The first stage in the acceleration process takes place in the Cockcroft–Walton generator. It involves taking hydrogen gas and turning it into H ions by introducing it into a container lined with molybdenum electrodes: a matchbox-sized, oval-shaped cathode and a surrounding anode, separated by 1 mm and held in place by glass ceramic insulators. A magnetron is used to generate a plasma to form H near the metal surface. A 750 keV electrostatic field is applied by the Cockcroft–Walton generator, and the ions are accelerated out of the container. The next step is the linear accelerator (or linac), which accelerates the particles to 400 MeV, or about 70% of the speed of light. Right before entering the next accelerator, the H ions pass through a carbon foil, becoming H ions (protons).