An ion implantation featuring an improved beam neutralizer. A cylindrical electron source encircles the ion beam at a location just before the ion beam enters an implantation chamber. Regularly spaced cavities in the electron source contain wire filaments which are energized to emit electrons. The electrons are accelerated through the region of the ion beam and impact an inwardly facing wall of the cylindrical electron support. This causes low-energy electron emissions which neutralize the ion beam. Performance of the beam neutralizer is enhanced by injecting an ionizable gas into the region between the electron emitting surface and the ion beam.