The thermal properties of the windowless gaseous tritium source of the KATRIN experiment

The Karlsruhe Tritium Neutrino (KATRIN) Experiment aims to determine the neutrino mass with an unreached sensitivity of 200 meV/c² (90% C.L.) by the investigation of the endpoint energy-region of the tritium β-spectrum in a direct and model-independent way. Molecular Tritium gas with purity 95% is injected continuously in the center of the Windowless Gaseous Tritium Source (WGTS) of KATRIN and pumped off at both ends. The beta electrons are guided by a strong magnetic field to the spectrometers and are analyzed there energetically. The statistical and systematic uncertainties of the m _{anti νe} measurement are closely related to the thermal and gas dynamic performance and stability of this source. In order to keep the source pressure profile stable at 0.1% level, injection pressure and temperature of the beam tube need to be stabilized. The beam tube itself will be operated at 30 K to reduce systematic uncertainties like Doppler Effect. To restrict systematic effects the thermal homogeneity and stability fluctuations therefore have to be lower than 30 mK. This talk provides an insight of the thermal and gas dynamic properties of the WGTS with a construction overview and planed commissioning measurements.