The proton pack, designed and built by Dr. Egon Spengler, is a portable cyclotron system that is used to create a charged particle beam, called a Proton Stream. The Prton Stream is fired by the particle thrower (also referred to as the "neutrona wand").

The beam allows a Ghostbuster to contain and hold "negatively charged ectoplasmic entities" until they can be put in Ghost Traps. The stream is also quite destructive to physical objects, and can cause extensive property damage.

Crossing the streams was discouraged, as the combination of that much energy could cause a massive explosion.