Cylindrical detector geometry

Flow through electrochemical detectors based on a cylindrical geometry, as opposed to a planar geometry, have also been developed Three cell designs using cy-... 

Since we use the laser geometry where both lasers are parallel and in the plane of the detector, the resultant 3D distributions are cylindrically symmetric about the laser polarization, and thus the angular distribution can be characterized by the single variable qj. When plotting the full angular distribution 1(0a) = P(u)[l + / P2(cos0d)]/deteCtion(0difference between the shapes of the m,j =0 and rrij = 2... 

Both flat and cylindrical transmission samples are commonly used in combination with position sensitive or image plate detectors. The major disadvantage of the transmission geometry arises from the fact that self-focusing of the diffracted beam is not as precise as in the Bragg-Brentano... 

Figure 3.10. Synchronization of the goniometer arms the x-ray source is stationary while the sample and the detector rotations are synchronized to fulfill the 0-20 requirement (left) the sample is stationary while the source and the deteetor arms are synchronized to realize the 0-0 condition (middle) - this geometry is in common use at present only the detector arm revolves around the goniometer axis in the case of a cylindrical sample (right). F - focus of the x-ray tube indicating the position of the x-ray source arm, D - detector arm, 0 - Bragg angle. The common goniometer axis (which is perpendicular to the plane of the projection) around which the rotations are synchronized is shown as the open circle in each of the three drawings. The location of the optical axis is shown as the dash-dotted line.

The vertical cylindrical fiimace consists of a graphite resistor surrounding a gas-tight alumina tube, with an inner diameter of 23 mm and a length of 600 mm, in which the calorimetric detector is placed and the experimental chamber, localized. The geometry of the resistor provides a 140-mm long constant temperature zone in the central part of the tube. The furnace has an external water-cooled jacket and can be heated up to about 2000°C. 

With respect to the design of the flow-through detector, the influence of flow cell geometry on the Schlieren effect for cylindrical and square capillaries, sheath flow cells and U and Z -pattem flow cells has been investigated by several researchers in relation to liquid chromatography [116], and a theoretical model describing the influence of the Schlieren effect on absorbance measurements has been proposed [83]. 

Figure 5 The different geometries of gas-filled detectors (a) parallel plate (b) cylindrical (c) spherical.

Geometry effects. The term geometry refers to size and shape of source (point, parallel beam, disk, rectangular), size and shape of detector aperture (cylindrical, rectangular, etc.), and distance between source and detector. 

In the simpler coaxial arrangement, the cylindrical surface of the germanium detector is fully covered by the scintillator. More sophisticated layouts partly cover the flat surfaces in the front and in the black, as well. In the latter geometry, only a small solid angle of the forward and of the backward scattering directions is not shielded (see O Fig. 31.6). 

For many years, a 3 x 3 Nal detector was the standard for routine measurements of y-active materials. The detector consisted of a cylindrical piece of thallium-activated Nal 7.6 cm (i.e., 3 in.) in diameter and 7.6 cm in height. The hygroscopic crystal was enclosed in an aluminum can (with a glass window on one end) to protect it from moisture. These crystals could be manufactured sufficiently reproducibly that efficiencies could be taken from tabulations. Another useful geometry was similar except for a coaxial well where small samples could be counted at nearly 100% detection efficiency. 

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