Range Of Beam Sizes Research Articles

Upgrade of a high flux MX beamline BL41XU at SPring-8

BL41XU is the oldest macromolecular crystallography (MX) beamline at SPring-8 [1]. Although it has been contributing to the structure determination of difficult samples since its start of operation in 1997, the targets for the structural study is still getting more challenging and the crystal quality brought to the beamline is getting worse. Therefore, we have upgraded the focusing optics and diffractometer of BL41XU to cope with these targets. Our goal is to achieve an environment which can offer a stable beam with a photon flux of >1013photons/s in the beam size range of 5 ~ 50μm. It is a complementary specification with our micro-focus beamline BL32XU [2], and allows both micro-crystallography and data collection using crystal volume. The new optics adopts a two-step focusing with elliptical figured mirrors: the first optics is a single horizontal mirror and the second one adopts Kirkpatrick–Baez (KB) configuration. At the middle of the two focusing optics, a high precision horizontal slit is installed to define secondary source size. The beam size can be changed either by changing the secondary source size, by offsetting the sample position, or by tilting the vertical mirror. For the stable use of small beam, both KB mirror and diffractometer were equipped on the granite stage, and enclosed in a booth in which the temperature is keep stable. On the new diffractometer, we equipped PILATUS3 6M that enables rapid data collection combining with high flux beam. Together with the upgrade of hardware, software tools, which support diffraction based centering and determination of measurement condition, have been implemented in order to make full use of the renewed beamline. The upgrade was conducted in the long shut-down period between January and March of this year, and the beamline was opened for users in the middle of May after commissioning of one month. The result of commissioning and initial results will be presented. This study was supported by the MEXT of Japan.

Crack Extension Resistance Curve of Concrete Considering Variation of FPZ Length

Owing to its importance in evaluating the fracture behavior of concrete, the crack extension resistance curve of concrete has been widely studied, both experimentally and theoretically. In this paper, a numerical approach is developed for the crack extension resistance curve of concrete by considering the variation of the fracture process zone (FPZ) length during the whole fracture process. In this approach, the FPZ length is determined by using the linear asymptotic superposition assumption. Dividing the whole fracture process into three different stages of the cohesive stress distribution within the FPZ, the crack extension resistance curve is formulated by superposition of the intrinsic fracture toughness of concrete and the fracture toughness caused by the cohesive stress within the FPZ. The developed numerical approach is applied to the tested and simulated standard three-point bending notched concrete beams. The effect of the variation of the FPZ length on the crack extension resistance curve is evaluated on the basis of the numerical results. The crack extension resistance first increases with an increase in ratio of the effective crack length to the beam depth and then reaches a plateau value when the FPZ is fully developed. When the effective crack length is normalized to the beam depth, the crack extension resistance is basically independent of the beam depth within the beam size range studied.

Dual-prism interferometer for collimation testing

An air-wedge lateral-shear interferometer using two prisms is presented. With a variable shear, the interferometer is suitable for testing collimation of a wide range of beam sizes down to a few millimeters in diameter. No antireflection coatings are necessary. Collimation for a light source with short coherent length is also demonstrated.

Shear Strength of Solid-Sawn Douglas-Fir Beams

The objective of this study was to improve current shear design criteria by establishing a test method for creating a database of beam shear strength of solid-sawn Douglas-fir lumber and correlating it to shear block test results; verifying whether the beam-size equation is a valid correlation between shear strength and beam size for solid-sawn material; and determining whether shear strength is more dependent on shear area, volume, or depth for modeling purposes. Experimental results are presented for 160 shear strength tests on unsplit, green, sawn No. 2 or better Douglas-fir lumber. Five different size specimens, ranging from 38 by 89 mm (2 by 4 in.) to 38 by 337 mm (4 by 14 in.), were tested in five-point beam shear. ASTM D143 shear block minors were cut and tested from each beam. Results adjusted to 12% moisture content were compared with prior research on southern pine and Douglas-fir glued-laminated timber beams. Statistical methods of censored statistics and regression investigated the following possible correlations: shear strength to beam size and beam shear strength to ASTM shear block strength. Results indicate that (1) a five-point test setup can consistently produce beam shear failures over a wide range of beam sizes; (2) shear strength is dependent on beam shear area; and (3) beam shear strength is related to ASTM D143 shear block strength values provided the reentrant corner stress-concentration effects are considered.

Electron-probe microanalysis of light elements in coal and other kerogen

Recent advances in electron microprobe technology including development of layered synthetic microstructures, more stable electronics and better matrix-correction programs facilitated routine microanalysis of the light elements in coal. Utilizing an appropriately equipped electron micro-probe with suitable standards, it is now possible to analyze directly the light elements (C, O and N, if abundant) in coal macerals and other kerogen. The analytical results are both accurate compared to ASTM methods and highly precise, and provide an opportunity to access the variation in coal chemistry at the micrometre scale. Our experiments show that analyses using a 10 kV accelerating voltage and 10 nA beam current yield the most reliable data and result in minimum sample damage and contamination. High sample counts were obtained for C, O and N using a bi-elemental nickel-carbon pseudo-crystal (2 d = 9.5 nm) as an analyzing crystal. Vitrinite isolated from anthracite rank coal proves the best carbon standard and is more desirable than graphite which has higher porosity, whereas lower rank vitrinite is too heterogeneous to use routinely as a standard. Other standards utilized were magnesite for oxygen and BN for nitrogen. No significant carbon, oxygen or nitrogen X-ray peak shifts or peak-shape changes occur between standards and the kerogen analyzed. Counting rates for carbon and oxygen were found to be constant over a range of beam sizes and currents for counting times up to 160 s. Probe-determined carbon and oxygen contents agree closely with those reported from ASTM analyses. Nitrogen analyses compare poorly to ASTM values which probably is in response to overlap between the nitrogen K α peak with the carbon K-adsorption edge and the overall low nitrogen content of most of our samples. Our results show that the electron microprobe technique provides accurate compositional data for both minor and major elements in coal without the necessity and inherent problems associated with mechanically isolating macerals. Studies to date have demonstrated the level of compositional variability within and between macerals in suites of Canadian coals.

Direct determination of carbon, oxygen and nitrogen content in coal using the electron microprobe

Recent advances in electron microprobe technology together with the development of synthetic crystals have enabled development of techniques for direct light element (C, O, N) analyses of coal macerals. The analytical results are both accurate compared to ASTM methods and highly precise, and provide an opportunity to assess the variation in coal chemistry at the micrometre scale. Our experiments show that analyses using a 10 kV accelerating voltage and 10 nA beam current yield the most reliable data and result in minimum sample damage. High sample counts were obtained for C, O and N using PC2, a nickel-carbon pseudocrystal ( d = 9.5 nm), as an analysing crystal. Vitrinite isolated from anthracite rank coal proves the best carbon standard and was more desirable than graphite which has higher porosity, whereas lower rank vitrinite is too heterogeneous to use routinely as a standard. No significant carbon or oxygen X-ray peak to be constant over a range of beam sizes and currents for counting times to 160 s, and no correction factor was necessary in determination of oxygen content. Probe-determined carbon contents agree closely with those reported from ASTM analyses and some minor deviations are attributed to heterogeneity of the vitrinite on the micrometre scale. Our results show that the electron microprobe technique can provide accurate compositional data for both minor and major elements in coal without the necessity and inherent problems associated with mechanical separation of macerals.

Log-Amplitude Mean for Laser-Beam Propagation in the Atmosphere*

An integral expression is evaluated for the log-amplitude mean value of a gaussian or laser-like optical beam propagating along a horizontal path in a turbulent atmosphere. The mean-value integral expression has been taken from an analysis by Schmeltzer for a gaussian beam in the atmosphere. The expressions presented here for the log-amplitude mean value depend on the product of a strength factor, which is the log-amplitude variance for a point source, and a multiplying factor that depends on the source beam size. Numerical results for the beam-size-dependent factor are given for a wide range of beam sizes, wavelengths, and path lengths. Numerical results are also presented for the mean on-axis irradiance and mean beam size, for focused and collimated gaussian beams. These will find application in the design of systems for laser communication in the atmosphere. The data are obtained by combining our results for the log-amplitude mean with published data for the variance. The integral expression used here for the log-amplitude mean value is based on an assumption which restricts the range of validity of our results. The conditions necessary for its validity are discussed.