LHC Collimators Phase 2 - Visit to Plansee 28th August Materials for Phase II collimators

LHC Collimators Phase 2 - Visit to Plansee 28th August Rib Stiffener, why molybdenum Active part where most of heat is deposited tends to deflect due to thermal gradient Stiffener linked in a midpoint to limit deflection of the active part X-deflection simulation Stiffener material requirements: Minimise own thermal distortion Low CTE High thermal conductivity Minimise deflection by the force in the midpoint link High Young’s modulus Shafts, fixed points Link

LHC Collimators Phase 2 - Visit to Plansee 28th August Stiffener, why molybdenum Al-C-fiber composites

LHC Collimators Phase 2 - Visit to Plansee 28th August Stiffener made of Mo, old monolithic version

LHC Collimators Phase 2 - Visit to Plansee 28th August Stiffeners made of Mo, assembled by bolts and pins How are the stiffners Long plates 15 x 47 x 1100 mm³ Thinner extremities Circular holes and slots Tolerance ~0.1 mm Threaded holes for cooling clamps Spacers Positioning system Bolts and pins

LHC Collimators Phase 2 - Visit to Plansee 28th August Stiffener, raw material Overall dimension of long plate (mm) –≥15 x 47 x 1100 Standard dimensions by Plansee –12.7 x 500 x 600 –20 x 500 x 600 Possibility of having customized production Ideas to make it out of standard dimension plate for prototypes (4÷8 plates), eventually for series (~250 plates) –EB butt weld –Connect overlapped plates, bolted or riveted Also –Spacers –Positioning system –Bolts and pins EBW

LHC Collimators Phase 2 - Visit to Plansee 28th August Stiffener, machining Recommended machining parameters Plansee as possible supplier of finished components –Tolerances achievable Extremity holes Positioning system elements –Do you see any other issue not mentioned?

LHC Collimators Phase 2 - Visit to Plansee 28th August Cooling coil, interest of using molybdenum Phase 1, implemented solution:Phase 2, increased energy deposition. -Cooling capacity has to be increased - 6 x tubes ID8 mm - reduce contact thermal resistance -Geometrical stability has to be maintained - use material with optimised k/CTE Ideal solution: Cooling coil back-casted in M-CD block C-C GlidCop CuNi Brazing Contact

LHC Collimators Phase 2 - Visit to Plansee 28th August Cooling coil, interest of using molybdenum Cooling coil material for Ideal solution requires –Metallurgical compatibility with metal of the block Avoid dissolution of the coil in the liquid metal Avoid inconvenient inter-metallic phases at the interface –CTE matching with M-CD Avoid distortion, residual stresses or debonding at the interface when solidifying and cooling from infiltration temperature Gaps at the interface leads to poor thermal conduction and virtual leaks –Feasibility of the coil Cooling coil materials believed to be good candidates from the first two points of view –For Cu-CD: molybdenum, niobium, tantalum –For Al-CD: zirconium (preliminary test program is in progress in cooperation with L. Weber EPFL including also stainless steel)

LHC Collimators Phase 2 - Visit to Plansee 28th August Cooling coil, interest of using molybdenum Molybdenum coil in Cu-CD block –CTE –Phase diagram –Feasibility of the coil Cu-CD Al-CD

LHC Collimators Phase 2 - Visit to Plansee 28th August Cooling coil, interest of using molybdenum Liquid Cu would dissolve Ti or Zr tube !

LHC Collimators Phase 2 - Visit to Plansee 28th August Cooling coil, interest of using molybdenum Mo, Nb and Ta have limited solubility in liquid Cu and do not form inter-metallic phases

LHC Collimators Phase 2 - Visit to Plansee 28th August Cooling coil, interest of using molybdenum Feasibility of long intricate coil is a question mark. –ID 8 mm x L 3800 mm –Bending radius as small as 18 mm Tests and trials –Tensile test at RT on molybdenum tube OD10xID8 (our CA ) Rp0.2 = 570 MPaRm = 685 MPa A ≥ 40% !!! but transversally very low ductility Inner wall of the tube is oxidised –Bending tests to be done at CERN workshop What are your recommendations? –Butt welding, your recommendations

LHC Collimators Phase 2 - Visit to Plansee 28th August Avoid virtual leaks (confined volumes with low aperture that make long time to evacuate) Avoid any welding or brazing between water and beam vacuum !  use of continuous seamless tube Other solutions if the last constrain can be relaxed: –Cooling circuit machined in a block, closed by brazing or welding Brazed to the main block Back-casted inside the main block –Any other? –Any experience in similar large surface brazing Cooling coil, vacuum related constrains