Joining Technologies for Accelerators at CERNFritz Motschmann (CERN) ADMACOM Workshop, 15 Sept 2016
CERN
European Organization of Nuclear ResearchCERN’s mission is to enable international collaboration in the field of high-energy particle physics research and to this end it designs, builds and operates particle accelerators and the associated experimental areas.
CERN Accelerator Complex
Large Hadron Collider
Compact Moun Solenoid-Detector
EN-Department at CERN
Activities:
• Operation, maintenance and consolidation of infrastructure systems (cooling, ventilation, transport, handling and electricity distribution);
• Development, operation and maintenance of special accelerator components (targets, collimators, beam dumps, photo cathodes etc.);
• Expertise on computation of radiation fields in the tunnels and experimental areas and the study, the prototyping and the implementation of measures to limit the impact of radiation;
• Mechanical engineering and materials expertise for the design, the prototyping, the manufacturing and the assembly of accelerator and detector components;
• Expertise on control systems based on industry-standard equipment and software;
• Design, modification and operation of the fixed target experimental areas and liaison with experiments as well as experiment proposals;
• Technical Coordination in the accelerators and experiments for the day-to-day running, the technical stops and the shutdowns.
EN-Department at CERN
The Forming and Welding-Section in Mechanical and Materials Engineering Group
EN-MME-FW
EN-Department at CERNForming and Welding-Section in Mechanical and Materials Eng. Department
• Forming, rolling and bending of accelerator components (cavities, vacuum chambers, cooling circuits…)
Copper cavities for RF-structures
CuNi-cooling circuits on collimator jaw
EN-Department at CERNForming and Welding-Section in Mechanical and Materials Eng. Department
• Manual and automatic TIG, MIG and MAG-welding of accelerator and detector components
Assembly of cryostat forSC-magnet facility
Assembly of target for nTOF experiment (aluminium structures)
EN-Department at CERNForming and Welding-Section in Mechanical and Materials Eng. Department
• EB- and laser welding
ATLAS UHV chamber LHC-beam screen (laser welded cooling tubes)
EN-Department at CERN
Forming and Welding-Section in Mechanical and Materials Eng. Department• Vacuum brazing
RF coupler assembly
Induction brazing underVacuum of Ti-cooling tubes(ATLAS Pixel detector)
EN-Department at CERNForming and Welding-Section in Mechanical and Materials Eng. Department
• Examples of Equipment
• Workshop for manual brazing/welding
• Equipment for works at the machinesTIG/Plasma automatic
Orbital TIG
EN-Department at CERNForming and Welding-Section in Mechanical and Materials Eng. Department
• Examples of Equipment
Laser for welding (450 W) and cutting (600 W) (ILS)
Three EBW-machines (PTR, Steigerwald) upt to 12 m3
EN-Department at CERNForming and Welding-Section in Mechanical and Materials Eng. Department
• Examples of Equipment
Air furnacesTmax up to 1150°C
Several vacuum furnaces (all-metal hot zones)Tmax 1350°C/1600°CUltimate Vacuum <10-7 mbarOne furnace with possibiltity to operate under hydrogen
Other:Induction systems on air/under vacuum
EN-Department at CERNForming and Welding-Section in Mechanical and Materials Eng. Department
• Examples of Equipment
Additive Manufacturing Facility
Joining technologies at CERN
Electron Beam Welding of Drift Chamber components (drift tubes)• Precise geometry
• Leak tight weld of cooling circuit (component in UHV)
• Welding after insertion of permanent magnet. Piece temperature is not allowed to exceed 80°C to avoid de-magnetization
Joining technologies at CERN
Electron Beam Welding of RF-cavities (copper and niobium)• High demands on surface finish and purity
• Application of high E-fields
• Nb-sputtering on copper-cavities (superconductive layer)
• Maintaining SC-properties
• Geometry crucial for RF-properties
Production of RF acceleratiing cavitiesBulk copper with supercond. Nb-thin film after assy.
LHC accelerating cavities operating at 400 MHz
Joining technologies at CERN
Electron Beam Welding of RF-cavities (copper and niobium)
Production of superconducting bulk-niobium cavities for SPL study (Superconducting Proton Linac)
Joining technologies at CERN
Vacuum Brazing of Accelerator Components
Realisation of RF-quadrupoles (1st accelerating section in CERN’s new Linac) via vac. Brazing.
Geometry of inner contour has to be kept with an accuracy <20 µm along the length of 1 m.
UHV tight brazing of all ss-ports for pumping, tuning and coupling.
Joining technologies at CERN
Vacuum Brazing of Accelerator Components• Brazing of Nb-stainless steel transitions
• Application in cryonic conditions (4 K, liquid He)
• UHV-leak tight
• Filler material pure copper (1085°C), compensation of different CTE necessary
SS-flange on Nb-tube for bulk-Nb cavities
Joining technologies at CERN
Vacuum Brazing of Accelerator Components• Brazing of ceramic-metal transitions
• RF-windows in couplers for air/UHV transition
Copper rings brazed Al2O3-tubes for LHC-400 MHz RF-couplers
Copper rings subsequently welded on metallic structure
Transition of some MW of RF-power D. Boussard (CERN)
Joining technologies at CERNVacuum Brazing of Accelerator Components• Brazing of ceramic-metal transitions – dielectric intersections
• Techniques for brazing of metal-ceramics with HT-filler materials (mostly based on AG/Cu)
• Al2O3 metallized by Mo/Mn-Ni• Other ceramics (AlN, SiC, Carbon etc.) brazed by active filler-
material (i.e. AgCuTi-alloys)
Brazing of metallized alumina ceramics to alloyswith similar CTE (Kovar, Monel…)
Diffusion brazing with copper counterparts by usinga silver-interlayer (electrochemicaly plated)
Saphir-laser window brazedon dilver-fitting
Joining technologies at CERN
Vacuum Brazing of Accelerator Components• Brazing of ceramic-metal transitions - RF-loads
• Joining SiC-components with copper structures
• Metallization of SiC-surface with:
• Active brazing alloy
• Sputtering of Ti/Cu-interface
• Soldering at low temperatures under vacuum
Cu-ring soldered undervacuum on SiC-ring
Assembly subsequentlyEB-welded on Cu-structure
Joining technologies at CERN
Diffusion Bonding of Copper• Realization of precise structures without filler material impeding the radio frequency
surface-conditions (high fields/gradients)
• Alignment in µm-range (<10 µm after bonding)
A. Solodko (CERN)
Joining Technologies
Outlook for future joining technologies at CERN• Graphite/CFC/Mo-Graphite to metallic (copper) structure to improve cooling efficiency
of collimator jaws and beam dumps
• Brazing of metallic beam absorbing materials to i.e. titanium-structures for fast moving beam dumps
• Different niobium-transitions like Nb-Ti for niobium cavities
• Joining of cooling tubes to lightweight/low density supports of Pixel-detectors (upgrades of LHC-detectors)
• Improvement of thermal cycling-resistance of SiC/Cu-transitions
• …
Thank you for your attention