Studying fission neutrons with 2E-2v and 2E

¹ Department of Physics and Astronomy, Uppsala University, Sweden
² European Commission, Joint Research Centre, Directorate G-2, Geel, Belgium
³ GANIL CEA/DRF-CNRS/IN2P3, Caen, France

^* e-mail: ali.al-adili@physics.uu.se

Published online: 6 March 2018

Abstract

This work aims at measuring prompt-fission neutrons at different excitation energies of the nucleus. Two independent techniques, the 2E-2v and the 2E techniques, are used to map the characteristics of the mass-dependent prompt fission neutron multiplicity, v(A), when the excitation energy is increased.

The VERDI 2E-2v spectrometer is being developed at JRC-GEEL. The Fission Fragment (FF) energies are measured using two arrays of 16 silicon (Si) detectors each. The FFs velocities are obtained by time-of-flight, measured between micro-channel plates (MCP) and Si detectors. With MCPs placed on both sides of the fission source, VERDI allows for independent timing measurements for both fragments. ²⁵²Cf(sf) was measured and the present results revealed particular features of the 2E-2v technique. Dedicated simulations were also performed using the GEF code to study important aspects of the 2E-2v technique. Our simulations show that prompt neutron emission has a non-negligible impact on the deduced fragment data and affects also the shape of v(A). Geometrical constraints lead to a total-kinetic energy-dependent detection efficiency.

The 2E technique utilizes an ionization chamber together with two liquid scintillator detectors. Two measurements have been performed, one of ²⁵²Cf(sf) and another one of thermal-neutron induced fission in ²³⁵U(n,f). Results from ²⁵²Cf(sf) are reported here.