Orateur
Description
DANSS is a scintillator detector of antineutrinos located on a lifting platform below the 4th reactor core of the Kalinin NPP in Russia. The detector position below the reactor core provides advantages of high neutrino rate and an overburden of 50 m w.e., which suppresses atmospheric muon flux by a factor of 5–6. The detector was commissioned in April 2016 and it has been operating continuously since October 2016. The antineutrino statistic is the largest in the world and exceeds 10M Inverse Beta Decay (IBD) events. The IBD spectrum dependence on the 239Pu fission fraction is presented. It agrees with the predictions of the Huber-Mueller model. Using this dependence, the ratio of IBD rates for 235U and 239Pu was extracted. It also agrees with the Huber-Mueller model and somewhat larger than in other experiments. The reactor power was measured using the IBD event rate during 7.5 years with a statistical accuracy of 1.0% in a week and with the relative systematic uncertainty of less than 0.8%. The fraction of the reactor antineutrino yield with energies above 10 MeV was measured. Such antineutrinos are important for searches of neutrino coherent scattering. Fission fractions of 239Pu and 235U during reactor campaigns were measured using a fit of the IBD positron spectra. They agree within better than 3% accuracy with the fission fractions obtained using neutron flux simulations in the reactor. Antineutrino spectra from 239Pu and 235U were reconstructed. Both spectra show evidence for a 6 MeV bump in comparison with the Huber-Mueller model.
