Materials%20for%20Phase%20II%20collimators

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Materials for Phase II collimators
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Rib Stiffener, why molybdenum
Stiffener material requirements Minimise own
thermal distortion Low CTE High thermal
conductivity Minimise deflection by the force in
the midpoint link High Youngs modulus
X-deflection simulation
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
Link
Shafts, fixed points
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Stiffener, why molybdenum
Al-C-fiber composites
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Stiffener made of Mo, old monolithic version
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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
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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 (48 plates), eventually for
  series (250 plates)
• EB butt weld
• Connect overlapped plates, bolted or riveted
• Also
• Spacers
• Positioning system
• Bolts and pins

7
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?

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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

9
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)

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Cooling coil, interest of using molybdenum

• Molybdenum coil in Cu-CD block
• CTE
• Phase diagram
• Feasibility of the coil

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Cooling coil, interest of using molybdenum
Liquid Cu would dissolve Ti or Zr tube !
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Cooling coil, interest of using molybdenum
Mo, Nb and Ta have limited solubility in liquid
Cu and do not form inter-metallic phases
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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 CA1491024)
• Rp0.2 570 MPa Rm 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

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Cooling coil, vacuum related constrains

• 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