Scientists operating the world’s biggest particle collider say they have set a new energy record ahead of the massive machine’s full restart in June.

The European Organization for Nuclear Research, or CERN, says it succeeded late Wednesday in smashing together protons at 13 trillion electronvolts.

That’s close to the 14 trillion electronvolts maximum that the Large Hadron Collider, located in a 27-km (16.8-mile) tunnel beneath the Swiss-French border, is designed to achieve.

CERN said in a statement Thursday that the collisions were a key part of the tests being done to prepare for a second run of experiments starting next month.

The collider underwent a $150 million upgrade after its first run, which produced results that helped confirm the existence of an elusive subatomic particle, the Higgs boson.