Open door to the experimental hall. Not a good sign if you want to take data.
Something is not right here. It is 7:30 in morning, I’m sitting in the CALICE MTBF control room… Well, been there, done that. But: I am actually feeling awake and well rested. While this is a very plesant surprise, the reason for it is a big disappointment: We are not taking data, have not taken any data today, and it is not looking good for the rest of the day either. The accelerator is down due to a broken quadrupole magnet in the Main Injector. While such things do happen occasionally, it is still very annoying. We are already behind with our program due to various problems (accelerator-related as well as detector related) over the last few weeks, so this additional hit is very bad news.
The current CALICE setup: Scintillator-Tungsten ECAL, Scintillator-Steel HCAL and tail catcher.
So, now the experimental area is open, and that gave me the chance to look around a bit. Everything seems to be fine, and I took a few pictures to show you what our setup looks like. Well, you can not see the real detectors, they are hidden behind the mass of cables and cooling fans. All three detectors currently in operation use 5 mm thick plastic scintillator as active material, read out with silicon photomultipliers, very small photon sensors based on semiconductor technology. The first section, with the white cooling box, is our electromagnetic calorimeter (ECAL in short), built out of Tungsten plates, and with small (1 cm x 4 cm) scintillator strips. The next, much larger section is the analog hadron calorimeter (HCAL), which uses iron absorber plates, and scintillator tiles varying in size from 3 cm x 3 cm to 12 cm x 12 cm.
The final section, with the massive orange frame, is the tail catcher and muon tracker (TCMT), designed to measure the energy that leaks out of the analog HCAL for highly energetic showers, and to identify muons in the beam. It also uses steel as absorber medium, and has large scintillator strips, 5 cm x 100 cm, as readout.To give you a feeling for the size: The HCAL is about 120 cm deep, with a front face of 90 cm x 90 cm, so it contains almost one cubic meter of steel, weighing more than 7 tons. The TCMT is even heavier, and even the small ECAL is a massive thing thanks to the extremely high density of Tungsten, which is the reason we use that material in the first place.
A whole tower of readout electronics.
The ECAL and the HCAL sit on a movable stage, so the can be translated and rotated, to investigate their performance under many different conditions. In addition to the detectors, also the front end electrons sit on that platform, collecting all the data from the detectors and then sending it off to computers and to our monitoring systems here in the control room. I hope all this equipment gets some action soon, since we really need to take quite a bit more data before our beam time ends on May 27.
For me, my brief test beam adventure is almost over, I’m heading back to Munich tonight. Let’s see if this “sleeping like a baby on the plane” plan works out, now that I actually got much more sleep than wished for. Well, the time here was a wild ride, with lots of interesting problems to solve (maybe some more in retrospect later), and even with the disappointment of no beam on the last day, certainly a very worthwhile trip for me.
