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Ion interpenetration, stagnation, and energization processes are studied in colliding laser-produced plasma configurations relevant to Trident [R. G. Watt, Rev. Sci. Instrum. 64, 1770 (1993)] experiments using four different numerical methods: one-dimensional Monte Carlo and Lagrangian multifluid codes, and one- and two-dimensional hybrid (particle ions, fluid electrons) and single-fluid Lagrangian codes. Results from the four methodologies are compared for plasmas generated with gold and deuterated polyethylene (CD2) targets. Overall, the various codes give similar results concerning the initial expansion of the plasmas and their collisional interaction, the degree of stagnation, stagnation time, and amount of ion thermalization for gold targets, while multispecies techniques indicate a much softer stagnation for CD2 plasmas than the single-fluid model. Variations in the results of the calculations due to somewhat different initializations and parameters, as well as to different physics in the codes, are discussed.

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The methods and results of benchmark experiments and calculations of the transport of 137 Cs, 60 Co, and 22 Na photons in iron, lead, bismuth, tungsten, and uranium are described. The results are photon spectra which served as the basis for determining the photon absorption coefficients in a wide geometry and the accumulation factors. A comprehensive analysis of the experimental and computational results revealed the regularities in the differences between the experimental and computational photon abosrption coefficients in a wide geometry.The problem of benchmark experiments on ionizing radiation transfer in the protective and structural components of nuclear facilities consists in obtaining reference experimental data for testing computational programs and constants libraries [1]. Attention is focused mainly on neutron transport because of the importance of neutron constants for calculating nuclear reactors, substantiating nuclear radiation safety, and radiation materials engineering. As a rule, sources of mixed neutron-photon radiation, which on the basis of the type of source corresponds to radiation from a nuclear reactor, are used in benchmark experiments. The results of such experiments are, ordinarily, neutron energy spectra; in rare cases the photon spectra are measured simultaneously with the neutron spectra. Of greatest value for testing radiation transfer constants are benchmark experiments in a one-dimensional geometry with spherical models radionuclide sources of radiation are placed at the center.The photon transport constants in iron and lead, which are most often used for shielding, for photons emitted from 137 Cs and 60 Co are of great importance. As a rule, these radionuclides determine the radiation properties of spent nuclear fuel and radioactive wastes as sources of γ radiation. Bismuth, tungsten, and uranium are also used as shielding from γ radiation.The present paper is devoted to a description of a method for performing and the results from benchmark experiments and calculations on the transport of 137 Cs, 60 Co, and 22 Na photons in iron, lead, bismuth, tungsten, and uranium in one-, two-and three-dimensional geometries. The spectra obtained were used to determine the absorption coefficients and the total photon fluxes.Importance of the Problem. The transfer of 0.5-10 MeV photons in matter in application to the physics of shielding was studied in the 1940s-1970s [2]. The basic data include, first and foremost, the interaction constants for photons interacting with matter and the accumulation factors obtained experimentally using integral detectors or theoretical methods. It should be noted that in the reference literature the differences between such constants can reach several percent (Table 1).At the present time, as a rule, spectrometers are used instead of integral-type instruments in experiments on γ-ray transfer. For example, an experiment where a wide-beam geometry was realized and the absorption coefficients for 137 Cs and 60 Co photons were obtained for 11 materials, includ...