Each year, around mid-spring, the giant LHC accelerator wakes up from its winter maintenance and gets ready for a new feverish period of data taking. But before smashing protons once again, some tests have to be done, to check that everything is in order and that the machine can accelerate and collide particles properly, as it did before the shutdown.

Spring is now in full bloom at the ATLAS experiment which recorded the year’s first collisions for physics on Monday, 9 May. Event displays from these collisions were immediately streaming on the ATLAS live website, with some shared across social media platforms.

On 20 May at around 22:24, ATLAS recorded the first 13 TeV test collisions delivered by the Large Hadron Collider. The proton collisions set a new high energy record, marking the beginning of ATLAS' journey into unexplored physics frontiers as we prepare for production data-taking, scheduled to start in early June.

After decades of planning. After years of delays and immeasureable amounts of patience and hard work. The physics operations of the LHC has begun!

After ramping of the beams to 3.5 TeV and tuning, final checks, and some emotions due to an unforeseen beam dump, the 7 TeV collisions finally appeared on the on-line monitors of the ATLAS Control Room.

At approximately 2:40 am Central European Time, ATLAS saw particles from the LHC for the first time in 2010.  As in previous LHC turn-on periods the first thing we see are beam splashes from the LHC beams as they slowly thread the beam through the LHC ring for the first time.

A few days ago, loud cheers and happy faces filled the ATLAS Control Room while the whole detector lit up: protons are back at the experiment's door, and everybody forgot in a second the long year of waiting for the Large Hadron Collider (LHC) to resume operation.

The full ATLAS Experiment has been operational and taking cosmic ray data since September 2008, and high-energy collisions are scheduled for late summer 2009. Data from cosmic rays that hit the ATLAS detector are valuable to calibrate and synchronize the many detector elements. Even more exciting were the so-called “splash events” that occurred as the LHC was being tuned up starting 10 September 2008.

ATLAS experimenters celebrated today as the first beams circulated the Large Hadron Collider in both directions. While everyone was cheering in the LHC control room, the cheers were echoed in the ATLAS and other control rooms, and in several auditoriums around CERN.

Data have recently been collected with the toroidal magnetic field will provide for the first time the measurement of the cosmic ray muons' momenta in the ATLAS experiment and allow studies on trigger optimization, chamber calibration, chamber alignment and magnetic field maps. More than one million events were acquired. They are now being analyzed by enthusiastic members of the collaboration.