Which to use—reactor or spallation source

Reactor sources are much more common than spallation sources there are around 20 reactors that produce core fluxes 10 cm s. To generate the proton beam needed for a spallation source requires considerable infrastructure and by 2004 there were only five spallation sources world-wide ISIS [8], IPNS (Argonne, USA) [12], LANSCE (Los Alamos, USA) [13], KENS (Tsukuba, Japan) [14] and SINQ (Villigen, Switzerland) [11] with two more under construction, SNS (Oak Ridge, USA) [9] and J-PARC (Tokai, Japan) [10]. Reactor sources are also much more developed, the first neutron experiments were carried out in the 1950s and the ILL opened in 1975. In contrast the first spallation user facility, opened only in 1980, with ISIS in 1985. 

The energy spectrum of the neutrons produced at the two types of source is distinctly different as shown in Fig. 3.8a. This provides a degree of complementarity whereas reactors produce large numbers of cold and thermal neutrons, spallation sources produce many more high-energy neutrons. However, it has become clear that there are significant 

Vibrational spectra obtained over the whole range requires relatively high neutron energies in the epithermal region and, as will be seen from later chapters in this book, spallation sources are pre-eminent in this field. However, where a limited energy range is acceptable reactor sources can be very powerful. 

As can be seen from Fig. 3.9, the future clearly lies with spallation sources. This is driven by engineering considerations, compared to a reactor, the heat-load per spallation neutron is much smaller. There are also broader political and environmental reasons fissile material is not required in spallation sources and less active waste is produced. 

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