Owing to its excellent source and spectrometer properties, the KATRIN experiment enables us to not only determine the neutrino mass, but also to search for a new variant of the particle: The so-called sterile neutrino. Unlike the known active neutrinos, this hypothetical particles interacts even weaker, and can have any mass.  
A sterile neutrino with a mass in the keV region is a viable dark matter candidate.
A sterile neutrino with a mass in the keV range can leave a characteristic signature in the tritium beta decay spectrum. As KATRIN operates one of the strongest tritium sources in the world for scientific research, it is the ideal place to conduct a search for sterile neutrinos. The KATRIN beam-line, however, is designed to precisely measure only the region close to the endpoint of the spectrum, where we expect the signature of the neutrino mass. In order to search for keV-scale sterile neutrinos the entire tritium spectrum must be detected. This extension leads to multiple challenges, for example the rate of beta-electrons will be many orders of magnitudes higher. This is why we develop a novel detector system, TRISTAN. Is consistes of more than 1000 Silicon Drift Detector pixels, over which the high flux of electrons will be distributed. Each pixel can measure precisely the energy of each electron.
We have finalized the design of the TRISTAN detector and we built a complete TRISTAN module, which comprises 166 SDD pixels (see photograph). In 2026 nine TRISTAN modules will be installed in the KATRIN beam-line.