Characteristics of electron gun to investigate the energy loss function in KATRIN

The KATRIN experiment aims to determine the mass of the neutrino by scanning the electron energy spectrum near the endpoint. Electrons can however scatter with tritium molecules in the source of the experiment and lose energy in the process. This energy loss function needs to be measured with high precision. At the back end of the KATRIN beam line a mono energetic and mono angular photo-electron source, the so called e-gun, is in place to perform this measurement in situ with high precision. This talk will focus on our new beam pulsing method for measurements using time of flight information in addition to energy scanning with the KATRIN main spectrometer. The combination of time of flight analysis with beam pulsing greatly reduces the background contribution in the measurement. With the much improved signal to noise ratio we performed a direct measurement of the function at 18.6 keV for energy losses of up to 200 eV.

This work is supported by the Helmholtz Association and by the Ministry for Education and Research BMBF (grant numbers 05A23PMA, 05A23PX2, 05A23VK2, and 05A23WO6)