Experimental determination of the Anti-neutrino spectrum of the fission products of 238U

Orateur : Dr. N. HAAG (TU Munchen)

Precise predictions of the antineutrino spectra emitted by nuclear reactors are a crucial input for many current and future neutrino experiments. But until recently, only the contributions from three of the four fuel isotopes (235U, 239Pu, and 241Pu) have been measured. The antineutrino spectrum from 238U - contributing 10 % to the total neutrino output - was only known by calculations and simulations. Recently, an experiment was performed at the scientific neutron source FRM II in Garching to determine the cumulative antineutrino spectrum of the fission products of 238U. Target foils of natural uranium were irradiated with a thermal and a fast neutron beam and the emitted beta spectra were recorded with a gamma-suppressing electron telescope. The obtained beta spectrum of the fission products of 235U was normalized to the data of the magnetic spectrometer BILL. This method strongly reduces systematic errors in the 238U measurement. The beta spectrum of 238 U was then converted into the corresponding antineutrino spectrum. The talk will discuss the experimental setup and the important part of the data analysis. Furthermore, the results will be compared to the actual calculations used in present reactor neutrino experiments.

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