I arrived this morning in Marrakech, Morocco, for ATLAS’s “Liquid Argon Week.” No, we’re not going out in search of liquid argon in the desert. I’m going to meet up with colleagues that I work with to make sure our part of ATLAS is ready go when the first collisions of the LHC take place.
The ATLAS experiment has many different pieces, and each piece measures different aspects of the collisions provided by the accelerator. The piece that I work on is called the Liquid Argon Calorimeter. A calorimeter is a device that measures energy. Ours is called the “Liquid Argon” (abbreviated to “LAr”) calorimeter because liquid argon is the substance inside the detector that lets us know that particles passed through it. As particles from the LHC collisions enter the argon, they ionize the argon and we can infer the energy of the particles from the ions they left behind. Argon is usually a gas at room temperature, but the gas would not be dense enough to help us measure the energy well. We have to cool the argon to -186 degrees Celsius (about -300 degrees F) to use it in ATLAS! If you want to learn more about how the calorimeter works, I recommend this video which explains many of the ATLAS subsystems with great illustrations. There are actually four different types of liquid argon calorimeters used in ATLAS, but they share many of the same tools and challenges, so all the people working on those detectors form the “Liquid Argon Calorimeter Group” within ATLAS.
People who work on these calorimeters get together every few months to share their progress and make plans for the future. The same thing is done for other systems of ATLAS: there is a “muon detector week” and an “inner detector week” and then there are weeks for all of ATLAS to get together. Usually these weeks are at held at CERN, but once a year, they may be held outside CERN. The outside-of-CERN weeks give one of the groups a chance to show their colleagues around their home town. It also gives people from that area a break from travelling all the way to CERN. Being away also allows/forces people to get away from their usual offices, tasks, and social circles at CERN. There are scheduled talks, and a lot of other important and useful discussions take place over coffee (or mint tea!) or lunch or dinner while people are away
from home, together.
This week, our Liquid Argon Calorimeter colleagues from Morocco have invited us all to meet in Marrakech. We’ll have four days of meetings on different topics relating to the calorimeters, and then a free day at the end of the week for exploring. There will be a big dinner one night with Moroccan food — I’m looking forward to that!