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. ATLAS is located at Point 1 (there are eight points all together) on the ring, and the injection points for the two beams are on either side of Point 1. Therefore ATLAS is the last point along the ring to see the beam. This year they start with Beam 2. This beam is injected between Point 1 and Point 2. It then gets steered into closed collimators and beam dumps as the LHC Control Room carefully adjusts various beam parameters to get the beam to circulate all the way through the machine with out losing any particles or scrapping into the magnets.
This Atlantis event view is from one of the splash events we got later in the day. One can see that all of the elements of the detector are lit up (compare this with other typical event views, obtainable from the ATLAS public web page). This indicates that the trigger was well timed (good job guys!). We will use these events to do some fine tuning and final checks of readout timing of the detector, as well as search for any dead channels that we may not have found before (hopefully we don't find many!). So the next step is for the LHC to do some more tests and checkouts of beam protection; add even more bunches to the beams and then a short run of collisions at 900 GeV center-of-mass energy; and finally ramp up the beams to 3.5 TeV and start colliding them to start off the Physics Program at the LHC! All of that is planned to happen in a little less than a month! So the next couple of weeks will see a busy Control Room.