1. Cell to cell alignment on GLC structures 24 Nov. 2014, CERN Toshi Higo (KEK) 2014/11/23CLIC Structure Review1

2. Contents Transition from GLC/NLC to CLIC Alignment target Alignment mechanism Machining Stacking/assembly Bookshelf Rotation alignment Bonding/brazing Bending 2014/11/23CLIC Structure Review2

3. Succeeding the technology of GLC/NLC to CLIC GLC/NLC : Targeting longer with wake field control CLIC: Focus to date on high-gradient Disk fabrication (KEK) Bonding (SLAC) CP (SLAC) VAC bake (SLAC) High power test 2014/11/233CLIC Structure Review

4. Key technologies are in hand in early 2000 except for proof of high gradient RDDS1 KX01 2014/11/234CLIC Structure Review

5. Precision machined Aligned to V-block Pre-bonding with V-block Diffusion bonding Precision brazing Straightening 2014/11/235CLIC Structure Review Quick glance at GLC/NLC

6. Target alignment tolerance Cell-to-cell alignment – A micron-level Bookshelving – 100 microradian Bending over a structure – 10 micron level – Can be corrected after bonding, as long as low- order smooth bow 2014/11/23CLIC Structure Review6

7. Alignment mechanism Disk stacking – Best with Outside diameter + reference V-block Short-stack based or long-stack at once – Others Alignment pin, Self fitting Less precise and worry about sticking during bonding Quad or half – Few experience 2014/11/23CLIC Structure Review7

8. Alignment mechanisms 2014/11/23CLIC Structure Review8 Self fitting for several micron Need care to keep stack Quad / Half several to 10μm? Stacking by a robot PSI How well? P. Craievich Swiss FEL HG 2013 Trieste OD and V-block for one micron level

9. Start with precision machining Outside diameter  R – Used for alignment with respect to beam axis – Reference for radial direction of cell shape – Can be realized with proper turning Chuck face self cut  Z – Mating surface flatness – Reference for axial direction of cell shape Other complex shape – Relative positioning accuracy in milling can be within a micron level unless re-chucking 2014/11/23CLIC Structure Review9

10. Start with precision machined cells 2014/11/2310CLIC Structure Review Keys are Outside diameter Flatness Both sides w.r.t. OD Parallelicity Notch for rotation

11. Precision machining 2014/11/2311CLIC Structure Review OD can easily and robustly be measured. Axial position can well be set by self cutting.

12. Stacking/assembly Stacking disks – OD reference – Removing air gap between disks – Rotational alignment by mark or key Alignment preservation until bonding process – During transportation – Keep with pushing to reference surfaces – Pre-bonding as needed with pushing to reference surface – Suppress mutual sliding by friction with axial force by bolts running through the stack 2014/11/23CLIC Structure Review12

13. 2014/11/23CLIC Structure Review13 SLAC: Start with short-stack bonding Easy handling size 1—2 feet Full-stacked on V-block to confirm RF property Straightforward to check RF Difficult handling for >1m

14. 1.3m stacking to bonding in 1996 2014/11/23CLIC Structure Review14 Hand stacking w.r.t. V-block checked by Microsense Extraction from stack jig Moving to furnace DB and braze

15. Cell alignment measured by gap sensors 2014/11/23CLIC Structure Review15 Gap between sensor and reference V-block Can measure cell offset and inclination

16. Vertical stack of  80 and 1.3m followed by diffusion bonding at 800 C 2014/11/23CLIC Structure Review16 Vertical stack followed by 800 degC diffusion bonding Cell-to-cell kept at 5 microns Bow changes 10 microns in smooth manner Bow of several 10 microns

17. Stacking followed by bonding at 900C for IHD1  80mm, 1.3m 2014/11/23CLIC Structure Review17

18. Cell stacking of IHD1 2014/11/23CLIC Structure Review18

19. Cell stacking and bonding 2014/11/23CLIC Structure Review19 Chose 60 deg stack Diffusion bonding at 900 degC Deviation from V-block by several microns Kink was not easy be corrected Bow of 10 microns

20. Cell alignment result of IHD1 2014/11/23CLIC Structure Review20 Cell-to-cell alignment was good;  <1 micron

21. Evolution toward 1.8m fabrication Cleanroom – to be free from dust migration Precise setting of base for stacking – precision V-block with fixed plane perpendicular to the V-block Careful stacking with – Microsenses to check floating from V – Autocollimator to check bookshelf and manual feedback to minimize assumed air gap Pre-bonding – to freeze the mutual movement of cells – at 150degC, 2.6MPa for 1 day with V-block Diffusion bonding – In vacuum furnace 2014/11/23CLIC Structure Review21

22.  45/  60 1.8m stack with pre-bonding (PB) 2014/11/23CLIC Structure Review22 Rotation on furnace base Move 800km sitting on V-block DB in vac furnace Stack in cleanroom RDDS1 stacking with two Microsenses

23. 1.8m DDS, RDDS, HDDS, …. made at IHI in ~1998 Precision stacking and pre-bonding 2014/11/23CLIC Structure Review23 Stacking Pre-bonding Cleaning

24. Improved cell-to-cell alignment in DDS3 and RDDS1 2014/11/23CLIC Structure Review24 Cell-to-cell within 1 microns,  <1micron RDDS1 after DB Smooth cell-to-cell but very big bow

25. Proof of wake field suppression in RDDS1 2014/11/2325CLIC Structure Review Precision cell Stacking + PB DB and shipping to SLAC Brazing ASSET Wake field confirmed Alignment confirmed

26. Bookshelf, rotation and bow Bookshelf – Until now we do not have any definite idea – We just try the air gap as small as possible – Parallelicity between two flat surfaces – OD perpendicular to the both surfaces – Check this OD profile with gap sensors running along beam axis Rotation – Mechanical reference, such as notch – Inscribed line by seeing optical device – Robotic stacking Bow – Smooth bow can bee corrected later. 2014/11/23CLIC Structure Review26

27. Less-friction smooth jig to press end surface during DB For less sticking with copper – Alumina ceramics  stick and make flare – Graphite  worry about fragile – Glassy carbon  good – Glass-like carbon coat GLASTIX KOTE  seems good Preserve good end surface – Needed for further assembly with good alignment – GLC/NLC used sheet brazing but not good from alignment point of view 2014/11/23CLIC Structure Review27

28. Care should be made on DB end surfaces to connect additional parts further 2014/11/23CLIC Structure Review28 Alumina ceramics → Graphite Scratch → Si 3 N 4 3 元系、 900 ℃ → sticking and makes flare → Glassy Carbon After DB Graphite Correction of flare Glassy carbon

29. Conclusion 1.Cells can be stacked w.r.t. mechanical reference with using outside diameter. 2.Cell alignment can be kept without slippage while handling, solid-phase bonding process. 3.One micron-level cell-to-cell alignment is feasible through man-made process. 4.Further mounting of beam-line parts on the bonded main body needs care on end surface quality 2014/11/23CLIC Structure Review29