| | 27 | || '''02.02.2018[[BR]](10hrs, HdA)''' || '''Joachim Wolf [[BR]](KIT-ETP)''' || '''KATRIN - the "Karlsruher Tritium Neutrino Experiment"'''[[BR]][[BR]]Apart from photons, neutrinos are the most abundant particles in the universe. Therefore even the small neutrino mass has an impact on the evolution of the visible universe. And also in particle physics the neutrino mass is an important parameter. The observation of neutrino oscillations confirmed for the very first time that neutrinos have a mass. But, those experiments only allow to measure the difference of squared mass values of the different neutrino generations, i.e. absolute mass values cannot be deduced. A model independent method to determine the neutrino mass is the precise measurement of the beta spectrum of a radioactive decay.[[BR]][[BR]]Goal of the KATRIN experiment, which is currently commissioned at the "Karlsruher Institut für Technologie" (KIT), is the determination of the neutrino mass, more specifically, the effective mass of electron anti-neutrinos in the decay of molecular tritium gas. A finite neutrino mass would lead to a tiny change in the form of the beta spectrum at its kinematic endpoint of 18,6 keV, which has to be measured with high precision. Since only about 2 x 10^-13^ of all beta electrons possess an energy in the last eV below this endpoint, the source requires a high intensity. With a sensitivity of m,,n,, = 0.2 eV/c^2^, KATRIN will improve all previous limits of tritium measurements by a factor of 10.[[BR]][[BR]]The complete setup of the KATRIN experiment has a total length of 70 m and can be divided into two main areas: In the source and transport range the tritium decay is happening (~10^11^ Bq), the electrons are guided to the spectrometer range using super conducting magnets and the remaining tritium gas is pumped with such a high efficiency that only a fraction of less than 10^-14^ of the original amount of gas reaches the spectrometer. Finally, in this spectrometer and detector area the energy of the electrons is measured with highest precision. This happens in the main spectrometer with 10m of diameter and 23m of length, comprising an ultra-high vacuum of 10^-11^ mbar in a volume of 1240 m^3^. For the energy measurement the so-called MAC-E filter technique is applied using an electrostatic high-pass filter, which only allow electrons above a certain voltage threshold to reach the detector, and finally getting counted. The talk explains the measurement of the neutrino mass and the KATRIN experiment and discusses the technological and physical challenges.[[BR]][[BR]]Presentation: German[[BR]][https://svn.mpia.de/trac/gulli/att/raw-attachment/wiki/AlteVortraege2018S1/2018-02-02_KATRIN.pdf Slides: English][[BR]]Questions: German, English || |
