The Physics of Spallation Processes

2.3. THE EUROPEAN SPALLATION NEUTRON SOURCE ESS 152.3.2 Technical design of ESSA spallation neutron source is an accelerator driven facility. The process involving thescientific community that has settled on the functional requirements for ESS has beenlong deliberate and evolutionary. There were rapid advances in neutron science not longafter the first neutron sources were built and utilized. As improved cold neutron sources,neutron guides and advanced instrumentation were developed, the applicability of neutronscattering to a much broader range of science became apparent. New research reactorsand accelerator based sources have been built during the last 20 years. The unanimousdemand for a short-pulse spallation source (proton pulses of 1.4 µs or shorter) resulted insubdividing the task into three major fields of study:1. the injector and the linear accelerator (linac)2. one or more ring(s) for compressing the (long) linac pulses3. the target station(s).Since the 1996 ESS-feasibility study [ess96-III] the reference concept remained largelyunchanged, because only little engineering work has been done in the meantime. Thereforein the following only a brief description is given and the most important changes are summarized.A schematical sketch of the currently anticipated facility comprising the linearaccelerator/compressor-ring/SP-and LP target-station is given in Fig. 2.3 [ess02-III].Figure 2.3: ESS - a possible layout: Artist’s view of the ESS facility showing the ionsource, the linac tunnel leading to the accumulator and compressor rings from where thebeam is distributed to the short pulse target station. The long pulse target station withinstruments is directly connected to the linac.