BNL Irradiation Studies and the LHC Collimators Nick Simos, BNL simos@bnl.gov May 16, 2006

R & D Overview PHASE I: Irradiation effects on 2D-weaved CC composite for Phase I LHC Collimators (exposure reached ~ 108,000 μA-hrs !!!!) PHASE II: Receiving protons since 11 AM, May 4, 2006 … (thus far accumulated ~ 23,000 μA-hrs and going…)

LHC-relevant Materials PHASE II - Overview PRIMARY Pure Copper (annealed) Glidcop_15AL – Cu alloyed with .15% Al (axial cut and transverse cut) 3D-weaved Carbon-Carbon Composite 2D-weaved Carbon-Carbon SECONDARY Super-Invar (most challenging of all materials in matrix!) Re-introduction of irradiated material into the assembly including annealed and non-annealed specimens Toyota “Gum Metal” (90% cold-worked plus typical grade tested during Phase II) Two Graphite Grades (IG-43 and IG-430) ALSO Ti Alloy (6Al-4V) Bonded graphite to Titanium and Copper (45 degree bond orientation and 90-degree orientation) Tungsten Tantalum Miscellaneous materials (AlBemet; Vascomax) Nickel-Plated Aluminum of the NuMI horn (expose it to more irradiation and compare the surface degradation between the two irradiation phases) Examine electrical resistivity degradation Examine effects of irradiation on thermal conductivity LHC-relevant Materials

Graphite vs. Carbon-Carbon 3D-weaved CC 2D CC (fibers only along parallel planes) CC superior to graphite in thermal shock Serious DAMAGE of 2D CC after heavy irradiation exposure Annealing (reversing irradiation damage) of 3D CC Dramatic Irradiation Effects on Graphite Conductivity Annealing is also exhibited by 2D CC !!! MOST IMPORTANTLY: CTE goes down with irradiation along weak direction

The Beam is ON (as of Thursday, May 4, 11 AM!!!!

Thermal Expansion of Annealed Copper and Glidcop_AL15 Analysis of Non-irradiated Material – Baseline Establishment BNL experiment confirmed the CTE value of Copper indicating stability and precision of the experimental process

Re-considering Super-Invar – Why? Initial study showed that low CTE disappears with irradiation Things did not look promising. Re-examination reveals self-annealing characteristics !! Irradiated invar undergone annealing through thermal cycling Has gone back in the beam for more irradiation.