DESIGN STUDY OF THE ACR ELECTRON-COOLER FOR RIBF

The Accumulator Cooler Ring (ACR) is under investigation at present for a storage ring complex called MUSES (Multi-Use Experimental Storage rings) [1] in RI-Beam Factory (RIBF) Project at RIKEN. An electron cooler (EC) device with the type of field expansion is installed in ACR. Magnetic field in the gun section and the central is 4T and 0.2T respectively, and the electron beam energy is varied from 30keV to 250keV with a maximum current of 4.1A. The details of the most recent design and technological issues in the gun section, the central solenoid and the collector section are discussed. Electron cooler device is installed for the reduction of the phase space volume in addition to stochastic cooling device in ACR [2-4]. The maximum electron beam energy in ACR-EC is 250keV in order that the injected ion beam from the Superconducting Ring Cyclotron (SRC) with 400MeV/u can be treated in this device. The magnetic field in the gun section and the central solenoid is 4T and 0.2T respectively and therefore the expansion factor is 20. The cathode diameter is 12.7mm. The basic design in the gun section was reported in [3,4], where the considerations were made about the maximum voltage gradient near anode, the emission current density of the cathode and the vacuum level near cathode. The electron trajectories and the transverse electron temperature are calculated in this new design of gun section. Moreover, the discharge tests in strong magnetic field were carried out experimentally and some useful data for actual design were obtained. In the central solenoid it is necessary to reduce the transverse component of magnetic field to the order of 10