Running CMS (or How I spent my Friday night)

There is something glorious about having an entire detector - or at least an entire subsystem of a detector - under your supervision and care for 8 hours. Work on CMS (the Compact Muon Solenoid) has been going on for over 20 years, involving over 2600 people from 180 institutions. The detector itself will include - when finished (which I'm told will be soon!) - the largest magnet built yet which will create a 4 Tesla field, several tons of brass from melted-down Russian artillery shells, over 2500 square feet of silicon detectors and a data rate roughly equivalent to that of the global telephone networks. (sources http://cmsinfo.cern.ch/outreach/CMStrivia/CMStrivia.html, http://en.wikipedia.org/wiki/Compact_Muon_Solenoid)

Last week, I took two of these 8 hour shifts learning how to run - and take care of - the CSC (Cathode Strip Chamber) muon detector system in CMS.

My shift on Thursday was a "day" shift, nominally running from 8:00 to 16:00. However, in order to get a ride to the detector (in Cessy, France, about 6mi/10km away from the Meyrin site where I'm staying) I left the Meyrin campus at 6:30, arriving sometime around 7. The shift started out fine. Around 8:45, just as my fellow shifter Ingo and I had just started to settle in, one of our monitoring screens started flashing red lights at us left and right. It started with 4 errors, then the low voltage monitoring subsystem reported so many errors we had to scroll, and - less than a minute after that - the temperature monitoring subsystem had as many errors as the low voltage system! Troubleshooting these errors (or, more like it, finding the right phone numbers to call and then watching the experts troubleshoot) took up a significant portion of my first shift.

A few hours later, the verdict was in: a worker in the detector pit had unplugged a few wires to do some work by the detector without informing the right people, tripping a fire alarm which subsequently cut power to half of our detector. The moral of this story? Even though there's literally thousands of wires on the detector, the scientists operating the detector really can tell if and when they get switched or unplugged!

My shift on Friday ("swing" shift, 16:00 - 24:00) was considerably calmer. I was on shift with Nick and Laszlo. Nick was by far the most experienced shifter of the three of us. He is a graduate student at the University of Florida and has done weeks if not months of commissioning shifts. Laszlo, a professor at Perdue (from what I understand), has been working on the CSC system since 1994 but hadn't taken any shifts before Friday. As for me, I had Thursday's system mess under my belt, but relatively little experience with "normal" operations.

On this shift, I made up for the casual conversation - and some cultural learning - that I missed out on during the troubleshooting of Thursday morning during this shift. There were a few moments that I felt very American. For example, Nick made some comment (which wasn't intended to be taken literally - it was full of hyperbole and creative interpretation of history) that credited his Greek heritage for a lot of Roman accomplishments. An older Italian gentleman taking a shift for the DT (Drift Tubes, another muon detection system, whose monitoring station is right next to the CSC's monitoring station) detection system didn't understand the joke and proceeded to give Nick a history lecture. Laslzo had to help put out the fire.

Thursday and Friday were pretty much the highlights of my weekend, even though my shift was work. The novelty of running CMS hasn't rubbed off yet! It was a rainy weekend in Geneva (there was a terrific downpour just as I was leaving Cessy on Friday), so I went to museums, found an English language bookstore and walked around the Botanical Gardens near the UN (they have a really cool exhibit on math through October, called jardin de maths. All the descriptions are in French, so my handy pocket dictionary got a workout!).

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