Guide Hall of the NIST Center for Neutron Research. The NIST Center for Neutron Research (NCNR) serves more customers than all other U.S. neutron facilities combined. Beams of cold, slowed down neutrons pass through guide tubes (blue structures) to reach specialized instruments where they are used as probes to see material structures. A neutron research facility is most commonly a big laboratory operating a large-scale neutron source that provides thermal neutrons to a suite of research instruments. The neutron source usually a research reactor or a spallation source.