Advanced Material Investigations for HL-LHC

The European Organization for Nuclear Research (CERN) is currently developing several technologies for the Large Hadron Collider (LHC) high – luminosity upgrade (HL-LHC), in order to fully exploit its potential. The objective is to increase the integrated luminosity by a factor of 10 beyond the LHC’s design value. Great technological advances are being made in high field magnets, radiofrequency equipment, and detector technology, many of them requiring stretching the boundaries of the materials to their ultimate performance. It is thus essential a comprehensive investigation of the wide variety of materials employed, from the most exotic ones such as ultra – high purity niobium, to the most conventional ones such as iron, given the very particular boundary and service conditions to which they are submitted. The present paper illustrates a wide – ranging collection of material investigations including destructive and non – destructive techniques, to assess the suitability of the materials for the intended in – service conditions. They reach from quality control via ultrasonic examination (UT) and tensile tests at room temperature, to particularly challenging failure analysis via advanced characterization techniques such as X – ray Computed Tomography (XCT), Focused Ion Beam (FIB) and fracture toughness at cryogenic temperature. Additionally, an innovative methodology of investigations, at several fabrication stages, of the root causes of degradation and performance limitation of Nb3Sn coils is presented.