First results of the commissioning of the Windowless Gaseous Tritium Source of the KATRIN experiment

KATRIN will perform a direct, kinematics-based measurement of the neutrino mass with a sensitivity of 200 meV (90 % C. L.) reached after 3 years of measurement time. The neutrino mass is obtained by determining the shape of the spectrum of tritium beta decay electrons close to the endpoint of 18.6 keV with a spectrometer of MAC-E filter type. Important requirements to achieve this goal are the temperature stability and homogeneity of the beam tube of the Windowless Gaseous Tritium Source (WGTS). The temperature stability is specified to be within ±30 mK/h and the temperature homogeneity is specified to be within ±30 mK along the 10 m long WGTS beam tube. During the first light measurement campaign in fall 2016, the cryogenic performance of the WGTS was tested in detail. This talk presents the results of this first cryo-test of the source cryostat showing that the WGTS is ready for standard KATRIN operation.