V. M. Tsoupko-Sitnikov

Measurement of the neutron fluence on the spallation source at Dubna

Abstract A 232Th activation sample was exposed directly to the spallation neutrons produced by 1GeV proton colliding with a lead target and other samples of 197Au, 209Bi, 59Co, 115In and 181Ta were irradiated by moderated neutrons after passing through 6 cm of paraffin. Different (n, γ) and (n, xn) reaction products in 232Th, 197Au and 209Bi samples are analyzed by gamma-ray spectrometry to measure the neutron fluence at the positions of the samples. For this purpose a histogram of ‘flat’ spectrum averaged neutron cross-sections in over thirty given energy groups was determined from the PREPRO-2000 software. Results of measurements are compared with Monte-Carlo simulations by the Dubna CASCADE code. Experimental values for both spallation and moderated neutron fluences are in reasonable agreement with the CASCADE code. Thus, the experimentally measured fluence of moderated neutrons was used to infer the ‘one group’ reaction cross-sections of 209Bi (n, xn) reactions for x = 6 to 9.

Formation of Light Isotopes by Protons and Deuterons of 3.65 GeV/nucleon on Separated Tin Isotopes

We measure cross sections for residual nuclide formation in the mass range 7 ≤ A ≤ 96 caused by bombardment with protons and deuterons of 3.65-GeV/nucleon energy of enriched tin isotopes (112,118,120,124Sn). The experimental data are compared with calculations by the codes FLUKA, LAHET, CEM03, and LAQGSM03. Scaling behavior is observed for the whole mass region of residual nuclei, showing a possible multifragmentation mechanism for the formation of light products (7 ≤ A ≤ 30). Our analysis of the isoscaling dependence also shows a possible contribution of multifragmentation to the production of heavier nuclides, in the mass region 40 ≤ A ≤ 80.

Precision half-life measurement of 140La with Ge-detector

Abstract Half-life is one of the fundamental properties of radioactive nuclei, and the precision required for its numerous applications in modern physics sometimes approaches the level of 10−4–10−5. Most part of the T1/2 measurements performed up to now was made with proportional chambers, and the results were sometimes hardly reproducible within the error limits. Using Ge-detectors for that purpose brought some significant advantages but electronic unit related effects and spectra analysis procedures still remain the sources of the errors influencing the accuracy of the T1/2 attained. In this work, 140 La samples were obtained in the 139 La(n,γ) 140 La reaction, employing a microtron as a neutron source and the half-life measurements were performed with a HPGe-detector. Influencing factors such as photopeak and background shape, electronic circuitry dead time and deadtime variations during the measurements, as well as pulse pileup are studied altogether. Values of the 140 La T1/2=1.6808(18) d, λ=0.47749(20)×10−5, agreeing within the uncertainities with the most accurate evaluated ones (T1/2=1.6781(3) d, λ=0.47807(9)×10−5) [2] were obtained in two series of measurements.

Studies of deuteron and neutron cross-sections important for ADS research

The collaboration Energy and Transmutation of Radioactive Waste uses different setups consisting of lead, natural uranium and graphite irradiated by relativistic protons and deuterons to study transmutation of radioactive materials by produced neutrons. The activation samples are used to determine integral of proton or deuteron beams and also produced neutron flux in different places of experimental set-ups. Unfortunately almost no experimental cross-section data for deuterons with GeV energies are available. The similar situation is also for threshold (n,xn) reactions of neutrons with higher energies. Therefore we carried out series of experiments devoted to determination of deuteron reactions on copper during uranium target QUINTA irradiations by deuterons with energies from 1 GeV up to 8 GeV. The cross-sections of various threshold reactions were studied by means of different quasi-monoenergetic neutron sources with possible energies from 14 MeV up to 100 MeV. Knowledge of such cross-sections is very important for all Accelerator Driven System studies.

Transmutation of 129I with High Energy Neutrons Produced in Spallation Reactions Induced by Protons in Massive Target

We studied the yields of several short half-life iodine isotopes produced by transmutation of long half-life iodine isotopes obtained from nuclear reactor waste products. Transmutation was induced by high energy neutrons produced in a lead spallation target with relativistic primary protons (1, 3 and 2, 5 GeV). The yields were determined by analyses of γ-spectra of produced isotopes. The spatial distribution of high-energy neutron field surrounding the target was determined using the activation method. All experimental results were compared with Monte Carlo simulations provided by the LAHET code.

Experimental studies and simulations of spallation neutron production on a thick lead target

An intensive beam of 660 MeV protons from the Dubna Phasotron was directed towards a thick, lead target (not surrounded by shielding or neutron reflector) for 10 minutes. Detectors and iodine samples were placed around the target. The neutron field and the transmutation of 129I were studied by the Activation Analysis Method. MCNPX v.2.4.0 was used to simulate the experimental setup. The results of the simulations were compared to the experimental values, and the influence of the setup parts to the neutron field was explored.

Target residues formed in the 4.4 GeV deuteron-induced reaction on gold

A. R. Balabekyan, N. A. Demekhina, G. S. Karapetyan, D. R. Drnoyan, V.I.Zhemenik, J.Adam, L.Zavorka, A.A.Solnyshkin, V.M.Tsoupko-Sitnikov, J.Khushvaktov, L. Karayan, A. Deppman, V. Guimarães a) Yerevan State University A. Manoogian, 1, 025, Yerevan, Armenia b) Yerevan Physics Institute, Alikhanyan Brothers 2, Yerevan 0036, Armenia Joint Institute for Nuclear Research (JINR), Flerov Laboratory of Nuclear Reactions (LNR), Joliot-Curie 6, Dubna 141980, Moscow region Russia c) Instituto de Fisica, Universidade de São Paulo Rua do Matao, Travessa R 187, 05508-900 São Paulo, SP, Brazil d) Joint Institute for Nuclear Research (JINR), Laboratory of Nuclear Problems (LNP), Joliot-Curie 6, Dubna 141980, Moscow region Russia

Comparison between experimental data and Monte-Carlo simulations of neutron production in spallation reactions of 0.7-1.5 GeV protons on a thick, lead target

Relativistic protons with energies 0.7-1.5 GeV interacting with a thick, cylindrical, lead target, surrounded by a uranium blanket and a polyethylene moderator, produced spallation neutrons. The spatial and energetic distributions of the produced neutron field were measured by the Activation Analysis Method using Al, Au, Bi, and Co radio-chemical sensors. The experimental yields of isotopes induced in the sensors were compared with Monte-Carlo calculations performed with the MCNPX 2.4.0 code.

Investigation of the Formation of Residual Nuclei in Reactions Induced by 660 MeV Protons Interacting with the Radioactive 237Np, 241Am and 129I Targets

241Am, 237Np and 129I radioactive targets were irradiated by proton beams with energy 0.66 GeV. The cross- sections of formation of 80, 53 and 86 residual nuclei from 241Am, 237Np and 129I are determined. The experimental results are compared with the theoretical cross-sections calculated by the cascade-evaporation model (CEM).

Recoil studies in the reaction of 12C ions with the enriched isotope 118Sn

The recoil properties of the product nuclei from the interaction of 2.2 GeV/nucleon 12C ions from Nuclotron of the Laboratory of High Energies, Joint Institute for Nuclear Research at Dubna with a 118Sn target have been studied via catcher foils method. The experimental data were analyzed using the mathematical formalism of the standard two-step vector model. The results for 12C ions are compared with those for deuterons and protons. Three different Los Alamos versions of the Quark-Gluon String Model were used for comparison with our experimental data.