 By the end of 2011, the Large Hadron Collider (LHC) at CERN had achieved a luminosity almost ten times higher than Tevatron's (at 3.65 cm−2 s−1) and a beam energy of 3.5 TeV each (doing so since March 18, 2010), already ~3.6 times the capabilities of the Tevatron (at 0.98 TeV).The acceleration occurred in a number of stages.The first stage was the 750 keV "Cockcroft-Walton" pre-accelerator, which ionized hydrogen gas and accelerated the negative ions created using a positive voltage.