Measurement of neutron-induced activation cross-sections using spallation source at JINR and neutronic validation of the Dubna code

A beam of 1 GeV proton coming from Dubna Nuclotron colliding with a lead target surrounded by 6 cm paraffin produces spallation neutrons. A Th-foil was kept on lead target (neutron spallation source) in a direct stream of neutrons for activation and other samples of ¹⁹⁷Au, ²⁰⁹Bi, ⁵⁹Co, ¹¹⁵In and ¹⁸¹Ta were irradiated by moderated beam of neutrons passing through 6 cm paraffin moderator. The gamma spectra of irradiated samples were analyzed using gamma spectrometry and DEIMOS software to measure the neutron cross-section. For this purpose neutron fluence at the positions of samples is also estimated using PREPRO software. The results of cross-sections for reactions ²³²Th(n, γ), ²³²Th(n, 2n), ¹⁹⁷Au(n, γ), ¹⁹⁷Au(n, α), ¹⁹⁷Au(n, xn), ⁵⁹Co(n, α), ⁵⁹Co(n, xn), ¹⁸¹Ta(n, γ) and ¹⁸¹Ta(n, xn) are given in this paper. Neutronics validation of the Dubna Cascade Code is also done using cross-section data by other experiments.      

Double-beta decay of 48Ca in the TGV experiment

The low-background, high-sensitivity Ge multidetector spectrometer TGV is used to study the double-beta decay of ⁴⁸Ca. Additional suppression of the recorded background is achieved with neutron shielding and a method for distinguishing β particles from γ rays by detector-pulse rise time. The estimates T _1/2 ^γγ2ν = (4.2 ± 2.4) × 10¹⁹ yr and T _1/2 ^γγ0ν > 1.5 × 10²¹ yr (at a 90% C.L.) for the double-beta decay of ⁴⁸Ca are obtained.     

Spallation neutron spectrum on a massive lead/paraffin target irradiated with 1 GeV protons

The gamma-ray spectra emitted by decaying of residual nuclei produced by spallation neutrons in (n, xn), (n, xnyp), (n, p), (n, ) reactions with activation threshold detectors, i.e. ²⁰⁹Bi, ¹⁹⁷Au, ⁵⁹Co, ¹¹⁵In, ²³²Th, were measured in the Laboratory of Nuclear Problems (LNP), JINR, Dubna, Russia. Spallation neutrons were generated by bombarding a 20 cm long cylindrical lead target with 8 cm diameter surrounded by a 6 cm thick layer of paraffin moderator with 1 GeV proton beam from the NUCLOTRON accelerator. Reaction rates and a spallation neutron spectrum were measured and compared with CASCADE code calculations.     

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.     

Isotopic Dependence of Fragment Production Cross Sections in the Reactions of Deuterons on Enriched Lead and Tin Isotopes

Physics of Atomic Nuclei - The isoscaling behavior of the fragment production cross section was studied for reactions with deuterons on enriched lead targets (204Pb, 206Pb, 207Pb, 208Pb). The...     

Investigation of the formation of residual nuclei from radioactive 237Np and 241Am targets in reactions with 660-MeV protons

The burning of radioactive waste is investigated. Targets from ²⁴¹Am and ²³⁷Np were irradiated with 0.66-GeV proton beams. The cross sections for the formation of 60 and 80 residual nuclei from ²³⁷Np and ²⁴¹Am are determined. The experimental results are compared with the theoretical cross sections calculated by the cascade-evaporation model.     

Properties of <Superscript>152</Superscript><Emphasis Type="Italic">Gd</Emphasis> collective states

The decays of ¹⁵²Tb (T _1/2 = 17.5 h) and ¹⁵²Gd excited states have been investigated by the analysis of -rays and -coincidences measured with the use of high-resolution HPGe detectors. The source of ¹⁵²Tb was prepared by chromatographic isolation followed by electromagnetic separation from a tantalum target irradiated by an internal proton beam of the LNP JINR phasotron. New and more precise data on the -transitions and excited states of ¹⁵²Gd are reported. Using previously published data on internal-conversion electrons many transition multipolarities are suggested, some of them with E0 admixture. The ratio was found for a number of low-lying levels, for most of the levels their spins, parities, and are given. The excited levels of ¹⁵²Gd were deduced from the analysis of -coincidences. The experimental level energies and reduced transition probabilities are compared with the calculations by phenomenological formulae as well as in the frameworks of theoretical models.Received: 21 May 2002, Revised: 26 May 2003, Published online: 18 November 2003PACS: 29.30.Kv X- and gamma-ray spectroscopy - 23.20.-g Electromagnetic transitions - 21.10.-k Properties of nuclei; nuclear energy levels - 21.60.-n Nuclear structure models and methodsJ. Adam: On leave from Nuclear Physics Institute of ASCR, e, Czech Republic.V.S. Pronskikh: On leave from Saint Petersburg State Institute of Technology, Russia     

Recoil products from p+118Sn and d+118Sn at 3.65 GeV/A

The recoil properties of the product nuclei from the interaction of 3.65-GeV/nucleon protons and deuterons from the Nuclotron and Synchrophasotron of the Laboratory of High Energies (LHE), Joint Institute for Nuclear Research (JINR) at Dubna, with a ¹¹⁸Sn target have been studied using catcher foils. The experimental data were analyzed using the mathematical formalism of the standard two-step vector model. The analysis of kinematical characteristics of the light and medium-mass reaction products confirmed the contribution of fragmentation (or multifragmentation) processes in the production of these nuclei. The comparison of the results for protons and deuterons was made. The longitudinal momenta transferred to the target in the interaction with protons and deuterons were similar and was shown to depend only on the velocity, but not on the mass of projectile. Three different Los Alamos versions of the quark—gluon-string model (LAQGSM) were used for the discussion of our experimental results. The text was submitted by the authors in English.     

Interaction of <Superscript>12</Superscript>C ions with nuclei of enriched tin isotopes at an energy of 2.2 GeV per nucleon

The formation cross sections for about 110 products of interaction between a ¹²C ion beam of energy 2.2 GeV per nucleon and tin targets from the isotopes ^{112,118,120,124}Sn were calculated. Massyield and charge distributions were obtained for ^112,118,124Sn targets. An analysis of these charge distributions reveals that the positions of their maxima, Z _p , are different for targets having different nucleon compositions. The formation cross sections for neutron-rich products originating from neutron-rich targets are found to increase in all product-mass regions considered in our study. Mass distributions are compared for proton-, deuteron- and ion-nucleus reactions.     

Transmutation of 239 Pu with spallation neutrons

Incineration studies of plutonium were carried out at the Synchrophasotron of the Joint Institute for Nuclear Research (JINR), Dubna, using proton beams with energies of 0.53 GeV and 1.0 GeV. Solid lead targets (8 cm in diameter and 20 cm long) were surrounded with 6 cm thick paraffin as neutron moderator and then irradiated. The transmutation of ²³⁹ Pu and the associated production of fission products ⁹¹ Sr, ⁹² Sr, ⁹⁷ Zr, ⁹⁹ Mo, ¹⁰³ Ru, ¹⁰⁵ Ru, ¹²⁹ Sb, ¹³² Te, ¹³³ I, ¹³⁵ I and ¹⁴³ Ce were studied in the present work. The plutonium samples (each 449 mg) were placed on the outer surface of moderator. For 1.0 GeV proton beam, the fission rate of ²³⁹ Pu is 0.0032 atoms per proton in one gram plutonium samples, for 0.53 GeV proton, this value is 0.0022. The experimental uncertainty is about 15%. The experiments are compared to two theoretical model calculations with moderate success, using the Dubna Cascade Model (CEM) and the LAHET code. The practical incineration rate of ²³⁹ Pu is very high. For example: if one uses 10 mA, 1 GeV proton beams under the same (fictive) experimental conditions, the incineration rate of ²³⁹ Pu via fission is 3 mg out of the 449 mg sample per day. For 0.53 GeV protons the corresponding rate is 2 mg per day.