Radioactive ion beam physics related to HIAF

This article aims to describe the key scientific problems, historical developments and prospects of the radioactive ion beam (RIB) physics. There exist only less than 300 stable nuclides in the universe, whereas the the number of unstable nuclei can be as high as 10000. The production and study of such radioactive nuclides (RIB physics) are an exploration of an undiscoveredarea, which necessities new experimental tools and theoretical models. Numerous new findings have been reported at the initial stage ofRIB physics research based on new observations. Typical examples include the halo and cluster structures, new magic numbers, shellevolution and soft dipole resonances. The study of unstable nuclei is also closely related to that of nuclear astrophysics processes as well as the synthesis of superheavy nuclei, which are belonging to the most important interdisciplinary problems worldwide. Investigations on unstable nucleus provide experimental data for nuclear energy systems; thus, they have strategic application value. The advantages of HIAF are associated with high beam intensity. When combined with advanced technologies for RIB separation and experimental detection, HIAF would play certain leading roles in the international community.