A system for correlation measurement of fission fragments and prompt neutrons for thermal neutron induced fission

For the purpose of the correlation measurement of fission fragments and prompt neutrons for thermal neutron induced fission, a system consisting of two fragment detectors and a neutron detector was developed. In this system, one fission fragment was detected with a silicon surface barrier detector (SSBD) and the other with a specially designed parallel plate avalanche counter (PPAC). The PPAC had double structures, one for fast timing and the other for position detection. A prompt neutron emitted from a fragment with a specified mass was detected with an organic liquid scintillator (NE213) in this system. The SSBD supplied not only the energy signal of one fragment but also the start timing signal to the time-of-flight (TOF) measurements of the other fragment and the prompt neutron. We tried to carry out the fragment-neutron correlation measurement for 235U(nth, f) with this system, and succeeded in obtaining the neutron energy spectrum in the center-of-mass system and the neutron multiplicity depending on the fragment mass.