Scintillating active Transverse Energy Filter: a novel detector concept for low-energy electron background discrimination

One of the leading sensitivity limiting factors in the Karlsruhe Tritium Neutrino (KATRIN) experiment are background electrons from the main spectrometer. These electrons, presumably low in energy at their creation point, are currently indistinguishable from the tritium beta electrons. Since they arrive at the detector with predominantly small angles relative to the guiding magnetic field lines in contrast to the signal electrons, an angular selective detector has great potential in increasing the sensitivity of the KATRIN experiment by enhancing the signal-to-background ratio.
Micro-structured detector configurations which exhibit angular selectivity due to their 3D structure, so-called active Transverse Energy Filters (aTEF), have been proposed by Eur. Phys. J. C 82 (2022) 922. One approach is a scintillator-based aTEF (scint-aTEF). This presentation gives an overview of the aTEF principle and in particular the scint-aTEF detector, including GEANT4 simulation-based studies and prototype micro-structures 3D printed via two-photon lithography.