The ERA 4 MeV Injector

A pulsed electron accelerator has been constructed and is now in operation at the Lawrence Radiation Laboratory, Berkeley. It was designed specifically for and is used as an injector for ERA (electron ring accelerator) studies. Electron bursts of 1200 amperes and 40 nanoseconds duration can be produced at energies of 1.0 MeV to 4.25 MeV. The present repetition rate is approximately one per second. Acceleration is accomplished by means of ferrite loaded accelerating sections, each of which is capable of maintaining a 250 kV voltage pulse across the accelerating gap for a period of 40 ns. The voltage pulse has a rise time of 12 ns and the total timing jitter is of the order of one nanosecond. Five sections stacked together and operated as a unit function as the electron gun. The gun employs a field emission cathode and is operated at approximately 1 MV. Additional acceleration is achieved by means of an iterated system of accelerator sections and solenoidal magnetic lenses.