They did get to 3 Tesla the other evening, and after a long set of safety checks making sure the residual magnetic field (100 mT~ 100 Gauss, still 100x the Earth’s field!) near the cooling and power supply racks didn’t affect their performance, they turned on the tracker and took some data – only about 5 minutes worth, as it was 2 AM on a Sunday morning, so you cannot really fault them for that, since they’d been at it all Saturday. In that 5 minutes we saw curved tracks:
You are looking at a schematic of our tracker end on – each concentric layer is made of many silicon wafers, and we have ten layers in the barrel region (6 outer layer in magenta, plus 4 in blue, and lest I draw the wrath of Freya the pixel detector is also part of the tracker and is the three innermost layers in green, so I guess we really have 13). The red line is a projection of the path of a muon, which left energy depositions in the layers at the little red points. This one just happened to graze our detector (remember – we aren’t built to measure Cosmic Rays, but really the tracks from the interaction point) but it is easy to see the curvature, which is of paramount importance to measuring the track energy.
The magnet tests went well, apparently the biggest trouble they had was that the elevator seems to be susceptible to high magnetic fields, so the fire brigade had to extract someone. Well, if I have to, I’ll take the stairs!
