The first time, to my knowledge, that an effort was made to collect all possible information about the many cold neutron sources (CNS) in the world, was by Guy Gistau (then L'Air Liquide) at the IGORR6 meeting in Taejon (now Daejeon), Korea. Guy’s findings, however, have never been really divulged.

Having been involved in the gestation and birth of quite a number of CNS myself, I decided to compile, from both my own files and Guy Gistau's data base, a first version of the "World Directory of CNS".

In view of the growing activity in the field of ultra-cold neutrons (UCN), I have renamed the “World Directory of CNS” (from version 3) to:

"World Directory of Cold and Ultra-cold Neutron Sources".

The CNS are presented in alphabetical order of the sites.

As of today (2007), I have identified 36 operating CNS, 6 under construction and about 6 planned. Some of the planned CNS are mentioned at sites which are already in the list for other reasons, like ISIS Second Target Station at Chilton, PIK at Gatchina and IBR-2M at Dubna.

The following sites that had used a CNS have since been shut down (with the year of shut down):

Grenoble (Siloette)              1970

Saclay (EL3)                         1977

Helsinki                                 1984 (?)

Harwell                                  1990

Brookhaven                          1999

Garching (FRM)                   2000

Juelich                                   2005

Argonne (ZING-P)                1975

Argonne (ZING-P')               1980

Karlsruhe                               1981

Aldermaston                         1988

Beijing (HWRR)                    1995 (?)

Risoe                                     2000

Cornell                                   2001

Dedicated existing or planned sources of UCN have been included in the site list below.  Most have been developed until now essentially at places which also exploit a classical cold source.  However, in future this may no longer be true (e.g. Mainz, CERN, PSI, LANL).

The last pages contain a Glossary of used and useful terms, and a list of people mentioned in this document.

To access useful links (site information, proceedings and transactions of conferences, workshops, meetings), click on the underlined blue text.

On the site, you can also find an extended bibliography on CNS and UCN sources.

The following site also lists some interesting neutron sources (not CNS!):

I wish to thank all former colleagues and all others, who contributed and helped me with their comments to write and edit this directory.

Klaus H. Gobrecht, HYERES, France, (e-mail:,         June 2007