Multi-section fission ionization chamber for measurement of 239Pu(n,γ) reaction in fission tagging method

The 239Pu(n,γ) reaction cross section is very important for operation of both thermal and fast reactors, when loaded with MOX fuels. According to the NEA/OECD High Priority Request List the precision of cross section data for this reaction should be improved. The cross section of (n,f) reaction is much higher compared to (n,γ) for this isotope. In such conditions the fission tagging technique could be applied to identify the fission background. In the past, this technique was successfully used for capture measurements at the n_TOF facility at CERN. The multi-section fission ionization chamber was constructed and used in the combination with Total Absorption Calorimeter (TAC) for detecting gamma rays for the precise measurement of 239Pu(n,γ) reaction cross section at the n_TOF facility.