| At present,nuclear Equation of State(nEoS)is one of the most popular topics in nuclear physics and astrophysics.Until now what we know about nEoS mainly relates to symmetric matter,while the nEoS of asymmetric matter(symmetry energy)is poorly known.Studies show the density-dependent symmetry energy,i.e.,Esym(ρ),plays a key role in the neutron skin thickness of nucleus,the isospin transport in heavy ion collisions,the mass-radius relation of neutron star,etc.Currently,what we know about Esym(ρ)mainly focuses on the region around normal density ρ0,and at ρ0,the value of symmetry energy Esym(ρ0)is well constrained,while the density slope L of the symmetry energy still remains large uncertainties.At high density region,the discrepancies of the results from different transport models are still too large.Therefore,more experiments and new probes are required to constrain Esym(ρ)more precisely.In terrestrial laboratories,heavy ion collision is almost the unique way to create nuclear matter at different densities,thus served as an important method for studying Esym(ρ).For this purpose,the 25 MeV/u 86Kr+208Pb experiment has been conducted at HIRFL-RIBLL.In this thesis,we firstly introduce the CSHINE spectrometer and the overview of the experiment.CSHINE at current stage includes four Silicon Strip Detector Telescopes(SSD-Tels)and three Parallel Plate Avalanche Counters(PPACs),which can measure light charged particles and fission fragments,respectively.The SSD-Tel array can cover θ angle in the range of 10° to 60°,and can achieve particle identification for various types of charged particles.Then the thesis introduces the framework of data calibration for the experiment,which mainly includes energy calibration of the silicon strip detectors,particle identification,energy calibration of the CsI(Tl)crystals,track recognition,coordinate transformation,etc.We propose a new algorithm for track recognition of the silicon strip telescope.With this algorithm,we can quantitatively discriminate the charge sharing and multi-hit effects in the silicon strip detectors,and high track recognition efficiency is achieved.In this experiment particle identification for particles with Z≤10 has been achieved.Furthermore,we fit the spectra of particles with Z≤2 using the two-source model and get pretty good fitting results.By studying the isospin characteristics of light particles,we find that the neutron richness of the emitted particles gradually decreases as the angle increases,i.e.,the isospin characteristics of the emitted light particles are associated with angles.By constructing neutron excess variable,Yn,ex/Yp,CI,we see that it shows a trend of increasing first and then decreasing as the angle increases.Meanwhile,Yn,ex/Yp,CI decreases as the rapidity or transverse momentum increases.By constructing the probe R[(t/d)/(3He/4He)],the yield ratio of the mirror nuclei,i.e.,t and 3He,we observe similar isospin effects.Thus,we verified that the isospin effect does exist in the experiment.We will be expected to give constraints on both the symmetry energy value Esym(ρ0)and the slope L at normal density by further comparison with ImQMD calculation results. |
