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Ultraefficient superconducting RF cavities for FCC Alexander Romanenko FCC Week 2015, Washington, DC 24 Mar 2015 Summary Recent breakthroughs at Fermilab allow record Qs at gradients of interest to FCC in bulk Nb cavities Nitrogen


  1. Ultraefficient superconducting RF cavities for FCC Alexander Romanenko FCC Week 2015, Washington, DC 24 Mar 2015

  2. Summary • Recent breakthroughs at Fermilab allow record Qs at gradients of interest to FCC in bulk Nb cavities – Nitrogen doping => record low BCS surface resistance, reduced non-flux residual – Tuning Meissner effect => no/low contribution from trapped magnetic flux => record low residual resistance • Cryo cost savings (capital and operating) is the main advantage • Thanks to LCLS-II at SLAC nitrogen doping has received a strong technological push to make it production-ready – Q and Eacc statistics on 9-cells • Doping of lower frequencies cavities shows a proof-or- principle for FCC – 650 MHz for PIP-II 2 Alexander Romanenko | FCC Week 2015 3/24/15

  3. Nitrogen doping: a breakthrough in Q Record after nitrogen doping – up to 4 times higher Q! 11 10 This was the highest Q possible up to 2012 Since the discovery -> Q 0 10 10 Standard state-of-the art developed to production- preparation ready for LCLS-II within the context of high Q collaboration 1.3 GHz T= 2K (FNAL/Cornell/Jlab) 9 10 0 5 10 15 20 25 30 35 40 A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 E acc (MV/m) 102001 (Rapid Communication) – highlights of 2013 3 Alexander Romanenko | FCC Week 2015 3/24/15

  4. N Doping – small deviation from standard ILC treatment A. Grassellino et al, 2013 Supercond. Sci. Technol. 26 102001 (Rapid Example from FNAL 2/6 doping process: Communication) • Bulk EP Ship to DESY Cavity after Equator Welding • 800 C anneal for 2 hours in vacuum HOM Tuning • 2 minutes @ 800C nitrogen diffusion EP 140 um X • 800 C for 6 minutes in vacuum 120C bake • Vacuum cooling Short HPR Leak Check • 5 microns EP XFEL External 20 um BCP Final Assembly Long HPR Ethanol Rinse VT Assembly 800C HT Bake Helium Tank Welding RF Tuning Procedure EP 40 um Long HPR Ethanol Rinse HPR 4 Alexander Romanenko | FCC Week 2015 3/24/15

  5. “Production” recipe for LCLS -II – 9-cells for prototype cryomodule(s) A. Crawford et al, IPAC’14, WEPRI062 Work in collaboration with Jlab and Cornell to demonstrate transfer and validation of best recipe 5 Alexander Romanenko | FCC Week 2015 3/24/15

  6. Statistics for two doping recipes on 1.3 GHz 9-cells Recipe 2/6 16 MV/m 2.7e10 Data from FNAL/JLab <Q>=3.6e10 <E max >=22.2 MV/m E max median=22.8MV/m Recipe 20/30 Data from Cornell/Jlab/FNAL <Q>=3.24e10 <E max >=16.3 MV/m E max median=16.5MV/m 6 Alexander Romanenko | FCC Week 2015 3/24/15

  7. Minimizing residual resistance (maximize Q) by avoiding the ambient magnetic flux to be trapped Same cavity, just cooled differently through 9.2K 10 4.0x10 10 3.8x10 10 Flux expelled 3.6x10 10 3.4x10 efficiently 10 3.2x10 10 3.0x10 10 2.8x10 10 2.6x10 Q 0 #1: First fast from 300K 10 2.4x10 #2: Slow from 15K 10 2.2x10 #3: Fast from 15K 10 2.0x10 10 1.8x10 Flux mostly 10 1.6x10 trapped 10 1.4x10 10 1.2x10 2K, 1.3 GHz 10 1.0x10 0 5 10 15 20 25 E acc (MV/m) 7 Alexander Romanenko | FCC Week 2015 3/24/15

  8. Magnetic probes reveal the new physics Full expulsion of the It turns out the expulsion efficiency can be magnetic field should controlled by the cooldown procedure give ~2x higher field at (fast/slow, uniform or not) the equator in superconducting state Efficient flux expulsion Poor flux expulsion H Fluxgate magnetometers A. Romanenko, A. Grassellino, O. Melnychuk, D. A. Sergatskov, J. Appl. Phys. 115 , 184903 (2014) 8 Alexander Romanenko | FCC Week 2015 3/24/15

  9. Experimental proof that thermogradient at NC/SC interface is key parameter for flux expulsion A. Romanenko, A. Grassellino, A. C. Crawford, D. A. Sergatskov, and O. Melnychuk, Appl. Phys. Lett. 105 , 234103 (2014) Temperature difference at the phase front (dT/dx) 9 Alexander Romanenko | FCC Week 2015 3/24/15

  10. Differences between fast/slow Difference in geometry of transition A. Romanenko, A. Grassellino, O. Melnychuk, D. A. Sergatskov, J. Appl. Phys. 115 , 184903 (2014) 10 Alexander Romanenko | FCC Week 2015 3/24/15

  11. Observing fast and slow cooldown dynamics 11 Alexander Romanenko | FCC Week 2015 3/24/15

  12. Fast and slow cooldown dynamics captured Slow from 12K Fast from 300K Top Bottom M. Martinello, M. Checchin - PhD work 12 Alexander Romanenko | FCC Week 2015 3/24/15

  13. • Fast cooldown 13 Alexander Romanenko | FCC Week 2015 3/24/15

  14. Iris Sx Equator Iris Dx 9.250 1 10.03 10.80 11.57 8 12.35 13.13 13.90 Board Number 15 14.68 15.45 16.23 22 17.00 29 36 1 4 7 10 13 16 Thermometer Number 14

  15. Iris Sx Equator Iris Dx 9.250 1 10.03 10.80 11.57 8 12.35 13.13 13.90 Board Number 15 14.68 15.45 16.23 22 17.00 29 36 1 4 7 10 13 16 Thermometer Number 15

  16. Equator Iris Sx Iris Dx 9.250 1 10.03 10.80 11.57 8 12.35 13.13 13.90 Board Number 15 14.68 15.45 16.23 22 17.00 29 36 1 4 7 10 13 16 Thermometer Number 16

  17. Iris Sx Equator Iris Dx 9.250 1 10.03 10.80 11.57 8 12.35 13.13 13.90 Board Number 15 14.68 15.45 16.23 22 17.00 29 36 1 4 7 10 13 16 Thermometer Number 17

  18. Iris Sx Equator Iris Dx 9.250 1 10.03 10.80 11.57 8 12.35 13.13 13.90 Board Number 15 14.68 15.45 16.23 22 17.00 29 36 1 4 7 10 13 16 Thermometer Number 18

  19. Iris Sx Equator Iris Dx 9.250 1 10.03 10.80 11.57 8 12.35 13.13 13.90 Board Number 15 14.68 15.45 16.23 22 17.00 29 36 1 4 7 10 13 16 Thermometer Number 19

  20. Iris Sx Equator Iris Dx 9.250 1 10.03 10.80 11.57 8 12.35 13.13 13.90 Board Number 15 14.68 15.45 16.23 22 17.00 29 36 1 4 7 10 13 16 Thermometer Number 20

  21. Equator Iris Sx Iris Dx 9.250 1 9.825 10.40 10.98 8 11.55 12.13 12.70 Board Number 15 13.27 13.85 14.43 22 15.00 29 36 1 4 7 10 13 16 Thermometer Number 21

  22. • Slow cooldown – encircling normal areas 22 Alexander Romanenko | FCC Week 2015 3/24/15

  23. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 23

  24. Equator Iris Sx Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 24

  25. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 25

  26. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 26

  27. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 27

  28. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 28

  29. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 29

  30. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 30

  31. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 31

  32. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 32

  33. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 33

  34. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 6 9.415 9.470 11 9.525 9.580 Board Number 16 9.635 9.690 21 9.745 9.800 26 31 36 1 4 7 10 13 16 Thermometer number 34

  35. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 35

  36. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 36

  37. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 37

  38. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 38

  39. Iris Sx Equator Iris Dx 9.250 1 9.305 9.360 9.415 8 9.470 9.525 9.580 Board Number 15 9.635 9.690 9.745 22 9.800 29 36 1 4 7 10 13 16 Thermometer number 39

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