Cameras, X rays

The X-ray instrumentation requires a commercial small angle X-ray camera, a standard fine structure X-ray generator and a sample manipulator if scanning is requested. The essential signal is the relative difference between the refraction level Ir and the absorption level Ia. Both levels are measured simultaneously by two scintillation detectors. At fixed angles of deflection this signal depends solely on the inner surface density factor C and thickness d of the sample [2] ... 

The system uses a remote controlled manipulator system whieh scans the volume of interest. It also positions the x-ray source and x-ray camera at different angles relative the crack and create projection images of the craek. By using a tomographic reconstruction of these images a 3-D representation of the crack can be used for analysis and sizing. 

The manipulator consist of two parts, an outer part and an inner part. The pipe is x-rayed through single wall with the x-ray camera placed inside the pipe and the x-ray source placed outside the pipe (see figure 2). In this figure the two welds to be tested can be seen. 

Figure 4.2. Sketch of a laboratory setup comprising a rotating anode, conventional beam shaping optics, and an X-ray camera with the sample in normal-transmission geometry...

The Fig. 19 shows schematically a typical instrumental set-up in which a thermobalance is combined with a high temperature X-ray camera and with a quadrupole mass spectrometer. 

A special film holder allows transportation of the film with various rates. Time marks are printed automatically on the film for correlating the X-ray patterns to specific times and temperatures in the TMBA curves. The temperature program of the X-ray camera furnace is regulated by the thermobalance heating control system. Up to the maximum temperature of 1200 °C usual heating rates can be varied from 0.2 to 4 °C/min. The temperature of the impact plates can be held constant between room temperature and 450 °C and is recorded during the... 

SAXS Small angle diffraction patterns were obtained a room temperature using a "Searle" X-ray camera with Cu Ka (1.54A) radiation (35 kV, 25 mA). The exposure times were about 65 hours. 

The X-ray camera is prepared to accept a loop-mounted sample. The X-ray camera should be properly aligned with the X-ray beam and the cold nitrogen cold stream should be aimed at the eucentric point of the X-ray camera. 

Figure 4.4 Procedure for shock-cooling a crystal using a gaseous cryogen. (a) The goniometer head is assembled on the X-ray camera and the cold gaseous nitrogen stream is centred on the eucentric point of the camera, (b) The stream is deflected with some appropriate obstruction.

The next step is for a protein crystallographer to mount a small perfect crystal in a closed silica capillary tube and to use an X-ray camera to record diffraction patterns such as that in Fig. 3-20. These patterns indicate how perfectly the crystal is formed and how well it diffracts X-rays. The patterns are also used to calculate the dimensions of the unit cell and to assign the crystal to one of the seven crystal systems and one of the 65 enantiomorphic space groups. This provides important information about the relationship of one molecule to another within the unit cell of the crystal. The unit cell (Fig. 3-21) is a parallelopiped... 

Of the many types of X-ray cameras, only two are still in even occasional use in protein crystallography — the Buerger or precession camera and the rotation/oscillation camera. The precession camera is used primarily in... 

Fig. 20. Meridional intensity profile from frog sartorius muscle recorded on a long laboratory-based X-ray camera by Haselgrove (1975). This shows the effects of interference on peaks arising from C-protein, troponin, and myosin. For details, see text.

X-ray diffraction patterns of vitamin Bg and other vitamins by a precision x-ray camera, have been determined. Elementary cell-dimension studies have been reported (11). 

Figure 4.3.10 Full-field X-ray microscopy on a 5 wt% Rh/Al2C>3 catalyst during catalytic partial oxidation of methane (A) amount of oxidized Rh species (corresponds to XANES species 1 in [D]), (B) reduced Rh species (reduced species 2 in [D]), (C) the distribution of other elements that show a featureless absorption spectrum in the given energy range, and (D) spectra used for X-ray absorption contrast (original image taken by X-ray camera was 3.0 mm x 1.5 mm the reaction gas mixture 6% CH4/3% ()2/I Ie enters from the left) (reproduced with permission from ref. [69], Copyright ACS, 2006).

The coupling of a microreactor array in combination with an X-ray camera was used by Grunwaldt et al. (2007) to record the XAFS spectra of ten catalysts simultaneously. In this feasibility exercise, the arrangement comprised a spectroscopic cell with ten sample compartments (2 or 5 mm in thickness) that were filled with meshed and sieved catalyst particles. There was little detail provided about the heating and gas flow arrangement, but the cell could be heated (although the preliminary data were all recorded after flowing either a Ff2 helium or Cb—helium mixture at room temperature). 

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