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 an d prompt neutrons for thermal neutron induced fission, a system consis ting of two fragment detectors and a neutron detector was developed. I n this system, one fission fragment was detected with a silicon surfac e barrier detector (SSBD) and the other with a specially designed para llel plate avalanche counter (PPAC). The PPAC had double structures, o ne for fast timing and the other for position detection. A prompt neut ron 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 cor relation measurement for U-235(n(th), f) With this system, and succeed ed in obtaining the neutron energy spectrum in the center-of-mass syst em and the neutron multiplicity depending on the fragment mass.