 |
Theses
Mesure dans le $^{19}$Ne des résonances d’intérêt pour l’´étude des novæ par une nouvelle méthode de diffusion inélastique
Mesure dans le $^{19}$Ne des résonances d’intérêt pour l’´étude des novæ par une nouvelle méthode de diffusion inélastique
Abstract : A nova is a thermonuclear runaway occurring in binary system of stars. The observation of the gamma rays emitted after a
nova is a way to better understand this phenomenon. According to the models, the
line at 511 keV, produced in the annihilation
between positrons and electrons, would be the most intense line several hours after the explosion. One of the main positron emitters
would be the $^{18}$F radioactive isotope. In order to improve the predictive power of the models, it is crucial to better determine the
amount of $^{18}$F produced in the nova. Yet, the $^{18}$F destruction rate $^{18}$F(p,$\alpha$)$^{15}$O is given with large uncertainties. Measuring the
spectroscopic properties (energy, width, spin) of states in the compound nucleus 19Ne should allow us to constrain the reaction rate.
In this context, an experiment based on a new inelastic scattering method ($^{19}$Ne(p,p’)$^{19}$Ne∗) was performed at GANIL with the
VAMOS spectrometer. The detection system has been adapted to detect for the first time high energy protons (p’). A good energy
resolution in inverse kinematic has been reached ($\sigma$=33 keV). The angular distribution measurement of decaying particles should
provide the spin assignment of the states in a model independent way. Unfortunately, an unforeseen contamination has prevented
us to complete this measurement. New spectroscopic information have been extracted and contributed to reduce the uncertainty
of the $^{18}$F(p,$\alpha$)$^{15}$O reaction rate in a significant way. The data are compatible with a new broad state below the proton threshold
(6.41 MeV). This state seems to be sufficiently broad to contribute to the destruction reaction rate of $^{18}$F and reduces the chances
for satellite detection.
http://hal.in2p3.fr/tel-01252983
Contributor : Michel Lion Connect in order to contact the contributor
Submitted on : Friday, January 8, 2016 - 2:59:09 PM
Last modification on : Friday, January 21, 2022 - 9:30:17 AM
Long-term archiving on: : Friday, April 15, 2016 - 6:50:13 PM
Contributor : Michel Lion Connect in order to contact the contributor
Submitted on : Friday, January 8, 2016 - 2:59:09 PM
Last modification on : Friday, January 21, 2022 - 9:30:17 AM
Long-term archiving on: : Friday, April 15, 2016 - 6:50:13 PM