Conceptual design of the HIRFL-CSR external-target experiment

One of the main purposes of heavy-ion collisions over a wide range of beam energy is to study the bulk properties of strong interaction matter and understand the Quantum Chromo Dy- namics （QCD） phase diagram, which carries wealth of infor- mation of the phase transition and the possibly existing criti- cal point of the strongly interacting system [1]. Such system exists as hadron gases at lower temperature and low baryon density. By increasing the temperature or density, the bound- ary of the hadrons disappears and the confined quarks move freely in the whole system.