Continued development of the RFI linac structure

The Rf-Focused Interdigital (RFI) linac structure is under development at Linac Systems. It promises very efficient acceleration of protons, light ions, and heavy ions to tens of MeV in relatively small packages. Recent developments include the discovery of effective geometries for the support of the two-part drift tubes, which provide the rf focusing, and efficient geometries for the end terminations of the interdigital linac tanks. These developments required extensive use of our 3d rf cavity calculational capability. A "cold model" of an RFI linac has been fabricated and tested. The measured and calculated field distributions are in reasonable agreement. The beam dynamics of the structure has been studied with TRACE-3D and a modified version of PARMILA. The structure is capable of remarkably high beam currents (space charge limits). The results of these studies will be presented. The high rf efficiency of the structure promotes the possibility of cw operation. A prime application for the RFI linac structure is the challenging job of providing intense fluxes of epithermal neutrons for the boron neutron capture therapy (BNCT) application. Mechanical designs of the RFI linac structure for that application will be presented. Other applications for the RFI linac structure will be described.