Speaker
Description
The degradation and Carbon contamination of X-ray optics is a well-known problem in X-ray beamlines with harmful effects on beamline performance. This is particularly problematic, as such optics are usually highly specialized and coated with various materials. Consequences of such contamination include the distortion of the wavefront, reduction in focusing power and resolution, and loss of flux. In several places in the world, new and upgraded light sources with much higher photon intensity and repetition rates are being built. For them, contamination and damage will accumulate more rapidly. Therefore, carbon contamination causes X-ray optics to be amongst the most expensive consumables at SRs and FELs, in terms of cost and beamline downtime. With that, the option of refurbishing and cleaning X-ray mirrors to overcome this problem is substantial.
Discussions ran within the community for a long time and on several occasions in metrology and X-ray optics meetings, emphasizing the need to find suitable methods. Numerous trials have been made, independently conducted in recent years by European experts in X-ray optics. Different treatments to remove organic residues from the samples have been tested, such as adding a partial pressure of oxygen into the vacuum vessel; illumination with UV light or plasma treatment; chemical stripping of contaminated optical coatings; or repolishing the substrate. Research has progressed slowly, on an ad-hoc basis, with minimal funding. Due to a lack of time and samples, extending those single tests to systematic studies was difficult. First experiences also point to hidden complexities, such as temperature, X-ray flux, and wavelength spectra. These issues clearly show that coordinated action is now required.
For that purpose, a workshop dedicated to “Cleaning and Refurbishment of Optics” was held at Trieste in February 2025. It was attended by many experts representing most synchrotron and XFEL labs in Europe, and the collaboration project REMINISCE (Refurbishment of Mirrors to Increase Sustainability at Light Sources) has been created. Funded by the Horizon Europe LEAPS-TECH EU project, REMINISCE will build on the aforementioned numerous independent trials. With an intense collaboration of 14 project partners from SR and FEL facilities, universities and research institutes, this will be the first large-scale, systematic exploration and refinement of contamination mitigation strategies.
The principal objectives of the REMINISCE work package are:
• in-operando and in-situ prevention and reversal of carbon growth
• ex-situ cleaning of new and contaminated optics
• removal of coatings and refurbishment of optics ready for beamline deployment
The outline of this joint project is presented here, and the first results and preliminary studies of cleaning and refurbishment methods of X-ray mirrors are shown.