München 2009 – scientific programme

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T: Fachverband Teilchenphysik

T 103: Niederenergie-Neutrinophysik & Suche nach dunkler Materie 4

T 103.7: Talk

Thursday, March 12, 2009, 18:20–18:35, A140

Determination of the antineutrino spectrum of the fission products of U-238 — •Nils Haag, Franz von Feilitzsch, Martin Hofmann, Tobias Lachenmaier, Lothar Oberauer, Walter Potzel, and Klaus Schreckenbach — E15 Physik Department, Technische Universität München

Fission of U-238 contributes with ∼ 10 % to the total power of a nuclear reactor. Up to now the antineutrino spectrum emitted during this fission could only be estimated by simulations and calculations, whereas the contribution from the other isotopes (U-235, Pu-239, Pu-241) are well known since the late 1980s. This lack of knowledge limits the accuracy of reactor neutrino experiments. The talk describes the setup and first results of an experiment aiming at the determination of this unknown antineutrino spectrum. A plastic scintillator in coincidence with a multi-wire chamber to veto γ-ray pulses is used to measure the total beta spectrum of all fission products of U-238, irradiated with fast neutrons from the FRM-II in Garching. This beta spectrum thereafter is converted into the correlated antineutrino spectrum. Calibration is performed with Co-60 and Bi-207 sources and with neutron activated In and PVDC foils. With a gamma discrimination better than 99.8 % and an energy resolution of < 8 % the spectrum can be determined with an accuracy of 10 % in the energy range from 2 to 10 MeV.

This work has been supported by funds of the DFG (Transregio 27: Neutrinos and beyond), the Excellence Cluster Universe and the Maier-Leibnitz-Laboratorium in Garching.