Eur. Phys. J. A (2011) 47: 70
https://doi.org/10.1140/epja/i2011-11070-y

Regular Article - Experimental Physics

Secondary neutrons as the main source of neutron-rich fission products in the bombardment of a thick U target by 1 GeV protons

¹ Petersburg Nuclear Physics Institute RAS, 188300, Gatchina, Russia
² GANIL, F-14076, Caen Cedex 5, France
³ INFN Laboratori Nazionali di Legnaro, 35020, Legnaro, Padova, Italy
⁴ National Institute for Physics and Nuclear Engineering “Horia Hulubei”, 407 Atomistilor st., 077125, Magurele, Bucharest, Romania

^* e-mail: barzakh@mail.ru

Received: 26 November 2010
Revised: 7 February 2011
Accepted: 16 April 2011
Published online: 31 May 2011

Abstract

The diffusion-effusion model has been used to analyse the release and yields of Fr and Cs isotopes from uranium carbide targets of very different thicknesses (6.3 and 148 g/cm²) bombarded by a 1 GeV proton beam. Release curves of several isotopes of the same element and production efficiency versus decay half-life are well fitted with the same set of parameters. Comparison of efficiencies for neutron-rich and neutron-deficient Cs isotopes enables separation of the contributions from the primary (p + ²³⁸U) and secondary (n + ²³⁸U) reactions to the production of neutron-rich Cs isotopes. A rather simple calculation of the neutron contribution describes these data fairly well. The FLUKA code describes the primary and secondary-reaction contributions to the Cs isotopes production efficiencies for different targets quite well.