Neutron research facilities

The European Spallation Source, ESS, is a neutron research facility. It can be compared to a giant microscope to study different materials. At ESS the structure, dynamics, and other aspects of materials can be studied using neutrons. Unlike particle accelerators and other such facilities where specific types of particles are investigated, it is not the neutrons that are investigated, but they are rather used as a probe used to make the observation we are after. Neutrons are not easy to produce for this reason large scale research facilities like ESS are needed.

Figure. The European Spallation Source, ESS

ESS is used for materials science, but you may not know that materials science is needed in many different research disciplines and applications. For instance polymer plastics are used in the food industry, magnetic materials are used in your laptop, you eat chemical powders as drugs, the strength of the building you are sitting may depend on the water diffusion in concrete, and you wouldn’t want to cut open a rare archeological artifact to figure out if it is corroded on the inside. All these things and many more can be studied and developed by neutron scattering.

ESS is a European collaboration between 15 countries with Sweden and Denmark as host countries. The spallation facility itself is placed in Lund, Sweden, and the Data Management and Software Center is placed in Copenhagen, Denmark. The construction of ESS was started in the summer 2014, but the project had been in planning for a decade before that. The construction cost of ESS was more than 1.8 billion euros, with the two host countries contributing about half of the cost. ESS has a scientific staff of about 500 and the entire facility covers an area of 74.2 hectares. The proton accelerator which is used to create the neutrons, is operating in pulses, where each pulse uses 380 megawatts, which is the same amount of energy that is consumed by roughly 10 million 40-Watt light bulbs.

At ESS there are 15 different instrument for different scientific analysis, with extra slots for up to 42 instruments. These instruments utilize the neutrons for imaging of materials and devices, diffraction of crystals and powders to find their chemical structures, molecular dynamic investigations, nuclear and magnetic structures of compounds, and much more. One of the things that sets ESS apart from other neutron facilities is the intensity of the neutron source. The beam was designed to be 30 times brighter than all existing neutron sources at the time of construction. This is an advantage since measurements can be performed much faster at ESS, which enables us to investigate new scientific cases. You can compare neutron experiments at older neutron facilities to taking a photo of an object under the glow of a candle-light which would need a long exposure time; whereas performing neutron experiments at the ESS is like to taking a photo of an object lit by a flash-bulb, needing a much shorter exposure time.

Many areas of materials research profit from the bright neutron beam at ESS. One example are chemical reactions that happen on a timescale so short that we need bright beams to get a good measurement during the reaction. Another example could be in cases where only a small amount of sample is available which would at older sources mean that the experiments could either not be carried out conclusively or would have to go on for too long to be economically feasible.