Electron-RI collider and internal target operation of RIKEN storage ring project

A versatile heavy-ion accelerator system is under construction at RIKEN which is composed of a cascade of cyclotrons. The ions, from proton to Uranium, are planned to be accelerated up to around 400 MeV/u. As a second phase of the project, MUSES was planned which is composed of an accumulator/cooler ring for RI beam and an electron–RI collider. The available luminosity of collider is dependent upon the production cross-section of RI beam through the projectile fragmentation process, cooling time of RI beams and the intensity limit of electron beam in the electron ring. We investigated the feasibility of experiments to determine the charge distribution in the unstable nuclei. On the other hand, internal target experiments at the accumulator ring will open new and precise physics with use of inverse kinematics. A new scheme of internal target experiments is conceived where a quite thick target is installed and high repetition of beam injection is used from the injector cyclotron. In the present paper, essence of design works of electron–RI collision experiments and accumulator/cooler ring are described emphasizing the role of stochastic and electron cooling, as well as new scheme of internal target operation.