First nuclear activation experiments using the new accelerator NUCLOTRON in Dubna

Abstract

Abstract First nuclear activation experiments have been carried out using the new accelerator for relativistic particles NUCLOTRON in Dubna. The distribution of neutrons emitted during the irradiation with 0.65, 1.0 and 1.5 GeV protons from a lead target (∅ = 8 cm, l = 20 cm) and moderated by surrounding paraffin of 6 cm thickness was studied with radiochemical sensors along the beam axis on top of the moderator. Small 139Lasensors of approximately 1 g each were used to measure essentially the thermal neutron fluence at different depths near the surface: i. e. on top of the moderator, in 10 mm deep holes and in 20 mm deep holes, respectively. The reaction 139La (n, γ) 140La (τ1/2 = 40.27 h) was studied using standard procedures of gamma-ray spectrometry and data analysis. The induced activity of 140La increases strongly with the depth of the hole inside the moderator. Its activity distribution along the beam direction on top of the moderator has its maximum about 10 cm downstream the entrance of the protons into the lead and the activity increases about linearily with the proton energy. Some comparisons of the experimental results with model estimations based on the LAHET code are also presented. The experiments were carried out in the Veksler and Baldin Laboratory of High Energies of the Joint Institute for Nuclear Research in Dubna, Russian Federation.