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G. Riddone 13.05.2008

2 nd collaboration meeting on X-band Accelerator Structure Design and Test-Program Structure fabrication Comparative analysis of disk and quadrant manufacture. G. Riddone 13.05.2008. Acknowledgement: S. Atieh, A. Samoshkin, M. Taborelli, R. Zennaro. Quadrant-type structures (50 to 300 mm)

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G. Riddone 13.05.2008

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  1. 2nd collaboration meeting on X-band Accelerator Structure Design and Test-ProgramStructure fabricationComparative analysis of disk and quadrant manufacture G. Riddone 13.05.2008 Acknowledgement: S. Atieh, A. Samoshkin, M. Taborelli, R. Zennaro

  2. Quadrant-type structures (50 to 300 mm) Octant-type structures (300 to 1000 mm) Milling- technology used so far: CNC milling, at high cutting speed (spindles at 20000-50000 rpm)- positioning accuracy of the machine tools is 1 to 5 µm Disk-type structure (f = 35 to 80 mm) Turning - carbide or diamond (on copper only) tools (ball nose mills) Milling Structure fabrication Accuracy requirements Accuracy of manufacturing Surface quality Summary of what seems to be feasible

  3. Accuracy requirements x x x x x x • e.g. CLIC_G, 120⁰ • df/dB~ 1 MHz/mm,  d/dB~ 1 ⁰ /mm) • (B= radius of the cell)

  4. Quadrant structures Frequency matching or tuning Avoid steps and kinks on the surfaces (field enhancement b) Ra should be around ¼ of the skin depth to preserve electrical conductivity

  5. Octant structures

  6. Quadrants/octants: machining by milling • machining by 3D milling (carbide or diamond tools) • alignment of the quadrants by pins or balls and gooves (plastic deformation of copper) difficulty in controlling the gap between quadrant, errors in the groove • assembly by brazing or by bolting • damping implemented in the design 160 mm 30 GHz 11.4 GHz 300 mm

  7. Achieved shape accuracy (quadrant/octants)

  8. Possible sources of errors in 3D milling TOOL ERRORS • Error on tool diameter, tool length, tool run-out: dynamic dimensions • Error on tool shape • Tool flexure (larger tools at 11.4 GHz should be favorable) • Tool consumption during machining TEMPERATURE • Thermal expansion of the piece • Temperature stability, dynamics of the machine tool POSITIONING ERRORS • Positioning accuracy (originated from geometric, cutting force, dynamic loading) of the machine tool (machine tool with higher nominal accuracy give better surface finish)

  9. Surface quality (str. in quadrants) Diamond milling Conventional tools milling Ra= 0.2-0.4 Ra=0.02-0.2 1 mm 1 mm 0.01 mm 0.01 mm

  10. Disks: machining by turning and milling • Disks: machining by diamond turning • Adding damping features  Needs milling (no circular symmetry) with smooth transition between milled and turned surfaces. Relative positioning at mm level is necessary! alignment of the damping waveguides is necessary: wake-fields are used by BPM • Alignment of the disks on V-shaped marble before assembly in a stack: use external “cylinder” surface as reference. • Assembly by vacuum brazing or by bolting

  11. Disk dumped structures

  12. Assembly by brazing The type of error depends on the assembly procedure • Achieved accuracy for brazing assembly of disc structures: better than 5 µm Smaller and random error: assembly on vertical V-bench as a tower Bookshelfing: assembly on a slope V-bench gives “tilted” discs 5 μm

  13. Surface quality (str. in disks, Cu OFE) Recrystallization after thermal treatment (vacuum brazing cycle at 820 C) 0.1 mm 1 mm Ra = 0.05 mm 1 mm 0.01 mm

  14. Disk undamped structure (prototype) 11WNSDvg1Cu

  15. Achieved accuracy (prototype) 11WNSDvg1Cu Specification

  16. Summary – what seems to be feasible • Structure in quadrants • Milling accuracy for structures up to 500 mm < +/-2.5 μm • Millingaccuracy for structures up to 1000 mm < +/-20 μm • Ra_best = 0.05 μm • Assembly is a critical point: accurate assembly method to be developed (optical methods) • Structures in disks • TurningØ 35 mm, accuracy < +/-1 μmØ 80 mm, accuracy < +/-1.5 μmRa_best = 0.001 μm • MillingAccuracy < +/- 2.5 μmRa_best = 0.05 μm • Assembly by brazing (vertical assembly better): < +/- 2.5 μm

  17. Effect on thermal treatment Milled surface (carbide tools) Solvent cleaned 10 µm Vacuum baked 750C x 1h 10 µm

  18. Diamond tools vs. Carbide tools

  19. High speed milling machine tool Diamond fly-cut

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