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INFN-MI: Status

INFN-MI: Status. Angelo Bosotti, Nicola Panzeri, Paolo Pierini. Planning. Milestones : Report on final tuner design by end 2005 Tuner construction and testing by mid 2006 Parallel “historical” tuner activity Started within TTF, now ILC/XFEL In CARE/JRA1/WP8

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INFN-MI: Status

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  1. INFN-MI: Status Angelo Bosotti, Nicola Panzeri, Paolo Pierini

  2. Planning • Milestones : • Report on final tuner design by end 2005 • Tuner construction and testing by mid 2006 • Parallel “historical” tuner activity • Started within TTF, now ILC/XFEL • In CARE/JRA1/WP8 • Report in preparation for 1.3 GHz b=1 cavities (Angelo Bosotti) HIPPI05

  3. Displ Stroke Piezo Structure dmax Force Fmax LFD compensation at high gradients (Dn = KL E2) Evolution of the tuner concept, with integration of the fast LFD action 1.3 GHz system under fabrication right now HIPPI05

  4. Cavity A characterization Previous estimation [7 Hz/(MV/m)2] only on half-cell geometry, but also, mechanical load condition was overestimated by a factor of 2. Present calculation on the full geometry. HIPPI05

  5. Where did we stand in tests with cavity A? • Vertical tests: 3 at Saclay, 3 at JLAB Huge spread in static measurements! And off by a factor 10 HIPPI05

  6. Influence of boundary conditions • Linear superposition of 2 effects: • Shape deformation (fixed boundary) • Cavity shortening (cavity+boundary combined stiffness) Analytical derivation of full behavior requires solution of only 2 load cases HIPPI05

  7. Cavity frequency response under arbitrary b.c. • Frequency response of the cavity can be then understood as a function of the external boundary condition • Using values from the cavity mechanical characterization and Slater perturbation theorem HIPPI05

  8. The RF test frames Jlab tests in 2003/2005 Saclay tests in 2004 Q: Are they sufficiently stiff? HIPPI05

  9. JLAB frame • Cavity is held at He tank disks with a bar • Dish stiffness is greatly reduced! HIPPI05

  10. Saclay frame A: NO, both are not stiff enough HIPPI05

  11. Mechanical models assume perfect joints and no slack contacts between components In reality: joints, screws, etc. Correlation with measured KL HIPPI05

  12. Alternative check • From the Saclay data at low temperatures (2.2 to 1.7 K, where the bath pressure is more stable), an average value of Dn/DP of -462 Hz/mbar can be evaluated • Kext of 1.15 kN/mm can be estimated, coherent with the model discussed before • From the JLab data an average of Dn/DP of -1020 Hz/mbar in the same temperature range can be estimated. • Comparable to a nearly “free” cavity behavior (nominal -966 Hz/mbar), with a negligible external stiffness condition with respect to the cavity stiffness, again, coherent with the model discussed before HIPPI05

  13. Summary on static KL • RF test data is understood • Weak constraints for the cavity length • Low beta geometry very sensible to external boundary condition (low cavity stiffness) • Behavior of KL agains Kext allows to set tuner stiffness requirements under operating conditions • Interaction with CEA (GD) has shown a nearly perfect agreement of static LFD modeling • both calculation modes based on Slater perturbation theorem, but different and independent implementations, especially concerning the mechanical part of the codes (ANSYS vs CASTEM) • Planning for dynamic LFD calculations • harmonic analysis + Slater for cavity transfer function and piezo tf • time dependent analysis: overelongation? • need time for the development and check the procedures HIPPI05

  14. Requirements for 704.4 MHz • One of the uncertainties of the piezo materials is still their stroke capabilities at the low operating temperatures • Assuming a 3 mm stroke to cavity (long piezos) • [safe? SRF/WP8 work in progress] • a ~1000 Hz frequency offset can be compensated during the fast tuning action • With a design accelerating field of 8.5 MV/m, this implies that the overall KL in the operating condition should be limited to around -10 Hz/(MV/m)2 • We took a 50% margin for dynamic LFD? [M.Liepe: factor 2] • In order to achieve this condition with these rather soft cavities the combined stiffness of the He Tank and tuner system needs to provide ~ 10 kN/mm • At 20 kN/mm we are hitting limit with He tank dish stiffness HIPPI05

  15. Tuner requirements • Extracting out the Tank and end dish stiffness contribution (total of 15 kN/mm), the requirement for the tuner becomes about 20 kN/mm Actual experimental stiffness including leverage (TTF) HIPPI05

  16. On the road to finalize tuner design Now we are fine-tuning the tuner stiffness by slight adjustments of the blade number length and slope for final optimization before emitting final drawings for Cavity A Will ask for bids in late 2005 and Order main tuner mechanical components before end of year (INFN contribution is available) Then fabrication time will take 4-6 months HIPPI05

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