Measurement of the nuclear structure properties of astrophysical importance in 19Ne via a strongly improved inelastic scattering experiment

Classical novae occur in close binary star systems consisting of white dwarf accreting matter from its companion, main sequence or red giant star (Fig. 1). The accreting material provides fuel and the conditions necessary to initiate a thermonuclear explosion on the White Dwarf surface, leading to the synthesis of some heavier types of nuclei and the ejection of material into space.

Among else, novae produce radioactive isotopes, such as ¹⁸F, that could be detected by their gamma–ray emission (one of the scientific objective of the INTEGRAL satellite) . Why do we focus on ¹⁸F? Because the annihilation of positrons generated by its β+ decay is the dominant source of gamma rays during the first hours of a nova explosion. So, The knowledge of the abundance of the ¹⁸F in novae is essential because its gamma rays (≤511 keV) are one of the observables, which give insight into nuclear processes of novae.

Depending on the temperature, the b⁺ decay and two nuclear reactions are in competition for the destruction of ¹⁸F : ¹⁸F(p,α)¹⁵O and ¹⁸F(p,γ)¹⁹Ne. Unfortunately, present radioactive beams intensities are not sufficient for a direct measurement of those reactions. Nevertheless, these two reactions rates strongly depend on the structure of ¹⁹Ne. In particular, the energies, spins, and decay widths of important ¹⁹Ne resonances must be determined in order to reduce their uncertainty. Today, only a few intrinsic properties of states have been measured yet experimentally in the excitation energy range of astrophysical interest (commonly called the Gamow window).

Based on the success of the experiment performed at Louvain-La-Neuve (Belgium) in the past, we will realize soon at GANIL a new and accurate spectroscopy of ¹⁹Ne inside the Gamow window via an improved p,p’ inelastic scattering reaction. The experimental setup combines an annular silicon detector and the magnetic spectrometer VAMOS. The latter will be used for the first time to detect protons at zero degree, on the spectrograph mode (Fig. 2).  

This experimental project lead by several GANIL physicist will be realized inside an international collaboration, which includes 23 institutes and 70 physicists in total.

During his/her master training and thesis afterwards, the student will participate strongly on the preparation and realisation of the experiment. He/she will take in charge the analysis of the data. If he/she wishes and according to his/her progress, the student could also perform nuclear reaction rate calculations and even simulate the effect of the new rate calculation on the nova explosion.

The student will frequently travel in France and abroad during his/her master training and thesis in order to expend his/her field of expertise, communicate the results and provide support to the collaboration (join experiments, meetings, workshops, schools, conferences…).

Required skills :

Affinity on experimental work and within a group. Mastery of informatics languages (C/C++ more particularly). Correct mastery of English.

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