NEUTRON GENERATION IN MASSIVE CU-TARGETS DURING THE IRRADIATION WITH 22-GEV AND 44-GEV CARBON-IONS

An extended Cu-target was irradiated with 22 and 44 GeV carbon ions fo r about 11.3 and 14.7 hours, respectively. The upper side of the targe t was in contact with a paraffin-block for the moderation of secondary neutrons. Small holes in the moderator were filled with either lantha num salts or uranium oxide. The reaction La-139(n,gamma)La-140(beta-)- -> studied via the decay of La-140(40 h) using radiochemical methods, as has been published. The reaction U-238(n,gamma)U-239(beta-)-->Np-23 9(beta-)--> was studied via the decay of Np-239(2,3d) as well as the r eaction U(n,f) using radiochemical methods. In addition, solid state n uclear track detectors were used for fission studies in gold. The yiel ds for the formation of(n,gamma) products agree essentially with other experiments on extended targets carried out at the Dubna Synchrophaso tron (LHE, JINR). To a first approximation, the breeding rate of (n,ga mma) products doubles when the carbon energy increases from 22 to 44 G eV. 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 observe d Np-234-breeding rate over theoretical estimations. Experiments using solid state nuclear track detectors give similar results. We present a conception for the interpretation of this fact: There is the evident connection between anomalies we observe in the yield of secondary par ticles in relativistic heavy ion interactions above a total energy of approximately 30-35 GeV and increased yield of neutrons in this energy region.