RECENT RESULTS FROM INVESTIGATION OF PROMPT FISSION NEUTRON EMISSION IN SPONTANEOUS FISSION OF ~(252)CF

摘要

The main motivation of the present work was investigation of the nature of anomalous (from the point of view of modern theory) dependence of the average prompt fission neutron number on the total kinetic energy of the fission fragments using modern digital signal processing approach. A twin Frisch-grid ionization chamber was used for fission fragment mass and kinetic energy spectroscopy. A fast neutron detector with NE213 (or analog) scintillation liquid was used for prompt fission neutron time of flight measurement. About 10~7 fission events, coinciding with prompt fission neutron detection was acquired in the experiment. Correlated fission fragment kinetic energies, their masses, an angle between fission axis and the prompt fission neutron, the prompt fission neutron velocity were measured with help of eight channel set-up of synchronized waveform digitizers, having 100 MHz sampling frequency and 12-bit pulse height resolution. Analysis of the acquired data revealed effects causing distortion of measured angular distribution of prompt fission neutron and the dependence of their average number on total kinetic energy of the fission fragment. Special modification of the experiment and respective modifications in the data analysis procedure brought to reasonable agreement between experimental results and theoretical calculations. In the first time the linear dependence of the average number of prompt fission neutron on total kinetic energy in the range of (140 - 220) MeV was demonstrated. The long time existing contradiction between experiment and theory was resolved and, a new measurement procedure allowing avoidance of above mentioned systematic errors in experiments with actinide targets like ~(235)U, ~(239)Pu, etc. was proposed.