In the story, the ghost-hunting weapons wielded by the Ghostbusters, or "proton packs", consisted of a portable cyclotron worn as a backpack by each Ghostbuster, capable of releasing a stream of directed protons through a neutrona wand, or proton gun, which counteracts the "negatively-charged ectoplasmic energy" of a ghost or similar creature. The packs were designed by design consultant Stephen Dane, who "went home and got foam pieces and just threw a bunch of stuff together to get the look. It was highly machined but it had to look off-the-shelf and military surplus. " The actual fiberglass props used by the actors were created by special effects supervisor Chuck Gaspar, based on Dane's design. Gaspar used rubber molds to create identical fiberglass shells, attached them to aluminum back plates and Army surplus ALICE (All-purpose Lightweight Individual Carrying Equipment) frames. Each pack weighed about 30 pounds (14 kg), and nearly 50 pounds (23 kg) with the batteries installed, and strained the actors' backs during the long shoots. Lightweight packs made of foam rubber were used for stunt work. The PKE meter prop was built using an Iona SP-1 handheld shoe polisher as a base, to which lights and advanced-looking electronics were affixed.