Beam, collimation

The physical properties of the Selenium also offer big advantages with respect to radiation shielding and beam collimation. Within the comparison of radiation isodose areas the required area-radius for a survey of 40pSv/h result in a shut off area that is for Selenium only half the size as for iridium. Sources of similar activity and collimators of same absorbtion value (95%) have been used to obtain values as mentioned in Table 3 below. 

A relatively high He background is obviously inherent in all He-beam experiments. Even a highly collimated beam puts a continuous, heavy He load on the pumps evacuating the sample chamber. In the case of the apparatus shown in Fig. 2, the beam collimated to 0.2° (1.5 x 10 sr) supplies the sample chamber with about 1.5 x 10 He/sec (5.7 x 10" mbarl/s). In view of some... 

Beam collimation using a microaperture foil with a hole of 5 to 10 pm in diameter or a precisely manufactured slit is an easy method for the microbeam production [33,34]. The minimum beam spot size was limited to around 5 pm due to the size of the microaperture and contamination of particles scattered at the edge of the microaperture. 

A typical arrangement for an on-line process refractometer is shown in Fig. 6.45. Besides the prism, which is in contact with the process liquid, there is commonly a light source, a beam collimator and a photo-conductive sensor. As the nature or concentration of the process liquid varies, the critical angle changes, so moving the internally reflected collimated beam of light across the photo-detector. The latter is divided into two sections, one of which is arranged to receive a constant amount of... 

The fibers were annealed at 200 C for 5 min. in N2, wound parallel on a sample holder and flat plate X-ray photographs taken by exposing the fibers for 1 h (WAXS) to a beam collimated at 90° to the fiber axis, uatorial diffractometer traces of uniaxially oriented fibers were taken uring slit collimation. WAXS patterns were obtained on polaroid film and the difoctometer traces with a Siemens X-ray system. Nickel filtered CuKa radiation was used. The X-ray unit was operated at 30 KV and 20 mA. The sample to film distance was 71.4 mm. 

A. M. Rossi, G. Amato, L. Boarino, and C. Novero, Realization of membranes for atomic beam collimator by macropore micromachining technique (MMT), Mater. Sci. Eng. B69-70, 66, 2000. 

Figure 2.10. The schematic showing how the x-ray beam is collimated by using both the divergence and Soller slits (top). The beam, collimated in-plane by the divergence slit, is further collimated axially by the Soller slits. The coordinates in the middle of the drawing indicate the corresponding directions. The bottom part of the figure illustrates the analogy of Eq. 2.6 with Eq. 2.5.

Fig. 7-23 Energy-dispersive diffractometry. (a) Experimental arrangement. The x-ray tube is seen end on. Diffracted-beam collimator not shown, (b) Diffraction pattern of polycrystalline platinum at 29 = 21.4° obtained with a Si(Li) counter and an iron-target x-ray tube operated at 45 kV and 8 mA. SWC = short wave cutoff = short-wavelength lintit of incident beam. Giessen and Gordon [7.20].

S. Tanaka and Y. Takahashi, "Effects of X-ray Beam Collimation on the Measurement of Residual Stress Distribution in a Si3N4/Steel Joint," ISIJ International, 30 [12] 1086-1091 (1990). 

The analytical sensitivity is enhanced by increasing the b value (Eqs. 4.4, 4.9, 4.17) hence, flow cells can be designed to provide long optical path lengths. However, the b value in classical, Z-shaped or spiral flow cells cannot be increased indefinitely due to limitations in cell geometry and radiation beam collimation. 

Figure 6.4 The use of short wavelengths also benefits the signal to noise of a diffraction spot intensity measurement. The detector can be moved further from the ciystal for a given resolution limit. As a result the background per unit area on the film is reduced according to the inverse square law, excluding the diffuse scattering. The diffraction spot hardly increases in size because of the beam collimation. The reduced scattering at short wavelengths (equation (6.1)) is compensated for by the strength of the SR beam intensity.

In order that an relevant to the CD study may be experimentally obtained, it is important to have the same beam collimation and sample-phototube configuration for the absorption and CD measurements. This problem is well solved by simultaneously determining absorption and circular dichroism on the same phototube with a single beam and sample. A relatively simple modification of the Cary instrument allows this to be achieved. ... 

Certain user-defined imaging parameters are unique to helical CT scanning. Pitch refers to the ratio between table increment per gantry rotation and X-ray beam collimation [28]. 

The schematic interferometer diagrams given do not show most of the optics, such as beam collimators and focusing mirrors. Mirrors in an FTIR are generally made of metal. The mirrors are polished on the front surface and may be gold-coated to improve corrosion resistance. Commercial FTlRs use a variety of flat and curved mirrors to move light within the spectrometer, to focus the source onto the beam splitter, and to focus light from the sample onto the detector. 

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