Transmitted Photon Spectra Research Articles

Gamma radiation shielding properties of some Bi-Sn-Zn alloys

We investigate the gamma radiation shielding properties of some Bi-Sn-Zn alloys. For this study, we synthesised five bismuth-based lead-free alloy samples using the melt quench technique with the composition Bi50SnZn where Apart from physical parameters such as the weight, density, and thickness of the alloy samples, we estimated their optimum thickness range at photon energies of 122, 511, 662, and 1250 keV. The mass attenuation coefficients and effective atomic number, measured experimentally, were found to be in close agreement with values computed using WinXCom software, within a ± 4% error. From the transmitted photon spectra, the radiation protection efficiency (RPE) was determined and analysed for different alloy compositions. A correlation between RPE and effective atomic number was established at different photon energies. The Bi50Sn50 binary alloy composition is reported to exhibit maximum shielding efficiency.

P.780 Apathy and anxiety are early markers of Alzheimer's disease

Studies of radiation interactions with tissue equivalent material find importance in efforts that seek to avoid unjustifiable dose to patients, also in ensuring quality control of for instance nuclear medicine imaging equipment. Use of the Monte Carlo (MC) simulation tool in such characterization processes allows for the avoidance of costly experiments involving transmitted X- and γ-ray spectrometry. Present work investigates MC simulations of γ-ray transmission through tissue equivalent solid phantoms. Use has been made of a range of radionuclide gamma ray sources, 99mTc, 131I, 137Cs, 60Co (offering photons in the energy range from a few keV up to low MeV), popularly applied in medicine and in some cases for gauging in industry, obtaining the transmission spectra following their interaction with various phantom materials and thicknesses. In validation of the model, the simulated values of mass attenuation coefficients (μ/ρ) for different phantom materials and thicknesses were found to be in good agreement with reference values (NIST, 2004) to within 1.1% for all material compositions. For all of the primary photon energies and medium thicknesses of interest herein, results show that multiple scattering peaks are generally located at energies lower than 100 keV, although for the larger phantom thicknesses it is more difficult to distinguish single, double and multiple scattering in the gamma spectra. Transmitted photon spectra investigated for water, soft tissue, breast, brain and lung tissue slab phantoms are demonstrated to be practically independent of the phantom material, while a significant difference is observed for the spectra transmitted through bone that was proved to be due to the density effect and not material composition.

Monte Carlo simulations and analysis of transmitted gamma ray spectra through various tissue phantoms

Studies of radiation interactions with tissue equivalent material find importance in efforts that seek to avoid unjustifiable dose to patients, also in ensuring quality control of for instance nuclear medicine imaging equipment. Use of the Monte Carlo (MC) simulation tool in such characterization processes allows for the avoidance of costly experiments involving transmitted X- and γ-ray spectrometry. Present work investigates MC simulations of γ-ray transmission through tissue equivalent solid phantoms. Use has been made of a range of radionuclide gamma ray sources, 99mTc, 131I, 137Cs, 60Co (offering photons in the energy range from a few keV up to low MeV), popularly applied in medicine and in some cases for gauging in industry, obtaining the transmission spectra following their interaction with various phantom materials and thicknesses. In validation of the model, the simulated values of mass attenuation coefficients (μ/ρ) for different phantom materials and thicknesses were found to be in good agreement with reference values (NIST, 2004) to within 1.1% for all material compositions. For all of the primary photon energies and medium thicknesses of interest herein, results show that multiple scattering peaks are generally located at energies lower than 100 keV, although for the larger phantom thicknesses it is more difficult to distinguish single, double and multiple scattering in the gamma spectra. Transmitted photon spectra investigated for water, soft tissue, breast, brain and lung tissue slab phantoms are demonstrated to be practically independent of the phantom material, while a significant difference is observed for the spectra transmitted through bone that was proved to be due to the density effect and not material composition.

Experimental evaluation of gamma rays shielding parameters for Zn-Cd-Sn-Pb quaternary alloy

Gamma rays shielding parameters viz. mass attenuation coefficient (μm), effective atomic number (Zeff), electron density (Ne), mean free path (mfp), half value layer (HVL), tenth value layer (TVL) and exposure buildup factor (EBF) has been determined experimentally at 511 keV (22Na) and 662 keV (137Cs) using transmission geometry for quaternary alloys of Pb60Sn20ZnxCd(20-x) (where x = 0, 5, 10, 15, 20) which has been prepared by melt quench technique. Sodium iodide-thallium activated (NaI-Tl) scintillator detector (GAMMARAD5) having 76 mm diameter and 76 mm thickness has been used to record the transmitted photon spectra. Lambert-Beer's law has been used to evaluate the mass attenuation coefficient. The parameters Zeff, Ne, mfp, HVL and TVL are deduced from μm values. As the thickness of sample increases, the Lambert-Beer law is modified by a factor known as buildup factor (B) which include the contribution of scattered photon flux due to accumulation of gamma photons that occurs from collided part of incident photon energy inside the target media. The results of experimentally obtained shielding parameters shows good agreement with theoretical values.

Gamma rays’ shielding parameters for some Pb-Cu binary alloys

Binary alloys of xPb-(1-x)Cu where x varies from 0.1 to 0.9 with the increment of 0.1 were prepared. The physical properties and gamma rays’ shielding parameters in terms of density (ρ), attenuation coefficient (μm), mean free path (mfp), half value thickness (HVT), tenth value thickness (TVT), effective atomic number (Zeff), effective electron number (Ne), radiation protection efficiency (RPE) and exposure buildup factor (EBF) were studied for the prepared alloys. Using narrow beam geometry, transmitted photon spectra were recorded with the help of GAMMARAD5 (scintillator detector of NaI(Tl) crystal dimensions 3″ × 3″ having resolution of 6.5% at 662 keV) and radioactive isotopes of Na22 (511 keV), Cs137 (662 keV) and Mn54 (835 keV). These recorded spectra were analysed to compute μm values; which were further used to compute mfp, HVT, TVT, Zeff, Ne (in energy region 1 keV–100 GeV) and EBF (in energy region 15 keV–15 MeV). Good agreement has been observed between the experimentally measured and theoretically generated results. The shielding parameters for the alloy samples were analysed on the basis of chemical composition, energy and penetration thickness.

Thickness optimization of Sn–Pb alloys for experimentally measuring mass attenuation coefficients

An attempt has been made to experimentally investigate the optimum thickness in order to measure mass attenuation coefficients for some Sn–Pb alloy systems at incident photon energies 122, 511 and 662keV. The Sn–Pb alloys were synthesized with different compositions and different thicknesses using melt-quench technique and cast iron mould. The physical parameters such as mass, thickness, density have been measured for all the prepared alloys. Further, the transmitted photon spectra of Cs-137, Co-57 and Na-22 radioactive isotopes were recorded using GAMMARAD5 (scintillator detector) of dimensions 76mm×76mm with and without inserting different alloy samples between the radioactive isotopes and detector. The experimental results so obtained were compared with the theoretical ones of WinXCom and optimum thickness for measuring mass attenuation coefficients for the selected alloys has been recommended.

Intensity of transmitted photon spectra as a function of transverse and longitudinal dimensions of soil medium using 137Cs

Transmitted photon spectra (pulse-height distribution) of (137)Cs gamma rays are measured through longitudinal and transverse dimensions of the soil medium. The intensity (photon fluence rate) of the multiple-scattered peak, appearing in the lower energy part of the spectrum, has been studied as a function of longitudinal as well as transverse thickness of the soil medium. The intensity of multiple-scatter peak decreases exponentially with the increase in longitudinal thickness of the soil medium, whereas a reverse trend of multiple-scatter peak intensity with transverse thickness occurs as the longitudinal dimension increases. The soil medium as a whole takes part in multiple scattering affecting the intensities of transmitted photons.

Variation of photon intensities in transmitted photon spectra of 60Co as a function of dimensions of a soil medium

The transmitted photon spectra of a point gamma-ray source of 60Co have been measured through the longitudinal and transverse dimensions of a soil medium. The simultaneous effect of longitudinal and transverse thicknesses has been studied on the intensity of an appeared multiple-scatter peak in the soft part of the spectrum. The intensity of peak decreases exponentially with the increase of longitudinal thickness of soil medium whereas a reversal of the trend of multiple-scatter peak intensity with the transverse thickness observed as longitudinal dimension increases.

A Study of Transmitted Photon Spectra of 133Ba through a Soil Medium

The transmitted photon spectra of 133Ba gamma rays have been recorded and studied as a function of dimensions of a soil medium. In these studies a multiple-scatter peak is observed in the soft part of the spectrum. The longitudinal thickness of the soil medium is seen to affect only the intensity of the peak, whereas the variation in transverse thickness affects both the intensity and energy of the peak. A reversal of the trend of the multiple-scatter peak intensity to increase with transverse thickness occurs as the longitudinal dimension increases.

Multiple scattering of gamma rays in water, concrete and sand

The transmitted photon spectra of133Ba,22Na,137Cs,54Mn and60Co point sources are measured through different thicknesses of water, concrete and sand. The multiple-scatter peaks observed in these materials at 60, 90 and 100 keV energies respectively are found to be independent of incident photon energy and thickness of the medium.

Transmitted Photon Spectra of Gamma Rays Through a Soil Medium

The transmitted photon spectra of [sup 133]Ba, [sup 137]Cs, and [sup 60]Co sources are measured through different thicknesses of a soil medium. A multiple-scatter peak is observed at an energy of 100 keV independent of incident photon energy and thickness of the medium. A linear relationship between the effective atomic number of the medium and the multiple-scatter peak energy is observed.

Transmitted photon spectra of low-energy gamma rays through nuclear grade graphite

Transmitted γ-ray spectra of 241Am, 57Co and 203Hg point sources are measured through different thicknesses of nuclear grade graphite (density 1.6 g/cm 3) with a collimated NaI(Tl) detector assembly, and unfolded by the iterative technique. Irrespective of the energy of the primary photon entering the medium, the spectra show a multiple-scatter peak at 50 keV energy. The intensity of the peak decreases exponentially with the thickness of the medium. Measured build-up factors are compared with the calculated ones available in the literature.

Transmitted photon spectra of low-energy gamma rays through water

From the transmitted spectra of point sources it is concluded that in a medium of low effective atomic number, a multiple-scatter peak is observed at an energy below 100 keV where Compton collisions are not very effective in energy-degradation and photoelectric cross-section is negligible. The energy of the peak does not depend on the thickness and physical state of the medium, or on the primary photon energy. The intensity of the peak decreases exponentially with the thickness of the medium. Measured build-up factors are compared with the calculated ones available in the literature.