Scattering incoherent Compton

Schrodinger s equation is widely known as a wave equation and the quantum formalism developed on the basis thereof is called wave mechanics. This terminology reflects historical developments in the theory of matter following various conjectures and experimental demonstration that matter and radiation alike, both exhibit wave-like and particle-like behaviour under appropriate conditions. The synthesis of quantum theory and a wave model was first achieved by De Broglie. By analogy with the dual character of light as revealed by the photoelectric effect and the incoherent Compton scattering... 

Figure 5 X-ray mass attenuation coefficients for aluminum as a function of photon energy. At low energies, photoelectric absorption predominates. At higher energy, incoherent (Compton) scatter becomes almost the exclusive contributing mode. Eventually, pair production dominates at very high energies (above 10 MeV).

Figure 26 shows the spectra from four explosive samples and as well as nonthreat materials. These spectra exhibit strong peaks slightly below 59 and 69 keV, which are unrelated to coherent scatter. These peaks arise from incoherent (Compton) scatter of fluorescent radiation at 59 and 69keV, which is produced from tungsten anodes. Scatter off water shows no apparent CXRS peaks. The four explosive samples clearly show characteristics peaks, which differentiate them from the non-threat materials and from each other. HeuristicaUy, the location and relative amplitudes of these peaks provide an effective means for detecting explosives. 

Placement of the monochromator in the diffracted beam has the advantage of suppressing background radiation originating in the specimen, such as fluorescent radiation and incoherent (Compton modified) scattered radiation. For example, if a steel specimen or any iron-rich material is examined with copper radiation in an ordinary diffractometer, the background due to fluorescent Fe K radiation will be unacceptably high. But if a monochromator is added and oriented to reflect only Cu Aa, the background is reduced practically to zero, because the fluoresced Fe Kol and Fe K(i do not enter the counter. A monochromator may therefore... 

The beam of secondary radiation issuing from the sample consists largely of fluorescent radiation, but there are some other weak components present as well. These are coherent scattered radiation, coherent diffracted radiation, and incoherent (Compton modified) radiation. These components appear as a background on which the spectral lines are superimposed. This background is normally low (see Fig. 15-3), but it may become rather high if the sample contains a large proportion of elements of low atomic number, because the sample will then emit a large amount of Compton modified radiation. 

In traversing through matter. X-rays are attenuated by coherent (Rayleigh) and incoherent (Compton)scattering and are absorbed by the photoelectric process (6, 7). X-rays of energy below 100 keV are mainly absorbed by the photoelectric process with a cross section (i.e., the probability for absorption) proportional to (6), where E is the X-ray energy and Z... 

The m values for a tissue vary in the range 4-5 for the photoelectric effect 2-3 for the coherent (Rayleigh) scattering 1 for the incoherent (Compton) scattering. K E) is a function of photon energy for each partial process. For a specific interaction the mass attenuation coefficient for the individual element is given by... 

The change of X (incoherent scattering or Compton effect for x-rays) is due to an inelastic collision between the incident wave (photons, x-rays, or electrons) and the atom electronic cloud. The incoherent scattering is independent of the atom positions. The atoms of the target are thus incoherent sources of wavelets, not able to produce interference. 

Figure 6.5 shows the scattering geometry from the two-point center of an assembled matter. Neglecting the insignificant incoherent (Compton) scattering at... 

Scattering, which can be coherent (Rayleigh, Thomson) and in which the photon changes direction without energy loss, or incoherent (Compton) in which the photon changes direction with partial energy transfer to an electron. 

Not all photons involved in the attenuation process lose their energy in the irradiated system. In the case of coherent (Rayleigh) scattering, photons are scattered without a change in photon energy, whereas in the case of incoherent (Compton) scattering, part of the incident photon energy (hv) is released with the... 

The total atomic cross-section <7totai can be expressed as the sum of the cross-sections of the different elementary processes - that is, the photoelectric effect (r), coherent (Rayleigh) scattering (cTooh). incoherent (Compton scattering) (Omooh). photonudear absorption Oph.n and pair production, which is to be distinguished in nudear-field pah-production (k- ) and dectron-field pair production (iCe) (see Equation 4.3). 

It is important to note that expression (23) can be applied to the crystalline phase intensities only if we include, in the first integral, its own smooth diffuse background and not just the intensity belonging to the crystalline peaks. In fact, a pure crystalline sample also has a smooth background due to the incoherent inelastic scattering (i.e. Compton scattering), the TDS, disorder scattering and, very often, unresolved tails of overlapped peaks. 

Expression (25) describes the smooth background belonging to a crystalline phase due to the incoherent (or Compton) scattering and the TDS or disorder scattering. The last contribution in (25) is very approximate because it is known that the TDS has a very complicated shape with very large peaks centered in the same position as the Bragg ones [56]. 

X-ray attenuation occurs via four basic modes of interaction, shown schematically in Figure 4. Coherent X-ray scatter (CXRS) is an energy preserving interaction between an X-ray photon and an entire atom or crystalline matrix. Incoherent or Compton scatter represents a direct interaction between an X-ray and an... 

Incoherent (or Compton) scattering, in which the wavelength of the scattered beam increases due to partial loss of photon energy in collisions with core electrons (the Compton effect). 

---