the higher order was more than 0.7mm. The large deviation enables to eliminate the higher-order reflections by spatial screening with horizontal blade slits. The intensity ratio of the higher-order reflection to the first order was less than 10−5 over the whole energy range.

Crystallization experiments were carried out on powdered glasses having the composition Di₂₃Es₅₃An₂₄ at temperatures of 1250, 1275, 1300, 1325 and 1350°C. The resulting crystalline phases are clinopyroxenes and a trace of unknown oxide crystals. The pyroxenes grown at 1325 and 1350°C are stoichiometric clinopyroxenes rich in Al and Fe. Those grown at the lower three temperatures are non-stoichiometric clinopyroxenes which are extremely rich in Al and contain only negligibly small amounts of Mg. Non-stoichiometric clinopyroxenes are shown not to be characteristic products of high pressure conditions.

Structure refinement was carried out on a nonstoichiometric clinopyroxene grown under the ambient pressure from a glass with composition of 23%(mol)Di+53%Es+24%An. The degree of nonstoichiometry in this crystal is significantly larger than those of clinopyroxenes reported previously, which were found in high pressure products. The refinement gave the empirical chemical formula (Ca0.742Fe0.087)(Mg0.016Al0.888Fe0.075)(Al0.500Si1.500)O6 for the crystal and showed that vacancies are located mainly at M2 sites. Despite replacement of Si by Al, the crystal has a smaller cell volume than diopside primarily owing to a significant amount of Mg at M1 being replaced by Al.

Crystals of ferrian aluminian diopside were synthesized and the structures were investigated by means of a single-crystal X-ray diffraction method in detail. EPMA gave the chemical formula of Ca1.00(Mg0.55Fe3+0.37Al0.08)(Si1.55Al0.45)O6 for the crystals as an average. Structure refinement indicated that about 9 % of Fe3+ ions are at T sites, giving the formula of Ca1.00(Mg0.55Fe3+0.34Al0.11)(Si1.55Al0.42Fe3+0.03)O6. Existence of Fe3+ at T sites was, however, not confirmed on a difference Fourier map synthesized by making use of anomalous dispersion effect at the Fe K absorption edge. The bond distances are reasonable for a ferrian aluminian diopside with a chemical composition found for the present crystals.