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Register a new userPrecision measurement of the electron energy-loss function in tritium and deuterium gas for the KATRIN experiment
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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.
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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 Karlsruhe Tritium Neutrino (KATRIN) experiment is designed to directly measure the effective electron antineutrino mass with a sensitivity of 0.2 eV 90% CL. In this work we report on the first operation of KATRIN with tritium which took place in 2018. During this commissioning phase of the tritium circulation system, excellent agreement of the theoretical prediction with the recorded spectra was found and stable conditions over a time period of 13 days could be established. These results are an essential prerequisite for the subsequent neutrino mass measurements with KATRIN in 2019.
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 endpoint of tritium beta decay. In order to achieve the planned sensitivity the transmission properties of the spectrometer have to be understood with high precision for all initial conditions. For this purpose an electron source has been developed that emits single electrons at adjustable total energy and adjustable emission angle. The emission is pointlike and can be moved across the full flux tube that is imaged onto the detector. Here, we demonstrate that this novel type of electron source can be used to investigate the transmission properties of a MAC-E filter in detail.
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 to measure the shape of the high-energy tail of the tritium-decay beta spectrum. The shape measurement will also be sensitive to new physics, including sterile neutrinos and Lorentz violation. This report summarizes recent progress in the experiment.
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 this relation with 0.1$%$ precision in the course of an electron-proton elastic scattering experiment to be performed in the 720 MeV electron beam at the Mainz Microtron (MAMI). This experiment, aimed at precision measurement of the proton charge radius, exploits a large hydrogen active target to detect the recoiled protons and a forward tracker to detect the scattered electrons. The angles of the scattered electrons are measured with $2cdot10^{-4}$ absolute precision. Also, the electron beam momentum is known at MAMI with $2cdot10^{-4}$ absolute precision. This gives a possibility to determine with 0.1$%$ absolute precision the four-momentum transfer $Q^2$ which, in its turn, is a direct measure of the recoiled proton energy $T_{p}$: $Q^2 = 2M_{p}T_{p}$, where M$_{p}$ is the proton mass. From this point of view, this experimental setup can be considered as a source of protons with well defined energies inside an active target, which is a specially designed hydrogen high-pressure Time Projection Chamber (TPC). The design of the TPC allows to measure with high precision the energy of the protons corresponding to some selected values of the proton range. In this way, the Range-Energy relation can be established for the proton energies from 1 MeV to 9.3 MeV with 0.1$%$ absolute precision, the maximal energy being limited by the size of the TPC and by the hydrogen gas pressure.
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, requiring very high stability of the electric filtering potential. This work proves the feasibility of implanted 83Rb/83mKr calibration electron sources which will be utilised in the additional monitor spectrometer sharing the high voltage with the main spectrometer of KATRIN. The source employs conversion electrons of 83mKr which is continuously generated by 83Rb. The K-32 conversion line (kinetic energy of 17.8 keV, natural line width of 2.7 eV) is shown to fulfill the KATRIN requirement of the relative energy stability of +/-1.6 ppm/month. The sources will serve as a standard tool for continuous monitoring of KATRINs energy scale stability with sub-ppm precision. They may also be used in other applications where the precise conversion lines can be separated from the low energy spectrum caused by the electron inelastic scattering in the substrate.
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