A modified rf ion source with a ceramic bottle

The generation of negative He ions for acceleration at tandem accelerators requires an ion source with alkali vapor charge exchange canal. The diffusion of the Li or Rb vapor into the surrounding vacuum chamber limits the operation time of the ion source and increases the necessary maintenance. On the other hand, the modified rf ion source at the Rossendorf single ended 2 MV Van de Graaff accelerator has a life time of some thousands hours. The installation of this ion source inside the terminal of the Rossendorf 5 MV tandem accelerator would allow high-energy implantation of He ions in the energy range of 1-5 MeV without the difficulties of the charge-exchange canal. To reduce the risk for breaking of the ion source glass bottle under the pressure of the insulating gas a ceramic source bottle has been tested. First results of its operation at the 2 MV VdG are presented.