“I am working on the Project 8 experiment, with which we want to directly measure the neutrino mass. For this, we use the beta decay of tritium – an unstable hydrogen isotope – into a helium isotope, an electron, and a neutrino. Project 8 is backed by an international collaboration. In Mainz, we are investigating how to build a tritium source for the later experiment.”

Neutrinos are ubiquitous particles, and we have known about them for quite some time. In the Standard Model of Particle Physics, neutrinos have no mass at all – similar to light particles, the photons. However, experiments have proven that neutrinos do have mass.

But why don’t we know the mass of neutrinos yet? Because they hardly interact with matter at all. That’s why we also call them ghost particles. So, we have to be very clever, and at Project 8, we came up with a new technique: CRES or Cyclotron Radiation Emission Spectroscopy. In this process, we measure the energy of the electrons produced during the beta decay of tritium via their orbital frequency in a magnetic field.

Using a mini-version of the experiment, we were already able to show that the CRES Technics Department works. We are currently developing a tritium source for the later large experiment. A special feature is that we need individual tritium atoms for this – which we generate from the splitting of tritium molecules. Since tritium is highly radioactive, we are initially developing a similar but safer source. For this, we use “normal” hydrogen in Mainz, which we can now break down very well into individual atoms. As soon as we are able to generate a beam from these hydrogen atoms, we can transfer the technique to tritium. The work we are doing now is part of a five-year research and development program that serves as the basis for the final Project 8 experiment.

Neutrino physics fascinates me because mass is such a fundamental property, and we don’t know it yet. What I particularly like about physics in Mainz is that even Bachelor students are intensively involved in current research projects. In this way, female students in particular can learn from role models very early on.”

Dr. Larisa Thorne is a postdoctoral researcher in the group of Prof. Dr. Martin Fertl. She came to neutrino physics rather by chance, after a detour via a nuclear physics topic. She received her doctoral degree with a thesis on the KATRIN neutrino experiment and began working as a postdoctoral researcher in Mainz two weeks after her doctoral examination in July 2021.