Brilliant Principle

An atomic nucleus consists of neutrons and protons held together by a strong force. This force must be overcome in order to release the neutrons. In the High Brilliance neutron Source (HBS), the energy required for this comes from protons accelerated to 15 to 45 percent of the speed of light. When such a proton collides with the atomic nucleus of a heavy metal such as tantalum, several processes occur:

• The proton leaves the atomic nucleus again and is deflected in a different direction without emitting any further particles.

• The proton unites – fuses – with the atomic nucleus, creating a high-energy compound nucleus for a very short time. This decays and emits one or more neutrons.

Common neutron sources that operate according to this principle of proton capture have a significant disadvantage: they produce only a very weak neutron beam and are therefore not very ‘bright’. The HBS, on the other hand, is a ‘brilliant’ neutron source.

This is because 10 to 100 times more accelerated protons strike the metallic target simultaneously than with conventional compact accelerator-driven neutron sources (CANS). Accordingly, the target also releases 10 to 100 times more neutrons.

Two advances in particular over the last decade have made the HBS with its brilliant beam technically feasible: firstly, science and industry have developed accelerators that reliably deliver a strong proton beam. Secondly, researchers at Jülich designed and built targets that have been proven to withstand extremely high heat loads and react only slowly to proton bombardment with embrittlement and crack formation.

Thanks to its brilliant neutron beam, the HBS can be used with several very different measuring instruments at the same time, unlike a CANS. The HBS neutron beam has a cross-section of just a few millimetres, is emitted in pulses of adjustable length and has a very good signal-to-background ratio. These properties of the brilliant beam make the HBS particularly suitable for researching materials at the atomic level. In addition, the HBS can also be used to examine samples that are only available in very small quantities.

The HBS has significant advantages over neutron sources based on other processes.