The neutron capture cross section of 238U is fundamental to the design and operation of current reactors and future fast nuclear reactors, and thus must be measured to a high level of accuracy. An experiment has been performed at the CERN n TOF facility using a 4π Total Absorption Calorimeter (TAC) to measure the capture cross section in the resolved resonance region between 1 eV and 25 keV.
A preliminary analysis of the TAC data is presented with particular emphasis to the experimental background in this energy region of interest.