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.      

Threshold for a cumulative resonant microwave streamer discharge in a high-pressure gas

Results are reported from experiments aimed at investigating how the structure of a microwave streamer discharge depends on the gas pressure. The formation of a bright core in the streamer channel is shown to be of a threshold nature: in discharges initiated in the field of a standing electromagnetic wave of an open two-mirror cavity, a bright core forms in air and hydrogen in the pressure ranges p ₀≥540±50 torr and p ₀≥740±70 torr, respectively. Estimates are presented, according to which the appearance of a bright core can be attributed to the onset of a local microwave pinch effect.     

Targets for accelerator-driven system SAD

Properties of several target designs for the accelerator-driven system being created in Dubna at the 660 MeV proton beam of the JINR phasotron are modeled by the Monte Carlo method. Heat generation and neutron, gamma-quanta and charged particles yields are discussed. It is shown that the 19-rod target currently considered as the basic one can be considerably simplified.     

Breakdown in air in a rising microwave field

Results are presented from studies of a high-pressure electrodeless breakdown in air at the focus of a standing wave in a high-Q quasi-optical two-mirror resonator pumped by single microwave pulses. In the experiment, the breakdown occurred at the front of the pulse of the resonator field. The breakdown field substantially exceeded the critical level and, under fixed conditions, showed a scatter from pulse to pulse. It is shown that the experimentally found excess in the threshold breakdown field over the critical level is due to the fact that the resonator field increases as a discharge plasmoid forms during breakdown and that the appearance of an electron initiating breakdown in a gas is a random event.     

Emission von Spallationsprodukten aus metallischen Targets

Emission of spoliation products with mass numbers A = 147 ? 173 from tantalum targets irradiated by 660 MeV protons has been investigated. Cascade-evaporation model calculations are compared to experimental results and data for smaller energies and various targets. Calculations are in agreement with experiments. Relations allowing to estimate the “practical range” of neutron deficient nuclides in thick targets have been obtained.     

Production of residual radioactive nuclei in thin <Superscript>209</Superscript>Bi, <Superscript>nat</Superscript>Pb, <Superscript>206</Superscript>Pb, <Superscript>207</Superscript>Pb,and <Superscript>208</Superscript>Pb targets bombarded with 0.04–2.6 GeV protons

The results of the experimental measurement and numerical simulation of the cross sections for residual radioactive nuclei production in thin ²⁰⁹Bi, ^natPb, ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb targets bombarded with protons in the energy range from 0.04 to 2.6 GeV are reported. The nuclide production cross sections were measured using γ spectrometry with a high-resolution Ge detector. The experimental data include a total of 5972 reaction cross sections at 11 proton energy values. The results are compared to the data from other laboratories reported in 80 papers. The model calculations were carried out using eight simulation code packages: LAHET, INCL4 + ABLA, CEM03, LAQGSM + GEM2, CASCADE, CASCADE-2004, CASCADO, and LAHETO. A detailed analysis of discrepancies between the measured and calculated data is presented.     

Multisoliton solutions in the scheme for unified description of integrable relativistic massive fields. Non-degeneratesl(2, ℂ) case

A scheme allowing systematic construction of integrable two-dimensional models of the Lorentz-invariant Lagrangian massive field theory is presented for the case when the associated linear problem is formulated onsl(2, ?) algebra. A natural dressing procedure is developed then for the generic system of two (either scalar or spinor) fields inherent in the scheme and an explicitN-soliton solution on zero background is calculated. Solutions of reduced systems which include both familiar and new equations are extracted from the solution of the generic system, not all of these reductions being related immediately tosl(2, ?) real forms. Finally, in the case of scalar equations we present the Miura-type transformations relating solutions with different boundary conditions.     

Inelastic interactions of high energy nucleons with heavy nuclei

The intranuclear cascade model including the effect of changes in the properties of the target nucleus due to development of the shower of cascade particles is applied to calculations of the interactions of protons with fissioning nuclei in the energy region T ≈ 0.1–30 GeV. The fission cross sections, yields of different isotopes after the evaporation stage, and the characteristics of accompanying particles are calculated. The properties of the excited evaporating and fissioning nuclei are discussed. The calculated results are compared with experiment.