10 research outputs found
Modelling of an imaging beamline at the ISIS pulsed neutron source
A combined neutron imaging and neutron diffraction facility, IMAT, is currently being built at the pulsed neutron spallation source ISIS in the U.K. A supermirror neutron guide is required to combine imaging and diffraction modes at the sample position in order to obtain suitable time of flight resolutions for energy selective imaging and diffraction experiments. IMAT will make use of a straight neutron guide and we consider here the optimization of the supermirror guide dimensions and characterisation of the resulting beam characteristics, including the homogeneity of the flux distribution in space and energy and the average and peak neutron fluxes. These investigations take into account some main design criteria: to maximise the neutron flux, to minimise geometrical artefacts in the open beam image at the sample position and to obtain a good energy resolution whilst retaining a large neutron bandwidth. All of these are desirable beam characteristics for the proposed imaging and diffraction analysis modes of IMAT
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MCNP calculations for Russian criticality-safety benchmarks
The current edition of the International Handbook of Evaluated Criticality Safety Benchmark Experiments contains evaluations of 20 critical experiments performed and evaluated by the Institute for Experimental Physics of the Russian Federal Nuclear Center (VNIIEF) at Arzamas-16 and 16 critical experiments performed and evaluated by the Institute for Technical Physics of the Russian Federal Nuclear Center (VNIITF) at Chelyabinsk-70. These fast-spectrum experiments are of particular interest for data testing of ENDF/B-VI because they contain uranium metal systems of intermediate enrichment as well as uranium and plutonium metal systems with reflectors such as graphite, stainless steel, polyethylene, beryllium, and beryllium oxide. This paper presents the first published results for such systems using cross-section libraries based on ENDF/B-VI