Emittance and plasma potential measurements in double-frequency heating mode with the 14 GHz electron cyclotron resonance ion source at the university of Jyvyskyly

The performance of electron cyclotron resonance ion sources can be improved through the use of multiple-frequency heating. However, the physical processes leading into enhanced production of highly charged ions are still mainly unknown. This gave us a strong motivation to perform a set of emittance and plasma potential measurements with the 14 GHz electron cyclotron resonance ion source at the university of Jyvyskyly to compare the results obtained in single- and double-frequency heating modes. The measurements were performed with different microwave frequencies and combinations of primary and secondary powers. It was observed that both the emittance of different ion beams and the plasma potential decreased in the single-frequency heating mode as the microwave frequency was increased. The emittance of highly charged ion beams and the plasma potential was slightly lower in double-frequency heating mode than in single-frequency mode with the same source settings and total power