  Sterile neutrinos are a minimal extension of the Standard Model of Particle
Physics. If their mass is in the kilo-electron-volt regime, they are viable
dark matter candidates. One way to search for sterile neutrinos in a
laboratory-based experiment is via tritium-beta decay, where the new neutrino
mass eigenstate would manifest itself as a kink-like distortion of the
$\beta$-decay spectrum. The objective of the TRISTAN project is to extend the
KATRIN setup with a new multi-pixel silicon drift detector system to search for
a keV-scale sterile neutrino signal. In this paper we describe the requirements
of such a new detector, and present first characterization measurement results
obtained with a 7-pixel prototype system.
