Description: We measured neutron beam fluxes at LANSCE using gold foil activation techniques. We did an extensive computer simulation of the as-built LANSCE Target/Moderator/Reflector/Shield geometry. We used this mockup in a Monte Carlo calculation to predict LANSCE neutronic performance for comparison with measured results. For neutron beam fluxes at 1 eV, the ratio of measured data to calculated varies from /approx/0.6-0.9. The computed 1 eV neutron leakage at the moderator surface is 3.9 /times/ 10/sup 10/ n/eV-sr-s-/mu/A for LANSCE high-intensity water moderators. The corresponding values for the LANSCE high-resolution water moderator and the liquid hydrogen moderator are 3.3 and 2.9 /times/ 10/sup 10/, respectively. LANSCE predicted moderator intensities (per proton) for a tungsten target are essentially the same as ISIS predicted moderator intensities for a depleted uranium target. The calculated LANSCE steady state unperturbed thermal (E < 0.625 eV) neutron flux (at 100 /mu/A of 800 MeV-protons) is 2 /times/ 10/sup 13/ n/cm/sup 2/-s. The unique LANSCE split-target/flux-trap-moderator system is performing exceedingly well. The system has operated without a target or moderator change for over three years at nominal proton currents of /approx/25 /mu/A of 800-MeV protons. 17 refs., 8 figs., 3 tabs.
Date: January 1, 1989
Creator: Russell, G.J.; Gilmore, J.S.; Robinson, H.; Legate, G.L.; Bridge, A.; Sanchez, R.J. et al.
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