What's cubed, made of plastic, and detects charged sub-atomic particles? The new detector for the T2K (Tokai-to-Kamioka) neutrino oscillation experiment of course! This new detector is called the Super Fine-Grained Detector (SFGD) and has been proposed for the upgrade of the near detector of T2K. It's planned for installation in 2021. There are also plans for a similar detector called 3DST (3 Dimensional Scintillator Tracker) on the DUNE experiment, which is under construction. Two prototypes of the detector have been made, and several of us from the T2K and DUNE experiments headed over to Los Alamos, New Mexico to use their neutron beam in the Los Alamos National Laboratory (LANL).
I am a 3rd year PhD student at Imperial. Most of my work so far has been relating to the upgrade of T2K's near detector, hence why I was able to help out at this beam test. In fact, I've already been to CERN to help out with a beam test of one of the detector prototypes, where we fired lots of charged particles at it. That beam test was useful for getting to grips with the detector and measuring some of its inherent properties, such as its time resolution. At LANL, we were firing neutral particles at the detector, which cannot be directly detected in the scintillating material. Instead, we relied on the neutrons interacting with the plastic in our detector and knocking out protons or some other charged particles, which we could see in the detector. The whole design of the detector is built around trying to identify particles from neutron events as close to the interaction point as possible. This will be extremely useful for experiments looking at anti-neutrino interactions, as it is important to identify the interaction process that caused a neutron to be produced from an anti-neutrino interaction, so that the energy of the original neutrino can be calculated.
But enough about the physics, because I also want to talk about Los Alamos itself. It was a privilege to work in a place so steeped in history, as this was the laboratory where the original atomic bombs, Fat Man and Little Boy, were developed, with help from many famous names such as Oppenheimer and Feynman. It's also very scenic, and a totally different environment to that of London, or anywhere in the UK! The town is at an altitude of 7000 ft (that's about 3000 m for us metric users), and surrounded by a desert of rocky cliffs and mesas. I didn't get much chance to explore the area, but I went on a hike one day by a town called White Rock. We climbed down into a canyon and walked along the Rio Grande river before climbing back up the canyon (not for the faint hearted!). The views of the canyon and the skyline with mountains in the distance were spectacular. As you can see from the photos, the weather was very clear on the hike, as it was for most of my stay there. Although, when I first arrived at the end of November, there was a snow storm for the first few days and there was a good 6 inches of snow covering the area. I had rented a car for the trip, and the snow mixed with the fact that I'd never driven on the right side of the road before made for some nervous driving! I got the hang of it in the end though.
I may not have had many days off to explore the surroundings, but I was able to go into Los Alamos and Santa Fe to sample the local cuisine. There were a plethora of restaurants serving New Mexican food, which is similar to Mexican food but with a few twists (mainly the twist is more chile!). I'm vegetarian but there was normally plenty of choice for meat-free meals, which I was pleasantly surprised by. At most places I got the vegetarian platter so I could try as many things as possible! We went to a restaurant called Gabriel's on my birthday and I got a surprise rendition of "Happy Birthday" in Mexican (I think), with me wearing a sombrero! And to top it all off a free dessert :). Would definitely recommend a birthday in New Mexico!
Back to the beam test of the SFGD prototype, the test itself was successful. We managed to see events in the detector that coincided with the beam position, and we could see the structure of the beam extremely well with our timing electronics. There has already been some data analysis but there is still a lot more to be done before we can completely gauge how successful the beam test was. One of our aims is to measure the cross-section of the neutrons in our detector, which requires the detection of a very large number of neutrinos. We believe we've gathered enough data over the last month for an accurate measurement, but the result is yet to be calculated.
I mentioned at the start that there were two prototypes at the beam test. The SFGD prototype was in the beamline for the whole month of the beam test, yet the US-Japan prototype wasn't put in until the last day! This was due to some hardware issues, which is to be expected since this was a completely new and untested machine. Initial glances at the data we collected with it indicate it was working as expected, but again, we will have to wait until further data analysis is done before we reach any hard conclusions.
Of course, I wasn't carrying out this beam test all by myself! There were a number of other T2K/DUNE collaborators that helped out. I was one of the three run coordinators that spent the most time at LANL and became most familiar with the detector and the procedures, hence had the job of organising the tasks for the day and figuring out problems that occurred. The other two run coordinators were Guang Yang of Stony Brook University and David Last from the University of Pennsylvania. One of the benefits of working in high energy physics is the opportunity to meet people from all over the world, and I thoroughly enjoyed my time working with these two and the other volunteers that came to LANL. We had plenty of meals together and went to see a few movies too!
In summary, my visit to Los Alamos is not one I will ever forget. Friendships were formed and, perhaps secondarily, physics was performed! Now begins the long but satisfying process of data analysis! I'll leave you with some more pictures of the beautiful White Rock area and a picture of we three run coordinators next to the SFGD prototype detector. Thanks!
