Particle beam weapons

The term particle beam weapon may refer to any number of directed-energy technologies that use particles with limited mass to form the beam, most commonly referring to neutral particle beams (NPB), which are ionized, accelerated, and neutralised when being fired, as was the case with the U.S. Strategic Defense Initiative's BEAR (Beam Experiment Aboard Rocket) linear accelerator that generated a neutral hydrogen beam. Such weapons would be comparable with the death ray of the early twentieth-century, a hypothetical technology that was not known to have been publicly demonstrated though was the object of much popular interest.