Electron Injector Designs for Cern-Lep, Rijksuniversiteit-Gent and Self-Focusing Linacs

We present three recent electron injector designs characteristics of Thomson CGR MeV realizations (table 1). The quantitative need for high intensity electron beam further accelerated for conversion to neutrons or positrons is illustrated by the LEP injector giving 15 A at 30 MeV for short pulses of 10 ns (2). The qualitative need for a good emittance and a narrow energy spectrum is illustrated by the Rijksuniversiteit-Gent accelerator giving 20 to 50 milliamperes peak current from 1.5 MeV to 12 MeV. The energy spread is less than 1 percent at 2 MeV for a duty factor of 2 percent. Simplicity and compactness synonym of reliability and low cost are illustrated by the Orion medical design giving 5 MeV for a 0.22 metre accelerating length at 100 milliamperes. Simultaneous radial and axial beam focusing is achieved by the RF field alone.