Jefferson "Jax" Jackson is played by Franz Drameh. After Ronnie Raymond sacrifices his life to save Central City from a black hole in the finale of Season 1, Martin Stein starts to have health issues. Martin and Ronnie were affected by the Particle Accelerator explosion and could combine to become Firestorm. Without Ronnie to combine with on a frequent basis, he starts dying. Cisco Ramon and Caitlin Snow try to find people who were affected by the explosion and could be compatible with the Firestorm Matrix. Their only compatible options were Henry Hewitt and Jefferson Jackson. They asked both if they would be willing to join Professor Stein as Firestorm but Jax wasn't interested and Henry was excited about it. Martin and Henry attempted to combine but it didn't work. Instead, it gave Henry nuclear superpowers and he became the villain known as Tokamak. Jax changes his mind and joins Martin and they become the new Firestorm. They team up with the Flash to take down Tokamak.
Legends of Tomorrow
Franz Drameh reprises his role as Jefferson Jackson. He and Martin Stein are enlisted by Rip Hunter onto his team to stop Vandal Savage from rising to power and taking over the world in the year 2166. Other members on the team include Hawkman, Hawkgirl, the Atom, White Canary, Captain Cold, and Heat Wave.