[ Innovation ]
[ Innovation ]
Stainless steels for particle accelerators , detectors and fusion magnet systems
The construction of particle accelerators like CERN ' s Large Hadron Collider ( LHC ) and the HL-LHC project represents a pinnacle of scientific and engineering prowess . These endeavors demand precise materials and manufacturing processes , particularly stainless steel and nickel-base superalloys , to meet stringent requirements . This articles explores how innovation in materials drives progress in particle physics and high-energy experimentation .
By Stefano Sgobba , Katie Elizabeth Buchanan , CERN
The construction of the world ’ s largest and most powerful particle accelerator ever built , CERN ’ s Large Hadron Collider ( LHC ) and its ongoing upgrade , the High Luminosity LHC ( HL-LHC ) project , required a wide application of tightly specified advanced materials and manufacturing processes . “ In modern large superconducting accelerators , stringent requirements are placed on the materials used for vacuum , cryogenic and structural systems . Their physical and mechanical properties , machinability , weldability and brazeability are key parameters . Adequate strength , ductility , magnetic properties at room as well as low temperatures are paramount factors ”, says Stefano Sgobba , head of the Materials section at CERN , the European Organization for Nuclear Research based in Geneva , that operates the largest particle physics laboratory in the world . “ Stainless steels ”, continues Stefano Sgobba , “ play a crucial role in most components of modern particle accelerators and high-energy physics experiments , of fusion reactors and their superconducting magnet structures working at cryogenic temperatures . The material challenges of such projects are enormous , requiring a wide application of tightly specified stainless steel and nickel-base superalloys products and grades . The final products must feature a controlled microstructure and adequate mechanical , physical , magnetic or vacuum properties and often a combination of them ”. applied to achieve the final stringent properties , acquired within decades of building large systems that must guarantee a reliable , long-lasting service with limited interventions . ITER Organization , which is building in Cadarache , south of France , the largest and most integrated superconducting magnet system ever - with similar material challenges as featured by CERN - has had a Cooperation Agreement in place with the Materials service of CERN since 2009 to draw on the expertise in material assessment for magnets that was developed during the construction of the LHC machine and its large experiments . The example of the dipole and quadrupole magnets of the LHC and
HL-LHC is largely representative in this regard . A special austenitic high manganese and high nitrogen stainless steel was developed already in the mid-nineties in cooperation with Böhler Edelstahl for the beam screen and the cooling capillaries of the machine vacuum system . The steel retains high strength , ductility , and very low magnetic susceptibility at the working temperature between 10 K and 20 K . Since , several tens of kilometres of components had been produced in this special Electroslag Remelted ( ESR ) grade that will be used again for the beam screens of the HL- LHC project ( 3.1 km of finished strip for the beam screen and 4.6 km of seamless cold-drawn cooling tubes in lengths of up to 14 m , Fig . 1 ).
Material assessment CERN gained a deep experience in developing , selecting , specifying and assessing stainless steel grades , steelmaking and processing solutions
Figure 1 . Complex shape beam screens for the HL-LHC triplet magnets in a high Mn – high N grade specially developed for the LHC beam screens , equipped of four seamless cold-drawn cooling tubes in the same grade and inserted into their 316LN cold bores . Image courtesy of CERN .
24 Stainless Steel World March 2024 www . stainless-steel-world . net