Experimental Research For ¹⁷F+p Via The Thick-Target Method

The immense Universe is composed by countless galaxies and their clusters, which consist of numberless stars, planets and nebulae et al. Up to nowadays, the Universe has undergone a tremendously long era of evolution, which is far beyond the imagination of human beings. The life spans for some stars are relatively short, while others usually undergo a long period of evolution before the end of their lives. According to the current theory for the stellar evolution, the life spans of the stars are correlated to their initial masses. For those with great masses, they will transfer to the explosive stages, super novae are typical phenomena of those explosive events.After entering to the explosive stages, hydrogen burnings usually occur in explosive modes due to the extremely high temperatures and densities within the stars. Explosive hydrogen burning events, such as hot p-p(proton-proton) chain, hot CNO cycle(Hot Carbon-Nitrogen-Oxygen cycle) and rp process(rapid proton capture process), will take place under different conditions, such as temperatures and densities. The waiting-point nuclei 14O and 15O limit the hot CNO cycle to generate energy, until the temperature increases to such that theβdecay of 14O and 15O can be bypassed via 14O(α, p)17F and 15O(α,γ)19Ne.The reaction 14O(α, p)17F takes place at T9>0.4, further reactions such as 17F(p,γ)18Ne and 18Ne(α, p)21Na will eventually lead the reaction stream to rp-process. Since the im-portance of the 14O(a, p)17F(p,γ)18Ne reaction sequence to critical constraints on ignition conditions and thermonuclear runaway timescale, the properties of the relevant states in 18Ne are crucial to calculate the reaction rates.The 17F+p elastic resonance scattering was carried out on the radioactive secondary beam line(GIRAFFE) at Beijing Tandem Accelerator Nuclear Physics National Laboratory, aiming to study the properties of the state above the proton threshold in 18Ne. The excitation function for 17F+p elastic resonance scattering was measured by applying the thick-target method. Two prominent resonant peaks were observed from the experimental excitation function:ER=0.6 MeV and ER=1.19 MeV, corresponding to 4.52 MeV and 5.11 MeV states in 18Ne respectively. The excitation function was analyzed with a multilevel R-matrix code MULTI7, properties of the two populated states in 18Ne were deduced, such as spins and parities. Moreover, a group of a particles were observed from the 6.15 MeV state in 18Ne. The highlights of this thesis are as follows:1. Reconstruction for kinematics in the thick target. The kinematical processes were reconstructed according to different angles via Monte Carlo simulation by taking the energy loss into consideration, consequently, the experimental accuracy is guaranteed within an acceptable scale.2. Analyzing the events in different Ec,m. units. A pure carbon target was employed to relatively measure the background events. The normalization was done for individual Ec,m, units while analyzing the experimental data.3.R-Matrix analysis for the experimental excitation function. The resonant parameters of the populated states in 18Ne i.e. JπandΓp were finally deduced by careful fitting.