The KATRIN Neutrino Mass Measurement: Experiment, Status, and Outlook
The Karlsruhe Tritium Neutrino (KATRIN) experiment will provide a measurement of the effective electron-neutrino mass, $m(ν_e)$, based on a precision measurement of the tritium beta decay spectrum near its endpoint. The effective mass is an average of the neutrino mass eigenvalues $m_i$ weighted by the flavor-mass mixing parameters $U_{ei}$ according to the relation $m^2(ν_e)= \sum_{i=1}^3 |U_{ei} |^2 m_i^2$. The KATRIN apparatus uses a windowless gaseous tritium source (WGTS) and a spectrometer based on the MAC-E filter concept to measure the beta energy spectrum. The KATRIN program is designed to reach a mass sensitivity of 0.2~eV (90\% C.L.). The collaboration has completed a series of commissioning measurements and is moving into the first running of tritium. The KATRIN measurement technique, early commissioning results, and the future outlook will be presented.