Development of Novel Support System for HL-LHC Crab Cavity Cryomodule

1. Crab Cavity Support and Alignment ….. and some transport issues Peter McIntosh (STFC Daresbury Laboratory) Prepared by Tom Jones – Cryomodule Designer

2. Outline • HL-LHC crab cavity cryomodule • Cavity string support optimisation • Vibration analysis • Transportation issues • Conclusions

3. Overview of DQW Cryomodule • Collaborative CM design between CERN and STFC. • Design based upon TRIUMF ARIEL module but with a novel support system. 3

4. Support boundary conditions • Decision was made early in the design process that the FPC used to support the cavities. • Primary reason for this was the elimination of bellows in the FPC. These bellows can lead to leaks, potential for damage, and potential for copper plating issues. • It was also decided that the cavity would only be supported from the top, to allow a ‘top loaded’ cryostat design. • The coupler and additional supports are mounted to a common support plate which adjusts the cavity position. 4

5. Support System development • Various options for the additional supports were compared in detail. • Blade support was the optimum configuration: – target >15 Hz for support structure. • Further studies performed to optimise parameter for the chosen design. 5

6. Cool Down Analysis • No stresses induced in cavity due to support system. • Local stressed due to using 316LN flanges on the Nb tubes. 6

7. Modal Analysis • Fundamental mode of the support system at 19.1Hz (tuner frame). • Analysis identified low frequency modes in the tuner which may have caused detuning. • Additional support between tuner frame and helium vessel which was added and assessed. 7

8. Ground vibration assessment • Transmissibility of ground vibration was assessed for the first 10 modes of the support system using the following equation; • Two ground spectra were considered, the conditions in the SPS (where the module was to be installed) and Diamond Light Source (DLS), which was used as a relatively ‘noisy’ reference. • In general the stiffer the system the lower the RMS vibration as high frequency ground excitation has lower amplitude. 8 Integrated RMS Displacement from 1 to 100Hz (nm) for first 10 modes with 35mm flexures Integrated RMS Displacement from 1 to 100Hz (nm) for first 10 modes with 75mm flexures

9. Ground vibration assessment SPS Ground data Tuner mode 9

10. Stiffness Assessment Lateral Longitudinal Vertical 1kN 1kN 1kN 10

11. Short Transportation Load Transportation analysis for local movement around CERN site only. For international transport expect to remove side panels on module to fit temporary internal support structures. 9.81m/s2 11

12. Support system final design Warm Tuner Mechanism Fundamental Power Coupler Common support plate Blade support DQW in Helium Vessel Fixed Retroreflectors for FSI System Cold Tuner Mechanism with Flexural Guides Targets for BCAM Monitoring System Ref: Jones, T. (2017)Development of a Novel Supporting System for High Luminosity LHC SRF Crab Cavities, SRF17 12

13. DQW Cryomodule in SPS Note: Large side-access ports for provision of internal clamping for transport 13

14. Typical ELI girder ELI-NP Module Transport Upper welded assembly Attached to girder • Considerable amount of experience and data gained from transportation of 12 modules (4m long) from Daresbury (UK) to Romania. • Transportation is by road, then rail through channel tunnel, then road (almost 3000 km total distance). • Modules transported on a dedicated Air Ride Trailer. • Configuration similar to a cryomodule transportation frame. • Accelerometers capture all vibration over 7 day period. Accelerometers fitted to lower frame (fixed to trailer) and upper accelerator (sprung) frame. CavoflexSprings Lower welded assembly Attached to trailer Y X Z 14

15. ELI-NP Module Transport • Shocks observed at up to 2G at equipment in longitudinal direction (on road). • Anti-Shock frame reduces shock loading by >2 times in all directions (excellent in reducing vertical shock). • Identified requirement for damping in next design. Shock on upper frame on ‘noisy’ European road Shock event – 2G in lateral direction 15

16. SCA Cryomodules from Stanford Probably earliest example of TESLA technology utilisation! Provided courtesy of Todd Smith. SCA Cryomodule ALICE/ELBE Cryomodule

17. Cryomodule Transport from Stanford to Daresbury Laboratory Outer vessel clamps Anti-Shock frame Support from cantilevered components to Outer Vacuum Chamber 17

18. Cryomodule Transport from Stanford to Daresbury Laboratory Additional internal supports (new coupler port flange, support to Cavity He Vessels) Both cryomodules available for anyone interested!!! • Large amount of adjustment to account for ‘unknown’ internal configuration. • Support designed using similar but not identical module design. • 2 x cryomodules transported by sea (~8000 miles) • Both arrived safely – no internal damage observed. 18

19. Transportation Considerations • Transportation frame can be designed to minimise shock loading to as low as reasonably practicable, but never to Zero. • Shock impact to sensitive components needs to be assessed, preferably this should be done at the design stage: • Components internal to the beam line vacuum cannot have temporary supports therefore need to be sufficiently stiff to prevent damage from shocks. • Design stage activities are a combination of calculation, FEAand real component testing (e.g. shock to ceramics). • Need to ensure fasteners are sufficiently lockedand torqued to prevent loosening during transport. • For the lateral and longitudinal shocks, need to ensure that bolted joints will not slide under shock loading particularly important for large mass components. 19

20. Conclusions and further work • Novel Support System for the DQW Crab Cavity Cryomodule developed and implemented. • In depth analysis for system stability under ground vibration conditions (to minimise microphonics) led to development of relatively rigid system. • Some consideration for local transportation, however, requires further development for international transportation. • Lessons to be learned from previous shipment of accelerator hardware, in particular importance of assessing residual transportation loads in design of all hardware. • STFC to play a leading role in development of transportation solutions for HL-LHC Crab Cryomodules. 20

21. Many Thanks