Synchrotron-driven spallation sources

The use of synchrotrons for pulsed neutron spallation sources is an example of scientific and technological spin-off from the accelerator development for particle physics. Accelerator-driven sources provide an alternative to the continuous-flux, nuclear reactors that currently furnish the majority of neutrons for research and development. Although the present demand for neutrons can be adequately met by the existing reactors, this situation is unlikely to continue due to the increasing severity of safety regulations and the declared policies of many countries to close down their reactors within the next decade or so. Since the demand for neutrons as a research tool is, in any case,expected to grow, there has been a corresponding interest in sources that are synchrotron-driven or linac-driven with a pulse compression ring and currently several design studies are being made. These accelerator-driven sources also have the advantage of a time structure with a high peak neutron flux. The basic requirement is for a fast-cycling, medium-energy, high-intensity accelerator complex. In the synchrotron-driven sources, the synchrotrons typically work at the limit of the technology used in their design and require sophisticated injection and "painting" systems, RF cages in ceramic vacuum chambers, large resonant power converters and powerful RF systems. Radiation management is one of the main concerns. The activation of the exhaust air and ground water must be kept below limits agreed with licensing authorities and where possible the activation of machine elements should be kept within the limits for "hands-on-maintenance". The degradation of materials such as the coil insulation needs to be estimated and radiation-hard elements used in critical places. These requirements imply tight tolerances and high efficiencies for the collimator systems, the ventilation system, the shielding and the parameters of the incoming linac beam. Presently operating neutron sources and newly-proposed sources are listed with their main parameters after the discussion of the above points.