Speaker
Description
60Fe, with its half-life of 2.6 My, is a great indicative isotope for recording the violent events in the cosmos. By measuring its abundances in the deep-sea sediment, lunar soil and the gammy-ray in space, scientists identified two accretion events (1.5–3.2) My and (6.5–8.7) My ago. These two events can be varying scenarios in the universe, like He- and C-burning shells inside massive stars, core-collapse supernovae, supernova shock running through the carbon and helium shells, electron-capture supernovae, SAGB stars and Type Ia supernova. No matter which scenario the it happens, 60Fe is only can be produced via the key nuclear reaction 59Fe(n,g)60Fe. Previous researches already indicated the rate plays significant role in the nucleosynthesis, however it is pretty difficult to measure this reaction directly as the neutron and 59Fe are both unstable.
In this talk, I will introduce the measurement of the reaction rate on 59Fe(n,g)60Fe. This experiment is performed on the Lanzhou Radioactive Ion Beam Line in China, the 60Mn beam is selected and delivered to the center of a BGO detector array named LAMBDA (LArge-scale Modular BGO Detection array). The LAMBDA covers about 85% of 4-pi solid angle and consists of 49 BGO crystal modules. By the measuring the total gamma ray of the beta decay from 60Mn to 60Fe, we can extract the nuclear level density and gamma strength function of 60Fe, then input them to the Hauser-Feshbach model to get the reaction rate on 59Fe(n,g)60Fe. This is so called beta-oslo method and firstly run in China. The uncertainty of reaction rate we get from this experiment is much less than the theoretical prediction, which lead us to better understand the formation of 60Fe in the universe.