![]() ![]() The dominant source of background arises from α-decays of 210Po (refs. The current background level of KATRIN of about 220 mcps mainly originates from the spectrometer section. The magnetic fields are determined with a high-precision magnetic-field sensor system 43. The high voltage of the main spectrometer is continuously measured at the parts-per-million level with a high-precision voltage divider system 40, 41 and an additional monitoring spectrometer 42. A silicon drift detector system installed in the transport section and a β-induced X-ray system at the rear section 39 continuously monitor the tritium activity, yielding a result at the 0.03%-precision level each minute. A laser Raman system continuously monitors the gas composition, providing a measurement at the ≤0.05%-precision level each minute. The throughput of tritium gas within the tritium source tube and tritium circulation loop is measured by a flow meter. The beamline is equipped with multiple monitoring devices. ![]() In -decay, a quark decays into another type of quark, releasing a particle and a neutrino. The methods of calibration are described in more detail in Methods. In beta ( -) decay, a down quark changes to an up quark, with the release of an electron ( -) and an antineutrino. These variations are caused by a weak cold-magnetized plasma, which arises from the high magnetic field (2.5 T) and a large number of ions and low-energy electrons (~1 × 10 12 m −3) in the tritium source. Mono-energetic conversion electrons from the decay of the metastable state 83mKr are used to determine spatial and temporal variations in the electric potential of the tritium source. Another key calibration source is gaseous krypton, which can be co-circulated with the tritium gas 38. Furthermore, we use the electron gun to measure the distribution of energy losses for 18.6 keV electrons scattering off the molecular tritium gas, providing one of the most precise energy-loss functions for this process to date 37. The rear section is equipped with an angular- and energy-selective electron gun 36, which is used to precisely determine the scattering probability of electrons with the source gas, governed by the product of column density (number of molecules per square centimetre along the length of the source) and scattering cross section. The best fit to the spectral data yields \(\) (100 mV) to minimize the difference in the surface potential to that of the beam tube, which minimizes the inhomogeneity of the source electric potential. By increasing the source activity and reducing the background with respect to the first physics campaign, we reached a sensitivity on m ν of 0.7 eV c –2 at a 90% confidence level (CL). This method is independent of any cosmological model and does not rely on assumptions whether the neutrino is a Dirac or Majorana particle. In this experiment, m ν is probed via a high-precision measurement of the tritium β-decay spectrum close to its endpoint. Here we report the upper limits on effective electron anti-neutrino mass, m ν, from the second physics run of the Karlsruhe Tritium Neutrino experiment. However, the absolute neutrino-mass scale remains unknown. Since the discovery of neutrino oscillations, we know that neutrinos have non-zero mass.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |