Searching for neutrinos using the Short Baseline Neutrino Detector at Fermilab
Like many particle physics PhD students, LIV.DAT student Beth Slater had the opportunity to spend time seeing the detector she was working on in action. For her this meant a transatlantic trip to Illinois, home to the Short Baseline Neutrino Detector (SBND) at Fermilab. Once she had arrived, Beth found herself surrounded by people who were all working on similar projects. It was unlike anywhere she had worked before; the sense of kinship and collaboration felt really special and helped to welcome her as she began her onsite research.
Neutrinos are notoriously difficult to detect so the community is always working to develop and improve the technologies they use. SBND is on the brink of collecting physics-quality data, meaning the whole collaboration is incredibly busy working hard to ensure readiness for the task ahead. With that in mind Beth wanted to maximise her time there, both to expand her experience and prepare the detector. Until now all her research work had been software based so she was excited, and a little scared, at the prospect of getting some hands-on hardware experience.
Once she had arrived, Beth joined the trigger group to work on testing all the subsystems to ensure they could efficiently record high-quality neutrino-rich data. SBND is special in that it will detect around two million neutrino events in a year, meaning it will quickly have one of the largest neutrino datasets in the world, resulting in exceptional statistics. Due to storage space limitations, it is impossible to record everything that happens in the detector so the trigger system is essential to set the conditions to record data when there is a potential to see a neutrino.
Beth’s first task was to become familiar with each of the different subsystems at SBND and understand the intricacies of how they connect to record neutrino interaction data. The key areas she worked in were the light detection and cosmic ray tagger (CRT) subsystems. The light detection subsystem captures scintillation light to construct 3- dimensional tracks of particles passing through the detector and the CRT subsystem is to record cosmic ray events, the highest background in SBND. The CRT data has further applications for the commissioning and calibration of the detector. Detecting light is exceptionally important for the trigger as it is the fastest way to detect that something interesting is occurring.
Once Beth’s understanding fully developed, she worked within the trigger team to test that each of the trigger types, which the collaboration desired was possible and produced the correct data. Timing is essential to reconstructing the events, so Beth spent a lot of time focusing on comparing the timestamps of various signals and ensuring the correct information was saved for each event.
A minor inconvenience of working through the summer at Fermilab is that the neutrino beam, which sends bursts of the particles to the detector, is not running. The trigger system relies on input signals from the beam to ensure the equipment is ready to record data every time there are neutrinos in the building so a simulated beam setup had to be devised to test the trigger system fully.
Working collaboratively with the Beam and Timing Group, Beth helped to set up a series of function generators, fan out devices, and delay generators to simulate all relevant beam signals which are sent to a variety of components. Rigorous testing to ensure all systems ran as expected followed this. The simulated beam setup had the advantage of being adjustable to various frequencies, allowing a wider variety of tests of different trigger rates and beam frequencies to be possible.
Beth thoroughly enjoyed her time at Fermilab. She said: “Working with the trigger group was a completely different experience, and it felt amazing to be there in person, actively collaborating with people.”