Further development of the precision HV divider for the KATRIN experiment

To determine the mass of the νe with a sub-eV sensitivity the KATRIN-(Karlsruhe Tritium Neutrino-) experiment measures the tritium β spectrum in the endpoint region using a MAC-E type spectrometer. To reach the desired sensitivity the retarding potential of the MAC-E-filter of -18.6 kV must be monitored with a precision of 3 ppm. For that purpose a precision high voltage divider for voltages of up to 30 kV was developed in cooperation with the PTB (Physikalisch-Technische Bundesanstalt) Braunschweig. This first divider has been proven to deliver the necessary accuracy and stability. For redundancy reasons and as a replacement during the calibration periods a second high voltage divider was developed based upon the experience gained from the first divider. The main goal of the development of the second divider was the improvement of the longterm stability and to expand the possible field of application to other experiments. In this talk the improvements of the second divider are shown along with calibration results obtained at the PTB.