We have calculated the performance of five similar target-moderator-reflector geometries that are reasonably well optimized for long-pulse source applications. For all cases, the moderators are fully coupled; that is, no poisons, decouplers, or liners are used. For each case, the energy- and time-dependent characteristics of the moderator source brightness have been parameteterized using empirical functions. These parameterizations have been made available to users of the Monte Carlo neutron scattering instrument design code MCLIB for use in evaluating the performance of neutron scattering instruments on a long-pulse source.

The facilities at the Los Alamos Neutron Science Center are described first. The target is being redesigned so that the Flight Paths (FP) in the upper tier provide a higher intensity in the epithermal and medium energy range. It is found that a 3-piece design looks promising: intensity in epithermal and medium energy range in upper tier is an order of magnitude higher than current Mark III, and intensity in the thermal energy range is higher in the lower tier than current Mark III. Time emission spectra show a bump due to the scattering of fast neutrons. Other investigations such as the addition of wings around the upper target will be conducted.

In the present work, the target station of the accelerator-driven neutron source HBS is optimized in comprehensive parameter studies using the Monto-Carlo method. The dependence of the most important performance characteristics of such a system on the external parameters is investigated neglecting technical and mechanical limitations. In this way, qualitative and quantitative statements for all possible configurations and envisaged applications can be derived and should be considered in the detailed planning of such facilities. For this purpose, different scenarios are considered that place completely different requirements on the design of the target station. The central statements derived in this thesis can be transferred to any framework conditions, such as different accelerator energies, so that these results can be used in the development of other neutron sources, which together with the HBS form a European network and provide a prosperous community in neutron science.

We report the calculated results of neutronic performance of cold moderators in a reference target-moderator-reflector system at the projected 5 MW pulsed spallation neutron source in Japan Atomic Energy Research Institute (JAERI). The cold neutron intensities in present reference model are about 2.3-2.5 times higher than that from the decoupled solid methane (S-CH4) and close to the values obtained at other facilities (LANSCE Upgrade, NSNS, etc.). The H2O premoderator (PM) reduces the energy deposition in a liquid-hydrogen (L-H2) moderator by about a factor of 2 compared with that in a decoupled L-H2 moderator. The dependence of reflector on the neutron intensity and the energy deposition in the cryogenic moderators is also discussed. Although the pulse shapes were not obtained because of time consuming Monte Carlo calculations, we will discuss the pulse shapes based on experiments. (auth).