[en] Published in summary form only

[en] The individual roles played by cooling, ionization, recombination and ambipolar diffusion are quantitatively studied in an argon arc burning at atmospheric pressure. Complete and partial local thermodynamic equilibria are examined before, during and after cutting off the electric field. Electron cooling is represented by relaxation of the excited states of the atom, measurement of this parameter allows evaluation of the exact role of ionization in the electron density balance. The use of different arc chamber diameters allowed the contribution of ambipolar diffusion and that of electron-ion recombination, on the disappearance of electrons, to be isolated and the corresponding coefficients, Dsub(a) and α to be determined. (orig.)

No abstract available

[en] The individual roles played by cooling, ionization, recombination and ambipolar diffusion are quantitatively studied in an argon arc burning at atmospheric pressure. Complete and partial local thermodynamic equilibria are examined before, during and after cutting off the electric field. Electron cooling is represented by relaxation of the excited states of the atom, measurement of this parameter allows evaluation of the exact role of ionization in the electron density balance. The use of different arc chamber diameters allowed the contribution of ambipolar diffusion and that of electron-ion recombination, on the disappearence of electrons, to be isolated and the corresponding coefficients, Dsub(a) and α to be determined. (Auth.)

[en] The study of SF₆ arc plasmas requires the determination of the number densities of the various species. A previous study showed that demixing could be considered for temperatures below 11 700 K, the discrepancy between the experimental values and those obtained assuming LTE was low. The aim of the present study is to proceed in this direction by using other diagnostic methods, independent of the demixing effects. (author)

[en] Radioactive implants in interstitial radiotherapy using the Paris system were initially to be for lines which were radioactive along the whole of their lengths. The use of 'source trains' made up of a set of individual sources a given interval apart led to study being made of the conditions for which discrete sources could replace continuous sources in the Paris system. A systematic study of the dose distributions around both types of source was carried out. The distributions were calculated, on a VAX 8600 computer using a program devloped by the Gustave-Roussy Institute, taking into account oblique filtration and attenuation by the tissues. The program makes it possible to calculate volumes within an isodose of a chosen value on the basis of a dose matrix with a basic grid size of 2 mm. The geometrical conditions for which the dose distributions round continuous sources and discrete series of individual sources are not significantly different, were calculated beforehand; this gave a simple equivalence rule between a continuous source of length L and total activity dK/dt_N and n individual sources of activity dK/dt_Ns with a spacing of s between them: L=n·s and dK/dt_N=n·dK/dt_Ns. On this basis, a more thorough study was made of the dose distributions using the volume-dose distributions for the main volumes used in the Paris system to describe radioactive implantation. The study made it possible to compare continuous sources with series of individual sources of equivalent length for some source devices of similar configurations to those used in clinical practice according to the rules of the Paris system. (author). 6 refs, 6 figs, 3 tabs

[en] The values of electronic density measured by Stark broadening of Hsub(β) line in an Ar-H₂ plasma lower than those measured in pure argon plasma. (Auth.)

No abstract available

No abstract available

[en] In order to optimize the protection of healthy tissues, notably by improving the homogenization of dose distribution within the breast volume, the authors report the development of a dose distribution segmentation method: the optimization with pre segmentation. Based on twelve clinic cases, they report the dosimetric validation of this method by comparing it with the three-dimensional-conformational irradiation. They obtain an improved conformity index of 0.984 compared to 0.910. Short communication