Commissioning of the third n_TOF spallation target: characterization of the neutron flux and beam profile using PPACs

Beyond their application in fundamental nuclear physics and nuclear astrophysics research, neutron-induced reactions play an increasingly important role in emerging nuclear technologies. For instance, in the fields of sustainable low-carbon power production (ADS, generation four fission and fusion reactors), medicine and industry, neutron data are required with high accuracy in a wide energy range. The measurement of neutron-induced reaction cross sections is therefore crucial and it is indeed the main objective of the n_TOF facility, a pulsed white neutron spallation source at CERN. Recently the facility has been upgraded with the installation of its new third-generation spallation target and a subsequent commissioning was carried out in order to characterize the performances of the experimental areas in terms of neutron flux, energy resolution and background in view of the future experimental campaigns. I was involved in the first phase of the commissioning at CERN, testing the DAQ system and taking care in particular of one of the employed detectors: a fission chamber based on Parallel Plate Avalanche Counters (PPACs). The data collected in the first experimental area (EAR1) were analyzed to obtain the neutron flux from near thermal energy (0.025 eV) to 1 GeV and the spatial beam profile. The flux from the present analysis is compared to the Monte Carlo simulations and to the preliminary results of another flux detector, while the spatial beam profile is compared to the one obtained with a Timepix Quad detector. In addition, a preliminary analysis of the data collected in the second experimental area (EAR2) was also carried out.