(Feri Mezei , Peter Tindemans, Klaus Bongardt )
Since the ESS project was formally presented in 2002, further considerations in the ESS Initiative have led to the conclusion that a 5 MW LP spallation source, upgradeable, would be the European option of choice. It is complementary to existing and planned sources, highly innovative, very cost-effective and is based on proven technologies. This has been endorsed by ESFRI and this is the facility that is on the ESFRI Road Map.

More recent investigations and simulations have only reinforced the conclusion of the ESFRI Neutron Working Group of early 2003 that such a facility would give Europe a world-leading position in many of the most vital areas of modern materials research.

The original ESS design was for a 10 MW proton accelerator on the basis of H- ion sources, with a 5 MW Short Pulse Target Station and a 5 MW Long Pulse Target Station, each with 20 instruments. The 5 MW LP ESS is a straightforward derivative of the 2003 ESS SC Reference Linac. Instead of H- ion sources there will be H+ ion sources; there is no SP Target Station and hence the accumulator ring is left out as well; the linear accelerator is exactly similar and the use for long pulse only opens up additional opportunities for optimization, such as selecting 1 GeV final energy of the protons instead of 1.34 GeV, which would make the superconducting accelerator section shorter. The Target Station for the 5 MW LP ESS is the same Target Station as the LP Target Station of the 2002/2003 design.

This paper analyses the 5 MW Long Pulse ESS and shows why this is the best facility to continue Europe’s world-lead in neutron science for a long time to come.