[en] The relation between absorbed dose in a source region with a uniform concentration of electron emitters and in a target region separated by a plane interface, derived by Charlton and Cormack [Rad. Res. 17, 34-49(1962)], has geen generalized to the case of an interface of arbitrary shape. The present schema is designed to facilitate the use of the improved point kernels calculated by Berger [Natl. Bur. Stand. (U.S.) NBSIR 73-107(1973)]. A general expression for the geometric reduction factor for a target region is derived and applied to the case of a cylindrical interface. Notable differences between the present results and the existing data are presented

[en] Estimates of absorbed dose in a reference man immersed in a semi-infinite cloud of air, uniformly contaminated with radioactivity, which provides useful basic data for assessing the potential hazard from the release of radioactive materials into air normally refer only to photons, and the dose delivered by the associated electron flux produced by the interactions of photons in air is not evaluated. Since dose to the basal layer of the skin may be a crucial factor in many cases of external exposure, it is desirable to have estimates of dose from this additional source as well. Such a calculation is here described from which it is seen that the electron dose-rate can by no means be ignored. (U.K.)

[en] It is shown that the S matrix for a system exposed to a classical electromagnetic field, when the fully interacting system can be represented by normalized Floquet states, can be determined nonperturbatively, provided adiabatic switching of the interaction and wave function renormalization are taken into account. Numerical results for an electron in a model potential are presented to demonstrate that the nonperturbative transition amplitudes agree with lowest order perturbation theory for weak fields, but deviate towards lower values at high intensities. Gauge-dependence of the level shifts and transition amplitudes is also studied, both theoretically and numerically

[en] An approximate method which seeks to extend the use of the available isotropic electron point kernels to situations where the electron emission is anisotropic is introduced and applied to the calculation of dose near a bone-tissue interface irradiated by photons. The correct angular distribution of photoelectrons is used, and dose profiles are constructed for both directions of irradiaion. The results of these calculations clearly bring out the strong dependence of the dose upon the direction of irradiation at low photon energies. Variation of the total dose obtained by adding the constant contribution from the Compton electrons to the dose from photoelectrons is also presented for four representative photon energies

[en] The absorbed doses in bone and in a tissue-filled cavity at the center of a bone incorporating photon-emitting radionuclides, are calculated on the basis of a mathematical model which permits use of the reciprocity principle for flux computations. First, the densities of secondary electrons per unit energy interval produced at the point of interest as a result of photoelectric and Compton interactions are determined separately by Monte Carlo sampling. These are subsequently used in conjunction with the appropriate geometric factors for the cavity, to determine the required doses. The main features are discussed with reference to /sup 99m/Tc, which emits γ rays of energy 0.14 MeV and is widely used for bone scanning. To facilitate estimation of dose due to characteristic x rays emitted by various radionuclides, results are also presented for photons in the energy range 10 to 20 keV

[en] The difference between corresponding geometric factors for two media of comparable atomic numbers is expressible as the product of an associated scaling factor between the two media and an auxiliary function dependent on the properties of only one of the media. Evaluation of this function is illustrated by considering the case of a plane interface. Associated scaling factors for a few tissue-like media, deduced from published data on β dose distribution, are also tabulated

[en] Monte Carlo calculations encompassing various aspects of energy deposition by electrons in argon are described in this paper. Particular attention is paid to fluctuations in ionization, and representative data on the probability distribution of the number of ion pairs are presented. The variations of W and the Fano factor as well as of the efficiencies for the production of various excited species are also evaluated. Further, degradation spectra and subexcitation electron spectra including Auger electrons are presented and discussed

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No abstract available

[en] The integral equation for the probability density of the number of ions produced in matter as a result of complete degradation of electrons is solved numerically using a Fourier transform. Data are presented with reference to argon, which show that if inner-shell contributions are neglected, the probability distribution becomes Gaussian around a source energy of 5 keV. However, results obtained including the contributions from L-shell and Auger electrons indicate that a normal distribution of ions can be expected only at higher energies