the lhc ionizes hydrogen atoms to get their protons. a hydrogen atom consists of only one proton and one electron. when they ionize the atoms, they are removing the one electron to give it a net positive charge. the hydrogen protons are then directed through the circle by electromagnets. in order for the magnets to be strong enough, it must be very cold. the inside of the tunnel is cooled by liquid helium. they keep the temperature at just above absolute zero. the protons hit one another at close to the speed of light and this creates lots of particles, many of which only live a short time before decaying to lighter particles. at the four collision sites, there are large detectors called alice, atlas, cms and lhcb.