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AbstractAbstract
[en] The average energy loss W per ion pair when heavy charged particles pass through a gas was considered for a long time as independent of the particle energy. Recent measurements showed that W varied with particle energy. In order to calculate these variations, it is necessary to study the slowing down in gases of heavy charged particles. This study was done for particle energies in the range 1 to 500 keV. It was carried out as following: 1 - The stopping power of heavy charged particles was calculated. This stopping power was divided into two components. One is due to elastic collisions and is called 'nuclear' stopping power. The other one is due to inelastic collisions, it is called 'electronic' stopping power. 2 - The particle and ionization ranges were calculated by the resolution of a transport equation in which the two components of the stopping power were introduced. Comparisons between measured and calculated values were made in order to test different theoretical models. The agreement between these values was within 6%. It was also possible, from the resolution of the transport equation to determine the average energy going into ionization μ. The ratio of the ion energy to μ, can be compared to the measured ratio W(E)/W(infinite). The agreement between these values was found within 5%. The good agreement between calculated and measured values shows that the theoretical models used in determining 'nuclear' and 'electronic' stopping cross section are suitable. The study of heavy charged particles slowing down can describe W value variations relatively well
[fr]
L'energie moyenne correspondant a la creation d'une paire d'ions W a ete consideree pendant longtemps comme independante de l'energie de la particule incidente. Mais des mesures recentes ont montre que W variait avec l'energie. Pour expliquer ces variations, une etude du ralentissement des particules lourdes chargees dans des milieux gazeux a ete necessaire. Cette etude comporte deux etapes necessaires pour atteindre W: - La premiere etape a porte sur les pouvoirs d'arrets (energie perdue par unite de longueur), electronique (chocs inelastiques) et nucleaire (chocs elastiques).- La seconde etape a porte sur le parcours de la trajectoire de la particule et sur celui ou l'ionisation se cree. Des comparaisons avec des valeurs experimentales ont ete effectuees pour tester les differents modeles theoriques utilises. Les accords obtenus sont inferieurs a 6%. A partir des pouvoirs d'arrets precites, la resolution d'une equation de bilan de type transport a permis de calculer un parametre: energie moyenne perdue sous forme d'ionisation. Le rapport de ce parametre sur l'energie de la particule incidente permet une comparaison avec le W experimental. L'accord obtenu a partir de cette derniere comparaison est inferieur a 5%. L'etude du ralentissement de particules lourdes chargees dans des milieux gazeux explique relativement bien les variations experimentales de WOriginal Title
Contribution a l'etude theorique du ralentissement des particules lourdes chargees d'energie cinetique de 1 a 500 keV dans des milieux gazeux. Calcul du pouvoir d'arret electronique et des parcours - calcul de l'energie dissipee par ionisation-excitation et par collisions elastiques
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May 1978; 148 p; These (3e Cycle).
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Report
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Thesis/Dissertation
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