Neutron Generation in an Extended Cu Target Irradiated with 22 and 44 GeV Carbon Ions (Preliminary Results)

An extended Cu target was centrally irradiated with 22 and 44 GeV carbon ions for about 11 and 15 hours, respectively. The upper side of the target was in contact with a paraffin block for the moderation of secondary neutrons. Small holes in the moderator were filled with lanthanum salts (LaCl₃7H₂O) where the neutrons induced the ¹³⁹La(n,γ) ¹⁴⁰La reaction. The β-decay of ¹⁴⁰La(40h) was followed using radiochemical methods. The yields for the formation of ¹⁴⁰La agree within large errors with other experiments on extended targets carried out at the LHE, JINR (Dubna). To a first approximation, the breeding rate of ¹⁴⁰La doubles when the ¹²C energy is increased from 22 to 44 GeV. If results at 44 GeV are compared to those at 22 GeV, there cannot be excluded an excess of (20 ± 7)% in the experimentally observed ¹⁴⁰La production over theoretical estimates. A definite conclusion in this respect must await further experimental and theoretical work.

These experiments are the beginning of a research program to develop a subcritical reactor with neutron fluxes sufficiently high to permit the TRANSMUTATION of long-lived radioactive waste into short-lived or stable nuclei. Such transmutation would considerably relieve the ecological problems related to the final deposition of radioactive waste.