Electron beam injector for longitudinal beam physics experiments

Abstract

An electron beam injector has been constructed to study the longitudinal beam physics in the University of Maryland electron beam transport experiments, including studies of longitudinal beam pulse compression and resistive-wall instability. The injector consists of a variable-perveance gridded electron gun followed by three matching lenses and one induction acceleration module. In the beam pulse compression experiment, it produces a 50 ns, 40 mA and 2.5 to 7.5 keV electron beam pulse with an approximately linear time-dependent velocity tilt. This beam will be injected into an existing 5 m long periodic transport channel with 36 short solenoid lenses. With the given beam parameters and initial conditions, the beam pulse is expected to be compressed by a factor of 3 or greater when reaching the end of the solenoid channel. In the resistive-wall instability experiment, the injector produces an electron beam pulse of 5 to 50 ns in duration, about 100 mA in current and a few kilovolts in energy. This beam will be guided into a resistive-wall channel of a couple of meters in length for study of the longitudinal resistive-wall instability. This paper reports on the design features and the general performance characteritics of the injector system including its mechanical, electrical, and beam-optical properties.