Ultracold neutrons (UCN) can be stored in suitable bottles and observed for
several hundreds of seconds. Therefore UCN can be used to study in detail the
fundamental properties of the neutron. A new user facility providing ultracold
neutrons for fundamental physics research has been constructed at the Paul
Scherrer Institute, the PSI UCN source. Assembly of the facility finished in
December 2010 with the first production of ultracold neutrons. Operation
approval was received in June 2011. We give an overview of the source and the
status at startup.Comment: Proceedings of the International Conference on Exotic Atoms and
Related Topics - EXA2011 September 5-9, 2011 Austrian Academy of Sciences,
Theatersaal, Sonnenfelsgasse 19, 1010 Wien, Austria 6 pages, 3 figure