Desicn and status of an experimental superconducting linear accelerator for electrons

We report on the design and status of a small superconducting linear accelerator for electrons in the 3 MeV range. It is operated at 8 GHz. Primary goals are: a high energy gradient by choosing a high frequency, a working temperature of 4.2 K by using Nb₃Sn, and to gain information about the performance of multicell structures at 8 GHz. At present the 80 keV electron gun, the vacuum beam line, and the cryostat are set up. A three cell Nb₃Sn covered cavity was used for the first experiment with the accelerator and a beam of 1 μA was accelerated to 160 keV. The performance of four 30-cell Nb-accelerating structures operated in the π/2-mode and the observed field limitations around 2 MV/m are analysed. Higher field values (up to 8.8 MV/m) were achieved in structures of a smaller number of cells.