The Proton Cannon is a giant Proton Accelerator built on and connected to a truck in an alternate timeline.
With whatever design specification and parts they could salvage, The Griffinites worked on a prototype Proton Accelerator of their own after the Great Ghost War, when all Proton Packs were destroyed. The new accelerator was far from ready to be tested but was sound on paper. The return of Kylie Griffin exacerbated its use in the field. Once Tempus invaded headquarters, the male tech started the truck and Kylie nailed Tempus with a direct hit. However, the primary coil overloaded and forced the group to abandon the base. They watched as the accelerator blew up and took the building with it.