In the Large Facilities Report to the Commission of the European Community (CEC) in 1990, the Neutron Study Panel underlined the continuing need for neutron scattering as a microscopic probe of the condensed state, and recognised that a major initiative was necessary. The Panel recommended that a design study be initiated forthwith for a next generation neutron source.

Forschungszentrum Jülich (FZ-J) and Rutherford Appleton Laboratory (RAL) arranged a series of meetings in 1991 and 1992 to explore options for an advanced high-power accelerator-driven pulsed spallation source. This formed the basis for the specification of the ESS.

This initiative was joined by further laboratories from Austria, Denmark, Germany, Italy, the Netherlands, Sweden, Switzerland and the UK. They all together carried out a two year site independent feasibility study for a third generation neutron source. A council of representatives from the partners together with observers from France and Spain was formed to oversee the study, which began in June 1993, and continued from December 1994 with CEC support. This feasibility study was published by the end of 1996 and proposed a 5 MW facility with two SP target stations - operating at 50 Hz (4MW) and 10 Hz (1 MW) respectively. The institutions behind this study continued their joint efforts, co-ordinated by the ESS R&D council, on important R&D issues, which had been identified during the feasibility study.

In the late nineties the Organisation for Economic Cooperation and Development (OECD) initiated a discussion among governments, science agencies and scientists worldwide about the strategy that one should follow for the provision of neutrons. A key component in these OECD recommendations, endorsed in 1999 by the science and technology ministers of the OECD countries, was to build a new, high intensity spallation neutron source in each of the major scientific regions of the globe - in North America, in the Asia-Pacific area and in Europe.

Both the US and Japan are now rapidly constructing their Megawatt Spallation Neutron Sources, each of which will be far more powerful than any existing neutron facility in Europe. The American SNS will be ready in 2006, the Japanese one is part of the J-PARC project and scheduled for completion in 2007.

The ESS Partners concluded the R&D Phase in 2000, and then moved into the Project Proposal Phase. In May 2002 the ESS Project Proposal was officially presented with an updated Science Case, a revised design including a 5MW short pulse and a 5 MW long pulse target station, and a new cost estimate of 1.5 B€. Also 5 sites presented their candidature to host ESS. The Memorandum of Understanding between the Partners specifiied two more activities: a baseline engineering design that should eb ready end 2003, and trying to get a decision end 2003/early 2004.

The European Strategy Forum on Research Infrastructures in which high level representatives of the EU countries consult each other since April 2003 on research infrastructures, commissioned a comparative analysis on ESS, a staged approach to ESS with a long pulse TS first, and a 1 MW SP source which could be an upgrade from ISIS, or a greenfield option based on the AUSTRON proposal. Compared to SNS ESS clearly is the superior option, the long pulse option too will provide world leadership in several fields of science, whereas the 1MW option will still be competitive unless SNS will be upgraded, which is now likely, to 2.5 or 3 MW.

After the governments in Europe had concluded that while in the long run a next generation source is needed a decision will not be taken in the short term, the ESS Council could only conclude that a decision in 2003 or 2004 is not possible, that further delays are likely, and that continuation of the baseline engineering work is not meaningful. As of 1 September 2003, the ESS Council therefore no longer exists.

A new phase in the process to arrive at a next generation spallation neutron source has now been entered into. The UK government has announced that a UK review of options for a new source, including ESS, will be held with a view to arrive at a decision mid 2005 by the UK Science Minister to yes or no bid for funds in the UK. The UK is also organising a consultation with other governments to arrive at a common position in Europe. A new organisation, the European Spallation Source-Initiative, is now ( October 2003) being set up to work with the governemnts to reach a decision end 2007. It will be based at ILL.

	ESS: History
2003	Details in Project status/September 2003 - ECNS
2002	Bonn Conference, Presentation of the ESS proposal: the science case, the technical design, the costs and the organisation.
2000	The Japanese start to construct a 1 MW Spallation Source as part of a multipurpose facility.
1999	Construction of the American Spallation Source SNS - a 1 MW facility - begins.
1999	The OECD recognises the urgent need for action and recommends the construction of modern spallation sources in the three global economic regions of North America, East Asia and Europe.
1999	A technical study demonstrates the feasibility of the ESS, a spallation source which, with 5 MW, exceeds the neutrons intensity of ISIS by a factor of 30.
1991/    1992	Initiatives by the Jülich Research Centre and the Rutherford Appleton Laboratory (UK) to draw up a plan for a European Spallation Source (ESS).
1986	CEC Large Facilities Panel recommends to study a third generation spallation source in Europe.
1985	The construction of a German Spallation Source (SNQ) is not approved.
1984	The British national Spallation Source ISIS (156 kW) at the Rutherford Appleton Laboratory near Oxford starts operation.