 The ions then passed into the 150 meter long linear accelerator (linac) which used oscillating electrical fields to accelerate the ions to 400 MeV.The ions then passed through a carbon foil, to remove the electrons, and the charged protons then moved into the "Booster".The Booster was a small circular synchrotron, around which the protons passed up to 20,000 times to attain an energy of around 8 GeV.