Study Of Interaction Cross Sections For Neutron-rich Carbon Isotopes

The measurement of interaction cross sections(reaction cross sections)is one of the basic experimental methods to study the density distribution of unstable nuclei,and it is also the most commonly used method to find halo nuclei.In recent years,an important topic in the research of interaction cross sections is:what is the beam energy dependence of the interaction cross sections of halo nuclei,and how high the beam energy can extract the structure information of halo nuclei more accurately.Some studies believe that in the case of high-energy beams,it is mainly the core part of the halo nuclei that contributes to the reaction cross sections,and the halo part outside the core contributes less to the cross sections;while in the case of low-energy beams,the low-density halo part outside the core contributes greatly to the cross sections.Therefore,low-energy beams are more suitable for studying halo nuclei.But other studies believe that in the case of low-energy beams,the breakup effect of the halo nuclei has a great contribution to the reaction cross sections,which will affect the accurate extraction of nuclear structure information;while in the case of high-energy beams,the breakup effect is not significant,so the structural information of the halo nuclei can be extracted more accurately.Experimentally,the structural information extracted from the cross-section of different energy regions has also been inconsistent.For example,the interaction cross sections of ¹⁵C measured at high energy combined with theoretical analysis shows that ¹⁵C has no obvious halo structure;while the measurement results under low-energy beams show that ¹⁵C is a good halo nucleus.When using the Glauber model to study the relationship between the ¹⁵C reaction cross section and the beam energy,it also appears that the calculation results cannot reproduce the measured cross sections.There is no reasonable explanation for the contradiction between the theory and the experimental results.The experimental data of the interaction cross section(reaction cross section)of¹⁵C and its adjacent carbon isotopes are mainly concentrated in the low energy region(<100 Me V/u)and the high energy region(>500 Me V/u);while in the intermediate energy region,there are a lack of experimental data to verify or constraint theory calculations.Based on the HIRFL-CSR External Target Facility,the interaction cross sections of ^14-16C on the carbon target were measured for the first time in the intermediate energy region(240 Me V/u)in this thesis.Combined with the data of other energy points in the literature,this thesis uses the Coulomb-modified Glauber model and the MOL-Glauber model to analyze the relationship between the ^14-16C reaction cross sections and the beam energy,and the density distribution of ^14-16C is also extracted at the same time.The results show that the relationship between reaction cross sections and beam energy calculated by the two Glauber models can well reproduce the experimental results of ¹⁴C and ¹⁶C in different energy regions;while for ¹⁵C,the calculated results of the two Glauber models cannot reproduce the experimental results of different energy regions simultaneously.However,the experimental results of this thesis combined with the calculations of the two Glauber models show that the neutron density distribution of ¹⁵C has a large tail,indicating that ¹⁵C is a neutron halo nucleus,which is consistent with the conclusion of low-energy experiment.The odd-even deviation parameter of the reaction cross sections is an important physical quantity used to study whether the nucleus has a halo structure.Recently,the dependence of the odd-even deviation parameter on the beam energy has attracted the attention of theoretical research.Based on the experimental cross-sections of ^14,15,16C in different energy regions,we extracted the ¹⁵C odd-even deviation parameters and compared them with the calculated results of the Glauber model.The results show that the odd-even deviation parameter obtained in this thesis is consistent with the results obtained in the low-energy beam.Both experimental results show that ¹⁵C has a large odd-even deviation parameter.However,the value of the odd-even deviation parameter extracted in the case of high-energy beam is small,which is inconsistent with the experimental results of intermediate and low energy.The calculation results of the two Glauber models show that the odd-even deviation parameter is slightly related to the beam energy in the low energy region,while in the intermediate and high energy region,the odd-even deviation parameter is almost independent of the beam energy.And the theoretical calculation results can well reproduce the experimental results at low and intermediate energy.Projectile fragmentation cross sections model is a useful tool in the fields of radioactive ion beam physics,heavy-ion cancer therapy,and radiation protection.Another part of this thesis is to systematically measure the elemental fragmentation cross sections of boron fragments produced by stable and neutron-rich ^12-16C beams with a carbon target at an incident beam energy of approximately 240 Me V/nucleon.The measured cross sections were found to increase as the projectile neutron number increases.The observed feature is explained qualitatively based on the abrasion-ablation two-stage reaction model and is compared quantitatively with predictions from various reaction models,including empirical and statistical models.All models agree with the measured cross sections within a factor of 2.