Aluminium-B4C composite for neutron absorption

At the European Spallation Source (ESS) in Lund, Sweden, an aluminium-B₄C composite panel from Alumeco has proven more efficient at neutron absorption than B₄C-coated aluminium – and at a much lower cost.

Neutron scattering research at ESS

ESS is similar to CERN in Switzerland and contains the world’s most powerful accelerator-based neutron source.

Neutron scattering (diffraction and spectroscopy) is valuable for studying the structure and dynamics of chemical substances – such as alloys, plastics and advanced ceramics.

Understanding the materials on an atomic or molecular level is an important step in developing new materials, medicines, etc. That is why accurate measurements of the scattered neutrons are essential to the research at ESS.

B₄C coatings vs. B₄C-aluminium composites

Boron metal is well-suited for neutron absorption, but it is too brittle to be used on its own. The usual solution is to use aluminium as a base metal, which is then coated with B₄C enriched in boron-10. This provides a high concentration of ¹⁰B that is essential for absorbing the neutrons, but at a very high cost.

To determine the efficiency of the ¹⁰B coating compared to more cost-efficient options, the researchers tested various boron-aluminium materials:

The results showed that the Al-B₄C composite material was not only more cost-effective but also performed much better in terms of both low neutron scattering and high absorption.

The researchers conclude that despite the high concentration of ¹⁰B in the coatings, these materials were less efficient than uncoated aluminium-B₄C composite plates with a natural concentration of ¹⁰B (19.9%).

Development of the T-REX

The T-REX is designed to measure a wide dynamic range of energy transfer of both polarized and non-polarized neutrons from 0.020 meV to 140 meV with good wave-vector resolution and polarization analysis. This is particularly useful in neutron spectroscopy where the energy of the scattered neutrons must be determined.

Based on the research regarding neutron absorption, a Multi-Grid prototype for the T-REX instrument was constructed using Al-B4C composite for both the blades and for the rear of the device. This was then tested in real use and found to be very effective at suppressing internal neutron scattering and was adopted in the current design.