[en] Measurements of the number of secondaries as a function of the residual range have been performed along α tracks (Esub(α)<=11MeV) recorded in nuclear emulsions at various gelatin concentrations with convenient criteria, in order to discriminate between ejected electrons and protons. It could be shown that the electron yields measured in detectors with different concentrations of the CNOH compound are in good agreement with the calculated data, provided that on the one hand the binding energies of the orbitals and on the other hand that the increasing ''transparency'' of the materialized trajectory of the incoming particle, resulting in a lowering of the detection thereshold T₀ are taken into account. As far as the secondary protons are concerned, an excellent concordance of the measured values with the yields calculated by means of a treatment of LINDHARD has been obtained for different gelatin concentrations. Furthermore, the production of secondary protons along medium energy proton tracks (Esub(p)<=1MeV) has also been demonstrated. The results mentioned lead us to the extension of determinations to the region confined within the materialized track, as well as to other hydrogenous media. It appears that the arborescent track structure, foreseen in earlier papers, is verified

[en] The activation procedure consists not only of the introduction of more or less sophisticated treatments in the development phase, but also of the setting up of a specific ionographic methodology which will be described. The working hypotheses which led to the formulation of the so-called activation treatments will be outlined, notably the concept of the stable sub-latent image. The consequences of the activation procedure in ionography will be recalled, e.g. the drastic increase of the signal/noise ratio ranging from 1.5 to 20 and more, as well as the remarkable stability of the fog. The interest of the activation procedure for corpuscular physics as well as for the life sciences will be illustrated by first applications in autoradiography, electron microscopy and microdosimetry. As far as the autoradiographic methods are concerned, the considerable increase in efficiency and in resolution results in a drastic decrease of the exposure time or/and of the quantity of tracer elements applied, as well as in the possibility to carry out studies implying the detection of very small amounts of activity. The activation of the latent image can also be applied to exposed electron microscope photographic plates in order to allow a non-destructive observation of very sensitive specimens (macromolecules, etc.). In the field of corpuscular physics, the activation treatments led to the detection of secondary events distributed along α tracks of medium and low energy recorded in nuclear emulsions. An analytical study confirmed the hypotheses that the largest part of these protuberances are tracks of electrons and H-nuclei ejected by the incoming particle. These investigations are intended to lead to a description of the ionizing track pattern as well as to the interpretation of experimentally determined fluctuations of the track width. (author)

[en] Various theoretical approaches proposed in literature have been used in order to calculate the production of delta-rays along trajectories of α-particles traversing tissue-like media, e.g. the gelatin constituting part of the nuclear emulsions. The calculated values have been compared with measurements carried out in 3 different ionographic emulsions with various CNOH/AgBr ratios. It appeared that formulas of the Rutherford type led to a poor agreement with the experimental data, even when the binding energy of each orbital is introduced in the expression of the differential cross section. A first attempt to apply a so-called 'mixed' treatment combining a quantum formalism of Merzbacher with a rutherfordian expression resulted in a relatively acceptable agreement in the lower energy region (Esub(α) approximately < 9 MeV) of the incident particles. Up until now, the Binary Encounter Approximation (BEA) has not allowed us to reach a completely satisfying fit with the experimental data, especially at the higher concentrations of the CNOH (tissue-like) compound and in the low energy region of the incident particle. At the actual stage of our studies, the best fit with the measured values could be obtained by means of an improved 'mixed' treatment, where the BEA differential cross section has been used for the orbitals excluded by the conditions of the Plane Wave Born Approximation (PWBA) (K,L,M shells, β approximately < βsub(s), Z₁ < Z₂). As an illustration of the determination of the delta-ray production along medium energy α-particle trajectories, this treatment has been applied to the case of gelatin, taken as an example of a tissue-like medium

[en] The interest in nuclear emulsions for heavy charged particle track analysis is recalled, with emphasis on the possiblity of modifying at will the concentration of its tissue-like component and recording simultaneously various track parameters within a large interval of the incident particle's energy. By means of semi-automatic image analysing assemblies developed for this purpose, track parameter investigations have been carried out along α particle tracks, leading to the development of a double-differential ionisation cross section mixed treatment (DDCS-MT) which allowed the reproduction of experimental DDCS of protons and α particles bombarding nuclear emulsions, atomic gases, water and organic compounds. Track analysis resulted also in the finding of strong ionising events, which are partly interpretable in terms of total elastic scattering by means of the optical model, and in the observation of a statistical non uniform ''gap'' distribution, both track features being related to the energy loss of the primary. (author)

[en] Practical, semi-empirical expressions are proposed, which describe the differential cross sections (DCS) and cross sections (CS) for the elastic scattering of low energy (< or approx 200 eV) electrons by various molecules (N₂, H₂O). These formalisms are partly based on the screened Rutherford formula, and completed by non-Rutherfordian terms whose parameters have been determined by fitting to experimental data from the literature. These parameters were expressed in terms of simple analytical functions of the electron's energy. A satisfactory accord has been obtained over the largest part of the angular domain covered. (author)

[en] This paper describes an approach (DDCS-MT), based on the plane wave Born approximation, intended to calculate double-differential ionisation cross-sections (DDCS) under heavy charged particle impact. A procedure is proposed in order to adapt this formalism to the treatment of molecules, which consists essentially to break up each molecular orbital into its atomic components and to sum up the partial DDCS. The increase of the binding energies in respect to the ion energy, as well as the post-collisional interaction between the passing ion and the ejected electron were taken into account. The method proposed the passing ion and the ejected electron were taken into account. The method proposed led generally to a satisfactory agreement with measurements from the literature for electron ejection energies larger than 10 to 20 eV, in the case of a variety of low-Z molecules (NH₃, CH₄, CH₃NH₂, N₂, O₂, CO₂) bombarded by 0.25- to 2.0-MeV protons. The whole procedure is free from any fitting parameter and requires no experimental ionisation cross-sections as input data. (orig.)

[en] The double differential cross-section mixed treatment (DDCS-MT), which has been developed in order to calculate the relatively energetic delta-rays measured along 4 to 12 MeV α particle tracks recorded in ionographic emulsions of various compositions, reproduces quite rigorously experimental DDCS for medium energy protons and α particles crossing not only helium and argon, but also molecular gases like water vapour, hydrocarbons, etc. In the latter case, a special procedure is required to describe the molecular target in terms of atomic quantities, notably by taking into account the binding energies of the molecular orbitals, as well as the breaking up of the molecular orbitals in terms of atomic orbitals. (orig.)

[en] A double differential cross-section mixed treatment (DDCS-MT), developed in order to calculate double differential ionization cross-sections (DDCS), had allowed not only to reproduce with a good approximation Δ-ray yields measured in nuclear emulsions along 4- to 12-MeV α particle tracks, but also to interprete quantitatively experimental DDCS of atoms bombarded by heavy charged particles (h.c.p.). It will be shown in this paper that the DDCS-MT can be extended to the case of molecules, like water and hydrocarbons, for ejection energies at least as low as approximatly 10 eV, provided that the binding energies of the molecular orbitals are taken into account, as well as the breaking up of these orbitals in therms of atomic orbitals. Very preliminary attempts to introduce the DDCS-MT in microdosimetric determinations will be mentioned, namely the assessment of the ionization energy loss distribution for protons bombarding water molecules, and of the probability of the number of ionizations produced in a small water sphere by incoming protons

[en] The delta-ray productions calculated by means of a classical double differential cross-section expression (DDCS-BEA), or obtained by applying a quantum-mechanical formula (DDCS-PWBA), could not be made to agree with the experimental delta-ray yields measured in ionographic detectors of various compositions over the whole incident particle's energy range (4 MeV <= Esub(α) <= 12 MeV). In order to reach a better assessment of the experimental delta-ray distributions, the form factors given by Merzbacher have been introduced in the quantum-mechanical DDCS, the resulting expression being completed by the DDCS-BEA for the N- and higher shells. This DDCS-mixed treatment (DDCS-MT) leads to a good overall agreement with our experimental results, as well as with experimental DDCS from the literature. (orig.)

[en] A modified DDCS formalism is proposed for the determination of delta-ray yields in nuclear emulsions, as well as for the calculation of double differential ionization cross-sections of noble gases and organic molecules, under bombardment by protons and α particles. (author)