Friday, July 9, 2010

Day 4 at CERN: quality data, the linear history of linear accelerators and CERN control room

Yesterday was moving day for me, so I got to work later than usual. However, I was able to catch the same amount of part 2 of the heavy ions lecture and also met with a CMS experimental physicist to get a better understanding of how 'quality' data is being hierarchically determined across different groups and the thousands of people entasked with selecting and optimizing usable data. I will not go into details here at this point, as he drew the diagrams for me in my notebook. However, if I can get a more comprehensive diagram somewhere, I'll have that posted here. Needless to say, it takes many layers of data shifting in a experiment such as the CMS before we even reach the layer where the muon particle group come in. The system is so complex that each little section is handled by a group of people, and by the time the synchronization takes place between directors of these different groups, very intensive analysis work would already have been done by hundreds of brainpower (as well as software power). There is also the difficult task of reconstructing interpretable data from raw data obtained by the different crystal cells. To give a bird's eye view of what goes on there, I encourage reference to these two slides given to the summer school students here and here. These slides give a very good understanding of how physics work takes place from the level of apparatuses and empirical to the final publication of the papers. I think it is vital that humanists interested in the study of the sciences should really consider the details here.

Today I also managed to visit the CERN main control room at Prevessin, on the French side. I hope to be able to spend some time shadowing the engineers and control room people at work next week. I managed to take some not very nice pictures with my cellphone (unfortunately, I forgot to bring my camera) which I will upload here once I get back. The accelerator physicists who took me on a tour of the place also showed me the coordinates and physical relationship between the different accelerators built at different time scales and are now re-commissioned in the service of the LHC. Below is one of the charts I saw.

And below is just an example of the pretty screens (containing millions of vital information) in the room. I'll put it here as an example before I upload my version

And in relation to what I was talking about in terms of some possible issues that may had led to the shutdown in 2008, it's this important part in picture.

Welding between the magnetic dipoles and cryostats are happening here.

I think I should add that I've been getting questions from physicists as to why am I studying the philosophy of physics (a few of them whom I'd met had never encountered a philosopher of science, so this is a pretty telling picture) and why not just read people like Camus or Nietzsche (I suppose that Nietzsche had quite some things to say about science, though not in the way in which they're taking, has perhaps escaped them).

That's all for CERN Day-4 for now and I'll have more to say about today later

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