UKAEA’s Special Techniques Group (STG) has recently been awarded two new assignments, worth around €800k, under an existing framework contract to support the construction of the ITER fusion energy research mega-project in Cadarache, in the south of France.
STG has been working with ITER Organisation (IO) for more than 10 years, helping to develop its diagnostic window requirements. These recent contracts will focus on the qualification, to ITER and applicable nuclear standards, of various aspects of the window optical components and the production methods used in their manufacture. The work includes:
- Managing the acquisition and qualification testing of the fused silica optical elements
- Working with suppliers to develop anti-reflective coatings
- Finalising the design of test windows to be use in mechanical, environmental and cyclic tests
- Procuring all parts for the manufacture of test windows
- Preparing inspection assembly and test procedures for the test windows
The test windows will be used by IO to assess their suitability for the conditions that will be present at ITER. When ITER is operational, the windows will be incorporated into optics-based diagnostics – firing a laser through the optic and analysing the returning signal can determine a range of conditions, for example the density of the plasma and the energy it contains.
Dr Michael Walsh, the Head of ITER’s Diagnostics Division, said: “UKAEA’s Special Techniques Group has been supporting ITER for a number of years. Our close working relationship, which has built up over that time, gives us the assurance that they are the right team to advance an important element of the ITER design, and we look forward to the results of the qualification.”
Window integrity and optical performance can be compromised by the materials selected and joining procedures used to make the finished component. STG’s expertise lies in minimising the stress between the optic part and its metal housing by using a low temperature diffusion bonding technique.
The origins of UKAEA’s work with windows goes back to the 1960s, when they developed lower temperature diffusion bonding techniques to support early fusion research. STG retains significant expertise in creating windows with low stress compliant solid phase bonds that can withstand fusion conditions and maintain the integrity and performance of the optic. This experience is now being translated into other sectors, not least in the ultra-high vacuums used in quantum computing.