Institution: | * Flerov Laboratory for Nuclear Reactions, Joint Institute for Nuclear Research, Dubna, Russia ? Centre de Recherche Nucleaires, Strasburg, France ? Physics Department, University for Rail Transport Engineers, Moscow, Russia § Kernchemie, F.B. 14, Philipps-University, Marburg, Germany | Laboratory for High Energies, Joint Institute for Nuclear Research, Dubna, Russia ¶ Institute of High Energy Physics, Academia Sinica, Beijing, China ** Department of Chemistry, North-Eastern Hill University, Shillong, India ?? Nuclear Science Division, Lawrence Berkeley Laboratory, University of California, Berkeley, U.S.A. ?? Institute of Atomic Energy, Beijing, China §§ Physics Department, Aristotle University of Thessaloniki, Thessaloniki, Greece |
Abstract: | An extended Cu-target was irradiated with 22 and 44 GeV carbon ions. The target was in contact with a (CH2)n-block for the moderation of secondary neutrons. Small holes in the moderator were filled with either lanthanium salts or uranium oxide. The reaction 139La (n,γ) 140La
was studied via the decay of 140La (40 h), and the reaction 238U (n, γ) 239U
239Np
was studied via the decay of 239Np (2.3 d). In addition, a variety of solid state nuclear track detectors (SSNTD) were used. Results will be presented. The yields for the formation of (n, γ) products agree essentially with other experiments on extended targets carried out at the Synchrophasotron LHE, JINR (Dubna). To a first approximation, the breeding rate of (n, γ) products, as well as the specific track density, seen with several SSNTDs, doubles when the carbon energy is increased from 22 to 44 GeV. If, however, results at 44 GeV are compared in detail to those at 22 GeV, we observe an excess of (37 ± 9) % in the experimentally observed 239Np-breeding rate over theoretical estimations. Experiments using solid state nuclear track detectors are giving similar results. We also observed in the past such excess in the yield of other secondary particles in relativistic heavy ion interactions above a total energy of approximately 35–40 GeV. |