THE ATOM smasher at Cern has achieved yet another milestone, in the process simulating conditions last seen after the Big Bang that formed the universe.
The 27km accelerator has now begun smashing together lead particles, each collision delivering a kind of miniature Big Bang.
And while these collisions generate temperatures 100,000 times hotter than the temperature at the centre of the sun they occur in a tiny space and last less than a millionth of a second.
Cern is the European organisation for nuclear research and is based on the French-Swiss border near Geneva.
Cern’s Large Hadron Collider (LHC) ranks as the most powerful anywhere in the world and holds the world record for collision energy. Yet when it begins to reach its highest energies after 2012 the current record will double, according to Cern’s operators.
It cost about €4 billion to build the LHC. It sits in a 27km oval tunnel deep under the Jura mountains, and was built to re-create the conditions as they existed a millionth of a second after the Big Bang.
It uses powerful magnets to send two beams of particles around the LHC ring in opposite directions and then crosses the beams to cause collisions.
It has been circulating lightweight particles – protons, which are hydrogen atoms stripped of their electrons – constantly since last March but now it has switched to lead ions. The lead packs a much greater punch given these ions are 82 times heavier than the protons.
The proton beams were stopped last Thursday and it only took Cern staff until Sunday to complete the switch and start colliding lead ions, a spokeswoman at Cern said.
These are now reaching energy levels that match the highest achieved using protons. The switch was not about energy, however, but density, she said.
Only two protons are involved in the lightweight but powerful collisions when hydrogen nuclei are used, but 164 protons are involved with lead, 82 per ion.
This causes the same kind of dense, crowded space seen after the Big Bang.
Massive experiments track the fragments created in these collisions and scientists use the data to understand the structure of matter.
Lead ion beams will circulate until a shutdown early next month for maintenance. A restart is set for February 2011 and will continue until 2012 when the LCH undergoes an upgrade to reach higher energies.
