Spallation is the process for producing neutrons by means of a particle accelerator and a heavy metal target. Protons derived from hydrogen gas are drawn through a linear accelerator to a velocity just below the speed of light, at which point they collide with the nuclei of the target metal, tungsten in the case of ESS.

The collision of protons and the nuclei of the target metal, tungsten, throws off, or scatters, a collection of high-energy neutrons, which in turn are assembled into beams that are directed toward an array of scientific instruments. Each of these instrument stations is uniquely calibrated to observe a different set of interactions between the neutron beam and the material or tissue sample the experiment is designed to analyze. It is in the design and operation of these tools that the experimental science at ESS takes place.

The more neutrons produced in the target collision, the “brighter” the neutron source is said to be. This is because each individual neutron plays its part in revealing the material sample placed in its path, either by colliding with the sample’s molecular mass, passing through it completely, or by interacting with whatever magnetic forces are already present in the material. Each additional neutron produced by the spallation source contributes to a higher resolution image of its target.

The enormous volume of data generated by what are essentially split-second encounters is picked up by detectors, recorded by computers and rendered, via software, into atomic models of the material under observation. Fortified with this information, there is virtually no limit to the practical and theoretical advances that may one day be traced back to experiments originating at ESS.