Measurement of the ratio of C3+ and O4+ ions produced by ECRIS to prepare a laser cooling experiment at storage rings

To prepare the upcoming laser cooling of relativistic C3+ ion beams at the experimental Cooler Storage Ring (CSRe), a novel experiment was performed using a reaction microscope to determine the ratio of C3+ ions in mixed ion beams of C3+ and O4+ that are produced by an Electron Cyclotron Resonance Ion Source (ECRIS). The mixed ion beams at an energy of 4 keV/u were directed to collide on a supersonic helium gas target. Using the single-electron capture channel and the coincidence technique, the fractions of C3+ and O4+ ions in the primary beam were obtained. Using different injection gases for ECRIS, including O2, CO, CO2, and CH4, at a fixed radio-frequency power of 300 W, the measured results showed that the fraction of C3+ ions was greater than 70% for the injection gases of CO and CO2. These measured results are very important and helpful for the upcoming laser cooling experiments.