How to optimize pulse shape

It is very important to place moderators with pulse characteristics suitable for the neutron scattering spectrometers to construct a high performance spallation neutron source. However, choice of the moderators is rather complicated problem since the requirement from the spectrometer side is not unique and also no single moderator can satisfy the requirements although there are various kinds of moderator types giving a variety of neutronic characteristics. Therefore, to decide moderator types, we need to know the information of both neutronics and spectrometers. We have indicated that the pulse characteristics are affected by the type of moderator (coupled or decoupled), the choice of reflector material and decoupler, and so on. Here, we explain the methods to control the pulse characteristics and also show various neutronic characteristics we can obtain, in order to offer the data for the discussion of the moderator characteristics suitable for the instruments. (author)