Energy Dependence of Parameters Characterizing Multiply Backscattering of Gamma Photons (original) (raw)
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The response function, converting the observed pulse-height distribution of a NaI(Tl) detector to a true photon spectrum, is obtained experimentally with the help of an inverse matrix approach. The energy of gamma-ray photons continuously decreases as the number of scatterings increases in a sample having finite dimensions when one deals with the depth of the sample. The present experiments are undertaken to study the effect of target thickness on intensity distribution of gamma photons multiply backscattered from an aluminium target. A NaI(Tl) gamma-ray detector detects the photons backscattered from the aluminium target. The subtraction of analytically estimated singly scattered distribution from the observed intensity distribution (originating from interactions of primary gammaray photons with the target) results in multiply backscattered events. We observe that for each incident gamma photon energy, the number of multiply backscattered photons increases with increase in target thickness and then saturates at a particular target thickness called the saturation thickness (depth). Saturation thickness for multiply backscattering of gamma photons is found to decrease with increase in energy of incident gamma-ray photons.
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Angular differential number and energy albedo were measured 137 at a scattering angle of 60° for narrow beam of Cs gamma rays normally incident on finite thickness scattering media of various atomic numbers. Measurements were made using a collimated 3 cc Ge(Li) detector with suitable electronics and a 400 channel pulseheight analyzer. The calculation of the energy spectrum of the scattered photons was carried out by using a response matrix with 51 energy intervals over the range 0.04 -0.3 MeV.
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Applied Radiation and Isotopes, 2008
The energy, intensity and angular distributions of multiple scattering of 662 keV gamma photons, emerging from targets of pure elements and binary alloys, are observed as a function of target thickness in reflection and transmission geometries. The observed spectra recorded by a properly shielded NaI (Tl) scintillation detector, in addition to singly scattered events, consist of photons scattered more than once for thick targets. To extract the contribution of multiply scattered photons from the measured spectra, a singly scattered distribution is reconstructed analytically. We observe that the numbers of multiply scattered events increase with increase in target thickness, and saturate for a particular thickness called saturation thickness. The saturation thickness decreases with increasing atomic number. The multiple scattering, an interfering background noise in Compton profiles and Compton cross-section measurements, has been successfully used as a new technique to assign the ''effective atomic number'' to binary alloys. Monte Carlo calculations support the present experimental results. r
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A simple relation between the total photoeffect cross section of an element and the total attenuation cross section of its compound has been derived. Total attenuation cross sections of some: 15 simple compounds have been measured by performing transmission experiments in a good geometry set up. Using these values and with the aid of the present relation, total photoeffect cross sections of elements of 2 2 47 at 514.0, 661.6, 1115.5, 1173.2 and 1332.5 keV gamma ray energies have been determined and compared with Scofield's theoretical cross sections.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2006
The gamma photons continue to soften in energy as the number of scatterings increases in the sample having finite dimensions both in depth and lateral dimensions. The number of multiply scattered photons increases with an increase in target thickness and saturates at a particular value of the target thickness known as saturation depth. The present experiment is undertaken to study the effect of atomic number of the target on saturation depth of 0.662 MeV incident gamma photons multiply scattered from targets of various thicknesses. The scattered photons are detected by an HPGe gamma detector placed at 90°to the incident beam direction. We observe that with an increase in target thickness, the number of multiply scattered photons also increases and saturates at a particular value of the target thickness. The saturation depth decreases with increasing atomic number. The double Compton scattered peak is also observed in the experimental spectra.