Th-U cycle elements measured at the n-TOF facility at CERN

One of the central goals of the EC-project n-TOF-ND-ADS was the measurement of capture, fission and (n,xn) cross sections relevant for the Th-U cycle. So far a complete analysis of the radiative neutron capture data of 232Th in the energy region between 1keV and 1MeV was performed. The data were normalised to the pair of saturated resonances at 20 eV and the uncertainties due to pulse height weighting technique, background due to scattered neutrons and in-beam γ-rays, multiple scattering and self absorption, finite energy resolution, isotopic composition, beam fraction and its energy dependence were taken into account. The statistical uncertainties are in average of the order of 1.5% while the systematic errors are typically at about 6%. A complete covariance matrix of the uncertainties has been determined. The analysis of the resonance region is still pending, but first resonance analyses with SAMMY of the resonance region between 1 and 10 eV are very promising. Extended measurements of the 232Th(n,f) reaction with the PPAC detectors were performed in the measurement campaigns of 2002 and 2003 and the analysis of the data is still going on. Furthermore first measurements of the 232Th(n,3n) and 232Th(n,5n) cross sections via prompt γ-spectroscopy were performed at the facility at Louvain-la-Neuve. At present the analysis of these data is still in progress. During the measurement campaign in 2003 the reactions 236U(n,f) and 234U(n,f) have been measured with the FIC and the latter also with the PPAC. For both data sets the analyses are in progress and only preliminary results are available. With the start of the measurement campaign 2004 a new 4π total absorption calorimeter (TAC) with 40 BaF2 crystals has been in operation. The new detector significantly improves the capability for capture measurements of small capture cross sections. First measurements of the radiative neutron capture of 243Am show high sensitivity of the detector system and the excellent energy resolution. During the campaign 2004 the TAC has been used to take data on radiative capture of 233U, 234U, 237Np, 240Pu and 243Am. Due to the new detector system the analyses will take some time because all features of the TAC have to be established before.