Back-scatter intensity

A relationship has been derived between average particle size and concentration and the back-scatter intensity of a light beam entering a slurry of non-transparent particles [333]. Concentrations used were 0.3 to 2.5% and the average sizes were 40 to 1200 pm. The light source and detector were built into one tube that was mounted on the wall of a 1 liter 

The suffixes refer to the back-scatter intensity from = total, = container walls, b = maximum possible. For aluminum silicate, experiment yieldedp = 0.77, q = 1.67, k = 0.20. 

In a second paper [334] the technique was extended to on-line. A similar technique to the above, but using ultrasonics, has also been described [332,336]. 

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To enable detection of fine mineral particles (<20pm),back-scattered electron imaging was used. Once the minerals were detected, EDS was used for analysis. Selected lignite particles were scanned to determine the distribution of minerals. Mineral types were then differentiated by variation in back scatter intensity and identified using EDS. The relative proportions (major, minor) and size and spatial distributions of the minerals were recorded. The overall surface of the polished section was viewed and massive minerals were analyzed and their distribution and size recorded. 

Along with the ever increasing demand for on-line or in-line particle characterization in process control, requests for direct measurements of particles in pipelines or reactors are on the rise. In process control, any bias of the characterization method or precise physical meaning of the parameters determined are not of the utmost importance. Robusmess, reliability, and precision of measurement are often the primary concerns. Besides focused beam reflectance and fiber optical PCS probe, back scattering intensity measurement is among the optical techniques preferred for in-process measurement due to the obvious reasons that when the concentration of a suspension is high, the... 

REELS will continue to be an important surface analytical tool having special features, such as very high surface sensitivity over lateral distances of the order of a few pm and a lateral resolution that is uniquely immune from back scattered electron effects that degrade the lateral resolution of SAM, SEM and EDS. Its universal availability on all types of electron-excited Auger spectrometers is appealing. However in its high-intensity VEELS-form spectral overlap problems prevent widespread application of REELS. 

Practically it is more convenient to measure intensity ratios instead of absolute intensities. Thus, e.g., Cu may serve as a reference material, relative to which the ion intensities back-scattered from the atoms of the surface under consideration are measured ... 

If we view the thin plate from the left where it is illmninated with intensity, L, what we see is the back-scattered light, or light diffusion from the surface. If the plate is a perfect diffuser, then we will see an exact amount of L scattered back along the same plane as L as a diffuse component. Note that we are not speaking of reflection (which is ein entirely different mechcinism where the... 

The detector itself may be shielded from background y-rays by means of an annular shield of W or Pb, and absorbers in the form of appropriate metal foils are placed between the detector and the specimen. These reduce the intensity of the continuum of Bremsstrahlung radiation and also prevent back-scattered protons from entering the detector which would degrade the observed spectrum. 

It was apparent that when the two immiscible fluids were stirred droplets of chloroform formed in the aqueous phase. It was hypothesised that the response of the phototrode was dominated by light scattered back from the droplets without reaching the mirror and that, as the droplet size decreases, the intensity of the back scattered light increases. This was confirmed in tests by increasing the rate of stirring and so decreasing the droplet size. 

Options of data analysis can be deduced from the magic square and our notions concerning the structure. As an example let us consider the case of small-angle X-ray scattering. Here it is, in general, assumed that the structure is described by a continuous density function. Although there is no9 way back from intensity to density, there are several options for data analysis ... 

In bulk samples, X-ray yields need to be adjusted by the so-called "ZAF" correction. Z stands for the element number (heavier elements reduce the electron beam intensity more than lighter elements, because they are more efficient back-scatterers), A for absorption (different elements have different cross sections for X-ray absorption), and F for secondary fluorescence (the effect described above). Corrections are much less important when the sample is a film with a thickness of 1 pm or less, because secondary effects are largely reduced. The detection limit is set by the accuracy with which a signal can be distinguished from the bremsstrahlung background. In practice, this corresponds to about 100 ppm for elements heavier than Mg. 

Fig. 6. Lower part angular dependence of the non-normalized static scattering intensity I(q) observerd with latex particles (R=265 nm). Upper part dependence of r/q =D on the scattering angle in dynamic LS. The sharp downturn at large scattering angles results from a weak back reflection of light on the boundary of the aqueous solution to the index matching bath, that consisted of toluene. This reflection results from the difference in the refractive indices of water (n = 1.333) and toluene (n =1.51). Reprinted with permission from [182]. Copyright [1982] American Society...

Mossbauer spectra are obtained by measuring the transmitted or back-scattered y-ray intensities as a function of velocity. Figures 2B and 2C show spectra obtained by transmission and by scattering, respectively. The shift of the peak location from zero velocity is typical and is an important parameter often called chemical shift. The amount of chemical shift is a function of the composition of the radioactive source as well. 

Figure 15. Intensity profile of light back-scattered from a food emulsion containing 20 wt% emulsified fat, at 5 °C, using green light (543 nm).

Raman spectroscopy Raman spectra from small SWNT pieces with typical dimensions of 100 pm were recorded in the back-scattering geometry using two different micro-Raman setups comprised of a triple monochromator DILOR XY and a CCD detector system, cooled either to liquid nitrogen temperature or -100°C. The 488 or 514.5 nm line of an Ar+ laser, as well as the 647.1 nm line of a Kr+ laser, were used for excitation, while the beam intensity on the sample was =0.5 mW. The laser line was focused on the sample by means of a lOOx objective with a spatial resolution of 1 pm. 

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