Workshop on Targets and Moderators for Spallation Sources

Abstract

The fast neutrons produced by the spallation process are slowed down to velocities adequate for neutron scattering experiments by a complex target-reflector-moderator system. The neutron performance of a spallation source depends decisively on the design and efficiency of this system. In spite of decades of accumulated experience, target-moderator systems still present major challenges in terms of understanding the basic principles and relationships, numerical and optimisation approaches and engineering solutions. A particularly important aspect is the interplay between moderator performance and instrument design. This is a two way street: the desires of instrument builders provide important input for the target people. At the same time, it is in the best interest of instrument builders to have an understanding of what happens in the target and moderators, to appreciate potentials and difficulties. This interaction between the two sides will help us get the most out of future spallation sources. In order to promote this process, Hahn-Meitner-Institut, as the lead laboratory for the ESS instrumentation task, organised an international workshop on 12–14 March 2001, in order to review the current state of moderator development and requirement by neutron instrumentation. The workshop was generously supported by a grant from the EU Neutron Round Table. About 40 participants attended, with strong contributions by the American and Japanese communities as well as from Europe. Constructive and lively discussions on the various aspects of the workshop topic demonstrated the importance of moderator design, target-moderator set-up and requirements by neutron instrumentation for future spallation sources. Although most presentations given during the workshop are published in the present volume, due to the very preliminary status of results, some work as recent calculations by Filges et al. on the neutronic performance of moderators for ESS appears elsewhere. The presented results and discussions will have an important influence on the ESS moderator and instrumentation R and D as well as other spallation source projects.