A National Focused Ion Beam Facility for Active Materials

Focused ion beam (FIB) is an essential tool in materials science, both for 3D characterisation of the structure and chemistry of materials, but also as a specimen preparation method for other techniques. Cutting-edge instruments for atom probe tomography (APT), transmission electron microscopy (TEM) and micro-mechanical testing all rely on the use of FIB to prepare suitable specimens for analysis. Crucially, there are few FIB instruments in the UK that can analyse active material, and this presents a bottleneck to the nuclear research community. This is particularly important for the recently funded NNUF National Nuclear Atom Probe Facility at the University of Oxford, which relies on FIB for specimen preparation of APT specimens but has no active FIB of its own. This proposal would add to the FIB capability at the UKAEA Materials Research Facility and the University of Bristol to create a national facility for focused ion beam on nuclear materials, concentrating on neutron-activated specimens critical for both the nuclear fission and fusion research communities.

The proposed facility would upgrade the existing gallium FIB instruments at MRF and Bristol to optimise their ability to prepare TEM and APT specimens, as well as adding a new plasma focused ion beam instrument (PFIB) at MRF. Conventional gallium FIB instruments have a limited sputtering rate, limiting their ability to characterise large volumes of material. A new generation of PFIB instruments is now available that generates a focused ion beam from a plasma source, which enables sputtering of volumes an order of magnitude higher than the conventional gallium ion beam approach. This proposal would add a multi-ion source PFIB at MRF equipped with xenon, argon, nitrogen and oxygen plasma sources, offering the most versatile ion beam instrument available.

Analysis of air-sensitive materials is complicated by having to transfer the sample to another instrument, and this proposal would integrate a vacuum cryo transfer module (VCTM) into the facility, as well as adding a cryogenic stage to the MRF Ga-FIB and modifiying all three FIB instruments with the ability to load samples from the VCTM. This would allow samples to be transferred between the FIBs and the APT instruments at Oxford under vacuum and/or cryogenic conditions, unlocking a huge new array of cutting-edge materials science experiments on challenges relevant to the nuclear community such as corrosion of actinides and cladding, tritium storage and hydrogen embrittlement.

This PFIB and the upgraded MRF Ga-FIB would be located within dedicated hot cell research rooms within the MRF, with remote operation and robotic handling equipment to allow the analysis of highly active materials. The upgraded Bristol Ga-FIB would supplement the combined facility on low activity materials and training new users prior to using the hot cell instruments. The facility will also work in partnership with the facilities at NNL and Manchester to ensure a true national infrastructure for FIB on active materials.