Analysis of vacuum stability at cryogenic temperature: Deliverable D4.1

Vacuum stability at cryogenic temperature is a key element for the design of the proton-proton future circular collider FCC-hh. To thermally screen the cold bore of all superconducting magnets a beam screen is a mandatory solution. Its design, operating temperature and structure must fulfil a number of different technical requirements. Other groups, within the EuroCirCol collaboration, are producing design studies and prototypes to be validated as base line beam screen for the final study objective of the collaboration. Among such requirements, vacuum stability at cryogenic temperature is indeed a very important one, being the object of the present report. The objective of the task 4.4, within the WP4, is to validate on small test samples, the proposed temperature and the various material surfaces produced by the collaboration. This task will be honored by using two dedicated UHV systems to study gas adsorbion/desorbtion on small test samples as indicated/produced by the others members of the collaboration. The ongoing activity to characterise the available systems and to set up an experimental strategy to study such test samples, once available, will be here presented. Secondary Electron Yield (SEY) has been individuated as a novel technique to be associated to Temperature Programmed Desorption (TPD) and mass spectrometry to qualify beam screen materials and their adsorption/desorption properties.