Experimental Research Of ²²Na+pResonance Scattering Via The Thick-Target Method

Cosmic γ-ray can penetrate through the entire universe, thus is a powerful tool to trace and locate new stellar events. Great progress in the field of γ-ray astronomy has been achieved in the past twenty years, brought largely by the Compton Gamma Ray Observatory (CGRO) of NASA launched in 1991, and the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) of European Space Agency launched in 2002. The motivation of these missions is to directly observe γ-rays from relatively long-lived 26Al,22Na,44Ti and 60Fe isotopes.22Na has a half-life of T1/2=2.6 y and decays to the first excited state of 22Ne which emits a 1.275 MeV γ-ray. In 1972,22Na was discovered in carbonaceous meteorites in the form of the extinct radioactivity, indicated by an extraordinarily large 22Ne/20Ne abundance ratio. These meteorites are generally originated from the nearby novae or supernova ejecta. The production of 22Na involves the so-called high-temperature NeNa-MgAl reaction sequences, i.e.20Ne(p,γ)21Na(β+)21Ne(p,γ)22Na or 20Ne(p,γ)21Na(p,γ)22Mg((3+)22Na. The 22Na(p,γ)23Mg reaction plays a crucial role in determining the overall 22Na abundance in the ejected shells. Due to the very complicated level structure of 23Mg close to the proton threshold, large uncertainties exist in the 22Na(p,γ)23Mg reaction rates due to the missing of critical resonances.The experiment was carried out at the radioactive beam line in Lanzhou (RIBLL1), and the resonance scattering of 22Na+p was measured with the conventional thick-target inverse kinematic method. A high-quality 22Na secondary beam with the energy of 4.1 AMeV was produced by using the 22Ne(p, n)22Na reaction. The 22Na beam particles bombarded a (CH2)n target in the TK chamber, and the lighter recoils were detected by two sets of ΔE-E silicon detector telescopes, installed at θlab≈0° and 14°. respectively. Two-body kinematic reconstruction for the 22Na(p,p) elastic scattering was processed on an event-by-event basis, and the excitation function was obtained up to Ec.m.=4.0 MeV. Several proton resonant states in 23Mg were observed in the experimental excitation function.