Study of (n,2n) reaction on ^191,193Ir isotopes and isomeric cross section ratios

¹ Department of Physics, National Technical University of Athens, Athens, Greece
² Hellenic Army Academy, Athens, Greece
³ Department of Physics, University of Ioannina, Ioannina, Greece
⁴ Institute of Nuclear and Particle Physics, NCSR “Demokritos”, Athens, Greece

^a e-mail: vlastou@central.ntua.gr

Published online: 13 September 2017

Abstract

The cross section of ¹⁹¹Ir(n,2n)¹⁹⁰Ir^g+m1 and ¹⁹¹Ir(n,2n)¹⁹⁰Ir^m2 reactions has been measured at 17.1 and 20.9 MeV neutron energies at the 5.5 MV tandem T11/25 Accelerator Laboratory of NCSR “Demokritos”, using the activation method. The neutron beams were produced by means of the ³H(d,n)⁴He reaction at a flux of the order of 2 × 10⁵ n/cm²s. The neutron flux has been deduced implementing the ²⁷Al(n,α) reaction, while the flux variation of the neutron beam was monitored by using a BF3 detector. The ¹⁹³Ir(n,2n)¹⁹²Ir reaction cross section has also been determined, taking into account the contribution from the contaminant ¹⁹¹Ir(n,γ)¹⁹²Ir reaction. The correction method is based on the existing data in ENDF for the contaminant reaction, convoluted with the neutron spectra which have been extensively studied by means of simulations using the NeusDesc and MCNP codes. Statistical model calculations using the code EMPIRE 3.2.2 and taking into account pre-equilibrium emission, have been performed on the data measured in this work as well as on data reported in literature.