Cold moderator systems for compact accelerator-based neutron sources

For brilliance-optimized compact accelerator driven neutron sources the gain factor provided by an optimized neutron moderation and extraction system is the most effective method to enhance the performance and compensate for the low value of “total number of produced neutrons” compared to research reactors. To maximize the gain provided by low dimensional moderators - first proposed for the ESS-”butterfly” cold source, a series of advanced features will be employed in the High Brilliance neutron Source project (HBS) of the Jülich Centre for Neutron Science (JCNS). Specifically, these advances include a novel cold source design, specifically tailored to produce the neutron phase-space for a certain instrument type, and neutron optical elements (like filters, guides and lenses) directly at the source and optimized from source to sample position for one dedicated scientific task. We will report on the design, construction and first measurements with a thermal moderating reflector prototype (MRP) and cold moderator system. In addition, we will inform on the current status of the cold ortho/para hydrogen finger moderator and mixing cryostat with on-line heat capacity measurement and the “in operation” conditioning of the ortho/para state ratio