Particle beams began circulating in the Large Hadron Collider (LHC) in Geneva on Sunday following a two-month technical break.
The European Organisation for Nuclear Research (Cern) said the “big bang” machine had been put on standby in December to prepare for higher energy collisions and the start of their main research programme.
Collisions at the highest possible energy level, emulating conditions in the moments after the creation of the universe 13.7 billion years ago, should occur within two to four weeks, spokeswoman Barbara Warmbein said.
"The plan is to run at those energies for 18 to 24 months to give the experimenters the data that they need to work," Warmbein said.
Scientists aim to increase the energy used to smash protons into each other next year far above previous levels in hopes of revealing secrets of matter and the universe.
The $10 billion (SFr10.47 billion) machine is the world's largest and most powerful particle accelerator. It is housed in a 27-kilometre circular tunnel 100 metres under the Swiss-French border at Geneva.
swissinfo.ch and agencies