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Design Verification (Components) 

Design Verification (Components) . Nikolay Solyak LCLS-II 3.9 GHz CM Delta Final Design Review January 29-30, 2019. Outline. Coupler - Design and specs, Q ext measurement, HTS test Thermal properties, heat removal, heat load HOM coupler Frequency Tuner Design and tuning experience

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Design Verification (Components) 

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  1. Design Verification (Components)  Nikolay Solyak LCLS-II 3.9 GHz CM Delta Final Design Review January 29-30, 2019

  2. Outline • Coupler - Design and specs, • Qextmeasurement, • HTS test • Thermal properties, heat removal, heat load • HOM coupler • Frequency Tuner • Design and tuning experience • Other components • Summary N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  3. Requirements for LCLS-II 3.9 GHz coupler. https://docs.slac.stanford.edu/sites/pub/Publications/SCRF_3.9_GHz_Cryomodule.pdf FRD: LCLSII-4.1_FR-0096-R1; PRD: LCLSII-4.1-PR-0097-R2 • *Available power (per Chris A): • 0.9kW -10% (overhead)-19%(losses) = 0.64 kW N.Solyak / 3.9GHz Coupler design

  4. Forward power and max. power in coupler for 0.3mA Eacc=14.9 MV/m, Beam current = 300µA; microphonics = ± 30Hz • Required Power < 600W if Beam-to-RF phase in range: [-120°… -200°]* • Cavity is tuned off-resonance (<40Hz) to minimize forward power • Power dissipation in coupler are below limit (set by 1.9 kW total power) *(C.Adolphsen, P.Emma) N.Solyak / 3.9GHz Coupler design

  5. 3.9 GHz power coupler for LCLS-II CW operation • Fix coupling; Q=2.7e7 (2.4e7-3.e7) • Cylindrical cold window (as 1.3GHz) • Waveguide warm window • XFEL/FNAL coupler for pulse operation (Pmax= 45kW, DF=1.3%: Pavrg < 0.6 kW). • LCLS-II: Pmax= 1.8 kW cwin quasi – TW regime: • Tmax ~1000K w/o modification (warm part inner conductor Cu plating 30um) N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  6. LCLS-II Main Coupler Design (modification from XFEL design) • 1. Cold part (upper picture) • Dimensions of ceramic window • Length of antenna (QL=2.7e7 vs.1.5e7) • Material of antenna - copper (vs. SS) • => Reduce antenna heating and Qext variation (HTS result) • 2. Warm outer part  No changes • 3. Inner conductor of warm section • Cu plating increased from 30 to 150 um. • Reduce number convolution in inner conductor bellows from 20 to 15 • 3 existing warm sections rebuilt to prototype: Tested at RT, power tests, HTS Cold part Warm part (outer conductor) Warm part (inner conductor) and WG box with warm window N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  7. Qext variation control CMM measurements on 4 pre-production cavities Drawing CMM meas. difference 3HRI01=70.128 (+0.378 mm) 3HRI04=69.185 (-0.565 mm) A=69.75+/-0.2mm Note: ~0.9mm difference in coupler port position To reduce coupling variation in production cavities: • RI measures antenna coupling through end-groups. S-parameters should be in specified range, if not coupler flange is trimmed. • 3 length of diamond seals (4.5; 5; 5.5) to reduce coupling variation. Presenter | Presentation Title A

  8. Qext variation control: simulations, errors and measurements (prototype cavities and couplers) - 1.5mm Qext measurements with prototype cavities • Sensitivity of QL to errors: • Field flatness (90%)  QL=20% • Antenna length: 27.5% per mm ~ 0.1  1mm • Antenna offset: ~ 5% per 1mm • Coupler-to-cav distance ~10% per mm • Other (beampipeelipticity, etc - ?) <1mm <1mm <1mm • QL variation mostly come from cavity errors • XFEL experience: QL=(4.1-8.3)·106 in CM N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  9. 3HRI08 production cavity with prototype coupler Qext measurement on the first production bare cavity. Linear-fit approximation AMAX Mode #9 Quadratic-fit approximation Qext based on S11 measurements Q09 ≈ 5700 @RT Slope subtracted *Antenna L=43.1mm=> for 42 mm (production) expected Qext~(2.6-3)*107; Will be re-checked on 2 dressed production cavities (5 & 8) with production coupler and corrected if needed N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  10. 3.9 GHz cavity: Horizontal testing • Conditions similar to cryomodule operation • Integrated testing of all components • Including: Magnetic shielding, power coupler, tuner, HOM couplers • Resolve possible interference N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  11. HTS 3.9 GHz system Integration test. 3.9 GHz coupler thermometry HTTP6 HTTX30 HTTXM4 HTTX29 Hardware: Cavity - 3HRI03 Coupler #2, antenna trimmed to 43.1 mm QL (RT) = 1.54e+7 QL(2K /static) = 1.70e+7 QL(2K/dynam)= 1.05e+7 1kW SW Coupling depends on RF power (due to antenna heating). Copper antenna (vs. SS) will fix that problem N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  12. Thermal simulations: Effect of antenna material, Copper vs. SS Antenna: SS+50 μm Cu covered / Solid copper Parameters:Pin= 1 kW SWON-resonance:10μm outer plating, ε=9.8, tan=3e-4, roughness 10: warm inner: 120 μm Cu coating of SS inner conductor, 15 bellow conv. TIR ~ 411/430 K HTS: 150K (CM: 110 K) 320K Tmax~ 469/475 K 10K short Port: 1kW Tant = 481/183 K Temperature distribution along inner conductor vs. Z N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  13. Coupler assembled at Cavity and Tested at HTS 0.8 kW SW, OFF-resonance 0.8 kW, SW, ON-resonance TCT100~167K PRF=0.8 kW CT flange~160K IR~390K TIR~385K ΔTbraid T80K_shield Expected maximum Temperatures in CM: • <130K at 50K flange – (from 170K at HT) • <400K at inner conductor bellows  (from <420K at HTS) Note: HTS uses LN2 line (90K) vs. CM He line (40K), all T related to this line will be by ~40K lower in CM N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  14. Thermal simulation summary Temp.boundaries:10/150/320 K; RF power = 1kW, SW. w/o thermal radiation *Confirm at HTS test Copper antenna reduce temperature at tip and provides smaller Qextdeviation in dynamic regime to compare with SS antenna N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  15. Temperature and power dissipation at 5K flange 392K > 387K Forward power (W) Note: expected Tmax (inner conductor bellow) ~20K above IR meas. (simul). 5K – end.  Cryo heat load Pstatic= 0.7W; Pdyn (on/off)= 1.9/1.6W; OFF-resonance ON-resonance Pdyn (on/off)= 14/12 W; ~ 12W ~14W Measured Power flux Braid temp gradient 80 K – end.  ΔT=HTTX30-HTTX29 Temperature, K Infra-red sensor Temperature (inner conductor, warm part) N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  16. Thermal intercept design in 3.9GHz CM Coupler uses same straps as in 1.3GHz cryomodule • power flux less than in 1.3GHz coupler • same straps are used as for 1.3GHz system (L~150mm, S=120mm2; 0.29 W/K) N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  17. Main Coupler Summary • Three coupler prototypes (warm part) were built and tested: • QC inspection and RF measurements • 2 couplers were HP processed at warm test stand at 2kW cw. • 1 assembled on dressed cavity and tested in HTS at 1kW SW (integrated system test). • Qext measurements with coupler installed on prototype cavity (1,2,4) and one production cavity (3HRI08) at room temperature. • It was found that major contribution to Qext variation is coming from cavity dimension errors. To minimize variation the RF coupling measurements of coupler end-group were included as part of cavity production process • Thermal design verified in HTS test and incorporated in CM design. • Coupler procurement in progress (8 couplers are received) • First production coupler will be assembled on production cavity (5 &8) to verify Qext N.Solyak - LCS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  18. HOM coupler design LCLS-II modified XFEL (INFN/FNAL) design to reduce risks of tuning and heating problems in CW operation. • Reduce beam pipe and bellow diameter from 40 to 38mm to move trapped parasitic mode away to improve the tuning of HOM notch frequency. • Modification of HOM coupler to reduce heating • F-part modification  less penetration of antenna inside HOM to reduce heating • Increase wall thickness of HOM hat to 1.3mm to prevent cracks and vacuum leak • Shorter length of HOM feedthrough antenna (Fermilab vs. XFEL) • In XFEL design lowest mode are closer to operation node (min ~10-20 MHz vs. 100MHz in simul.) • beam pipe aperture 38 mm allows to detune the HOM by ~ 100 MHz up. N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  19. HOM F-part modification to reduce antenna heating Reduce penetration to beam pipe. Increase length of bump in F-part XFEL/FLASH LCLS-II design G = 3.2e8  G = 1.74e9  • A. Lunin/khabiboulline • Current design HOM antenna quenches at ~20 MV/m in VTS. Expected that quench limit will even lower in CW regime at HTS and CM. • RF power dissipation on HOM antenna reduced by factor of 5.4 after modification N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  20. LCLS-II 3.9 GHz cavity HOM coupler notch frequency tuning • Thickness of hat was a concern • LCLS-II increases to 1.3mm • Past experience: • FLASH: 1mm => broken and vacuum leaks • XFEL: 1.15mm =>one prototype cavity has leak. MC to PU Tuning fixture MC to HOMpu HOMc to PU No damage, no tuning problem with HOM tuning at 6 cavities Courtesy of T.Khabiboulline N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019 S21 measurements before tuning of HOM coupler notch frequencies S21 measurements after tuning of HOM coupler notch frequencies. 35-40 dB lower signal at operating mode

  21. LCLS-II 3.9GHz Frequency Blade Tuner • Modified INFN slim blade tuner design • Added 2 piezo-capsules for fast tuning • Active elements same as used for 1.3 GHz LCLS-II tuner Tuner Specifications INFN (EuXFEL) tuner Other tuner related parameters Dressed 3.9GHz cavity with tuner assembled for test at HTS Courtesy of Yuriy Pischalnikov N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  22. Cold Tuner Tests: (Slow/Coarse Tuner test results) • Slow tuner performances: • Range more than 700kHz • Resolution 12Hz/step • Hysteresis ~500Hz Detuning the cavity with stepper motor Tuner operational region Cavity stretched by tuner (both piezo loaded) Cavity compressed through safety rods (non-operational region) Region where cavity non-constrained by tuner (cold) • During assembly tuner on the cavity safety gaps were set to 300um. • After cool-down gap decreased to 100um & both piezo were operational/ no locking by safety rods. Safety gaps 300um (warm) N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  23. Cold Tuner Tests: (Fast/Fine Tuner test results) • The piezo detuning measurement was done after the cavity was stretched 240 kHz from the end of section B • The sensitivity for both piezo is 120 Hz/V and at 100V a detuning of 13 kHz was observed (for just ½ of one piezo-stack detuning will be ~3kHz (with 1kHz specs) 120Hz/V Detuning the cavity with fast/piezo tuner in region C. N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  24. Tuner Summary • Design Verification Test of the cold dressed cavity/tuner system confirmed that tuner performances met or exceed specifications • Developed (and confirmed with tests) procedure of the tuner assembly on the dressed cavity (including setting safety gaps) • Dressed Cavity/Magnetic shielding/Tuner integration efforts lead to small modifications that incorporated into production drawings for tuners and magnetic shielding N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  25. BPM and HOM absorber same as for 1.3 GHz CM • Concept: Use 1.3GHz beam line components (ID=78mm) in transition between cavity string: • BPM, • Gate-valve, • Spool pieces, • Beamline HOM absorber • Optimize length and shape of transition from ø38mm (cavity) to ø78mm for minimum wakefields. • Short ~25mm in flange (XFEL) • Long >300mm in spool-piece (upstream end) N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  26. Component Design Verification Summary • Prototypes of all critical components (cavity, coupler, frequency tuner, thermal intercepts) of the 3.9 GHz system were built and tested at room temperature and at cold environment (HTS) in integrated system test. • As a result of tests a small modifications incorporated into the production drawings for coupler, tuners and magnetic shielding to meet requirements. • Developed (and confirmed with tests) procedure of the tuning and assembly of the components and QC inspection of the production components (J.Blower) N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

  27. Acknowledgements • Many thanks to everyone who contributed to this talk, special thanks to T.Khabiboulline, I.Gonin, A.Lunin, S.Kazakov, R.Stanek, C.Ginzburg, E.Harms, C.Grimm, M.Foley, Y.Pischalnikov, T.Arkan, A.Grassellino, G.Wu, O.Prokofiev, J.Ozelis, A.Saini, J.Kaluzny, S.Yakovlev, H.Awida, T.Peterson, Y.Orlov, Y.He, E. Borissov, … N.Solyak - LCLS-II 3.9 GHz CM Delta FDR, Jan.29-30 2019

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