Measurement of TOF of fast neutrons with 238U target

Abstract: We developed a Dual-PPACs detector for fast neutron measurements that consists of two sets of PPAC: conventional PPAC and fission PPAC. A 238U(U3O8) coating is placed in the fission PPAC’s anode, which is used as the neutrons conversion layer. An experiment was performed to measure neutron time-of-flight (TOF) in which 252Cf spontaneous fission source was used. An excellent time resolution of 164ps has been observed at 6mbar in isobutene gas. With the excellent time resolution of Dual-PPACs detector, exact neutron energy can be extracted from the timing measurement. The experimental detection efficiency was 1.9×10-7, consistent with the efficiency of 2.5×10-7 given by a Geant4 simulation. Ultimately, the results show that the Dual-PPACs detector is a suitable candidate for measuring fast neutrons in the future CiADS system.