Distance focal

For very large areas, such as assembly halls or sports arenas, jets of air will be required to obtain the large throw distances. Focalized draughts may be unavoidable in such installations. 

Fig. 9.11. Influence of the focusing conditions on crater shape and size. WD working distance, g lens-to-sample distance,/ focal distance, SEM scanning electron microscopy.

The sensitivity curves are plots of maximum achieved sensitivity as a function of thickness of the object for a given focal spot size and source to detector distance. The best attainable sensitivity in image intensifier systems is a function of tube voltage, current, scattered radiation and the screen gamma. As a first step, stainless steel plates with thicknesses ranging from 5 mm-30 mm in steps of 5 mm were chosen. These plates had a length of 950 mm and width of 280 mm. The plate is positioned very close and at the center to the LI. tube. The extraneous... 

Steel was used as the control object. During the experiments radiation energy, steel layer thickness, focal distance, roentgen films, screens were varied. Sensitivity was valued according to wire and groove standards. 

Exposures were detected at energies of 25 and 45 MeV for the home roentgen film types PT-1, PT-5 and import types D4, D7, Agfa-Gevaert , MX-5 Kodak . The lead strengthening screens were used for roentgen survey. Cassettes were loaded according to 2H3 scheme. In the experiments focal distances (F) came to 1.5, 2.0, and 3.0 m. 

As for BC-50 betatron it is possible to fulfill radiographic control of steel with thickness of 360 mm for the same time tmd energy at focal distance of 3.0m 450 mm steel at F=1.5m, and 480mm steel at F=3.0m with the help of PT-1 film type. 

At 45 MeV mode BC-50 betatron allows to x-ray steel barrier with 500mm thickness using PT-1 film type at F=3m in less than seven minutes. During one hour exposure and at the same focal distance betatron allows to x-ray 500mm thickness steel on PT-5 film type. And 700mm thickness steel on PT-1 film type. 

Fig. 2 shows the CFRP-sandwich specimen and the transducer mounted on the scanner. Fig. 23 presents a C-scan of the specimen as first interesting result. Only the defects visible from the outside are indicated. The distance between transducer and specimen was smaller than the focal length, so that the angle of incidence at the edge of the sound beam converts the longitudinal waves to Rayleigh-waves in the specimen. These waves provide a very sharp image of the surface. This method opens the possibility for a non-contact acoustic microscope. 

Greater depth of soil when there is a deep layer of soil, the intensity of the earthquake will reduce. The greater the distance from the focal point, the smaller will be ground movements. In such cases it is seen that the settlement of the soil below the structure may be negligible as it would have already settled by the time the shock reached the surface, and hence damage to the structure would be reduced. 

Figure 2. The focal length is the distance between the principal plane and the focus, where the principal plane is defined as the surface where tlic input and out-pul light rays would intercept.

Figure 1 Principle of confocal Raman microscopy A laser spot in the focal plane passes through the pinhole P. A laser spot at a distance z from the focal plane is projected in the image plane with size P, and is largely blocked by the pinhole P. [L — lens M = beam splitter fi, f2 = focal length of lens L, and L2, respectively b2 — image distance of out-of-focus laser spot). Reproduced from Tabaksblat et al. [14], with permission of the Society for Applied Spectroscopy. 2000.

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