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The KATRIN experiment is designed for a direct and model-independent determination of the effective electron anti-neutrino mass via a high-precision measurement of the tritium $beta$-decay endpoint region with a sensitivity on $m_ u$ of 0.2$,$eV/c$^2$ (90% CL). For this purpose, the $beta$-electrons from a high-luminosity windowless gaseous tritium source traversing an electrostatic retarding spectrometer are counted to obtain an integral spectrum around the endpoint energy of 18.6$,$keV. A dominant systematic effect of the response of the experimental setup is the energy loss of $beta$-electrons from elastic and inelastic scattering off tritium molecules within the source. We determined the linebreak energy-loss function in-situ with a pulsed angular-selective and monoenergetic photoelectron source at various tritium-source densities. The data was recorded in integral and differential modes; the latter was achieved by using a novel time-of-flight technique. We developed a semi-empirical parametrization for the energy-loss function for the scattering of 18.6-keV electrons from hydrogen isotopologs. This model was fit to measurement data with a 95% T$_2$ gas mixture at 30$,$K, as used in the first KATRIN neutrino mass analyses, as well as a D$_2$ gas mixture of 96% purity used in KATRIN commissioning runs. The achieved precision on the energy-loss function has abated the corresponding uncertainty of $sigma(m_ u^2)<10^{-2},mathrm{eV}^2$ [arXiv:2101.05253] in the KATRIN neutrino-mass measurement to a subdominant level.
The determination of the neutrino mass is one of the major challenges in astroparticle physics today. Direct neutrino mass experiments, based solely on the kinematics of beta-decay, provide a largely model-independent probe to the neutrino mass scale
The KATRIN experiment is going to search for the average mass of the electron antineutrino with a sensitivity of 0.2 eV/c2. It uses a retardation spectrometer of MAC-E filter type to accurately measure the shape of the electron spectrum at the endpoi
The KATRIN experiment, presently under construction in Karlsruhe, Germany, will improve on previous laboratory limits on the neutrino mass by a factor of ten. KATRIN will use a high-activity, gaseous T2 source and a very high-resolution spectrometer
The available experimental information on the Range-Energy relation for protons stopped in hydrogen gas is summarized in the SRIM software package. The estimated precision of this data is several percents. Here we describe a possibility to measure th
The KATRIN experiment aims at the direct model-independent determination of the average electron neutrino mass via the measurement of the endpoint region of the tritium beta decay spectrum. The electron spectrometer of the MAC-E filter type is used,