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