Global Study On Nuclear Fission Dynamics Of Actinide Nuclei

Otto Hahn（German radiochemist and physicist）and his research assistant Fritz Strassmann discovered nuclear fission of heavy elements On December 17,1938.Since that remarkable day,it has been about 80 years of discovering nuclear fission.Nuclear fission study attracts a lot of attention since the first day when it was discovered.It opened a whole new physical research field and many superior scientists did lots of work.Related achievements have been applied into people’s production and living conditions.Such as Engineering,medicine,agriculture,national defense,energy and so on.Nuclear fission study also plays an important role in theory and application.Firstly,it provides a very good platform to study nucleus large deformation collective movement and quantum many-body problem.Secondly,in fundamental research,fission is one of main reason to keep super heavy elements stable.Thirdly,it also decisions the key process of heavy elements synthesis in galactic evolution r-process.Last but not least,nuclear fission is a key method to produce short life exotic nuclei.So,nuclear fission is still one of important advanced research topics today.In this dissertation,we adopted the micro model of nuclear fission dynamics based on Covariant Density Functional Theory（CDFT）to study nuclear fission micromechanism.Here are the work contents:developing a CDFT to describe large deformation based on deformed harmonic oscillator bases;developing multidimensional Time-Dependent Generator Coordinate Method（TDGCM）to describe induced nuclear fission dynamics and calculating fission dynamics physical quantities.For more details about the procedure and processing method,the mean-field program code adopting PC-PK1 point coupled density functional theory is used to calculate nuclear fission statics physical quantities;The FELIX program code is used to solve local time dependent Schr?dinger like equation,which is used to simulate the nuclear fission dynamics procedure.Galerkin finite-element method（FEM）is used to deal with spatial discretization.Crank-Nicolson scheme is used to deal with time discretization.Using this methods listed above,fission multidimensional potential energy surface（PES）,collective mass parameters,scission line（which are nuclear fission statics physical quantities）and the distribution of charge and mass of fission fragments,total kinetic energy（which are nuclear fission dynamics physical quantities）of actinides Thorium isotopes chain nuclei(²²²²²⁸Th)are calculated.In this dissertation,one can find that many physical quantities change with nucleus mass number A increasing.Nucleus PES potential barriers prominently change with A.The distributions of final fission yields charge and mass change from symmetrical distribution to asymmetrical distribution.This work reproduced nuclear fission experiments data very well,which make us have more deep understanding of nuclear fission micromechanism.It also lay a solid foundation for studying fission dynamics of other nuclei of actinides in the future.