•Björn Flatt für die KATRIN-Kollaboration
Johannes Gutenberg Universität Mainz, 55099 Mainz

The KArlsruhe TRItium Neutrino experiment KATRIN is a planned next generation tritium beta decay experiment with sub-eV sensitivity on the electron neutrino mass. In order to determine the neutrino mass from the beta spectrum its endpoint region has to be analysed with a high precision. A MAC-E-Filter with 1 eV energy resolution will be used as main spectrometer. A second MAC-E-Filter will be installed as a pre-filter between b electron source and main spectrometer. The purpose of this so-called pre-spectrometer is to prevent the main, low energy, part of the b electrons from proceeding to the main spectrometer, where these electrons could become a major background source. The new design of the electrode system and the magnets of the pre-spectrometer follows the requirement of a low trapping probability for charged particles. This configuration, which is under construction at the FZ Karlsruhe, is presented.

Sponsored by BMBF under FKZ 05CK1UM1/5