The proton pack is a fictional energy-based holding device, used for controlling and lassoing ghosts in the Ghostbusters universe. First depicted in the film Ghostbusters, it has a hand-held wand ("Neutrona Wand" or particle thrower) connected to a backpack-sized nuclear accelerator. It controls a stream of highly focused and radially polarized protons that electrostatically controls the negatively charged energy of a ghost, allowing it to be held in the stream. In the Ghostbusters universe The proton pack, designed and built by Dr. Egon Spengler, is a man-portable cyclotron system (and indeed Dr. Peter Venkman refers to the proton packs in one scene as "unlicensed nuclear accelerators"), that is used to create a charged particle beam—composed of protons—that is fired by the particle thrower (also referred to as the "neutrona wand"). Described in the first movie as a "positron collider", it functions by colliding high-energy positrons to generate its proton beam. The beam allows a Ghostbuster to contain and hold "negatively charged ectoplasmic entities". This containment ability allows the wielder to position a ghost above a trap for capture. The stream is also quite destructive to physical objects, and can cause extensive property damage. The name proton pack is not used in the original movie at all, and is not used until the subway tunnel scene in Ghostbusters II, when Winston says that they should get their proton packs. The doorman to the Mayor's mansion also uses the term proton pack, asking the Ghostbusters if he can buy one from them for his little brother. Egon replies that "A proton pack is not a toy". In the 1984 novelization of Ghostbusters the Proton Packs are mentioned, eg. “Stantz hauls out the formidable weaponry from the back of the Ectomobile and the four men kit themselves up, buckling on their proton packs…” In the 2009 Ghostbusters game, Ray explains how the proton pack works early in the game; the energy emitted by the proton stream helps to dissipate psychokinetic (PK) energy which ghosts use to manifest themselves. Draining them of their PK energy weakens them, allowing them to be captured in their portable ghost traps. According to a line spoken by Egon in Ghostbusters II, each pack's energy cell has a half-life of 5,000 years. Knobs on the main stock of the proton pack can perform various functions to customize the proton stream, including adjustments for stream intensity, length, and degrees of