Operations of the SERSE superconducting ECR ion source at 28 GHz

The SERSE source has been efficiently working at the Laboratori Nazionali del Sud in Catania since 1998, by operating at 14 and 18 GHz, with a maximum power of about 2 kW. The performance of the source has been optimised for the beam injection into the K-800 Superconducting Cyclotron, i.e. the maximisation of the charge states was looked for, provided that the current of the beam was about 0.5 to 5 eμA, which is the typical analyzed current for routinely operations. In 2000 a collaboration was established in order to test the behavior of SERSE at 28 GHz, so that a new operating domain could be studied, featuring a very dense plasma (up to 1013 cm-3) and a very high ion current (1 emA of Pb27+ is the goal of CERN and GSI for future heavy ion projects and 0.5 emA was considered to be a challenge for our experiment). Tests were carried out with a generator based on a gyrotron tube which was refurbished and made available by CEA; Xenon ions were chosen as a reference being the ionization difficulty for Xe20+ similar to the one of Pb27+. The results were excellent and the current of Xe20+ exceeded our expectations (more than 0.5 emA in afterglow and about 0.3 emA in dc mode). These results, obtained with a power limited to 4 kW in dc mode and 6.5 kW in pulsed mode because of the poor chamber cooling, can be considered as a remarkable step, in view of the third generation of electron cyclotron resonance ion source (ECRIS). The details of the experiments will be described, along with the design of the next superconducting ECRIS, the GyroSERSE source, which is expected to produce beam currents above 1 mA for intermediate charge states as well as very high charge states, 50+ to 60+ for the heaviest ions, with currents above 1 eμA