Electron beam production and beam profile monitoring

Collision experiments between an ion beam and an atom beam are subject to inefficiencies without knowledge of the size, shape and intensity of the ion beam.  Here we describe the construction of a beam profile monitor (BPM) to accurately provide this data, and an electron beam system which will allow future testing of the BPM with an electron beam.

The BPM is comprised of a wire grid in which currents are induced when a charged particle beam strikes them. These currents can be measured to determine the size, shape, and intensity of the beam.

The electron beam system consists of a heated filament, an acceleration electrode, and a Faraday cup used to measure the intensity of the electron beam.  Electric and magnetic fields are also applied to steer the electrons accurately into the cup.

Our data shows electron beam currents of several hundred nano-amps. The current varies significantly with time, which we attribute to changes of the filament surface composition as it is heated.  Data showing the enhancement of the electron current with increased acceleration are also shown, in addition to a study of the secondary electrons emitted from the Faraday cup surface.