Engineering Department ENEN R&D on Advanced Materials: Status and Future Outlook N. Mariani, A. Bertarelli, F. Carra, A. Dallocchio, E. Krzyzak 1 st Meeting AdColMat Working Group N. Mariani – CERN119 August 2013

Engineering Department ENEN Outline N. Mariani – CERN219 August 2013  Review of materials adopted in LHC collimators  Metal-matrix composites under development  Figures of merit  Materials ranking  Conclusions

Engineering Department ENEN Materials for LHC collimators N. Mariani – CERN3  CFC (AC-150-K)  Graphite  Copper OFE  Inermet180  Molybdenum  Glidcop Al-15  Copper-Diamond  Molybdenum-Copper-Diamond  Silver-Diamond  Molybdenum-Graphite 19 August 2013 Already used in collimators active jaw Already used for collimators, but not in the active jaw Under R&D: never used for collimators TCP/TCS TCDI TCLP TCT - TCP/TCS TypeMaterial

Engineering Department ENEN N. Mariani – CERN419 August 2013  CFC and Graphite stand out as to thermo-mechanical performances. Adversely outweighed by poor electrical conductivity, expected degradation under irradiation.  High-Z metals and alloys (Cu, Mo, Glidcop, Inermet) possess very good electrical properties. High density adversely affects their thermal stability and accident robustness.  R&D focused on Metal Matrix Composites (MMC) with Diamond or Graphite reinforcements: goal is to combine the properties of Diamond and Graphite (high k, low  and low CTE) with those of Metals (strength, , …).  Powder Metallurgy production techniques including: Rapid Hot Pressing (RHP), Spark Plasma Sintering (SPS) and Liquid Infiltration. Graphite Punch Powders Graphite Die Vacuum Chamber Pressure DC Current (continuous or pulsed) Materials for LHC collimators

Engineering Department ENEN Materials investigated are Copper-Diamond (Cu-CD), Molybdenum-Diamond (Mo-CD), Silver-Diamond (Ag-CD), Molybdenum-Graphite (Mo-Gr) Most promising materials are Cu-CD and Mo-Gr. Ag-CD and Mo-CD are, by now, sidelined as they are limited by (relatively) low melting temperature (Ag- CD) and insufficient toughness (Mo-CD). Mo-Gr is particularly appealing as it can be cladded with a Mo layer dramatically increasing electrical conductivity … Cu-CD Mo-CD Ag-CD Mo-Gr 19 August 2013N. Mariani – CERN5 Metal-matrix composites

Engineering Department ENEN BC “bridge” stuck on CD surface. No CD graphitization Good thermal (~490 W/mK) and electrical conductivity (~12.6 MS/m). No diamond degradation (in reducing atmosphere graphitisation starts at ~ 1300 °C) No direct interface between Cu and CD (lack of affinity). Partial bonding bridging assured by Boron Carbides limits mechanical strength (~120 MPa). Cu low melting point (1083 °C) may limit Cu-CD applications for highly energetic accidents. CTE increases significantly with T due to high Cu content (from ~6 ppmK -1 at RT up to ~12 ppmK -1 at 900 °C) 150 x 150 x 4mm 3 Developed by RHP-Technology (Austria) inside EuCard WP8.2 activities. 19 August 2013N. Mariani – CERN6 Copper-Diamond

Engineering Department ENEN Why Graphite?  Low CTE  Low Density  High Thermal Conductivity (grade-dependent)  Very High Service Temperatures  High Shockwave Damping Very high melting point (2500+  C) Low Density Outstanding Thermal Conductivity (700+ W/mK). 180% Cu, 170% Ag !!! No reinforcement degradation Possibility to reach excellent electrical conductivity by Mo cladding. Mechanical strength to be improved … Co-developed by CERN EN/MME and Brevetti Bizz (Italy). R&D program still going on to further improve physical properties, particularly mechanical strength 19 August 2013N. Mariani – CERN7 Molybdenum-Graphite

Engineering Department ENEN  Molybdenum – Graphite core with pure Mo cladding having tailored thickness.  Excellent adhesion of Mo cladding thanks to carbide interface.  Sandwich structure drastically increases electrical conductivity:  Simulations foresee a factor 10 Collimator impedance reduction! Core: 1 MS/m Core: 1 MS/m Mo Coating: 18 MS/m Mo Coating: 18 MS/m Carbide layer: 1.5 MS/m N. Mounet et al., 2013 Collimation Review, May 2013  Wish to install a full collimator with Mo-coated jaw in LHC …  New challenge: turn material R&D into a suitably industrialized product in short time…  … and each new material should be validated by accident simulations and tests (HiRadMat) 19 August 2013N. Mariani – CERN8 Molybdenum-Graphite with Mo cladding

Engineering Department ENEN Objectives have been turned into a set of Figures of Merit to assess relevant materials Reduce RF impedance Maximize Electrical Conductivity Maintain/improve jaw geometrical stability in nominal conditions Maximize the stability indicator Steady-state Stability Normalized Index (SSNI) Maintain Phase I robustness in accidental scenarii Maximize the robustness indicator Transient Thermal Shock Normalized Index (TSNI) Improve cleaning efficiency (absorption rate) Increase Radiation and nuclear Interaction Lengths, i.e. Atomic Number Improve maximum operational temperature Increase Melting Temperature. 19 August 2013N. Mariani – CERN9 k  R(1- )c pv EE Z TmTm  Additional “standard” requirements include... Radiation Hardness, UHV Compatibility, Industrial producibility of large components, Possibility to machine, braze, join, coat..., Toughness, Cost … Objectives for material R&D

Engineering Department ENEN MaterialC-CGraphiteInermetMo Copper (annealed) Glidcop ®Cu-CDMo-Gr Density [g/cm 3 ] ~ Atomic Number (Z) ~ T m [°C] ~1083 ~2520 SSNI [kWm 2 /kg] ÷ * TSNI [kJ/kg] ÷ * Electrical Conductivity [MS/m] ~ ÷ 18 ** 19 August 2013N. Mariani – CERN10 Materials Ranking & Discussion * Estimated values ** with Mo coating worsebetter  Are figures of merit considered until now still valid or new requirements should be considered?  For actual figures of merit, Mo-Gr (eventually Mo-coated) seems the best solution for future LHC secondary collimators.  Other refractory metals like Molybdenum could be also of interest for tertiary collimators instead of Tungsten alloy. Need for Sixtrack/Fluka simulations to confirm effective cleaning efficiency of Mo instead of W alloy.

Engineering Department ENEN 19 August 2013N. Mariani – CERN11 Conclusions  Mo-Gr (eventually Mo-coated) looks like the best choice for future primary and secondary collimators.  It is recommended to prosecute with the development, industrialization and characterization of MoGr.  Additional in-house testing equipment to be acquired (Laser Flash, Dilatometer, …) Proposal for possible time-schedule:  Oct-Nov ‘13: Sintering furnace optimization.  End of ‘13: Production of a representative “large” MoGr piece (~140x40x20 mm).  Dec ‘13: Additional samples for radiation hardness tests in BNL.  Early ‘14: Development and manufacturing of Mo-cladded MoGr.  Nov ‘13 – Jun ‘14: Detailed characterization, including:  Thermal properties up to high T (dilatometry, calorimetry and thermal diffusivity)  Electrical properties (electrical conductivity, dedicated RF tests, …)  Static and Dynamic mechanical properties,  Radiation damage resistance.

Engineering Department ENEN N. Mariani – CERN1219 August 2013