A powerful US atom-smasher that was the world\'s biggest particle collider for nearly a quarter century will close down forever on Friday, solidifying Europe\'s place as the world leader in physics. The Tevatron began its work in 1985, as part of the US Department of Energy\'s Fermi National Accelerator Laboratory, and its shutdown comes at a tough time for budget-squeezed US science and space programs. Tevatron has been overtaken by a more powerful atom smasher -- the world\'s largest -- the Large Hadron Collider, built on the French-Swiss border by the European Center for Nuclear Research (CERN), a consortium of 20 member nations. But in its day, the Tevatron made some major contributions, including the identification of the top quark in 1995 and the discovery in 2000 of the tau neutrino, an elusive piece of the Standard Model of Physics. Now the only part of the Standard Model left to pin down is the Higgs-Boson particle which is believed to give objects mass. The Tevatron helped physicists narrow down where it might be, but could not find it. The Tevatron, which cost about 50 million dollars per year to operate, also led to a host of more concrete advances, chief among them the widespread use of magnetic resonance imaging (MRI) machines for medical diagnosis. Fermilab said it expects only about a five percent cut in workforce. American physicists will now concentrate on more precise -- and less expensive -- questions at home and work with CERN on high-energy projects like the search for the elusive Higgs-Boson, sometimes called the \'God\' particle. \"In our field we don\'t keep beating our heads if we have been outdone by another machine,\" said Pier Oddone, director of the Fermi National Accelerator Laboratory, which operates the Tevatron. \"The idea is we shift to those areas where we can make the greatest contributions to understanding,\" Oddone told AFP last week. A closing ceremony was set to start on Friday at 2:00 pm (1900 GMT).