Measurement of the 16O(n, α)13C cross-section using a Double Frisch Grid Ionization Chamber

The 16 O(n, α )13 C reaction was proposed to be measured at the neutron time-of-flight (n_TOF) facility of CERN. To this purpose, a Double Frisch Grid Ionization Chamber (DFGIC) containing the oxygen atoms as a component in the counting gas coupled with a switch device in order to prevent the charge collection from the so-called γ -flash has been developed at Helmholtz-Zentrum Dresden-Rossendorf (HZDR), in Germany. The first 16 O(n, α )13 C measurement without seeing the charge of the γ -flash at n_TOF has been performed in November 2018. After the electronics did not suffer from the y-flash any more, another huge charge collection was discovered. Due to the high instantaneous flux at the n_TOF facility [1] the amount of that induced charge from neutron induced background reactions was piling up so much that the recognition of 16 O(n, α )13 C reactions from that background was very difficult. For that reason another 16 O(n, α )13 C measurement at the time-of-flight facility nELBE at HZDR which has a low instantaneous flux [2], has been performed in April 2019. Both measurements from n_TOF and nELBE will be presented here.