Abstract
233U is the fissile nuclei in the Th-U fuel cycle with a particularily small neutron capture cross setion which is on average about one order of magnitude lower than its fission cross section. Hence, the measurement of the 233U(n, γ) cross section relies on a method to accurately distinguish between capture and fission γ-rays. A measurement of the 233U α-ratio has been performed at the n_TOF facility at CERN using a so-called fission tagging setup, coupling n_TOF 's Total Absorption Calorimeter with a novel fission chamber to tag the fission γ-rays. The experimental setup is described and essential parts of the analysis are discussed. Finally, a preliminary 233U α-ratio is presented.
Highlights
The Th-U fuel cycle [1, 2] poses an alternative to the U-Pu fuel cycle for nuclear power, its relevant cross-sections have to be accurately known
A critical part in the analysis concerns the calculation of the detection efficiency of the fission chamber εF ICH which is based on the assumption that a fission event is detected independently by the TAC and the FICH
In order to obtain the shape of the TAC response to 233U(n,γ) events from the total measured sum energy spectra all background components have to be carefully subtracted
Summary
The Th-U fuel cycle [1, 2] poses an alternative to the U-Pu fuel cycle for nuclear power, its relevant cross-sections have to be accurately known. The αratio is defined as the ratio between the capture and fission cross section of an isotope. The fission cross section of 233U is well known but the available data for the 233U(n,γ) cross section are scarce [3]. The measurement of the 233U(n,γ) cross section relies on an efficient discrimination of the fission γ-rays from the capture events. Coupling a γ-ray detector with a fission detector allows to tag the γ-rays from fission and efficiently subtract them from the total measured spectra. A similar technique was used in several experiments [4,5,6,7,8]
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