Abstract
The prompt neutron emission in thermal neutron induced fission of 235U and spontaneous fission of 252Cf was investigated by using digital signal electronics. The goal was to check a new revised data analysis software with fission fragment (FF) kinetic energy corrections after prompt fission neutron (PFN) emission. The revised software was used to reanalyze old data measured in EC-JRC-IRMM, where 252Cf(sf) reaction was investigated. Both measurements were done using similar twin Frisch grid ionization chamber for fission fragment detection with equivalent NE213 fast neutron detector. About 0.5*106 FF with PFN coincidences have been analyzed in both measurements. The fission fragment kinetic energy, mass and angular distribution were investigated along with prompt neutron time of flight and pulse shape analysis using a six channel synchronous waveform digitizer (WFD) with sampling frequency of 250 MHz and 12 bit resolution in the 235U(nth,f) reaction. Similar WFD with sampling frequency of 100 MHz was used for PFN investigation in 252Cf(sf) reaction. These two experiments were considered as a reference for further investigations with a new setup composed of position sensitive ionization chamber to detect FF and an array of 32 liquid scintillators recently constructed in Dubna to detect neutrons.
Highlights
The nuclear fission is considered as the process of a charged drop evolving under the competition between attractive nuclear and repulsing coulomb forces, leading eventually to the split of the nucleus mainly into two parts of comparable masses
In this work we report results of prompt fission neutron (PFN) investigation in thermal neutron-induced fission of 235U and spontaneous fission of 252Cf
The average PFN emission dependence on fission fragment (FF) mass and TKE are presented in Fig. 3 and Fig. 4 for 235U(nth,f) and 252Cf(sf) respectively
Summary
The nuclear fission is considered as the process of a charged drop evolving under the competition between attractive nuclear and repulsing coulomb forces, leading eventually to the split of the nucleus mainly into two parts of comparable masses. The main part of FF excitation energy is released by the prompt fission neutrons, emitted by FF after full acceleration by coulomb forces. The studies of PFN emission in fission induced by neutrons from energies extending from resonances up to a few MeV could possibly contribute to better understanding the mechanism of PFN emission from the excited FF. The experiments on sub-barrier fission, induced by thermal neutrons are of particular interest because no measurements were done so far on mass and energy distributions for this systems [2]. In this work we report results of PFN investigation in thermal neutron-induced fission of 235U and spontaneous fission of 252Cf. The main goal of the experiments was the feasibility check of the apparatus and the data analysis procedure
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