July 2020
The world's most precise neutrino scales
“In the TRIMS (Tritium Recoil-Ion Mass Spectrometer) experiment, we took a close look at the decay of molecular tritium and measured the frequency of different decay channels. We have succeeded in clarifying a long-standing discrepancy between theory and experiment with regard to the decay of molecular tritium. This in turn is an important precondition for the Project 8 experiment, which I am working on in my PhD thesis in Mainz, and for the KATRIN experiment at KIT in Karlsruhe.
In Project 8, we want to determine the neutrino mass using the decay of tritium and the associated decay spectrum. To do this, we need to know the exact form of the tritium decay spectrum. It is determined from theoretical calculations. The theoretically calculated frequency of individual decay channels has so far contradicted measurements from the 1950s. The TRIMS experiment has now resolved this contradiction and confirmed the theory.
The TRIMS experiment works with a combination of time-of-flight measurements and energy determination after electrostatic acceleration. This information can be used to determine the mass and charge of the incident particles produced during tritium decay. When I began my stay in Seattle, the tests on the prototype had been successfully completed and I was able to help set up the actual experiment.
In detail, I dealt with the characterization of the ion detectors. To this end, we measured the capacity and leakage current of the detectors, assembled them, set up a test ion source and recorded an americium-241 spectrum. My tasks also included installing and commissioning the magnets that form the magnetic guide field for the decay electrons. I also had contact with the Project 8 team during another stay in Seattle and worked on the associated data acquisition system.
My research stay in Seattle was a very enriching experience. I can apply a lot of what I learned there to my PhD in Mainz. It was a very exciting time, from which I also benefited personally in many ways. The TRIMS team made me feel very welcome and I am very grateful to everyone for the great collaboration and the extensive experience I was able to gain there. The fact that our work has produced such an important result with great significance for Project 8 and has now been successfully published is something very special for me. ”
Christine Claessens has been a PhD student in Experimental Particle and Astroparticle Physics (ETAP) at the Cluster of Excellence PRISMA+ since 2016. In her PhD thesis, she is working on data analysis and data acquisition for the Project 8 experiment. Within Project 8, the new method of cyclotron radiation emission spectroscopy was developed to measure the absolute neutrino mass with unprecedented precision. In 2016, Christine Claessens spent an extended research stay at the University of Washington in Seattle. She was involved in setting up the TRIMS experiment there – and has now published an important result together with her colleagues there in the renowned journal “Physical Reviews Letters”. Congratulations on this success!