A low background detection system for fragments and neutrons from spontaneous fission sources

Abstract A low background system for the detection and characterization of spontaneously fissioning nuclides has been developed. It allows the simultaneous registration of single and coincident fission fragments and their kinetic energies, and of the number of neutrons emitted per fission event together with the time intervals between fission-fragment and neutron pulses. In addition, α-particle spectra can also be measured. The system consists of six pairs of surface barrier detectors surrounded by 30 3 He-filled neutron counters embedded in paraffin. It is placed between two large plastic scintillation detectors in order to identify cosmic-ray induced background events. The detector assembly has been used in the search for superheavy elements in reactions of 238 U projectiles with 238 U and 248 Cm targets and of 48 Ca with 248 Cm at production rates of a few atoms per experiment.