First neutrons from next generation source in Jülich

Accelerator-driven, low-energy compact neutron sources are considered the next generation of neutron source for a wide range of applications. On 12 December 2022, researchers from the Jülich Centre for Neutron Science (JCNS) at Forschungszentrum Jülich achieved a significant breakthrough, delivering first neutrons with a powerful new target/moderator technology.

More than 16 years after the permanent shutdown of the DIDO research reactor at Forschungszentrum Jülich (FZJ), a new type of neutron research facility was put into operation on the FZJ site. Currently, this platform houses three beamlines: a detector test stand; a time-of-flight (ToF) diffractometer; and the HERMES neutron reflectometer from the decommissioned Orphée reactor, contributed through a collaboration with Laboratoire Léon Brillouin (LLB, CEA-Saclay).

This impressive milestone was achieved as part of the High Brilliance Neutron Source (HBS) project, with first neutrons at the Target-Moderator-Reflector (TMR) unit of an experimental test station for a High Current Accelerator-driven Neutron Source (HiCANS) in the ‘Big Karl’ area of the Institute of Nuclear Physics (IKP). Protons delivered by IKP’s JULIC cyclotron produced first neutrons at the tantalum target developed for the HBS project at TMR. Both thermal and cold neutrons were measured at all three positions around the TMR facility.

The team at JCNS in front of the Target-Moderator-Reflector unit celebrating first neutrons from the new research platform in Jülich. © Forschungszentrum Jülich GmbH

The TMR unit was developed over two years through collaboration between JCNS and Central Institute of Engineering, Electronics and Analytics (ZEA-1) at FZJ. The 68-ton biological shielding is a unique modular design that can accommodate up to eight individual experiments. It is connected to the IKP’s JULIC proton cyclotron via a dedicated proton transfer beamline. A newly developed high-power tantalum neutron target with an internal microfluidic water-cooling loop was installed to test its performance for the HBS neutron source project, and a methane-based cryogenic cold moderator system for cold neutron production was also introduced and tested.

In collaboration with CEA/LLB, the former HERMES time-of-flight reflectometer was transferred from Saclay to Jülich and installed in the Big Karl area. It will be used to demonstrate the performance of a reflectometer at a pulsed neutron source based on an accelerator.

The new neutron source will be used to gain experience in handling targets and moderators, and to develop advanced moderators and reflectors for the future HBS – as well as instrument concepts. Due to the low current of the proton beam, neutron flux is not very high, so proof-of-principle experiments can be performed and developed.

This great success required different expertise and was made possible by the excellent collaboration between several institutes and infrastructure units within FZJ, including engineering (ZEA-1) and infrastructure (T), nuclear physics (IKP) and neutron research (JCNS), as well as external collaborations, in particular with LLB, France.

With the installation of the mock-up of the HBS TMR unit, Forschungszentrum Jülich has taken an important step towards HiCANS that provide brilliant beams for science and industry at resilient, sustainable, flexible neutron research facilities with moderate operating costs and easy user access.