PostIrradiation Results of the LHC Collimator CarbonCarbon

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Post-Irradiation Results of the LHC Collimator
Carbon-Carbon

• Nick Simos
• BNL
• Report to the Collaboration
• March 28, 2006

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• There is good news bad news
• In the end the good news win !!!

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The Bad News First

• These good news follow the not-so-good
  observation that the material suffers damage when
  it is exposed to very high proton fluence
• The material damage, HOWEVER, is associated with
  material that has seen protons in excess of
  3x1021 protons/cm2. I do not believe that that
  will ever be anticipated at LHC. Therefore, that
  issue is put to rest.

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The Bad News First
Fiber (strong) direction
Weak direction
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Good News Regarding PHASE-I LHC Collimator
Material

• While the analysis of the 2D carbon-carbon
  material of the LHC PHASE I collimator is
  continuing, it is evident that there is good news
  regarding the ability of the material to maintain
  the 25 micron constrain
• These good news follow the not-so-good
  observation that the material suffers damage when
  it is exposed to very high proton fluence.
• The material damage, HOWEVER, is associated with
  material that has seen protons in excess of
  3x1021 protons/cm2. I do not believe that that
  will ever be anticipated at LHC. Therefore, that
  issue is put to rest.

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Non-Irradiated State of 2D carbon-carbon
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Shown below are some important and very relevant
findings regarding the self-healing of the 2D
carbon-carbon. While irradiation alters the
thermal expansion characteristics of the material
(key property in maintaining 25 micron movement
of the jaws), thermal cycling even of 200C
corrects the damage or change induced. The damage
is corrected even on the heavily irradiated
material (which is shown below). On the left is
the annealing at 300C. On the right is the search
for the temperature threshold. The experiment
revealed that most of the damage is annealed even
at 200C. It is likely that the damage is
continuously corrected for as long as the
operating temperature exceeds say 200 C.
2D CC annealing behavior along the fiber planes
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2D CC annealing behavior along the fiber planes
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2D CC annealing behavior along the fiber planes
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2D CC annealing behavior along the fiber planes
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The striking (and very positive thing for the
collimator jaws) is that self-healing also takes
place along the weak direction (direction with no
fiber reinforcement)
2D CC annealing behavior NORMAL to fiber planes
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• The 2D carbon-carbon apparently has company!
• Similar self-healing behavior is observed in the
  3D carbon-carbon (that has fibers normal to the
  x-y planes) and the super-Invar that has very low
  thermal expansion coefficient.

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annealing behavior of super-Invar
annealing behavior of 3D CC
AlBeMet apparent reduction in CTE
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Phase-II LHC Collimator Material Irradiation

• Primary Materials Copper, Glidcop (85 Cu 15
  Al)
• Other Potential Candidates Super Invar, Gum
  Metal,
• Test under same conditions 2D CC and 3D CC

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SUMMARY

• 2D carbon-carbon selected is expected to meet the
  25 micron requirement
• For as long as the collimator jaws intercepting
  the beam do not see more that 1.0 x 1020 p/cm2
  then there should not be any concern of material
  damage (even along the weak direction)
• It is in the plan to irradiate the 2D carbon
  again together with the 3D carbon this May and
  along with materials considered for Phase II.
  This way there will be direct correlation between
  2D and 3D carbon-carbon on the basis that they
  will both be exposed to the same conditions
• Further experimental scrutiny of the irradiated
  2D carbon for effects of irradiation on thermal
  conductivity is planned for this summer