Tritium ion blocking and detection in the KATRIN experiment

The aim of the KATRIN experiment is to determine the absolute neutrino mass scale in a model independent way by measuring the electron energy spectrum shape near the endpoint of molecular tritium beta decay. The beta electrons are guided from the source to the spectrometers by a high magnetic field. The beta decays and ionisations of the beta electrons in the source produce a variety of positive tritium ions that are not allowed to reach the spectrometers. Therefore they will be blocked by a positive potential and removed by dipole electrodes in the beam transport system. Various ion detection methods (Faraday cup, FT-ICR and ionisation of the residual gas in the spectrometers) will be used to test the ion blocking and removal efficiency.