The KATRIN (Karlsruhe Tritium Neutrino) experiment investigates the energetic endpoint of the tritium beta-decay spectrum to determine the effective mass of the electron anti-neutrino. The collaboration reported its first neutrino mass result in fall 2019. Its unprecedented tritium source luminosity and spectroscopic quality make it a unique instrument to also search for physics beyond the standard model such as eV or keV sterile neutrinos.

The TRISTAN project aims at detecting a keV-sterile neutrino signature by measuring the entire tritium beta-decay spectrum with an upgraded KATRIN system. One of the greatest challenges is to handle the high signal rates generated by the strong activity of the KATRIN tritium source while keeping a good energy resolution and stability over time. Therefore, a novel multi-pixels silicon drift detector and read-out are being designed to handle rates up to 100 Mcps with an energy resolution of 200~eV (FWHM) at 10~keV.

I will first introduce the KATRIN experiment and its latest results. I will then present the TRISTAN project, the challenges and the assembly of the first module. And finally I will discuss the possibility of using the TRISTAN detector to look for solar axions in the IAXO experiment.