Développement d'un dispositif expérimental bas bruit

: application à l'astrophysique nucléaire et à l'analyse ultra-sensible de matériaux

Abstract

This Ph.D. thesis focused on the setup of an experimental device providing low background conditions when detecting gamma rays. In this aim, a lead castle has been used in order to shield the germanium detector from the natural radioactivity. An anticoincidence has been applied between this detector and a plastic scintillator surmounting it to suppress the effect of a part of the cosmic rays. The motivation of this project was the study of nuclear reactions with an astrophysical interest which demands such conditions. A particular case is the proton capture reaction, which brings an additional source of noise when studied with a proton beam. Our idea is to work in reverse kinematics to avoid this problem, that is to inverse the function of the incident and target nuclei. We have therefore developed a hydrogen standard by means of ion implantation in silicon. Some other developments have been brought, including a new and clean beam line of the LARN accelerator, a cold trap, a target cooling system… After having determined the detection efficiency of the system and characterized the shieldings, we were able to use the setup to measure the cross section of the 13C(p,γ)14N and 15N(p,γ)16O reactions, which play a role in the stellar nucleosynthesis. The results are in good agreement with the literature. They validate our setup and the reverse kinematics measurement technique as well. An application in the field of highly sensitive material analysis is also presented.

Date of Award	25 Sept 2009
Original language	French
Awarding Institution	University of Namur
Supervisor	Guy Terwagne (Supervisor), Yves Caudano (Jury), Pierre DESCOUVEMONT (Jury), Guy G. Ross (Jury) & Anne Lemaitre (President)