Diffractometer optics

The widths of the peaks are related to crystallite size, possible lattice microdeformations, and the diffractometer optics used in experiments. 

Diffractometer optics Incident divergence slit 0.5° (fixed, programmable)... 

An x-ray area detector can be used to collect the intensities of many reflections at a time. The crystal must be oriented in many different settings with respect to the incident beam but the detector needs to be positioned at only a few positions to collect all of the data. A charge coupled device (CCD) is used as the area detector on the Siemens SMART single crystal diffractometer system. The SMART detector consists of a flat 6-cm circular phosphorescent screen that converts x-ray photons to visible light photons. The screen is coupled to a tapered fiber optics bundle which is then coupled to a one inch by one inch square CCD chip. The CCD chip has 1024 x 1024 pixels each of which stores an electrical charge proportional to the number of... 

The diffractometer has gradually evolved in terms of maximum power of sealed X-ray tubes, rotating anodes, new X-ray optics, better detector efficiency, position-sensitive detection and, lately, real-time multiple-strip (RTMS) fast X-ray detection, which replaces a single detector by an integrated array of parallel detectors to provide an up to 100-fold increase in efficiency compared with traditional detectors without compromise on resolution. Time-resolved powder diffraction is... 

Figure 6. Plan of the target preparation facilities consisting of UHV preparation chamber (a), (reactive) ion etching chamber (b), ion etching gun (c), laser (d), photon detector (e), transfer arms (f), Auger system for surface analysis (g), sample manipulator and annealing facility (h), load lock and optical microscope for viewing sample (i), evaporator (j), transmission diffractometer (k), and vacuum tank for main spectrometer (1).

The chemical compositions of the samples were obtained by ICP in a Varian 715-ES ICP-Optical Emission Spectrometer. Powder X-ray diffraction was performed in a Philips X pert diffractometer using monochromatized CuKa. The crystallinity of the zeolites was obtained from the intensity of the most intense reflection at 23° 20 considering the parent HZ5 sample as 100% crystalline. Textural properties were obtained by nitrogen physisorption at -196°C in a Micromeritics ASAP 2000 equipment. Surface areas were calculated by the B.E.T. approach and the micropore volumes were derived from the corresponding /-plots. Prior to the adsorption measurements the samples were degassed at 400°C and vacuum overnight. 

One important aspect of the electron diffractometer, is that any ED pattern can be captured before scanning by a CCD camera that is placed off-axis in relation with the ED pattern (can be any commercial CCD, even a webcam see fig.l). A dedicated software corrects for any type of optical distortions that may be produced due to the position of viewing angle of the CCD in relation with the ED pattern. This has the big advantage that the user that may observe and define interactively the reflections or the area of the ED pattern that will be scanned, allowing at the same time the main beam to be blanked, in order to avoid radiation damage. 

Fig. 63. X-ray optical system of a Geiger-counter diffractometer by Xorth American Philips Co. Inc. A, X-ray tube target B, Soller slits <7, scatter slit D, specimen Et diffractometer axis F, Soller slits G> counter entrance slit.

Fig. 166. An optical diffractometer. A, light source B, pinhole C and D, lenses E, optically flat mirror the diffraction pattern of an object placed at O is seen in plane F. (Taylor, Hinde, and Lipson, 1961.)...

Figure 6.2 (a)Example of overview of high-resolution X-ray diffractometer (PANalytical s X Pert PRO-MRD system), and (b) schematics of incident and diffracted side optics used in the present study. For incident beam optics, a hybrid X-ray mirror and X-ray polycapillaries are used in combination with line focus and point focus of X-ray tube, respectively. 

A Leitz Ortholux microscope was used for the optical micrographs. Electron micrographs were obtained by conventional techniques using an International Scientific Instrument Co. minielectron microscope. Crystallinities were determined calorimetrically from the ratio of the heats of fusion of the semicrystalline samples measured (17) experimentally on a Perkin Elmer DSC-1B to the heat of fusion for 100% crystalline HMS of 32 cal/g reported by O Malley (9, 16). Wide and small angle x-ray diffraction were obtained using a G.E. XRD-5 x-ray diffractometer. 

The goiuometer head is mounted on the cp circle of the diffractometer. The head has three mutually orthogonal micrometric screws, which permit optical centering of the crystal in the center of rotation of all diffractometer axes. The crystal must not appear to process at all when viewed through the telescope (or a video camera) mounted on the... 

The optical components of the diffractometer are shown in Figure 10. A line source of the X-ray tube is used... 

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