NEG coating deposition and characterisation of narrow-gap insertion devices and small-diameter chambers for light sources and particle accelerators

Abstract NEG-coating technology is becoming very popular in the particle accelerator community, as it provides a very effective mean to reduce the surface outgassing while significantly increasing the pumping efficiency of the beam pipes. An extensive use of NEG coatings is especially suitable in view of next-generation machines, for which long and small-aperture tubes ( i.e. , down to 4 mm) are envisaged in order to reach even higher luminosities and lower emittances. Such stringent requirements should be carefully addressed, as a number of technical issues arise—both in terms of coating deposition and characterisation—when dealing with narrow-gap beam pipes of this kind. The use of NEG coating for narrow-gap insertion devices has steadily grown over the past ten years; a review of both current R&D activities and future perspectives in this field is presented, together with an overview of the analytical techniques employed for the characterisation of the film deposited on small-section chambers. These include SEM morphological inspections, chemical composition analyses and thickness profiling made by EDS and measurements of the getter film's sorption capacity for CO.