Description of the moderator systems for the ESS project

This paper describes a suggestion for the arrangement of the Cold Neutron Sources for the two targets in the ESS project. (European Spallation Source). The suggestion is based upon the technique of the existing cold neutron sources at Risoe in Denmark, HMI and Geestacht in Germany. As moderating media all of them use H2 in supercritical condition, circulated by blowers, and the safety of the systems is based upon the triple-containment philosophy. This seems to be the most convenient principle to use near the ESS targets, as it provides a larger degree of freedom with respect to the arrangement of these sources and pipe connections to the chambers, especially because the space is limited and access to the target is relatively complicated. The moderator chambers have been designed by KFA, Juelich and the rest of the arrangement by Risoe, DK. The price calculations used for the ESS project are based upon this arrangement. (au)