Collimating effect

The indirect transformation technique models the r -multiplied autocorrelation function r (y(r)) , = r y(r) = p r) as a superposition of equidistant B-splines (up to a cutoff maximum particle size that needs to be given in advance) that are Fourier transformed, subjected to any applicable collimation effects (the method was originally developed for a Kratky slit collimation), and then least-squares fitted to the experimental intensity distribution, so that p r] can be computed using the fit coefficients and the untransformed B-splines. The shape of p(r) is known for many standard particles including solid spheres, core-shell hollow spheres, and rods. 

A hexapole assembly of rods (poles) is built similarly to the quadrupole, but now there are three sets of opposed rods evenly spaced around a central axis. The hexapole cannot act as a mass filter by applying a DC field and is used only in its all-RF mode. It is therefore a wide band-pass filter and is used to collimate an ion beam. (Like-charged particles repel each other, and an electrically charged beam will tend to spread apart because of mutual repulsion of ions unless steps are taken to reduce the effect.)... 

A beam from an actual sample will require a more elaborate slit S3rstem for collimation if the sample is broad. The Soller slit (Figure 4-7), a stack of thin parallel plates, is such a system. The reasoning that supports this construction is as follows. Were the sample a point or a line source, a slit between sample and crystal or a slit between crystal and detector would be enough for satisfactory collimation. With a two-dimensional sample, both slits would be needed to get this done. But this arrangement is wasteful of emitted intensity because the detector sees the sample as a line source. To use all the sample area effectively, a system of parallel slits is needed. To eliminate the divergent rays in such a system, the slits must be extended in the direction of the beam, and this leads to the parallel-plate construction in the Seller slit system. 

Excitation by Ao is the kind of excitation to which Equation 6-4 and its sequels apply this excitation leads to the absorption effects of the previous section. It can be treated successfully (as indicated above) by narrow, parallel beam geometry, which is certainly applicable to the well-collimated beam of a good spectrograph with a detector of small... 

Transmission, by collimator in x-ray optical system, 113 of x-rays by windows, 45 Transmittance of x-rays, as function of absorber thickness, 11 Transmitted beam, components, 18 Tubes, x-ray, see X-ray tubes Tungstate solutions, absorption effects in, 168-170... 

Fig. 3.11 Velocity distribution (cosine smearing effect) in the case of identical source and collimator radius, for different aperture a, the ratio of collimator radius to source-collimator separation (adapted from [30])...

To resolve the problem applying methods of collimated atom beams, equilibrium vapour as well as radioactive isotopes, the Hall effect and measurement of conductivity in thin layers of semiconductor-adsorbents using adsorption of atoms of silver and sodium as an example the relationship between the number of Ag-atoms adsorbed on a film of zinc oxide and the increase in concentration of current carriers in the film caused by a partial ionization of atoms in adsorbed layer were examined. 

On diffuse irradiation, Eqs. (8.10) through (8.15) become much simpler since all terms with the factor (3/m - 2) vanish, j (3/m - 2)fiod/xo = 0. Helpwise, collimated irradiation under //o = 2/3 (ao = 48.2°) has the same effect, but only for weak absorption. With increasing absorption the light fluxes inside the sample deviate more and more from the condition of diffuse irradiation. It has been often shown that the two-flux model derived first by Schuster<30) and then by Kubelka and Munk(28) has formally the same analytical solutions as the Pi-approximation under diffuse irradiation. Kubelka... 

If the specimen crystal is curved, there will be a range of positions where the diffraction conditions are satisfied even for a plane wave. The rocking curve is broadened. It is simple to reduce the effect of curvature by reducing the collimator aperture. For semiconductor crystals it is good practice never to mn rocking curves with a collimator size above 1 mm, and 0.5 mm is preferable. Curved specimens are common if a mismatched epilayer forms coherently on a substrate, then the substrate will bow to reduce the elastic strain. The effect is geometric and independent of the diffraction geometiy. Table 2.1 illustrates this effect. 

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