• P. Frigola, R.B. Agustsson, S. Boucher, A.Y. Murokh
  RadiaBeam, Marina del Rey
• H. Badakov, A. Fukasawa, P. Musumeci, J.B. Rosenzweig, G. Travish
  UCLA, Los Angeles, California
• D. Cormier, T. Mahale
  NCSU, Raleigh, North Carolina
• L. Faillace
  INFN/LNF, Frascati (Roma)

Electron beam based additive fabrication techniques have been successfully applied to produce a variety of complex, fully dense, metal structures. These methods, collectively known as Solid Freeform Fabrication (SFF) are now being explored for use in radio frequency (RF) structures. SFF technology may make it possible to design and produce near-netshape copper structures for the next generation of very high duty factor, high gradient RF photoinjectors. The SFF process discussed here, Arcam Electron Beam Melting (EBM), utilizes an electron beam to melt metal powder in a layer-by-layer fashion. The additive nature of the SFF process and its ability to produce fully dense parts are explored for the fabrication of internal cooling passages in RF photoinjectors. Following an initial feasibility study of the SFF process, we have fabricated a copper photocathode, suitable as a drop-in replacement for the UCLA 1.6 cell photoinjector, with internal cooling channels using SFF. Material analysis of the prototype cathode and new designs for a high duty factor photoinjector utilizing SFF technology will be presented.

• A. Fukasawa, H. Badakov, B.D. O'Shea, J.B. Rosenzweig
  UCLA, Los Angeles, California
• D. Alesini, L. Ficcadenti, B. Spataro
  INFN/LNF, Frascati (Roma)
• L. Palumbo
  Rome University La Sapienza, Roma

A hybrid photoinjector, which we present here, consists of a 6-cell traveling wave structure with a standard 1.6-cell RF gun attached to the one end and a 3-m long linac following for further acceleration. With this structure, no reflection observed at the input port. This enables to build the accelerator without a circulator which limits the power and the frequency of RF. From the beam dynamics point of view, the beam is produced as the normal RF guns and gets short by velocity bunching in the traveling wave section right after the gun. The peak current can reach more than 1 kA, with about 2 mm.mrad of the emittance at 20 MeV. We discuss more details about the beam dynamics as well as the RF structure.