Character and test of electron gun for HIRFL-CSR electron cooler

Due to the strong recombination between electrons and cooled ions in the center of beam and the transversal instability of beam aroused by over cooling, ions lose seriously in cooling intensive ion beams with a solid electron beam. To reduce this loss, a special electron gun was adopted for HIRFL-CSR electron cooling device, of which the profile and density distribution of electron beam can be adjusted by varying the voltages of control electrode and anode. Electron beams from solid to hollow are obtained. Analysis in theory and experimental results are presented. (authors)